WO2024078237A1 - 静电梳驱动的基于绝热耦合器的集成波导mems光开关 - Google Patents

静电梳驱动的基于绝热耦合器的集成波导mems光开关 Download PDF

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Publication number
WO2024078237A1
WO2024078237A1 PCT/CN2023/118315 CN2023118315W WO2024078237A1 WO 2024078237 A1 WO2024078237 A1 WO 2024078237A1 CN 2023118315 W CN2023118315 W CN 2023118315W WO 2024078237 A1 WO2024078237 A1 WO 2024078237A1
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Prior art keywords
fixed
waveguide
spring
electrostatic
tapered waveguide
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PCT/CN2023/118315
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English (en)
French (fr)
Inventor
李欢
胡寅鹏
戴道锌
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浙江大学
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Publication of WO2024078237A1 publication Critical patent/WO2024078237A1/zh

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/122—Basic optical elements, e.g. light-guiding paths
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/35—Optical coupling means having switching means

Definitions

  • the present invention belongs to the field of integrated optoelectronic devices and relates to an optical switch, in particular to an integrated waveguide MEMS optical switch and an array thereof, which adjust the distance between two tapered waveguides in an adiabatic coupler by electrostatic comb driving to achieve optical path adjustment.
  • optical interconnection technology has rapidly emerged with its advantages that traditional electrical interconnection cannot compete with, such as large bandwidth and low power consumption, providing a solution for improving the performance of data centers.
  • Optical interconnection has now become a key technology for large-scale data centers.
  • optical switch arrays are key devices for achieving flexible reconstruction of optical interconnection networks. They have become one of the research focuses.
  • Various optical switch structures based on different platforms have been proposed one after another, such as optical switches based on micromechanical systems (MEMS) and integrated waveguide optical switches based on Mach-Zehnder interferometers (MZI).
  • MEMS micromechanical systems
  • MZI Mach-Zehnder interferometers
  • MEMS-based optical switches have attracted much attention due to their low loss, fast speed, good reliability, and strong scalability.
  • Large-scale optical switch arrays based on MEMS have been applied in data center networks.
  • MEMS-based optical switches are divided into free space switches and integrated waveguide optical switches.
  • free space optical switches the optical signal propagates and switches in free space after entering the switch from the optical fiber and is then received by the output optical fiber.
  • Currently, most optical switches in data center networks are free space optical switches.
  • MEMS-based free space switches have good scalability and can currently achieve hundreds of ports while ensuring low insertion loss and low crosstalk.
  • the switching time of such switches is relatively long, generally at the level of several milliseconds and tens of milliseconds, which limits the reconstruction speed of large-scale data centers.
  • the optical signal is bound in the integrated waveguide after entering the chip from the input optical fiber, and the switching of the optical path is achieved through the integrated waveguide structure and mechanical structure.
  • MEMS-based integrated waveguide optical switches have made great progress, which can achieve sub-microsecond fast switching time, low insertion loss, low crosstalk and a large number of ports.
  • MEMS-based integrated waveguide optical switches are expected to break through the limiting factors of current optical switch arrays and be applied to large-scale optical interconnection networks.
  • the purpose of the present invention is to provide an integrated waveguide MEMS optical switch based on an adiabatic coupler driven by an electrostatic comb and an N ⁇ N array.
  • This switch applies a driving voltage to a fixed electrostatic comb to generate an attractive force between it and a grounded mobile electrostatic comb, thereby driving the mobile electrostatic comb to move, and further drives the mobile conical waveguide in the adiabatic coupler to move through a transmission rod, thereby changing the distance between it and the fixed conical waveguide, thereby achieving the effect of optical path switching.
  • the present invention includes at least one switch unit, each of which includes a substrate, a mechanical drive structure and an adiabatic coupler placed on the substrate, the adiabatic coupler mainly including a fixed tapered waveguide and a movable tapered waveguide, the fixed tapered waveguide remains fixed, the fixed tapered waveguide and the movable tapered waveguide are arranged in parallel along a direction perpendicular to the movement direction of the mechanical drive structure, both ends of the fixed tapered waveguide are connected with curved waveguides, both ends of the movable tapered waveguide are connected to the mechanical drive structure through a pair of multi-mode interference cross-waveguide structures, and the movable tapered waveguide is driven by the mechanical drive structure to move closer to or away from the fixed tapered waveguide.
  • Each end of the movable tapered waveguide is sequentially connected with a first meandering waveguide, a cross-shaped multimode interference cross waveguide and a second meandering waveguide.
  • the cross-shaped multimode interference cross waveguide is composed of a longer one and a shorter one.
  • the longer one is composed of a pair of symmetrical mode evolution tapered waveguides and a long multimode wide waveguide.
  • the wide ends of the pair of mode evolution tapered waveguides are respectively connected to the two ends of the long multimode wide waveguide, and the narrow ends are respectively connected to the two meandering curved waveguides; the shorter one is a short multimode wide waveguide, one end of the short multimode wide waveguide is connected to the mechanical driving structure, and the other end is not connected; the longer one of the cross-shaped multimode interference cross waveguides is used for the transmission of optical signals, and the shorter one is used for mechanical fixation.
  • the fixed tapered waveguide and the movable tapered waveguide have the same structure, both of which are tapered waveguides with gradually changing widths.
  • the fixed tapered waveguide and the movable tapered waveguide have the same lengths but opposite width gradually changing directions.
  • the input end width of the fixed tapered waveguide is the same as the output end width of the movable tapered waveguide
  • the output end width of the fixed tapered waveguide is the same as the input end width of the movable tapered waveguide
  • the gap size between the fixed tapered waveguide and the movable tapered waveguide always remains unchanged.
  • the mechanical drive structure includes an electrostatic comb driver consisting of a fixed electrostatic comb and a mobile electrostatic comb, a T-shaped transmission structure, and three sets of fixed islands and a spring structure;
  • the T-shaped transmission structure is suspended on the base, the top rod portion of the T-shaped transmission structure is parallel to the movable conical waveguide, the bottom rod portion is perpendicular to the movable conical waveguide, the bottom rod portion of the T-shaped transmission structure is sequentially arranged along the length direction from one end close to the movable conical waveguide on the first group of fixed islands and spring structures, the second group of fixed islands and spring structures, and the third group of fixed islands and spring structures, and the first group of fixed islands and spring structures, the second group of fixed islands and spring structures, and the third group of fixed islands and spring structures are all connected to the T-shaped transmission structure;
  • Electrostatic comb drives are arranged on both sides of the T-shaped transmission structure between the second group of fixed islands and spring structures and the third group of fixed islands and spring structures.
  • the electrostatic comb drive includes a pair of fixed electrostatic combs and a pair of mobile electrostatic combs.
  • the fixed electrostatic combs are fixed to the base, and the pair of fixed electrostatic combs are symmetrically distributed on both sides of the length direction of the bottom rod part of the T-shaped transmission structure and have no connection with the bottom rod part of the T-shaped transmission structure; the mobile electrostatic combs are suspended from the base, and the pair of mobile electrostatic combs are symmetrically distributed on both sides of the length direction of the bottom rod part of the T-shaped transmission structure, and one end of the pair of mobile electrostatic combs close to the bottom rod part of the T-shaped transmission structure is fixedly connected to the side of the bottom rod part; the comb teeth of the fixed electrostatic combs and the mobile electrostatic combs are opposite and staggered.
  • the first group of fixed island and spring structure mainly consists of a fixed island and a pair of semi-folded springs.
  • the fixed island is fixed to the base. Both ends of the fixed island are connected through a semi-folded spring and an end of the bottom rod of the T-shaped transmission structure close to the movable conical waveguide.
  • the semi-folded spring is suspended on the base.
  • the semi-folded spring is a suspended structure, comprising a spring handle and two beams connected at both ends of the spring handle and perpendicular to the length direction of the spring handle. Both beams extend toward the same side away from the spring handle and are respectively connected to the fixed island and the T-shaped transmission structure.
  • the second group of fixed islands and spring structures are the same as the third group of fixed islands and spring structures, and are both composed of four fixed islands and a pair of folding springs; the fixed islands are fixed to the base, and two fixed islands form a group among the four fixed islands, one group of fixed islands is arranged on the same side of the bottom rod of the T-shaped transmission structure, and the two groups of fixed islands are respectively arranged on both sides of the bottom rod of the T-shaped transmission structure, and the two fixed islands on the same side are connected to the side of the bottom rod of the T-shaped transmission structure through a folding spring, and the folding spring is suspended from the base.
  • the folding spring is a suspended structure, including a spring handle, two short beams connected to the two ends of the spring handle and perpendicular to the length direction of the spring handle, and two long beams connected to the middle of the spring handle and perpendicular to the length direction of the spring handle.
  • One end of the two short beams is respectively connected to the two ends of the spring handle, and the other ends of the two short beams away from the spring handle are respectively connected to two fixed islands located on the same side of the bottom rod of the T-shaped transmission structure.
  • One end of the two long beams is respectively connected to two places in the middle of the spring handle, and the other ends of the two long beams away from the spring handle are respectively connected to two places located on the same side of the bottom rod of the T-shaped transmission structure.
  • the pair of fixed electrostatic combs is connected to an external circuit, and the optical switch is regulated by applying or removing voltage to the pair of fixed electrostatic combs.
  • the fixed electrostatic comb is connected to an external circuit, and a potential difference is generated between the voltage applied by the external circuit and the mobile electrostatic comb, so that an attraction is generated between the fixed electrostatic comb and the mobile electrostatic comb, and the mobile electrostatic comb moves close to the fixed electrostatic comb.
  • the connection between the mobile electrostatic comb and the bottom rod of the T-shaped transmission structure drives the entire T-shaped transmission structure to generate a displacement perpendicular to the length direction of the fixed tapered waveguide, and the connection between the top edge of the T-shaped transmission structure and the multi-mode interference cross waveguide further drives the movable tapered waveguide to generate a displacement perpendicular to the length direction of the fixed tapered waveguide.
  • the displacement of the movable tapered waveguide can be controlled by adjusting the voltage applied by the external circuit, that is, the distance between the fixed tapered waveguide and the movable tapered waveguide is regulated, thereby realizing the function of switching the light propagation path of the integrated waveguide MEMS optical switch.
  • the fixed tapered waveguide, movable tapered waveguide, T-shaped transmission structure, three groups of fixed islands and spring structures and electrostatic comb drive are made of the same material and thickness, and the entire switch unit structure or N ⁇ N array can be manufactured by monolithic integration.
  • the fixed tapered waveguide, movable tapered waveguide, T-shaped transmission structure, semi-folded spring, folded spring and movable electrostatic comb are all suspended structures and are released by corrosion of the buried layer.
  • the fixing island and the fixing member of the present invention are connected to the substrate through the buried layer, and the remaining parts are suspended.
  • the N ⁇ N optical switch array should include at least four of the above-mentioned integrated waveguide MEMS optical switch units. Adjacent switch units are connected via single-mode waveguides and waveguide cross-connections. The connection between switch units can adopt but is not limited to topological structures such as Benes and Cross-Bar.
  • the innovation of the present invention mainly lies in the innovative use of the adiabatic coupler composed of the movable tapered waveguide 3 and the fixed tapered waveguide 2 in the optical switch.
  • the principle is the adiabatic evolution of the mode. Compared with the coupling structures based on the interference principle such as the directional coupler and the micro-bend directional coupler, it has the principle advantages of large process tolerance, ultra-large bandwidth and ultra-low loss.
  • the above-mentioned adiabatic coupler in the above-mentioned optical switch, it can bring the effect advantages of larger process tolerance, larger bandwidth and lower loss.
  • the present invention has a single material, a simple structure and a low production cost
  • the switch unit has low insertion loss, low crosstalk, and high extinction ratio over a wide wavelength range and large processing tolerance;
  • the switch unit uses a capacitive drive structure, and the energy consumption of the switch unit is extremely low;
  • the switch unit has two input ports and two output ports.
  • This 2 ⁇ 2 switch unit can be cascaded into a large-scale optical switch array using a variety of topological structures, and has strong scalability.
  • the present invention achieves the effect of optical path switching by driving the separated adiabatic coupler through an electrostatic comb, and has significant advantages such as a wide bandwidth range, low insertion loss, low crosstalk, high extinction ratio, simple manufacturing process, low processing cost, low power consumption, and strong scalability.
  • FIG1 is a top view of the structure of the present invention in an initial state (OFF);
  • Fig. 2 is a cross-sectional view taken along line A-A' in Fig. 1;
  • Fig. 3 is a cross-sectional view taken along line B-B' in Fig. 1;
  • FIG4 is a top view of the structure of the present invention after voltage is applied (ON);
  • FIG5 is a schematic diagram of a fixed tapered waveguide and a movable tapered waveguide
  • FIG6 is a schematic diagram of the structure of an N ⁇ N integrated waveguide MEMS optical switch based on a Benes topology
  • FIG7 is a light field transmission diagram of the adiabatic coupler portion of the present invention in the OFF and ON states, (a) represents the light field transmission diagram of the adiabatic coupler in the OFF state, and (b) represents the light field transmission diagram of the adiabatic coupler in the ON state.
  • the present invention mainly includes at least one switch unit, each switch unit includes a substrate 10 and a mechanical drive structure and an adiabatic coupler placed on the substrate, wherein the adiabatic coupler mainly includes a fixed tapered waveguide 2 and a movable tapered waveguide 3, the fixed tapered waveguide 2 remains fixed, the fixed tapered waveguide 2 and the movable tapered waveguide 3 are arranged in parallel along a direction perpendicular to the movement direction of the mechanical drive structure, and both ends of the fixed tapered waveguide 2 are connected with an S-shaped curved waveguide, and the curved waveguides at both ends serve as the input/output ends of the switch unit.
  • the curved waveguides at both ends are connected to external components, and the fixed tapered waveguide 2 is also supported by the curved waveguides at both ends so that the fixed tapered waveguide 2 is fixed.
  • the two ends of the movable tapered waveguide 3 are connected to the T-shaped transmission structure 4 of the mechanical drive structure through a pair of multi-mode interference cross-waveguide structures, and the movable tapered waveguide 3 is driven by the mechanical drive structure to move close to or away from the fixed tapered waveguide 2.
  • Both ends of the fixed tapered waveguide and the movable tapered waveguide include a set of curved waveguides, and a portion of the curved waveguides are gradually changing width waveguides, whose width gradually changes from the end width of the tapered waveguide to the single-mode waveguide width.
  • Both the fixed tapered waveguide 2 and the movable tapered waveguide 3 increase structural flexibility by setting curved waveguides.
  • Each end of the movable tapered waveguide 3 is connected in sequence with a first curved waveguide of a meander shape, a cross-shaped multimode interference cross waveguide and a second meander-shaped curved waveguide.
  • the cross-shaped multimode interference cross waveguide is composed of a longer one and a shorter one. The longer one is composed of a pair of symmetrical mode evolution tapered waveguides and a long multimode wide waveguide.
  • the wide ends of the pair of mode evolution tapered waveguides are respectively connected to the two ends of the long multimode wide waveguide, and the narrow ends are respectively connected to the two meander-shaped curved waveguides; the shorter one is a short multimode wide waveguide, one end of the short multimode wide waveguide is connected to the T-shaped transmission structure 4 of the mechanical drive structure, and the other end is not connected; the longer one of the cross-shaped multimode interference cross waveguide is used for the transmission of optical signals, and the shorter one is used for mechanical fixation.
  • the second curved waveguide is used as the input/output end of the switch unit at the other end not connected to the multimode interference cross waveguide.
  • the multimode interference cross waveguides include a pair of adiabatic tapered waveguides and a pair of orthogonal multimode wide waveguides.
  • the two ends of the multimode wide waveguide perpendicular to the length direction of the fixed tapered waveguide are respectively connected to an adiabatic tapered waveguide to achieve mutual adiabatic evolution between the mode in the multimode waveguide and the mode in the single-mode waveguide.
  • the multimode wide waveguide parallel to the length direction of the fixed tapered waveguide is not used to propagate signals, one end of which is connected to a T-shaped transmission structure and the other end is not connected.
  • the two form an adiabatic coupler.
  • the outer ends of the fixed tapered waveguide and the movable tapered waveguide are connected to single-mode waveguides.
  • Optical signals are input and output through the single-mode waveguides, and adjacent switch units in the N ⁇ N array are also connected to each other through single-mode waveguides.
  • Adjacent switch units are connected to each other through the curved waveguides of the switch units, and the curved waveguides serve as input and output waveguides of the switch units.
  • the fixed tapered waveguide 2 and the movable tapered waveguide 3 have the same structure, both of which are tapered waveguides with gradually changing widths.
  • the fixed tapered waveguide 2 and the movable tapered waveguide 3 have the same lengths but the directions of gradually changing widths are opposite along the waveguide direction.
  • the input end width of the fixed tapered waveguide 2 is the same as the output end width of the movable tapered waveguide 3.
  • the output end width of the fixed tapered waveguide 2 is the same as the input end width of the movable tapered waveguide 3.
  • the gap size between the fixed tapered waveguide 2 and the movable tapered waveguide 3 always remains unchanged, so that the fixed tapered waveguide 2 and the movable tapered waveguide 3 are finally arranged in a centrally symmetrical manner.
  • the mechanical drive structure includes an electrostatic comb driver composed of a fixed electrostatic comb 6 and a movable electrostatic comb 7, a T-shaped transmission structure 4, and three groups of fixed islands and spring structures 1, 5, and 8; the group of fixed islands and spring structures closest to the movable conical waveguide is the first group, and the two groups of fixed islands and spring structures far from the movable conical waveguide are the second group and the third group respectively. Openings are evenly distributed on the T-shaped transmission structure to facilitate the entry of chemical reagents that corrode the buried layer.
  • the three groups of fixed islands and springs are distributed along the length direction of the bottom rod of the T-shaped transmission structure.
  • the T-shaped transmission structure 4 is suspended on the base 10, the top rod portion of the T-shaped transmission structure 4 is parallel to the movable conical waveguide 3, and the bottom rod portion is perpendicular to the movable conical waveguide 3.
  • the bottom rod portion of the T-shaped transmission structure 4 is arranged in sequence along the length direction from one end close to the movable conical waveguide 3 to the first group of fixed islands and spring structures 1, the second group of fixed islands and spring structures 5, and the third group of fixed islands and spring structures 8.
  • the first group of fixed islands and spring structures 1, the second group of fixed islands and spring structures 5, and the third group of fixed islands and spring structures 8 are all connected to the T-shaped transmission structure 4; the T-shaped transmission structure 4 is connected to the mobile electrostatic comb 7.
  • An electrostatic comb drive is arranged on both sides of the T-shaped transmission structure 4 between the second group of fixed islands and spring structures 5 and the third group of fixed islands and spring structures 8.
  • the electrostatic comb drive includes a pair of fixed electrostatic combs 6 and a pair of mobile electrostatic combs 7.
  • the fixed electrostatic combs 6 are fixed to a substrate 10.
  • the pair of fixed electrostatic combs 6 are symmetrically distributed on both sides of the length direction of the bottom rod of the T-shaped transmission structure 4 and have no connection with the bottom rod of the T-shaped transmission structure 4. They are fixed to the substrate 10 and are located near the second group of fixed islands and spring structures 5, with a buried layer 9 supporting them below.
  • the mobile electrostatic combs 7 are suspended from the substrate 10 and are a suspended structure.
  • the pair of mobile electrostatic combs 7 are symmetrically distributed on both sides of the length direction of the bottom rod of the T-shaped transmission structure 4 and are located near the third group of fixed islands and spring structures 8.
  • One end of the pair of mobile electrostatic combs 7 close to the bottom rod of the T-shaped transmission structure 4 is fixedly connected to the side of the bottom rod, and one end away from the bottom rod of the T-shaped transmission structure 4 is not connected.
  • the comb teeth of the fixed electrostatic combs 6 and the mobile electrostatic combs 7 on both sides of the length direction of the bottom rod of the T-shaped transmission structure 4 are opposite and staggered.
  • the fixed islands are all rectangular structures, as shown in FIG. 2 and FIG. 3 .
  • the fixed islands and the fixed electrostatic combs 6 are connected to the substrate 10 through the buried layer 9 , and the remaining parts are not connected to the substrate 10 .
  • the first group of fixed island and spring structure 1 is mainly composed of a fixed island and a pair of half-folded springs.
  • the fixed island is connected and fixed on the substrate 10 through a buried layer 9.
  • the fixed island is fixed to the substrate 10. Both ends of the fixed island are connected through a half-folded spring and one end of the bottom rod of the T-shaped transmission structure 4 close to the movable conical waveguide 3.
  • the half-folded spring is suspended on the substrate 10.
  • the semi-folded spring in the first group of fixed island spring structures 1 is a suspended structure, including a spring handle and two beams connected at both ends of the spring handle and perpendicular to the length direction of the spring handle. Both beams extend toward the same side away from the spring handle and are respectively connected to the fixed island and the T-shaped transmission structure 4.
  • the second group of fixed islands and spring structure 5 has the same structure as the third group of fixed islands and spring structure 8, and both are composed of four fixed islands and a pair of folding springs; the fixed islands are connected and fixed on the substrate 10 through the buried layer 9, and the fixed islands are fixed to the substrate 10.
  • Two fixed islands form a group of four fixed islands, one group of fixed islands is arranged on the same side of the bottom rod of the T-shaped transmission structure 4, and two groups of fixed islands are respectively arranged on both sides of the bottom rod of the T-shaped transmission structure 4, and two fixed islands on the same side of one group of fixed islands are connected to the side of the bottom rod of the T-shaped transmission structure 4 through a folding spring, and the folding spring is suspended on the substrate 10.
  • the folding springs in the second group of fixed islands and spring structures 5 and the third group of fixed islands and spring structures 8 are suspended structures, including a spring handle, two short beams connected to the two ends of the spring handle and perpendicular to the length direction of the spring handle, and two long beams connected to the middle of the spring handle and perpendicular to the length direction of the spring handle.
  • One end of the two short beams is respectively connected to the two ends of the spring handle, and the other ends of the two short beams away from the spring handle are respectively connected to two fixed islands located on the same side of the length direction of the bottom rod of the T-shaped transmission structure 4, one end of the two long beams is respectively connected to two points in the middle of the spring handle, and the other ends of the two long beams away from the spring handle are respectively connected to two points on the same side of the length direction of the bottom rod of the T-shaped transmission structure 4.
  • a pair of fixed electrostatic combs 6 is connected to an external circuit, and the optical switch is regulated by applying or removing voltage to the pair of fixed electrostatic combs 6.
  • the top structure except the fixed electrostatic combs 6 and the silicon substrate 10 are grounded.
  • a voltage is applied by a pair of fixed electrostatic combs 6 to generate an attractive force or a repulsive force to drive the mobile electrostatic comb 7 to move toward or away from the fixed electrostatic comb 6, thereby driving the T-shaped transmission structure 4 to drive the movable tapered waveguide 3 to move toward or away from the fixed tapered waveguide 2 under the elastic control of the three groups of fixed islands and the spring structures 1, 5, and 8, thereby controlling the coupling connection/contact connection between the movable tapered waveguide 3 and the fixed tapered waveguide 2 to achieve the regulation of the optical switch.
  • the implementation process of the present invention is:
  • the fixed electrostatic combs 6 When the external circuit applies voltage to a pair of fixed electrostatic combs 6, the fixed electrostatic combs 6 generate an attractive force on the mobile electrostatic combs 7, driving the mobile electrostatic combs 7 to move toward the fixed electrostatic combs 6, and the portion where the mobile electrostatic combs 7 are connected to the bottom rod of the T-shaped transmission structure 4 drives the entire T-shaped transmission structure 4 to be displaced perpendicular to the length direction of the movable conical waveguide 3, and then the portion where the movable conical waveguide 3 is connected to the top edge of the T-shaped transmission structure 4 drives the movable conical waveguide 3 to be displaced, approaching the fixed conical waveguide 2, and the movement of the T-shaped transmission structure 4 causes the semi-folded springs in the first group of fixed islands and spring structures 1 connected thereto and the folded springs in the second and third groups of fixed islands and spring structures 5 and 8 to undergo elastic deformation.
  • the distance between the movable tapered waveguide 3 and the fixed tapered waveguide 2 can be controlled by adjusting the voltage applied to a pair of fixed electrostatic combs 6. When the two are close to a certain extent, the light propagation path can be adjusted.
  • the electrostatic comb drives 6, 7 in the embodiment are placed between the second set of fixed islands and spring structures 5 and the third set of fixed islands and spring structures 8.
  • the two sets of fixed islands and spring structures 5, 8 are beneficial to increase the stability of the electrostatic comb drives 6, 7 during operation.
  • the integrated waveguide MEMS optical switch in the embodiment when the integrated waveguide MEMS optical switch in the embodiment is in a natural state, i.e., in an OFF state without voltage, the spacing between the movable tapered waveguide 3 and the fixed tapered waveguide 2 is large, and the optical signals between the tapered waveguides 2 and 3 are not coupled.
  • the integrated waveguide MEMS optical switch in the embodiment when the integrated waveguide MEMS optical switch in the embodiment is in the ON state with a certain bias voltage applied, the movable tapered waveguide 3 is close to the fixed tapered waveguide 2, and a small gap is maintained between the two tapered waveguides.
  • the two tapered waveguides constitute a directional adiabatic coupler, and the optical signal can undergo adiabatic evolution to achieve path switching of the optical signal.
  • the fixed electrostatic comb 6 is always kept in the state of applying voltage, and the voltage is adjusted to stabilize the movable tapered waveguide 3 at a certain distance from the fixed tapered waveguide 2.
  • the integrated waveguide MEMS optical switch in the embodiment needs to be switched from the ON state to the OFF state, it is only necessary to remove the bias voltage applied to the fixed electrostatic comb 6.
  • the fixed tapered waveguide 2 and the movable tapered waveguide 3 in the embodiment are parts for optical transmission, and the fixed tapered waveguide 2 has single-mode curved waveguides connected at both ends, and the movable tapered waveguide 3 has single-mode curved waveguides and multi-mode interference cross waveguides connected at both ends.
  • the buried layers under the fixed tapered waveguide 2 and the movable tapered waveguide 3 are hollowed out, and both are suspended waveguide structures.
  • the fixed tapered waveguide 2 remains stationary, and the movable tapered waveguide 3 can be close to the fixed tapered waveguide 2 to form an adiabatic directional coupler.
  • the lengths of the fixed tapered waveguide 2 and the movable tapered waveguide 3 and the gap between the two should support the optical signal to complete adiabatic evolution therein.
  • the top structures of the adiabatic coupler and the electrostatic comb driver are made of the same material and are in the same plane regardless of whether the buried layer is hollowed out.
  • the other structures are suspended structures, and all the suspended structures except the fixed tapered waveguide 2 can move.
  • the top structures of the adiabatic coupler and the electrostatic comb drive are made of the same material, which can be processed and manufactured in a monolithic manner.
  • the integrated waveguide MEMS optical switch of the embodiment has a 2 ⁇ 2 port structure, which can be connected into an N ⁇ N switch array according to different topological structures, and the scale of the N ⁇ N array can be increased by increasing the number of switch units.
  • FIG6 is a schematic diagram of a 4 ⁇ 4 switch array cascaded with a Benes topology structure.
  • the 4 ⁇ 4 switch array includes six switch units, of which switch unit 1 and switch unit 2 are the first stage, switch unit 3 and switch unit 4 are the second stage, switch unit 5 and switch unit 6 are the third stage, and the switch units at different stages are connected to each other through straight waveguides or cross waveguides.
  • the two output ports of the switch unit 1 at the first stage are respectively connected to one of the input ports of the switch unit 3 and switch unit 4 at the second stage, and the two output ports of the switch unit 2 at the first stage are respectively connected to the remaining one input port of the switch unit 3 and switch unit 4 at the second stage, and the connection between the switch unit at the second stage and the switch unit at the third stage is the same.
  • FIG1 is the OFF state of the switch, in which the fixed electrostatic comb 6 has no bias applied, and a large gap is maintained between the fixed electrostatic comb 6 and the movable electrostatic comb 7, as well as between the fixed tapered waveguide 2 and the movable tapered waveguide 3.
  • the signal will be output from the top of the fixed tapered waveguide 2 without being affected.
  • the optical signal input from the bottom of the movable tapered waveguide 3 will also be output from the top of the movable tapered waveguide 3 without being affected.
  • the electrostatic force generated between the fixed electrostatic comb 6 and the movable electrostatic comb 7 becomes greater, the displacement generated when the mechanical structure reaches a state of equilibrium becomes greater, and the movable tapered waveguide 3 moves a greater distance, getting closer to the movable tapered waveguide 2.
  • the movable tapered waveguide 3 and the fixed tapered waveguide 2 form an adiabatic directional coupler, which is the ON state of the switch.
  • FIG4 depicts the ON state of the switch, where the fixed tapered waveguide 2 and the movable tapered waveguide 3 form an adiabatic directional coupler.
  • the optical signal in the fixed tapered waveguide 2 will adiabatically evolve into the movable tapered waveguide 3 and be output from the top of the movable tapered waveguide 3.
  • you want to restore the switch to the OFF state just remove the voltage applied to the fixed electrostatic comb 6. After the electrostatic force is lost, the mechanical structure is no longer balanced and will be restored to the initial OFF state under the elastic force generated by the spring deformation. This completes the state switching of the switch and realizes the adjustment of the light propagation path.
  • the integrated waveguide MEMS optical switch described in this embodiment has two input ports and two output ports, which is a 2 ⁇ 2 optical switch, and is more scalable than a 1 ⁇ 2 optical switch with one input port and two output ports.
  • a 1 ⁇ 2 optical switch generally adopts a Cross-bar topology structure, and the number of optical switch units required to form an N ⁇ N array is as high as N 2
  • a 2 ⁇ 2 silicon-based MEMS optical switch can also adopt a Benes topology structure, as shown in FIG7, and only N (log 2 N-0.5) optical switch units are required to form an N ⁇ N switch array.
  • other topologies can also be used for the switch array of the switch unit in the present invention.
  • Silicon on insulator is selected as the implementation platform, with a top layer of 220nm thick silicon, a buried layer of 2um thick silicon dioxide, and a substrate of silicon.
  • the wavelength range considered is 1500nm to 1600nm, and TE polarized optical signals are used.
  • the widths of the fixed tapered waveguide at both ends are 400nm and 300nm respectively, and the widths of the movable tapered waveguide at both ends are 300nm and 400nm respectively.
  • the lengths of the two are the same, which is 120um.
  • the distance between the fixed tapered waveguide and the movable tapered waveguide in the OFF state is 1um
  • the distance between the fixed tapered waveguide and the movable tapered waveguide in the ON state is 100nm
  • the optical performance of the device was simulated and verified by the three-dimensional finite-difference time-domain method (3D-FDTD).
  • 3D-FDTD three-dimensional finite-difference time-domain method
  • the incident light field almost completely propagates along the fixed tapered waveguide, as shown in Figure 7(a).
  • Low loss and high extinction ratio can be achieved in the 1500nm to 1600nm band, with a loss of less than 0.04dB and a crosstalk of less than -30dB.
  • the mobile electrostatic comb pushes the movable tapered waveguide to move toward the fixed tapered waveguide through the T-shaped transmission structure.
  • the switch enters the ON state.
  • the incident light field evolves almost adiabatically into the movable tapered waveguide, as shown in Figure 7(b).
  • the switch When the switch is in the OFF state, low loss and high extinction ratio can be achieved in the 1500nm to 1600nm band, with a loss of less than 0.03dB and a crosstalk of less than -25dB. It can be seen that the integrated waveguide MEMS optical switch proposed in the present invention can achieve the effects of ultra-large bandwidth, ultra-low loss, high extinction ratio and ultra-low energy consumption.

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Abstract

一种静电梳驱动的基于绝热耦合器的集成波导MEMS光开关，包括开关单元，开关单元包括基底(10)、机械驱动结构和绝热耦合器，绝热耦合器包括平行布置的固定锥形波导(2)和可移动锥形波导(3)，可移动锥形波导(3)与机械驱动结构相连，两种波导结构相同，长度相同但宽度渐变方向相反，呈中心对称排列。

Description

静电梳驱动的基于绝热耦合器的集成波导MEMS光开关 技术领域
本发明属于集成光电子器件领域的一种光开关，具体涉及一种通过静电梳驱动调节绝热耦合器中两根锥形波导的间距，从而实现光路调节的集成波导MEMS光开关以及其阵列。
 背景技术
近年来，数据中心网络规模急剧扩大，随着5G、物联网、云计算、人工智能等新技术的成熟应用，网络数据流量急剧增加，这对数据中心网络提出了新的要求，亟需更高性能的数据中心来支持以上述技术为关键内容的数字经济的飞速发展。在此背景下，光互联技术凭借大带宽、低功耗等传统电互联难以抗衡的优势迅速崛起，为提升数据中心的性能提供了解决方案，光互联目前已成为大规模数据中心的关键技术。
随着光互联网络的发展，其规模不断扩大，复杂程度也随之增加，因此如何实现光互联网络的灵活重构成为新的问题。大规模N×N光开关阵列是实现光互联网络灵活重构的关键器件，其已成为研究焦点之一，基于不同平台的多种多样的光开关结构被陆续提出，例如基于微机械***（MEMS）的光开关、基于马赫曾德干涉仪(MZI)的集成波导光开关等。
在众多的光开关结构中，基于MEMS的光开关凭借低损耗、速度快、可靠性好、可扩展性强等特点而备受关注，基于MEMS的大规模光开关阵列已应用于数据中心网络中。基于MEMS的光开关又分为自由空间开关和集成波导光开关。对于自由空间光开关而言，光信号从光纤输入开关以后在自由空间中完成传播和切换再被输出光纤接收，目前数据中心网络中的光开关多为自由空间光开关。基于MEMS的自由空间开关可扩展性好，目前已经能在保证低***损耗和低串扰的前提下实现数百的端口数目，但是此种开关的开关时间较长，一般在几毫秒和几十毫秒的水平，限制了大规模数据中心的重构速度。在集成波导光开关中，光信号从输入光纤输入芯片以后束缚在集成波导中传播，通过集成在一起的波导结构和机械结构实现光路的切换。近年来，基于MEMS的集成波导光开关取得了很大的进展，其能够实现亚微秒级的快切换时间、低***损耗、低串扰和大端口数目。基于MEMS的集成波导光开关有望突破目前光开关阵列的限制性因素，应用到大规模光互联网络中去。
 发明内容
针对上述背景技术，本发明的目的在于提供一种静电梳驱动的基于绝热耦合器的集成波导MEMS光开关及N×N阵列，此开关通过给固定静电梳施加驱动电压，使其与接地的移动静电梳之间产生吸引力，带动移动静电梳产生运动，进一步通过传动杆带动绝热耦合器中的移动锥形波导运动，改变其与固定锥形波导之间的距离，达到光路切换的效果。
本发明采用的技术方案是：
本发明包括至少一个开关单元，每个开关单元包括基底以及置于基底上的机械驱动结构和绝热耦合器，所述的绝热耦合器主要包括固定锥形波导和可移动锥形波导，固定锥形波导保持固定，固定锥形波导和可移动锥形波导均沿垂直于机械驱动结构的移动方向平行布置，固定锥形波导两端均连接有弯曲波导，可移动锥形波导的两端通过一对多模干涉交叉波导结构与机械驱动结构相连，由机械驱动结构带动可移动锥形波导靠近或远离固定锥形波导移动。
所述的可移动锥形波导两端的每端均依次连接有回形的第一根弯曲波导、十字形的多模干涉交叉波导和回形的第二根弯曲波导，十字形的多模干涉交叉波导由较长的一条和较短的一条构成，较长的一条由一对对称的模式演化锥形波导和一根长多模宽波导组成，一对模式演化锥形波导的宽端分别与长多模宽波导的两端相连，窄端分别与两根回形的弯曲波导相连；较短的一条是一根短多模宽波导，短多模宽波的一端与机械驱动结构相连，另一端无连接；十字形的多模干涉交叉波导中较长的一条用于光信号的传输，较短的一条用于机械固定。
固定锥形波导和可移动锥形波导结构相同，均为一根宽度渐变的锥形波导，固定锥形波导和可移动锥形波导长度相同但宽度渐变方向相反，固定锥形波导的输入端宽度和可移动锥形波导的输出端宽度相同，固定锥形波导的输出端宽度和可移动锥形波导的输入端宽度相同，且固定锥形波导和可移动锥形波导之间的间隙大小始终保持不变。
所述的机械驱动结构包括由固定静电梳和移动静电梳组成的静电梳驱动器、T形传动结构以及三组固定岛和弹簧结构；
T形传动结构悬空于基底布置，T形传动结构的顶杆部与可移动锥形波导平行，底杆部与可移动锥形波导垂直，T形传动结构的底杆部从靠近可移动锥形波导的一端开始沿着长度方向依次布置第一组固定岛和弹簧结构、第二组固定岛和弹簧结构、第三组固定岛和弹簧结构，第一组固定岛和弹簧结构、第二组固定岛和弹簧结构、第三组固定岛和弹簧结构均和T形传动结构连接；
第二组固定岛和弹簧结构、第三组固定岛和弹簧结构之间的T形传动结构两侧布置静电梳驱动器，静电梳驱动器包括一对固定静电梳和一对移动静电梳，固定静电梳固定于基底，一对固定静电梳对称分布在T形传动结构底杆部长度方向的两侧并且与T形传动结构的底杆部之间无连接；移动静电梳悬空于基底布置，一对移动静电梳对称分布在T形传动结构底杆部长度方向的两侧，一对移动静电梳靠近T形传动结构底杆部的一端与底杆部的侧边固定相连；固定静电梳和移动静电梳的梳齿呈对向、交错穿插分布。
所述的第一组固定岛和弹簧结构主要由一个固定岛和一对半折叠弹簧组成，固定岛固定于基底，固定岛的两端均通过一半折叠弹簧和T形传动结构底杆部靠近可移动锥形波导的一端连接，半折叠弹簧悬空于基底布置。
所述的半折叠弹簧为悬空结构，包括弹簧柄以及连接在弹簧柄两端且与弹簧柄长度方向垂直的两根梁组成，两根梁均朝向远离弹簧柄的同一侧延伸且分别与固定岛和T形传动结构相连。
所述的第二组固定岛和弹簧结构与第三组固定岛和弹簧结构的结构相同，均由四个固定岛和一对折叠弹簧组成；固定岛固定于基底，四个固定岛中以两个固定岛为一组，一组固定岛布置在T形传动结构底杆部的同一侧，两组固定岛分别布置在T形传动结构底杆部的两侧，同一侧的两个固定岛通过一折叠弹簧和T形传动结构底杆部侧部连接，折叠弹簧悬空于基底布置。
所述的折叠弹簧为悬空结构，包括弹簧柄、连接在弹簧柄两端且和弹簧柄长度方向垂直的两根短梁以及连接在弹簧柄中部且和弹簧柄长度方向垂直的两根长梁组成，两根短梁的一端分别连接到弹簧柄的两端，两根短梁远离弹簧柄的另一端分别与位于T形传动结构底杆部同侧的两个固定岛相连，两根长梁的一端分别连接到弹簧柄中部的两处，两根长梁远离弹簧柄的另一端分别与位于T形传动结构底杆部同侧的两处相连。
所述一对固定静电梳与外部电路连接，通过给一对固定静电梳施加或撤去电压实现对光开关的调控。
所述的固定静电梳与外部电路相连，通过外部电路施加电压与移动静电梳之间产生电势差，因此在固定静电梳和移动静电梳之间产生吸引力，移动静电梳产生靠近固定静电梳的运动，通过移动静电梳与T形传动结构底杆部之间的连接带动整个T形传动结构产生垂直于固定锥形波导长度方向的位移，通过T形传动结构顶边与多模干涉交叉波导的连接进一步带动可移动锥形波导产生垂直于固定锥形波导长度方向的位移，同时与T形传动结构相连的三组弹簧结构均发生一定的弹性形变。通过调节外部电路施加的电压大小可以控制可移动锥形波导的位移大小，即调控固定锥形波导和可移动锥形波导之间的距离，从而实现集成波导MEMS光开关的切换光传播路径的功能。
所述的固定锥形波导、可移动锥形波导、T形传动结构、三组固定岛和弹簧结构及静电梳驱动器的材料相同、厚度相同，整个开关单元结构或N×N阵列均可采用单片集成加工制作。
所述的固定锥形波导、可移动锥形波导、T形传动结构、半折叠弹簧、折叠弹簧及移动静电梳均为悬空结构，通过掩埋层腐蚀释放。
本发明的固定岛和固定件均通过掩埋层与基底相连，其余部分均悬空布置。
所述的N×N光开关阵列应至少包括四个上述的集成波导MEMS光开关单元，相邻的开关单元之间通过单模波导和波导交叉相连，开关单元之间的连接方式可以采用但不限于Benes、Cross-Bar等拓扑结构。
本发明的创新主要在于由可移动锥形波导3和固定锥形波导2构成的绝热耦合器在光开关的使用创新，原理是模式的绝热演化，与定向耦合器、微弯定向耦合器等基于干涉原理的耦合结构相比具有工艺容差大，可以实现超大带宽，可以实现超低损耗的原理性优势，通过上述绝热耦合器在上述光开关中的设置，能够带来工艺容差更大、带宽更大、损耗更低的效果优势。
本发明具有的有益效果是：
（1）本发明材料单一、结构简单、制作成本低；
（2）开关单元在大波长范围和大加工容差范围内具有低***损耗、低串扰和高消光比；
（3）开关单元采用的驱动方式为电容式结构，开关单元的能耗极低；
（4）开关单元具有两个输入端口和两个输出端口，此2×2的开关单元可以采用多种拓扑结构级联为大规模光开关阵列，可拓展性强。
总之，本发明通过静电梳驱动分开的绝热耦合器实现了光路切换的效果，具有带宽范围大、***损耗低、串扰低、消光比高、制作工艺简单、加工成本低、功耗低、可扩展性强等显著优势。
 附图说明
图1是本发明在初始状态(OFF)下的结构俯视图；
图2是图1中A-A’的截面图；
图3是图1中B-B’的截面图；
图4是本发明在施加电压后(ON)的结构俯视图；
图5是固定锥形波导和移动锥形波导的示意图；
图6是基于Benes拓扑结构的N×N集成波导MEMS光开关结构示意图；
图7是本发明的绝热耦合器部分在OFF和ON状态下的光场传输图，（a）表示OFF状态下绝热耦合器的光场传输图，（b）表示ON状态下绝热耦合器的光场传输图。
图中：1、第一组固定岛和弹簧结构，2、固定锥形波导，3、移动锥形波导，4、T形传动结构，5、第二组固定岛和弹簧结构，6、固定静电梳，7、移动静电梳，8、第三组固定岛和弹簧结构，9、掩埋层，10、基底。
 具体实施方式
下面结合附图和实施例对本发明做进一步说明，但不应以此限制本发明的保护范围。
如图1和图4所示，本发明主要包括至少一个开关单元，每个开关单元包括基底10以及置于基底上的机械驱动结构和绝热耦合器，其中绝热耦合器主要包括固定锥形波导2和可移动锥形波导3，固定锥形波导2保持固定，固定锥形波导2和可移动锥形波导3均沿垂直于机械驱动结构的移动方向平行布置，固定锥形波导2两端均连接有S形弯曲的弯曲波导，两端的弯曲波导作为开关单元的输入/输出端。通过两端的弯曲波导和外部元件连接，也是通过两端的弯曲波导支撑固定锥形波导2使得固定锥形波导2固定。可移动锥形波导3的两端通过一对多模干涉交叉波导结构与机械驱动结构的T形传动结构4相连，由机械驱动结构带动可移动锥形波导3靠近或远离固定锥形波导2移动。
固定锥形波导和可移动锥形波导两端均包含一组弯曲波导，并且弯曲波导中的一部分为宽度渐变波导，其宽度从锥形波导的端部宽度渐变到单模波导宽度。固定锥形波导2和可移动锥形波导3均通过设置弯曲波导来增加结构弹性。
可移动锥形波导3两端的每端均依次连接有回形的第一根弯曲波导、十字形的多模干涉交叉波导和回形的第二根回形弯曲波导，十字形的多模干涉交叉波导由较长的一条和较短的一条构成，较长的一条由一对对称的模式演化锥形波导和一根长多模宽波导组成，一对模式演化锥形波导的宽端分别与长多模宽波导的两端相连，窄端分别与两根回形的弯曲波导相连；较短的一条是一根短多模宽波导，短多模宽波的一端与机械驱动结构的T形传动结构4相连，另一端无连接；十字形的多模干涉交叉波导中较长的一条用于光信号的传输，较短的一条用于机械固定。第二根弯曲波导在未连接多模干涉交叉波导的另一端作为开关单元的输入/输出端。
多模干涉交叉波导均包含一对绝热锥形波导和一对正交的多模宽波导，与固定锥形波导长度方向垂直的多模宽波导两端分别连接一个绝热锥形波导，实现多模波导中的模式和单模波导中的模式两者之间互相绝热演化，与固定锥形波导长度方向平行的多模宽波导不用来传播信号，一端与T形传动结构相连，另一端无连接。
当可移动锥形波导及其两端相连的回形弯曲在MEMS驱动装置的驱动下靠近固定锥形波导时两者形成一个绝热耦合器，固定锥形波导和可移动锥形波导的外端均连接有单模波导，光信号通过单模波导输入输出，并且N×N阵列中相邻的开关单元也通过单模波导互相连接。
相邻的开关单元之间均通过开关单元的弯曲波导互相连接，弯曲波导作为开关单元的输入输出波导。
如图5所示，固定锥形波导2和可移动锥形波导3结构相同，均为一根宽度渐变的锥形波导，固定锥形波导2和可移动锥形波导3长度相同但宽度渐变方向沿波导方向相反，固定锥形波导2的输入端宽度和可移动锥形波导3的输出端宽度相同，固定锥形波导2的输出端宽度和可移动锥形波导3的输入端宽度相同，且固定锥形波导2和可移动锥形波导3之间的间隙大小始终保持不变，使得固定锥形波导2和可移动锥形波导3两者之间最终呈中心对称排列。
其中机械驱动结构包括由固定静电梳6和移动静电梳7组成的静电梳驱动器、T形传动结构4以及三组固定岛和弹簧结构1、5、8；最靠近可移动锥形波导的一组固定岛和弹簧结构为第一组，远离可移动锥形波导的两组固定岛和弹簧结构分别为第二组和第三组。T形传动结构上均匀分布着开孔，以便腐蚀掩埋层的化学试剂进入。三组固定岛和弹簧沿T形传动结构的底杆部长度方向分布。
T形传动结构4悬空于基底10布置，T形传动结构4的顶杆部与可移动锥形波导3平行，底杆部与可移动锥形波导3垂直，T形传动结构4的底杆部从靠近可移动锥形波导3的一端开始沿着长度方向依次布置第一组固定岛和弹簧结构1、第二组固定岛和弹簧结构5、第三组固定岛和弹簧结构8，第一组固定岛和弹簧结构1、第二组固定岛和弹簧结构5、第三组固定岛和弹簧结构8均和T形传动结构4连接；T形传动结构4与移动静电梳7相连。
第二组固定岛和弹簧结构5、第三组固定岛和弹簧结构8之间的T形传动结构4两侧布置静电梳驱动器，静电梳驱动器包括一对固定静电梳6和一对移动静电梳7，固定静电梳6固定于基底10，一对固定静电梳6对称分布在T形传动结构4底杆部长度方向的两侧并且与T形传动结构4的底杆部之间无连接，固定于基底10位于靠近第二组固定岛和弹簧结构5的位置，下方有掩埋层9支撑；移动静电梳7悬空于基底10布置，为悬空结构，一对移动静电梳7对称分布在T形传动结构4底杆部长度方向的两侧，位于靠近第三组固定岛和弹簧结构8的位置，一对移动静电梳7靠近T形传动结构4底杆部的一端与底杆部的侧边固定相连，远离T形传动结构4底杆部的一端无连接；T形传动结构4底杆部长度方向两侧的固定静电梳6和移动静电梳7的梳齿呈对向、交错穿插分布。
固定岛均为矩形结构，如图2和图3所示，固定岛和固定静电梳6均通过掩埋层9与基底10相连，其余部分均不和基底10相连。
第一组固定岛和弹簧结构1主要由一个固定岛和一对半折叠弹簧组成，固定岛通过掩埋层9相连固定于基底10上，固定岛固定于基底10，固定岛的两端均通过一半折叠弹簧和T形传动结构4底杆部靠近可移动锥形波导3的一端连接，半折叠弹簧悬空于基底10布置。
第一组固定岛弹簧结构1中的半折叠弹簧为悬空结构，包括弹簧柄以及连接在弹簧柄两端且与弹簧柄长度方向垂直的两根梁组成，两根梁均朝向远离弹簧柄的同一侧延伸且分别与固定岛和T形传动结构4相连。
第二组固定岛和弹簧结构5与第三组固定岛和弹簧结构8的结构相同，均由四个固定岛和一对折叠弹簧组成；固定岛通过掩埋层9相连固定于基底10上，固定岛固定于基底10，四个固定岛中以两个固定岛为一组，一组固定岛布置在T形传动结构4底杆部的同一侧，两组固定岛分别布置在T形传动结构4底杆部的两侧，一组固定岛下同一侧的两个固定岛通过一折叠弹簧和T形传动结构4底杆部侧部连接，折叠弹簧悬空于基底10布置。
第二组固定岛和弹簧结构5与第三组固定岛和弹簧结构8中的折叠弹簧为悬空结构，包括弹簧柄、连接在弹簧柄两端且和弹簧柄长度方向垂直的两根短梁以及连接在弹簧柄中部且和弹簧柄长度方向垂直的两根长梁组成，两根短梁的一端分别连接到弹簧柄的两端，两根短梁远离弹簧柄的另一端分别与位于T形传动结构4底杆部长度方向同侧的两个固定岛相连，两根长梁的一端分别连接到弹簧柄中部的两处，两根长梁远离弹簧柄的另一端分别与位于T形传动结构4底杆部长度方向同侧的两处相连。
一对固定静电梳6与外部电路连接，通过给一对固定静电梳6施加或撤去电压实现对光开关的调控，除了固定静电梳6以外的顶层结构以及硅基底10均接地。
由一对固定静电梳6施加电压，产生吸引力或者排斥力带动移动静电梳7向靠近或者远离固定静电梳6方向移动，进而带动T形传动结构4在三组固定岛和弹簧结构1、5、8的弹性控制下驱动可移动锥形波导3向靠近或者远离固定锥形波导2方向移动，进而控制可移动锥形波导3和固定锥形波导2之间的耦合连接/接触连接，实现光开关的调控。
本发明的实施工作过程是：
当外部电路对一对固定静电梳6施加电压时，则固定静电梳6对移动静电梳7产生吸引力，带动移动静电梳7朝着固定静电梳6移动，通过移动静电梳7与T形传动结构4底杆部相连接的部分带动整个T形传动结构4发生垂直于可移动锥形波导3长度方向的位移，再通过可移动锥形波导3与T形传动结构4的顶边相连接的部分带动可移动锥形波导3位移，靠近固定锥形波导2，T形传动结构4的运动导致与之相连的第一组固定岛和弹簧结构1中的半折叠弹簧和第二、三组固定岛和弹簧结构5、8中的折叠弹簧发生弹性形变。
通过调控施加在一对固定静电梳6上的电压大小可以控制可移动锥形波导3和固定锥形波导2之间的距离，当两者靠近到一定程度时实现光传播路径的调控。
实施例中的静电梳驱动器6、7放置于第二组固定岛和弹簧结构5以及第三组固定岛和弹簧结构8之间，两组固定岛和弹簧结构5、8有利于增加静电梳驱动器6、7工作过程中的稳定性。
如图1所示，当实施例中的集成波导MEMS光开关处于自然状态下即没有加电压的OFF状态下时，可移动锥形波导3和固定锥形波导2之间的间距较大，锥形波导2、3之间的光信号没有耦合。此状态下固定静电梳6和移动静电梳7的梳齿之间在T形传动结构的底杆部长度方向上有较大距离，该距离大于自然状态下可移动锥形波导3和固定锥形波导2之间的距离，以避免两锥形波导靠近，即处于图4所示的ON状态时静电梳6、7的梳齿之间发生碰撞。
如图4所示，当实施例中的集成波导MEMS光开关处于施加一定偏压的ON状态下时，可移动锥形波导3靠近固定锥形波导2，两锥形波导之间保持较小的空隙，此时两根锥形波导构成定向绝热耦合器，光信号可以发生绝热演化从而实现光信号的路径切换。
实施例中的集成波导MEMS光开关由自然的OFF状态切换到ON状态的过程中，固定静电梳6一直保持加电压的状态，调节电压使可移动锥形波导3稳定在固定锥形波导2的一定距离处。当实施例中的集成波导MEMS光开关需要由ON状态切换到OFF状态时，只需撤去施加在固定静电梳6上的偏压即可。
实施例中的固定锥形波导2和可移动锥形波导3是用于光学传输的部分，固定锥形波导2两端有连接的单模弯曲波导，可移动锥形波导3两端有连接的单模弯曲波导和多模干涉交叉波导。固定锥形波导2及可移动锥形波导3下方的掩埋层均被掏空，两者均为悬空波导结构，固定锥形波导2保持不动，可移动锥形波导3可以靠近固定锥形波导2以形成一个绝热定向耦合器，固定锥形波导2和可移动锥形波导3的长度以及两者之间的间隙应支持光信号在其中完成绝热演化。
具体实施中，绝热耦合器和静电梳驱动器的顶层结构均为同一材料，且无论掩埋层是否被掏空均处于同一平面。对于整个开关结构而言，除了固定岛和固定静电梳6有掩埋层支撑之外，其他的结构均为悬空结构，所有的悬空结构中除了固定锥形波导2之外，都可以发生移动。
具体实施中，绝热耦合器和静电梳驱动器的顶层结构均为同一材料，可以实现单片集成加工制造。实施例的集成波导MEMS光开关具有2×2的端口结构，可以按照不同的拓扑结构连接成N×N的开关阵列，并且可以通过增加开关单元的个数增大N×N阵列的规模。
图6为采用Benes拓扑结构级联的4×4开关阵列示意图，4×4的开关阵列共包含六个开关单元，其中开关单元1和开关单元2为第一级，开关单元3和开关单元4为第二级，开关单元5和开关单元6为第三级，不同级开关单元之间通过直波导或交叉波导相互连接。位于第一级的开关单元1的两个输出端口分别与位于第二级的开关单元3和开关单元4的其中一个输入端口连接，位于第一级的开关单元2的两个输出端口分别与位于第二级的开关单元3和开关单元4的剩余一个输入端口连接，第二级开关单元和第三级开关单元之间的连接与此相同。
以下说明本发明中的集成波导MEMS光开关的工作过程：
图1是开关的OFF状态，此时固定静电梳6没有施加偏压，固定静电梳6和移动静电梳7之间以及固定锥形波导2和可移动锥形波导3之间均保持较大的间隙。此时，对于从固定锥形波导2下方输入的信号而言，由于可移动锥形波导3距离较远，因此信号将不受影响的从固定锥形波导2的上方输出，同样的，此时从可移动锥形波导3的下方输入的光信号也将不受影响的从可移动锥形波导3的上方输出。
给固定静电梳6施加一定的电压，移动静电梳7上将产生感应电荷，两者之间产生静电吸引力，在该静电力吸引力的作用下，移动静电梳7靠近固定静电梳6运动，T形传动结构4沿着与可移动锥形波导3的长度方向相垂直的方向运动，并拉动三组固定岛和弹簧结构中的弹簧的一端使其发生形变。当形变所产生的弹力与静电梳齿之间的静电力平衡时，整个机械结构到达平衡状态。
随着施加的电压增加，那么固定静电梳6和移动静电梳7之间产生的静电力就越大，机械结构到达平衡状态时所产生的位移也就越大，可移动锥形波导3的移动距离也就越大，更靠近可移动锥形波导2。
当可移动锥形波导3和固定锥形波导2之间的间隙减小到一定程度时，可移动锥形波导3和固定锥形波导2就形成了一个绝热定向耦合器，此即为开关的ON状态。
图4描述开关的ON状态，此时固定锥形波导2和可移动锥形波导3形成了一个绝热定向耦合器，此时，对于从固定锥形波导2下方输入的光信号而言，由于可移动锥形波导3距离很近，因此固定锥形波导2中的光信号将绝热地演化到可移动锥形波导3中，从可移动锥形波导3的上方输出。如果想要恢复到开关的OFF状态，只需撤去施加在固定静电梳6上的电压即可，失去静电力后机械结构不再受力平衡，将在弹簧形变产生的弹力作用下恢复到初始的OFF状态，这就完成了开关的状态切换，实现了对光传播路径的调节。
本实施例描述的集成波导MEMS光开关具有两个输入端口和两个输出端口，为2×2光开关，与一个输入端口和两个输出端口的1×2光开关相比更具可扩展性。1×2光开关一般采用Cross-bar拓扑结构，形成N×N阵列所需的光开关单元数高达N 2个，而2×2硅基MEMS光开关还可以采用Benes拓扑结构，如图7所示，形成N×N的开关阵列仅需N(log 2N-0 .5)个光开关单元。除了Benes拓扑结构外，其他的拓扑结构也可以用于本发明中开关单元的开关阵列。
以下描述本发明的具体实施情况：
选用绝缘体上硅（SOI）作为实施平台，顶层材料为220nm厚的硅，掩埋层为2um厚的二氧化硅，基底为硅。考虑的波长范围是1500nm到1600nm，采用TE偏振的光信号。固定锥形波导的两端宽度分别为400nm和300nm，可移动锥形波导的两端宽度分别为300nm和400nm，两者的长度相同，为120um。OFF状态下的固定锥形波导和可移动锥形波导之间的距离为1um，ON状态下的固定锥形波导和可移动锥形波导之间的距离为100nm
经三维时域有限差分方法（3D-FDTD）对器件的光学性能进行仿真验证，OFF状态下入射光场几乎全部沿固定锥形波导传播，如图7(a)所示。在1500nm到1600nm波段上均能实现低损耗和高消光比，其损耗小于0.04dB，串扰低于-30dB。给固定静电梳施加电压，移动静电梳通过T形传动结构推动可移动锥形波导向固定锥形波导运动，两者之间的缝隙为100nm时开关进入ON状态，此时入射光场几乎绝热地演化进入可移动锥形波导，如图7(b)所示。开关处于OFF状态时在1500nm到1600nm波段上均能实现低损耗和高消光比，其损耗小于0.03dB，串扰低于-25dB。由此可见，本发明提出的集成波导MEMS光开关可以达到超大带宽、超低损耗、高消光比及超低能耗等效果。
上述实施例用来解释说明本发明，而不是对本发明进行限制，在本发明的精神和权利要求的保护范围内，对本发明作出的任何修改和改变，都落入本发明的保护范围。

Claims (9)

  1. 一种静电梳驱动的基于绝热耦合器的集成波导MEMS光开关，其特征在于：
    包括至少一个开关单元，每个开关单元包括基底（10）以及置于基底上的机械驱动结构和绝热耦合器，所述的绝热耦合器主要包括固定锥形波导（2）和可移动锥形波导（3），固定锥形波导（2）保持固定，固定锥形波导（2）和可移动锥形波导（3）均沿垂直于机械驱动结构的移动方向平行布置，固定锥形波导（2）两端均连接有弯曲波导，可移动锥形波导（3）的两端通过一对多模干涉交叉波导结构与机械驱动结构相连，由机械驱动结构带动可移动锥形波导（3）靠近或远离固定锥形波导（2）移动。
  2. 根据权利要求1所述的一种静电梳驱动的基于绝热耦合器的集成波导MEMS光开关，其特征在于：
    所述的可移动锥形波导（3）两端的每端均依次连接有回形的第一根弯曲波导、十字形的多模干涉交叉波导和回形的第二根弯曲波导，十字形的多模干涉交叉波导由较长的一条和较短的一条构成，较长的一条由一对对称的模式演化锥形波导和一根长多模宽波导组成，一对模式演化锥形波导的宽端分别与长多模宽波导的两端相连，窄端分别与两根回形的弯曲波导相连；较短的一条是一根短多模宽波导，短多模宽波的一端与机械驱动结构相连。
  3. 根据权利要求1所述的一种静电梳驱动的基于绝热耦合器的集成波导MEMS光开关，其特征在于：
    固定锥形波导（2）和可移动锥形波导（3）结构相同，均为一根宽度渐变的锥形波导，固定锥形波导（2）和可移动锥形波导（3）长度相同但宽度渐变方向相反，固定锥形波导（2）的输入端宽度和可移动锥形波导（3）的输出端宽度相同，固定锥形波导（2）的输出端宽度和可移动锥形波导（3）的输入端宽度相同，且固定锥形波导（2）和可移动锥形波导（3）之间的间隙大小始终保持不变。
  4. 根据权利要求1所述的一种静电梳驱动的基于绝热耦合器的集成波导MEMS光开关，其特征在于：
    所述的机械驱动结构包括由固定静电梳（6）和移动静电梳（7）组成的静电梳驱动器、T形传动结构（4）以及三组固定岛和弹簧结构（1、5、8）；
    T形传动结构（4）悬空于基底（10）布置，T形传动结构（4）的顶杆部与可移动锥形波导（3）平行，底杆部与可移动锥形波导（3）垂直，T形传动结构（4）的底杆部从靠近可移动锥形波导（3）的一端开始沿着长度方向依次布置第一组固定岛和弹簧结构（1）、第二组固定岛和弹簧结构（5）、第三组固定岛和弹簧结构（8），第一组固定岛和弹簧结构（1）、第二组固定岛和弹簧结构（5）、第三组固定岛和弹簧结构（8）均和T形传动结构（4）连接；
    第二组固定岛和弹簧结构（5）、第三组固定岛和弹簧结构（8）之间的T形传动结构（4）两侧布置静电梳驱动器，静电梳驱动器包括一对固定静电梳（6）和一对移动静电梳（7），固定静电梳（6）固定于基底（10），一对固定静电梳（6）对称分布在T形传动结构（4）底杆部长度方向的两侧并且与T形传动结构（4）的底杆部之间无连接；移动静电梳（7）悬空于基底（10）布置，一对移动静电梳（7）对称分布在T形传动结构（4）底杆部长度方向的两侧，一对移动静电梳（7）靠近T形传动结构（4）底杆部的一端与底杆部的侧边固定相连；固定静电梳（6）和移动静电梳（7）的梳齿呈对向、交错穿插分布。
  5. 根据权利要求4所述的一种静电梳驱动的基于绝热耦合器的集成波导MEMS光开关，其特征在于：
    所述的第一组固定岛和弹簧结构（1）主要由一个固定岛和一对半折叠弹簧组成，固定岛固定于基底（10），固定岛的两端均通过一半折叠弹簧和T形传动结构（4）底杆部靠近可移动锥形波导（3）的一端连接，半折叠弹簧悬空于基底（10）布置。
  6. 根据权利要求5所述的一种静电梳驱动的基于绝热耦合器的集成波导MEMS光开关，其特征在于：
    所述的半折叠弹簧为悬空结构，包括弹簧柄以及连接在弹簧柄两端且与弹簧柄长度方向垂直的两根梁组成，两根梁均朝向远离弹簧柄的同一侧延伸且分别与固定岛和T形传动结构（4）相连。
  7. 根据权利要求4所述的一种静电梳驱动的基于绝热耦合器的集成波导MEMS光开关，其特征在于：
    所述的第二组固定岛和弹簧结构（5）与第三组固定岛和弹簧结构（8）的结构相同，均由四个固定岛和一对折叠弹簧组成；固定岛固定于基底（10），四个固定岛中以两个固定岛为一组，一组固定岛布置在T形传动结构（4）底杆部的同一侧，两组固定岛分别布置在T形传动结构（4）底杆部的两侧，同一侧的两个固定岛通过一折叠弹簧和T形传动结构（4）底杆部侧部连接，折叠弹簧悬空于基底（10）布置。
  8. 根据权利要求7所述的一种静电梳驱动的基于绝热耦合器的集成波导MEMS光开关，其特征在于：
    所述的折叠弹簧为悬空结构，包括弹簧柄、连接在弹簧柄两端且和弹簧柄长度方向垂直的两根短梁以及连接在弹簧柄中部且和弹簧柄长度方向垂直的两根长梁组成，两根短梁的一端分别连接到弹簧柄的两端，两根短梁远离弹簧柄的另一端分别与位于T形传动结构（4）底杆部同侧的两个固定岛相连，两根长梁的一端分别连接到弹簧柄中部的两处，两根长梁远离弹簧柄的另一端分别与位于T形传动结构（4）底杆部同侧的两处相连。
  9. 根据权利要求4所述的一种静电梳驱动的基于绝热耦合器的集成波导MEMS光开关，其特征在于：
    所述一对固定静电梳（6）与外部电路连接，通过给一对固定静电梳（6）施加或撤去电压实现对光开关的调控。
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