CN112683400B - High-resolution spectrometer based on Euler micro-ring resonant cavity - Google Patents
High-resolution spectrometer based on Euler micro-ring resonant cavity Download PDFInfo
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Abstract
The invention discloses an on-chip high-resolution spectrometer based on an Euler micro-ring resonant cavity. The optical fiber multi-stage detector comprises three input/output ports, an Euler ring ultra-precise filter, a cascade ring coarse filter, a multi-section connecting waveguide and a detector array. The filtering process mainly comprises ultra-precise filtering and coarse filtering, for the ultra-precise filtering, based on multimode silicon optical wide waveguides, an Euler micro-ring resonant cavity with an ultrahigh quality factor is designed, the Euler micro-ring resonant cavity comprises two sections of wide waveguides and a curved wide waveguide based on a modified Euler curve, and an input/output coupling area and an output/input coupling area of the Euler ring ultra-precise filter can effectively inhibit excitation of a high-order mode. For coarse filtering, a runway type cascade micro-ring structure is adopted to construct a higher flat-top filter. The invention adopts the mode of ultra-precise filtering combination and rough filtering, can obtain complete data only by once scanning, simplifies the operation, improves the reliability, can be used in a plug-and-play mode, and has the advantages of small size, compact structure, high resolution and the like.
Description
Technical Field
The invention relates to a high-resolution spectrometer based on an Euler micro-ring resonant cavity, in particular to an on-chip spectrometer which combines an Euler micro-ring and a multi-channel runway type cascade ring, wherein the Euler micro-ring comprises two sections of wide waveguides and a bent wide waveguide designed according to a modified Euler curve.
Background
Spectral analysis is a technique for measuring light intensity in the ultraviolet, visible, near-infrared, and infrared bands. The spectrum measurement analysis has wide application fields, such as laboratory chemical analysis, clinical medical inspection, industrial monitoring, aerospace remote sensing and the like, and has great market application value. Compared with the traditional spectrometer, the micro spectrometer has the advantages of small volume, light weight, high detection speed, easy integration, convenient use and the like, and becomes a new research trend. When the spectrometer is integrated into a mobile phone, a consumer can identify the heat, fat and sugar content in food at any time, can also identify medicine components or track the body fat information of the consumer, and the spectrometer has a wide prospect in the aspect of life health.
Existing on-chip spectrometers are mainly classified into two major categories, one is a dispersive on-chip spectrometer, and the other is a fourier transform-based on-chip spectrometer. The dispersion on-chip spectrometer mainly comprises an etched diffraction grating on-silicon-substrate spectrometer, an array waveguide grating on-silicon-substrate spectrometer and a silicon multi-mode waveguide on-silicon-substrate spectrometer. For the etched diffraction grating type silicon substrate spectrometer, although the spectrometer has the advantages of small size, small tooth surface space, large number, single-side input and output and the like, a high-order mode is easy to excite and the crosstalk between channels is large. For the array waveguide grating type silicon substrate spectrometer, although the repeatability, the integration level and the stability are high, the loss and the crosstalk between channels must be considered. The silicon-based multimode waveguide on-chip spectrometer is still under research.
Disclosure of Invention
Aiming at the problems in the background art, the invention aims to provide a high-resolution spectrometer based on an Euler micro-ring resonant cavity, so that a wide waveguide is introduced into the Euler micro-ring resonant cavity, the waveguide transmission loss is greatly reduced, the quality factor of the Euler micro-ring resonant cavity is increased, and the resolution of the spectrometer is improved. Has important application value.
The Euler micro-ring resonant cavity is combined with the runway type cascade micro-ring, so that the requirements of spectral analysis on high resolution, large bandwidth and the like can be met.
The technical scheme adopted by the invention is as follows:
the device comprises a download end test port, a first connecting waveguide, an Euler ring ultra-precise filter, a second connecting waveguide, a transmission end test port, a calibration port, a third connecting waveguide, a single mode bus waveguide, a fourth connecting waveguide, a cascade ring coarse filter, a fifth connecting waveguide and a detector array, wherein the first connecting waveguide comprises a first single mode waveguide and a first tapered waveguide, the second connecting waveguide comprises a second single mode waveguide and a second tapered waveguide, the third connecting waveguide comprises a third tapered waveguide and a 180-degree bent waveguide, and the fourth connecting waveguide comprises a fourth single mode waveguide, a second 90-degree bent waveguide, a fifth single mode waveguide, a third 90-degree bent waveguide, a sixth single mode waveguide and a fourth tapered waveguide; the download end test port, the transmission end test port and the calibration port form three input/output ports.
The Euler ring ultra-precise filter comprises a first S-shaped bending wide waveguide, a first wide waveguide, a second S-shaped bending wide waveguide, a first Euler bending wide waveguide, a second Euler bending wide waveguide, a third wide waveguide, a fourth wide waveguide, a third S-shaped bending wide waveguide and a third S-shaped bending wide waveguide; the download end test port is connected with one end of a first single-mode waveguide, a first tapered waveguide, a first S-shaped bent wide waveguide and a first multi-mode wide waveguide in sequence, and the transmission end test port is connected with the other end of the first multi-mode wide waveguide in sequence through a second single-mode waveguide, a second tapered waveguide, a second S-shaped bent wide waveguide and a second S-shaped bent wide waveguide; the waveguide size of the first S-shaped wide bending waveguide is larger than that of the first single-mode waveguide, and the waveguide size of the second S-shaped wide bending waveguide is larger than that of the second single-mode waveguide. The second multi-mode wide waveguide is coupled and connected with the first multi-mode wide waveguide, two ends of the second multi-mode wide waveguide are respectively connected with two ends of the third multi-mode wide waveguide after passing through the first Euler bending wide waveguide and the second Euler bending wide waveguide, the first Euler bending wide waveguide and the second Euler bending wide waveguide are both bending waveguides, and the second multi-mode wide waveguide and the third multi-mode wide waveguide are both straight waveguides, so that a race track ring shape is formed; the fourth multi-mode wide waveguide is coupled and connected with the third multi-mode wide waveguide, one end of the fourth multi-mode wide waveguide is connected with one end of the single-mode bus waveguide after sequentially passing through a third S-shaped bent wide waveguide, a third conical waveguide and a 180-degree bent waveguide, the other end of the single-mode bus waveguide is connected with the first detector after sequentially passing through a first 90-degree bent waveguide and a third single-mode waveguide, and the other end of the fourth multi-mode wide waveguide is connected with the calibration port after sequentially passing through a third S-shaped bent wide waveguide, a fourth conical waveguide, a third straight waveguide, a third 90-degree bent waveguide, a second straight waveguide, a second 90-degree bent waveguide, a first straight waveguide; the waveguide size of the third S-shaped wide bending waveguide is larger than that of the 180-degree bending waveguide, and the waveguide size of the third S-shaped wide bending waveguide is larger than that of the third straight waveguide.
The first S-shaped bent wide waveguide, the first wide waveguide, the second S-shaped bent wide waveguide, the first Euler bent wide waveguide and the second Euler bent wide waveguide form an input/output directional coupling area of the Euler ring ultra-precise filter. The first Euler bending wide waveguide, the second Euler bending wide waveguide, the third wide waveguide, the fourth wide waveguide, the third S-shaped bending wide waveguide and the third S-shaped bending wide waveguide form an output/input directional coupling area of the Euler ring ultra-precise filter.
The invention can improve the resolution of the spectrometer by adding the wide waveguide, but is easy to excite a high-order mode. And the input/output directional coupling area and the output/input directional coupling area of the Euler ring ultra-precise filter are specially designed, so that a high-order mode can be effectively inhibited, and the transmission of a low-order mode of light is ensured.
The cascade ring coarse filter comprises at least two continuous runway type cascade micro rings and a section of coarse filter output waveguide, wherein the coarse filter output waveguide comprises a seventh single mode waveguide, a 90-degree bent waveguide, an eighth single mode waveguide, a 90-degree bent waveguide, a ninth single mode waveguide and a radiation spiral line; at least two runway-type cascaded micro-rings and a coarse filtering wave output waveguide are sequentially arranged in a cascade mode along the coupling direction between a cascaded ring coarse filter and a single mode bus waveguide, each runway-type micro-ring is formed by connecting two sections of single mode waveguides and two sections of 180-degree bent waveguides respectively positioned between two ends of the two sections of single mode waveguides, every two adjacent runway-type micro-rings are connected in a coupling mode, the runway-type micro-ring positioned on one side of the edge after the at least two continuous runway-type micro-rings are arranged in a cascade mode is connected with the single mode bus waveguide in a coupling mode, the runway-type micro-ring positioned on one side of the edge after the at least two continuous runway-type micro-rings are arranged in a cascade mode is connected with a seventh single mode waveguide, the 90-degree bent waveguide and the 90-degree bent waveguide, one end of the seventh single mode waveguide is connected with one end of the fourth single mode waveguide through the 90-degree bent waveguide, and the other end of the seventh single mode waveguide is sequentially connected with the 90-degree bent waveguide through the 90-bent waveguide, The ninth single-mode waveguide is connected with the radiation spiral line;
as shown in the figure, the runway type micro-ring structure comprises two runway type micro-rings, wherein one runway type micro-ring is formed by sequentially and annularly connecting a runway straight waveguide, a 180-degree bent waveguide, a runway straight waveguide and a 180-degree bent waveguide of a cascade double-ring, and the other runway type micro-ring is formed by sequentially and annularly connecting a runway straight waveguide, a runway 180-degree bent waveguide, a runway straight waveguide and a runway 180-degree bent waveguide of a cascade double-ring.
In the Euler ring ultra-precise filter, a first wide waveguide, a first Euler bent wide waveguide, a second Euler bent wide waveguide and a third wide waveguide form an Euler micro-ring resonant cavity structure; two ends of the second multi-mode wide waveguide are connected with two ends of the third multi-mode wide waveguide after passing through the first Euler bending wide waveguide and the second Euler bending wide waveguide respectively, the first Euler bending wide waveguide and the second Euler bending wide waveguide are both bending wide waveguides based on a modified Euler curve, and the second multi-mode wide waveguide and the third multi-mode wide waveguide are both straight waveguides. Thus, the Euler micro-ring resonant cavity is formed by alternately connecting two sections of wide waveguides and two sections of bent wide waveguides designed based on the modified Euler curve.
The waveguide curves of the first Euler bending wide waveguide and the second Euler bending wide waveguide adopt modified Euler curves, and the specific formula is as follows:
wherein, L is the arc length of the curve; theta is an arc center angle; the radius of curvature of the Euler curve is defined by RminChange to Rmax(ii) a A is a constant number equal to
LtotalIs the total length of the curve.
The detector array is composed of a plurality of detectors with the same number as the cascaded ring coarse filters, and each detector is connected to the other end of the eighth single-mode waveguide in the cascaded ring coarse filters.
The spectrometer is provided with a download end test port, a transmission end test port and a calibration port, light is input from the download end test port, passes through an input/output directional coupling area of the Euler ring ultra-precise filter, and is coupled into input light of the Euler micro-ring resonant cavity to generate resonance, and the directional coupling area of the Euler ring ultra-precise filter effectively inhibits a high-order mode and realizes ultra-precise filtering.
The cascade ring coarse filter is composed of a plurality of runway-shaped double rings which are horizontally arranged in a cascade mode, and a flat-top filter with a large free spectral range is generated. The detector array is thus acquired to obtain spectroscopic data.
The metal electrode, the bonding pad and the bonding pad are also included; the Euler ring ultra-precision filter is provided with a metal electrode, and the middle of the metal electrode is covered with a first wide waveguide, a second Euler bending wide waveguide, a third multi-mode wide waveguide and a fourth wide waveguide which pass through the Euler ring ultra-precision filter. When the waveguide passes through the second Euler bending wide waveguide, the waveguide passes through the waveguide according to the same curve as the second Euler bending wide waveguide; the two ends of the metal electrode are respectively connected with the first bonding pad and the second bonding pad.
The invention adopts the mode of ultra-precise filtering combination and rough filtering. In the aspect of ultra-precise filtering, an Euler micro-ring resonant cavity with an ultra-high quality factor is designed based on a silicon-based multi-mode wide waveguide, and comprises two sections of wide waveguides and an Euler bending wide waveguide designed based on a modified Euler curve. In the rough filtering aspect, a runway type second-order cascade micro-ring is adopted to construct a flat-top filter. Finally, the scheme of ultra-precise filtering and then coarse filtering is adopted, complete data can be obtained only by one-time scanning, the system is simplified, and the reliability is improved. After filtering, the filter passes through the detector array, so that the system is convenient to integrally test, and plug and play are realized. Has the advantages of small size, compact structure, high resolution and the like.
The combination relation of the Euler ring ultra-precise filter and the cascade ring coarse filter is as follows: input light firstly passes through an ultra-precise Euler ring filter and then passes through coarse filtering of a cascade ring, a spectrometer with larger free spectral range and higher resolution is realized under secondary filtering, and the design ensures that accurate spectral data can be obtained only by completing one-time scanning test, thereby improving the reliability of the system. Therefore, the combination of the Europe pull ring ultra-precise filter and the cascade ring coarse filter can effectively expand the working bandwidth of the spectrometer on the premise of ensuring high-resolution filtering, and the light path obtains a test result after the ultra-precise filtering and the coarse filtering, thereby realizing high-resolution spectral analysis.
The wide waveguides at two ends in the Euler micro-ring resonant cavity and the bent wide waveguides designed according to the modified Euler curve are wide waveguides, so that the scattering loss caused by the roughness of the side wall of the waveguide is small enough, the quality factor of the Euler micro-ring resonant cavity is improved, and the ultra-high resolution spectrometer is realized. Therefore, the multimode wide wave is guided into the Euler micro-ring resonant cavity, the waveguide transmission loss is greatly reduced, but high-order modes are easily excited, the maximum radius and minimum radius parameters of an Euler curve are optimized for ensuring the transmission of a basic mode, and meanwhile, an input/output directional coupling area and an output/input directional coupling area of the Euler ring ultra-precise filter are specially designed, so that the high-order modes are effectively inhibited, and the low loss characteristic of waveguide transmission is ensured.
The maximum radius and the minimum radius of the curved waveguide designed by correcting the Euler curve in the Euler ring ultra-precise filter are optimally designed, so that a high-order mode can be effectively prevented from being excited, and the low transmission loss of light in the Euler micro-ring resonant cavity is ensured.
The cascade ring coarse filter has a compact structure, and is easier to realize large-scale integration.
The cascade ring coarse filter adopts a runway type cascade micro-ring structure, so that the coupling strength between cascade double rings is enhanced, the characteristic size of the cascade ring coarse filter is increased, and the overall design is more in line with the standard semiconductor flow sheet process; the flat-top filter with larger free spectral range is conveniently constructed, compared with the traditional on-chip dispersion type spectrometer, the scheme is more compact, and the occupied area is greatly reduced.
The channel interval of the cascade ring coarse filter is specially designed, so that the crosstalk between adjacent channels of the system is greatly reduced.
The distance between adjacent channels of the cascade ring coarse filter is consistent with the full width at half maximum of the cascade ring coarse filter, namely the channel interval of the middle cascade ring is set to be the full width at half maximum of the cascade ring, and the requirement on consistency among the channels can be ensured. Meanwhile, the free spectral range of the euler micro-ring is designed according to the principle of minimizing crosstalk between waveguides.
The detector array is externally connected with acquisition equipment, so that the integrity of the system is conveniently improved, and plug and play is realized.
The filtering process mainly comprises ultra-precise filtering and coarse filtering, for the ultra-precise filtering, based on multimode silicon optical wide waveguides, an Euler micro-ring resonant cavity with an ultrahigh quality factor is designed, the Euler micro-ring resonant cavity comprises two sections of wide waveguides and a curved wide waveguide based on a modified Euler curve, and an input/output coupling area and an output/input coupling area of the Euler ring ultra-precise filter can effectively inhibit excitation of a high-order mode. For coarse filtering, a runway type cascade micro-ring structure is adopted to construct a higher flat-top filter. The invention adopts the mode of ultra-precise filtering combination and rough filtering, can obtain complete data only by once scanning, simplifies the operation, improves the reliability, can be used in a plug-and-play mode, and has the advantages of small size, compact structure, high resolution and the like.
The invention has the beneficial effects that:
the invention has the advantages of small transmission loss, high resolution, small crosstalk, large bandwidth, easy use, complete structure and the like.
The invention guides the wide wave into the Euler micro-ring resonant cavity, greatly reduces the waveguide transmission loss, increases the quality factor of the Euler micro-ring resonant cavity, and improves the resolution of the spectrometer.
The invention optimizes the maximum radius and minimum radius parameters of the Euler curve, and specially designs the input/output directional coupling region and the output/input directional coupling region of the Euler ring ultra-precise filter, thereby greatly inhibiting the high-order mode in the wide waveguide.
The invention greatly expands the working bandwidth of the system by introducing the runway type cascade ring.
The two-stage filter of the invention enlarges the free spectrum range, and the design of ultra-precise filtering and coarse filtering ensures that the data is only scanned once, thereby greatly reducing the power consumption of the system and improving the reliability of the system.
The spectrometer of the invention is a relatively complete system and is beneficial to realizing plug and play.
Drawings
FIG. 1 is a schematic diagram of a high resolution spectrometer based on an Euler micro-ring resonator.
FIG. 2 is a schematic structural diagram of an adiabatic tapered waveguide according to an embodiment;
FIG. 3 is a graph of the resonance spectrum of an input light after ultra-precise filtering.
Fig. 4 is a resonance spectrum of an input light after rough filtering.
In fig. 1: the device comprises a download end test port 1, a first single-mode waveguide 2, a first tapered waveguide 3, a first S-shaped bent wide waveguide 4, a first wide waveguide 5, a second wide waveguide 6, a first Euler bent wide waveguide 7, a second Euler bent wide waveguide 8, a third wide waveguide 9, a fourth wide waveguide 10, a third S-shaped bent wide waveguide 11, a third tapered waveguide 12, a 180-degree bent waveguide 13, a single-mode bus waveguide 14, a first 90-degree bent waveguide 15, a third single-mode waveguide 16, a first detector 17, a transmission end test port 18, a second single-mode waveguide 19, a second tapered waveguide 20, a second S-shaped bent wide waveguide 21 and a calibration port 22; a fourth single-mode waveguide 23, a second 90-degree curved waveguide 24, a fifth single-mode waveguide 25, a third 90-degree curved waveguide 26, a sixth single-mode waveguide 27, a fourth tapered waveguide 28, and a third S-shaped curved wide waveguide 29;
a cascaded double-ring runway straight waveguide 30, a 180-degree curved waveguide 31, a 180-degree curved waveguide 32, a cascaded double-ring runway straight waveguide 33, a cascaded double-ring runway straight waveguide 34, a cascaded double-ring runway straight waveguide 35, a cascaded double-ring runway 180-degree curved waveguide 36, a cascaded double-ring runway 180-degree curved waveguide 37, a seventh single-mode waveguide 38, a 90-degree curved waveguide 39, an eighth single-mode waveguide 40, a second detector 41, a 90-degree curved waveguide 42, a ninth single-mode waveguide 43, and a radiation helix 44;
Detailed Description
The invention is further illustrated by the following figures and examples.
As shown in fig. 1, there are three input/output ports, which are respectively a download port 1, a transmission port 18 and a calibration port 22, and the three input/output ports are all formed by vertical coupling gratings. Multiple coarse filters can be provided to extend the operating bandwidth of the spectrometer, in this case 10 coarse filters a1, a2 … a10 are provided to extend the operating bandwidth to 10 nm.
Light is input from a calibration port 22 and passes through a fourth single mode waveguide 23, a second 90-degree bent waveguide 24, a fifth single mode waveguide 25, a third 90-degree bent waveguide 26, a sixth single mode waveguide 27 and a fourth tapered waveguide 28 in a fourth connecting waveguide, after passing through an output/input directional coupling region of an Euler ring ultra-precise filter formed by a first Euler bent wide waveguide 7, a second Euler bent wide waveguide 8, a third wide waveguide 9, a fourth wide waveguide 10, a third S-shaped bent wide waveguide 11 and a third S-shaped bent wide waveguide 29, a part of the light is coupled into an Euler micro-ring resonant cavity to generate a resonant peak, and is coupled and output through an input/output directional coupling region of the Euler ultra-precise filter formed by a first S-shaped bent wide waveguide 4, a first wide waveguide 5, a second S-shaped bent wide waveguide 21, a first wide waveguide 6, a first Euler bent wide waveguide 7 and a second Euler bent wide waveguide 8, through the second connecting waveguide, a resonance peak is seen at the transmission-side test port 18. Light that is not coupled into the euler micro-ring resonator is received by the detector array after passing through the third connecting waveguide, the single mode bus waveguide 14, and the coarse filters a1 and a2 … a10, and the filter waveforms of 10 coarse filter channels are recorded. And heating the metal electrode 45, and observing a heating voltage range required by the resonance peak of the transmission end test port 18 to move in the effective working bandwidth range of each coarse filter a1 and a2 … a10 to obtain 10 calibration voltage ranges.
The euler ring ultra-precise filter comprises a first S-shaped bent wide waveguide 4, a first wide waveguide 5, a second S-shaped bent wide waveguide 21, a first wide waveguide 6, a first euler bent wide waveguide 7, a second euler bent wide waveguide 8, a third wide waveguide 9, a fourth wide waveguide 10, a third S-shaped bent wide waveguide 11 and a third S-shaped bent wide waveguide 29. The second multi-mode-width waveguide 6, the first Euler bending wide waveguide 7, the third multi-mode-width waveguide 9 and the second Euler bending wide waveguide 8 form an Euler micro-ring resonant cavity structure, and the maximum radius and the minimum radius of an Euler curve are optimally designed. The first Euler bending wide waveguide 7 and the second Euler bending wide waveguide 8180-degree bends are connected with the second multi-mode-width waveguide 6 and the third multi-mode-width waveguide 9 to form a closed loop.
The runway type cascade ring in the coarse filter a1 is formed by two runway type micro rings which are cascaded up and down. The upper runway type microring comprises a cascaded double-ring runway straight waveguide 30, a 180-degree bent waveguide 31, a cascaded double-ring runway straight waveguide 33 and a 180-degree bent waveguide 32. The lower runway type micro-ring comprises a cascaded double-ring runway straight waveguide 34, a cascaded double-ring runway 180-degree curved waveguide 36, a cascaded double-ring runway straight waveguide 35 and a cascaded double-ring runway 180-degree curved waveguide 37. The 180 ° curved waveguide 31, the cascaded double ring of racetrack straight waveguides 33, the 180 ° curved waveguides 32, the 180 ° curved waveguides 36, the cascaded double ring of racetrack straight waveguides 34, the 180 ° curved waveguides 37 form the middle coupling region of the coarse filter.
The first coarse filter a1 is composed of a racetrack cascaded ring, a seventh single-mode waveguide 38, a 90 ° curved waveguide 39, an eighth single-mode waveguide 40, a 90 ° curved waveguide 42, a ninth single-mode waveguide 43, and a radiating helix 44. A coarse-filtered wave input coupling region is formed between the single mode bus waveguide 14 and the cascaded dual ring racetrack straight waveguide 30, 180 ° curved waveguide 31, 180 ° curved waveguide 32. The 180 DEG curved waveguide 36, the straight waveguide 34, the 180 DEG curved waveguide 37 and the 180 DEG curved waveguide 31, the 180 DEG curved waveguide 32, the straight waveguide 33 form a coarse-wave filtering intermediate coupling region therebetween. Coarse filter output coupling regions are formed among the cascaded double-ring runway straight waveguide 35, the 180-degree bent waveguide 36, the 180-degree bent waveguide 37, the 90-degree bent waveguide 42, the seventh single-mode waveguide 38 and the 90-degree bent waveguide 39. Light enters the single-mode bus waveguide 14, passes through the coarse filtering input coupling region, enters the upper runway type cascade ring for resonance, passes through the coarse filtering intermediate coupling region for coupling output, enters the lower runway type cascade ring, and is coupled and output from the coarse filtering output coupling region. After being coupled out, it is received by a second detector 41 via an eighth single mode waveguide 40. Whereas the light coupled into the 90 deg. curved waveguide 42 is radiated by the radiation helix 44 after passing through the ninth single-mode waveguide 43.
10 coarse filtering channels are sequentially arranged under the single-mode bus waveguide 14 at equal intervals, and the waveguide structure of each filtering channel is consistent with that of the first coarse filtering channel. Thereby, spectral information can be detected in conjunction with the detector output of each channel. The bus waveguide output is connected by the first 90 ° bend waveguide 15 and the third single mode waveguide 16, and the light is received by the first detector 17 after passing through the first 90 ° bend waveguide 15 and the third single mode waveguide 16.
10 rough wave channels a1, a2 … a9 and a10 are arranged below the single-mode bus waveguide 14 at equal intervals horizontally, and the structures of the rough wave channels a2 … a9 and a10 are consistent with a1, so that the description is omitted.
A part of the metal electrode 45 is covered on the Euler ring ultra-precise filter, and both sides of the metal electrode 45 are connected with a bonding pad 46 and a bonding pad 47. When the optical download terminal test port 1 inputs, 10 calibration voltage values are sequentially added to the bonding pad 46 and the bonding pad 47, and then the spectrum information can be detected through the detector array.
3/20/12/28 is a tapered waveguide, as shown in fig. 2, the tapered waveguide connects the narrow waveguide and the wide waveguide, so as to guide the multi-mode wide wave into the structure, greatly reduce the loss, and improve the resolution of the spectrometer on chip.
The working process of the invention as a high resolution spectrometer based on euler micro-ring resonator is described below:
when light is input from the download end test port 1, the light enters a first connecting waveguide formed by a first S-shaped bent wide waveguide 4 and a first wide waveguide 5 through vertical coupling grating coupling, then enters an input/output directional coupling area of an Euler ring ultra-precise filter formed by a second S-shaped bent wide waveguide 21, a first wide waveguide 6, a first Euler bent wide waveguide 7 and a second Euler bent wide waveguide 8, is coupled and enters an Euler micro-ring resonant cavity, and resonance occurs. And then, an output/input directional coupling region coupling output of the Euler ring ultra-precise filter is formed by the first Euler bent wide waveguide 7, the second Euler bent wide waveguide 8, the third wide waveguide 9, the fourth wide waveguide 10, the third S-shaped bent wide waveguide 11 and the third S-shaped bent wide waveguide 29, so that ultra-precise filtering is completed.
For each coarse filter a1, a2 … a10, a voltage is applied to pad 46, pad 47 and electrode 45, respectively, within the respective nominal voltage range. After being subjected to ultra-precise filtering, the ultra-precise filtered wave is output to pass through a third connecting waveguide consisting of a third tapered waveguide 12 and a 180-degree bent waveguide 13 and a single-mode bus waveguide 14, and then is sequentially coupled into a first coarse filter a1, a second coarse filter a2 … and a tenth coarse filter a 10. For the first coarse filter a1, light is coupled in from the coarse filter input coupling region formed between the single mode bus waveguide 14 and the cascaded dual ring racetrack straight waveguide 30, 180 ° curved waveguide 31, 180 ° curved waveguide 32, and then oscillated in the upper racetrack micro-ring and coupled out from the coarse filter intermediate coupling region. The coarse filtering intermediate coupling region is formed by a cascaded double-ring racetrack straight waveguide 35, a 180-degree bent waveguide 36, a 180-degree bent waveguide 37, a 90-degree bent waveguide 42, a seventh single-mode waveguide 38 and a 90-degree bent waveguide 39. The input light is coupled and output from the coarse wave middle coupling area, enters the lower runway type micro-ring, resonates in the lower runway type micro-ring, and is coupled and output from the coarse wave output coupling area. Coarse filter output coupling regions are formed among the cascaded double-ring runway straight waveguide 35, the 180-degree bent waveguide 36, the 180-degree bent waveguide 37, the 90-degree bent waveguide 42, the seventh single-mode waveguide 38 and the 90-degree bent waveguide 39. The spectrum coupled out from the racetrack cascaded ring is received by the second detector 41 through the fourth single-mode waveguide 40, and the spectrum detection through ultra-precise filtering and coarse filtering is completed. Part of the light is coupled into the ninth single-mode waveguide 43 and radiated off by the radiating helix 44. The coarse filtering process of the other coarse filtering channels a2 and a3 … a10 is similar to that of the coarse filtering channel a1, and is not described again.
The specific embodiment of the invention is as follows:
silicon nanowire optical waveguides based on silicon-on-insulator (SOI) materials are selected: the core layer is made of silicon material, the thickness is 220nm, and the refractive index is 3.4744; the lower cladding materials are all SiO2, the thickness is 2 μm, and the refractive index is 1.4404; the upper cladding materials are all SiO2, the thickness is 1.5 mu m, and the refractive index is 1.4404; the metal material of the heating electrode is titanium gold.
The first single mode waveguide 2 has a width of 420nm and a length of 100 μm, and for the tapered waveguides 3, 20, 12, 28, a narrow waveguide width of 420nm, a wide waveguide width of 1600nm, and a length of 30 μm are set. Therefore, the wide waveguide is introduced, the waveguide transmission loss can be greatly reduced, and the resolution of the spectrometer is improved. The S-shaped curved waveguides 4, 21, 11 and 29 have transverse widths of 40 μm and longitudinal lengths of 0.5 μm, and the input and output port widths are all 420 nm. The wide waveguides 5, 6, 9, 10 have a width of 1600nm and a length of 100 μm, and the euler bent wide waveguides 7 and 8 are optimized to have a maximum radius of 600 μm and a minimum radius of 10 μm, and the distance between the wide waveguides 5 and 6 is 180 nm. The design of the directional coupler and the optimization of the minimum radius and the maximum radius of the Euler curve waveguide enable high-order modes in the wide waveguide to be difficult to excite, and therefore low-order mode transmission of light is guaranteed. For the coarse filter channel a1, in which the straight waveguides 30, 33, 34, 35 have a length of 4.052 μm and a width of 420nm, the 180 ° bent waveguides 31, 32, 36, 37 have a radius of 5.96 μm. The single mode bus waveguide 14, the straight waveguide 30, and the 180 ° bent waveguides 31 and 32 form a coupling region, and the distance between the single mode bus waveguide 14 and the straight waveguide 30 is 200 nm. The 180 ° curved waveguide 31, the 180 ° curved waveguide 32, the straight waveguide 33, the 180 ° curved waveguide 36, the 180 ° curved waveguide 37, and the straight waveguide 34 constitute a coupling region. Wherein the spacing between the straight waveguides 33, 34 is set to 384 nm. The 180 ° curved waveguide 36, the straight waveguide 35, the 180 ° curved waveguide 37, the fourth straight waveguide 38, the 90 ° curved waveguide 39, and the 90 ° curved waveguide 42 also constitute a coupling region, and the interval between the straight waveguides 35, 38 is set to 200 nm. The radius of the radiation helix 44 is 1 μm, and the remaining coarse filter channels a2, a3 … a10 have a structural size corresponding to the coarse filter channel a1, which are arranged at equal intervals below the single-mode bus waveguide 14, with a pitch of 45 μm.
The design of the Euler micro-ring resonant cavity is simulated through MATLAB. The input light is multiplied by a coupling coefficient matrix, enters the Euler micro-ring resonant cavity, is multiplied by a transmission matrix containing optical phase and frequency information, and is multiplied by the coupling coefficient matrix when being output. The simulation result is shown in fig. 3, and input light passes through the euler micro-ring resonant cavity to generate a resonance peak, so that ultra-precise filtering is realized. The free spectral range of the spectrum is 1.9nm, and the quality factor of the spectrometer is as high as 3.7 multiplied by 105The resolution achieved was 0.004 nm.
The filters of the coarse filter channels were simulated by MATLAB. Because each rough filtering channel adopts a runway type cascade double-ring structure, input and output are subjected to two-stage transmission matrixes and three-stage coupling matrixes. As shown in fig. 4, in the embodiment a1, a2 … a10, the full width at half maximum of 10 coarse filter channels is 1nm, and the distance between each adjacent coarse filter channel is also 1nm, so as to ensure the consistency of the filter structure of the coarse filter channels. Meanwhile, the full width at half maximum of the channel is smaller than the free spectral range of the resonant peak subjected to ultra-precise filtering by 1.9nm, so that the filtering effect of the filter is ensured. After input light passes through the Euler micro-ring resonant cavity, the resolution of the spectrometer can reach 0.004nm, and after the input light passes through multi-channel rough filtering, the working bandwidth can be expanded to 10 nm. Therefore, the design realizes the spectrometer-on-chip system with high resolution and large bandwidth.
Claims (5)
1. A high resolution spectrometer based on an Euler micro-ring resonant cavity is characterized in that:
the waveguide array comprises a download end test port (1), a first connecting waveguide, an Euler ring ultra-precise filter, a second connecting waveguide, a transmission end test port (18), a calibration port (22), a third connecting waveguide, a single-mode bus waveguide (14), a fourth connecting waveguide, a cascade ring coarse filter (a1), (a2) … (a10), a fifth connecting waveguide and a detector array, wherein the first connecting waveguide comprises a first single-mode waveguide (2) and a first tapered waveguide (3), the second connecting waveguide comprises a second single-mode waveguide (19) and a second tapered waveguide (20), the third connecting waveguide comprises a third tapered waveguide (12) and a 180-degree bent waveguide (13), and the fourth connecting waveguide comprises a fourth single-mode waveguide (23), a second 90-degree bent waveguide (24), a fifth single-mode waveguide (25), a third 90-degree bent waveguide (26), a sixth single-mode waveguide (27), A fourth tapered waveguide (28); the download end test port (1), the transmission end test port (18) and the calibration port (22) form three input/output ports;
the Euler ring ultra-precision filter comprises a first S-shaped bending wide waveguide (4), a first wide waveguide (5), a second S-shaped bending wide waveguide (21), a second wide waveguide (6), a first Euler bending wide waveguide (7), a second Euler bending wide waveguide (8), a third wide waveguide (9), a fourth wide waveguide (10), a third S-shaped bending wide waveguide (11) and a fourth S-shaped bending wide waveguide (29); the download end test port (1) is connected with one end of a first wide waveguide (5) through a first single mode waveguide (2), a first tapered waveguide (3), a first S-shaped bent wide waveguide (4) in sequence, and the transmission end test port (18) is connected with the other end of the first wide waveguide (5) through a second single mode waveguide (19), a second tapered waveguide (20), a second S-shaped bent wide waveguide (21) in sequence; the second wide waveguide (6) is coupled with the first wide waveguide (5), the first Euler bending wide waveguide (7) and the second Euler bending wide waveguide (8) are both bending waveguides, and the second wide waveguide (6) and the third wide waveguide (9) are both straight waveguides, so that a runway ring shape is formed; a fourth wide waveguide (10) is coupled with a third wide waveguide (9), one end of the fourth wide waveguide (10) is connected with one end of a single-mode bus waveguide (14) after sequentially passing through a third S-shaped bent wide waveguide (11), a third tapered waveguide (12) and a 180-degree bent waveguide (13), the other end of the single-mode bus waveguide (14) is connected with a first detector (17) after sequentially passing through a first 90-degree bent waveguide (15) and a third single-mode waveguide (16), and the other end of the fourth wide waveguide (10) is connected with a calibration port (22) after sequentially passing through a fourth S-shaped bent wide waveguide (29), a fourth tapered waveguide (28), a sixth single-mode waveguide (27), a third 90-degree bent waveguide (26), a fifth single-mode waveguide (25), a second 90-degree bent waveguide (24) and a fourth single-mode waveguide (23);
the cascade ring coarse filter comprises at least two continuous runway type cascade micro-rings and a section of coarse filter output waveguide, wherein the coarse filter output waveguide comprises a seventh single mode waveguide (38), a 90-degree bent waveguide (39), an eighth single mode waveguide (40), a 90-degree bent waveguide (42), a ninth single mode waveguide (43) and a radiation spiral line (44); at least two runway-type cascaded micro-rings and a coarse filtering wave output waveguide are sequentially arranged in a cascade mode along the coupling direction between a cascaded ring coarse filter and a single mode bus waveguide (14), each runway-type micro-ring is formed by connecting two sections of single mode waveguides and two sections of 180-degree bent waveguides respectively positioned between two ends of the two sections of single mode waveguides, every two adjacent runway-type micro-rings are connected in a coupling mode, the runway-type micro-ring positioned on one side of the edge after the at least two continuous runway-type micro-rings are arranged in a cascade mode is connected with the single mode bus waveguide (14) in a coupling mode, the runway-type micro-ring positioned on one side of the edge after the at least two continuous runway-type micro-rings are arranged in a cascade mode is connected with a seventh single mode waveguide (38), a 90-degree bent waveguide (39) and a 90-degree bent waveguide (42) in a coupling mode, one end of the seventh single mode waveguide (38) is connected with one end of an eighth single mode waveguide (40) through the 90-degree bent waveguide (39), the other end of the seventh single-mode waveguide (38) is connected with the radiation spiral line (44) after passing through the 90-degree bent waveguide (42) and the ninth single-mode waveguide (43) in sequence.
2. The high resolution spectrometer based on the Euler micro-ring resonator as claimed in claim 1, wherein: in the Euler ring ultra-precise filter, a second wide waveguide (6), a first Euler bending wide waveguide (7), a second Euler bending wide waveguide (8) and a third wide waveguide (9) form an Euler micro-ring resonant cavity structure; two ends of the second wide waveguide (6) are respectively connected with two ends of the third wide waveguide (9) after passing through the first Euler bending wide waveguide (7) and the second Euler bending wide waveguide (8), the first Euler bending wide waveguide (7) and the second Euler bending wide waveguide (8) are both bending wide waveguides based on the modified Euler curve, and the second wide waveguide (6) and the third wide waveguide (9) are both straight waveguides.
3. The high resolution spectrometer based on the Euler micro-ring resonator as claimed in claim 2, wherein: the waveguide curves of the first Euler bending wide waveguide (7) and the second Euler bending wide waveguide (8) adopt modified Euler curves, and the specific formula is as follows:
wherein, L is the arc length of the curve; theta is an arc center angle; the radius of curvature of the Euler curve is defined by RminChange to Rmax(ii) a A is a constant number equal to
LtotalIs the total length of the curve.
4. The high resolution spectrometer based on the Euler micro-ring resonator as claimed in claim 1, wherein: the detector array is composed of a plurality of detectors with the same number as the cascaded ring coarse filters, and each detector is connected to the other end of an eighth single-mode waveguide (40) in the cascaded ring coarse filter.
5. The high resolution spectrometer based on the Euler micro-ring resonator as claimed in claim 1, wherein: further comprising a metal electrode (45), a first pad (46) and a second pad (47); a metal electrode (45) is arranged on the Euler ring ultra-precise filter, and a first wide waveguide (5), a second wide waveguide (6), a second Euler bending wide waveguide (8), a third wide waveguide (9) and a fourth wide waveguide (10) which pass through the Euler ring ultra-precise filter are covered in the middle of the metal electrode (45); the two ends of the metal electrode (45) are respectively connected with the first bonding pad (46) and the second bonding pad (47).
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