GB2394598A - Reducing the number of stray charge carriers within an optical waveguide - Google Patents

Reducing the number of stray charge carriers within an optical waveguide Download PDF

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Publication number
GB2394598A
GB2394598A GB0224954A GB0224954A GB2394598A GB 2394598 A GB2394598 A GB 2394598A GB 0224954 A GB0224954 A GB 0224954A GB 0224954 A GB0224954 A GB 0224954A GB 2394598 A GB2394598 A GB 2394598A
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United Kingdom
Prior art keywords
waveguide
optical device
diode
integrated optical
charge carriers
Prior art date
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GB0224954A
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GB0224954D0 (en
Inventor
Andrew Alan House
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Lumentum Technology UK Ltd
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Bookham Technology PLC
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Priority to GB0224954A priority Critical patent/GB2394598A/en
Publication of GB0224954D0 publication Critical patent/GB0224954D0/en
Publication of GB2394598A publication Critical patent/GB2394598A/en
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/015—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on semiconductor elements having potential barriers, e.g. having a PN or PIN junction
    • G02F1/025—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on semiconductor elements having potential barriers, e.g. having a PN or PIN junction in an optical waveguide structure
    • 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
    • G02B6/264—Optical coupling means with optical elements between opposed fibre ends which perform a function other than beam splitting
    • G02B6/266—Optical coupling means with optical elements between opposed fibre ends which perform a function other than beam splitting the optical element being an attenuator
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F2201/00—Constructional arrangements not provided for in groups G02F1/00 - G02F7/00
    • G02F2201/58—Arrangements comprising a monitoring photodetector
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F2203/00—Function characteristic
    • G02F2203/48—Variable attenuator
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/02—Structural details or components not essential to laser action
    • H01S5/026—Monolithically integrated components, e.g. waveguides, monitoring photo-detectors, drivers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
    • H01S5/1028—Coupling to elements in the cavity, e.g. coupling to waveguides adjacent the active region, e.g. forward coupled [DFC] structures
    • H01S5/1032—Coupling to elements comprising an optical axis that is not aligned with the optical axis of the active region

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  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Light Receiving Elements (AREA)

Abstract

An integrated optical device comprises a waveguide 2; a source 1 such as a variable optical attenuator (VOA) formed as a p-i-n diode laterally across the waveguide, which can cause stray charge carriers to be present within the waveguide 2; and a diode 3 comprising a p-i-n diode laterally across the waveguide, arranged to sweep the stray charge carriers out of the waveguide. An application is reduction of electrical cross-talk in an optical monitor (fig 2: 4). An array of waveguides, for example optical channel monitors, may each have associated sources and diodes.

Description

1 2394598
REDUCING THE NUMBER OF STRAY CHARGE CARRIERS WITHIN AN
OPTICAL WAVEGUIDE
This invention relates to a method of reducing the number of stray charge carriers within an optical waveguide and to a device provided with means for effecting this.
Methods of reducing the number of stray charge carriers within an integrated optical device e.g. by means of isolation trenches and/or n-ip-i-n regions (forming back-to-back diodes) have been proposed in PCT/GB02/02521 and WO 02/025334. A limitation of such methods is that, whilst they are effective in providing electrical isolation between different regions of an optical device, they can only be used in the areas of the device between waveguides. If they are extended across a waveguide they would either form a break in the waveguide (in the case of isolation trenches) or cause attenuation of optical signals due to absorption in doped regions (in the case of n-i-p-i-n isolation devices).
Accordingly, if such electrical isolation means are formed around a source of stray charge carriers such as a variable optical attenuator (VOA), stray charge carriers are still able to escape along optical waveguides crossing said isolation means.
The present invention aims to reduce this problem.
According to a first aspect of the invention, there is provided an integrated optical device comprising a waveguide, a source which can cause stray charge carriers to be present within the waveguide and a diode arranged to sweep said stray charge carriers out of the waveguide.
According to a second aspect of the invention, there is provided a method of reducing the number of stray charge carriers within an optical waveguide comprising the provision of a diode arranged to sweep said stray charge carriers out of the waveguide.
The invention also relates to an array of waveguide each of which is provided with such a diode to sweep stray charge carriers out of the respective waveguide.
Preferred and optional features will be apparent from the subsidiary claims and from the following description.
The invention will now be further described, merely by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic plan view illustrating one form of the invention; Figure 2 is a schematic plan view illustrating a particular use of the arrangement shown in Figure 1; Figure 3 is a schematic plan view showing a preferred arrangement similar to that of Figure 2; Figure 4 is a schematic plan view of a first arrangement of the invention in relation to an array of optical waveguides; and Figure 5 is a schematic plan view of a second arrangement of the invention in relation to an array of optical waveguides.
Figure shows a source of stray free charge carriers in the form of a VOA 1 formed across an optical waveguide 2. The VOA comprises a p-doped region 1A on one side of the waveguide 2 and an e-doped region 1B on the other side of the waveguide 2, forming a PIN diode positioned laterally across the waveguide 2. Electrical connections would be provided to the doped regions 1A and 1B but are not shown. The doped regions 1A and 1B may each comprise a plurality of doped areas so as to provide multiple diodes across the waveguide connected in series as described in
WO02/14935. As indicated by the arrows in Figure 1, the VOA 1 is a source of stray charge carriers which may diffuse away from the VOA 1 in any direction. A typical VOA may have a length (parallel to the optical axis of the waveguide) of around 25 microns to 25000 microns and may consist of 1 to 10 serially connected diode sections (as disclosed in WO02/14935).
Figure 1 shows a PIN diode 3 formed across the waveguide 2 to sweep up stray charge carriers in the waveguide 2 on one side of the VOA 1. The diode comprises a p-doped region 3A and an e-doped region 3B on opposite sides of the waveguide 2 (which is formed of essentially intrinsic material). In the simplest arrangement, the diode 3 is unbiased, i.e. no electrical potential is applied between the doped regions 3A and 3B (in which case no electrical connections thereto would be required). The doped regions 3A and 3B will give rise to depletion fields adjacent thereto which will
extend into the waveguide 2 which serve to extract free charge carriers out of the waveguide towards the respective doped regions where they will be absorbed (by re-combination with the opposite form of charge carrier). The diode 3 thus serves to sweep free charge carriers out of the waveguide 2. It will also be appreciated that the source of stray charge carriers may be elsewhere on the device and need not be associated with the same waveguide as the diode 3.
The length L of the diode 3 (parallel to the optical axis of the waveguide) is selected to provide the desired level of reduction of stray charge carriers in the waveguide. It has been found the stray charge carriers can diffuse through an optical device an appreciable distance, even up to 1000 microns although their effect will diminish the further they travel from the source (due to absorption and reduction in density). The length L may be
relatively short, e.g. around 50 microns, or may be relatively long, e.g. up to 1000 microns. In many cases, a short length L, i.e. around 50 microns, will be sufficient to sweep up stray charge carriers and it has the advantage of helping to keep the device small.
Figure 2 shows the use of a diode such as that described above to reduce electrical cross-talk in an optical monitor 4 due to stray charge carriers within a waveguide 2. Figure 2 shows a source of stray charge carriers in the form of a VOA 1 as in Figure 1 and a diode 3 for sweeping up stray charge carriers emanating therefrom which are travelling along the waveguide 2 towards the optical monitor 4. In this case, electrical connections 5A and 5B are provided to enable a reverse bias, e.g. of 5 volts to be applied across the doped regions 3A and 3B although, again, this is not essential. Free charge carriers within the waveguide 2 are thus swept up by the reverse biased PIN diode 3. The application of an electrical potential across the doped regions 3A and 3B will generate a small dark current within the diode but as this is due to carrier drift rather than injection of charge carriers, its effect on the performance of the device is small.
The optical monitor 4 may be an in-line monitor as described, for example, in GB0131001.0 and GB0131003.6.
Such monitors absorb a small fraction of the light being transmitted along the waveguide 2 and the photocurrent produced thereby is detected by means of a diode formed across the waveguide 2. Figure 2 shows such a PIN diode comprising p-doped and e-doped regions 4A and 4B on opposite sides of the waveguide (which, as indicated above, is essentially formed of intrinsic, i.e. relatively undoped material).
Such optical monitors may be arranged to detect very small photocurrents, e.g. if the light signal being monitored is weak and/or if the fraction thereof absorbed by the monitor is small. In such
circumstances, it is important to minimise electrical cross-talk between the monitor and adjacent devices.
A VOAis commonly placed in series with an optical monitor. Thus, the present invention provides a method of sweeping up stray charge carriers within the waveguide between the VOA and the optical monitor which would otherwise result in electrical cross-talk therebetween and which would therefore compromise the accuracy of the monitor. The device used to sweep up the stray charge carriers may have a similar structure to the optical monitor (but without a material which generates a photocurrent). Indeed, the VOA 1, diode 3 and monitor 4 all have a very similar structure (although their functions are very different) and are therefore relatively simple to fabricate.
The diode used for sweeping up stray charge carriers may be positioned anywhere along a waveguide between a source of the stray carriers and the device it is designed to protect (as mentioned above, the stray charge carriers can drift up to 1000 microns from their source) but, in many cases, it may be desirable to position the diode relatively close to the source of the stray charge carriers.
Figure 3 illustrates an arrangement in which the VOA and the diode are formed on the same waveguide and in which it is advantageous to position the diode 4 close to the VOA1. In this case, the PIN diode 3is arranged so that its p-doped area 3Ais adjacent the e-doped area 1B of the VOA1 and its e-doped area 3B adjacent the p-doped are 1A of the VOA 1. By this means they can be electrically interconnected, as shown by electrical connections 6A and 6B,so that the circuitry (not shown) used to drive the VOA 1 can be used to apply a reverse bias to the PIN diode 3 so a separate circuit is not needed for this purpose. In this configuration a parasitic NIN resistor may be created between the doped regions 1B and 3B of the two diodes 1 and 3, which can impair the operation of diode 1 as an efficient attenuator as a proportion of the device current may be driven
through the path 1B to 3B, where it is essentially a drift current that is ineffective in attenuating light in waveguide 2, rather than through the path 1B to 1A, where it produces a mainly diffusion current useful for attenuation. This problem can be minimised if the NIN resistor is of high resistance, e.g. if the silicon waveguide 2 is essentially intrinsic material (so the background doping level of the waveguide is such that its
resistivity is greater than 1 ohm-cm) and the physical separation of regions 1B and 3B is sufficiently large, e.g. greater than 50 microns.
One or more PIN diodes such as that described above can be used to sweep up stray charge carriers in a waveguide alone or, preferably, in conjunction with other electrical isolation means such as the isolation trenches and n-i-p-i-n (and/or p-i-n-i-p) devices referred to above. Thus, an isolation trench may be formed around a source of stray charge carriers and a PIN diode provided at each point where there has to be a gap in the trench as it crosses a waveguide. Together, they can therefore form a continuous barrier to stray charge carriers all around the source producing the stray charge carriers.
The PIN diodes 3 described above are lateral PIN diodes formed across a waveguide. However, any arrangement of diode which has the effect of sweeping stray charge carriers out of the waveguide may be used. In some cases, vertical diodes (i.e. extending perpendicular to the plane of the device) or longitudinal diodes (extending parallel to the waveguide) or diodes positioned adjacent the waveguide may, for example, be used.
Figure 4 shows an array of waveguides 10 each of which has a source of stray charge carriers in the form of a VOA 11 associated therewith and an optical monitor 12 which is susceptible to cross-talk from such stray charge carriers. Electrical isolation n-i-p-i-n devices 13 are provided in the substrate around the VOAs 11 and the optical monitors 12 but these terminate where they meet the waveguides 10 as shown. PIN diodes 14, 15 and 16 are provided on the respective waveguides 10 between the
VOA 11 or the optical monitor 12 to sweep up stray charge carriers as described above. Each of these comprises a p-doped region 14A, 15A and 16A and an e-doped region 14B, 15B and 16B, respectively. However, between the e-doped region 14B of diode 14 and p-doped region 15A of diode 15 a further p-doped region 17 and e-doped region 18 are provided.
A p-doped region 19 and an e-doped region 20 are similarly provided between e-doped region 15B of diode 15 and p-doped region 16A of diode 16. The regions 14B, 17, 18, 15A and 15B, 19, 20, 16A provide additional diodes between adjacent waveguides to sweep up stray charge carriers in these areas. The waveguides 10 in such an array are typically spaced from each other by a distance of around 250 microns while the doped regions 14B, 17, 18, 15A and 15B, 19, 20, 16A are typically about 30 microns wide. If the doped regions 17, 18, 19 and 20 were omitted then the regions 14B and 15A and the regions 15B and 16A would form reverse biased (or unbiased) PIN diodes extending across the large undoped region (almost 200 microns) between adjacent waveguides. Such wide PIN diodes would be largely ineffective at sweeping up stray carriers and so the introduction of the regions 17, 18, 19 and 20 effectively create an
additional two diodes between adjacent waveguides that are of a size small enough to ensure that they function effectively as collectors of stray charge carriers.
Figure 4 also shows electrical connections 21 and 22 for the p-doped regions and e-doped regions, respectively. These may comprise a metal overlay the boundaries of which are shown by dashed lines in the Figure.
Figure 5 illustrates another arrangement of p- and e-doped regions for the PIN diodes in an array of waveguides 29. In this case, a first PIN diode 30 comprises p-doped region 30A and e-doped region 30B and a second PIN diode 31 comprising an e-doped region 31A and a p-doped region 31B, the e-doped regions 30B and 31A being connected by e-doped regions
32A and 32B. A p-doped region 33 is provided within the rectangle formed by e-doped regions BOB, 32B, 31A, 32A again to provide additional diodes between the adjacent waveguides to function as collections of stray charge carriers.
Figure 4 shows only 3 waveguides 10 and Figure 5 shows only two waveguides 29 but it will be appreciated that the arrangements shown can be extended to larger arrays, e.g. arrays comprising forty or more waveguides as commonly used in optical channel monitors (OCMs).
The device described above is particularly useful in relation to rib waveguides, for example silicon rib waveguides. Rib waveguides comprise a rib projecting from a slab region. In preferred forms of the device, these are formed in a silicon layer which is separated from a support substrate (typically also of silicon) by an optical confinement layer, e. g. of silicon dioxide or silicon nitride. Such devices may typically be formed on so called silicon-on-insulator chips. The device may, however, be used with other types of waveguides formed in other materials.

Claims (23)

1. An integrated optical device comprising a waveguide, a source which can cause stray charge carriers to be present within the waveguide and a diode arranged to sweep said stray charge carriers out of the waveguide.
2. An integrated optical device as claimed in claim I in which said diode comprises a PIN diode.
3. An integrated optical device as claimed in claim 2 in which the PIN diode comprises a p-doped region and an e-doped region on opposite sides of the waveguide.
4. An integrated optical device as claimed in claim 1, 2 or 3 in which drive means are provided for applying a reverse bias across the diode.
5. An integrated optical device as claimed in any preceding claim in which the waveguide is a rib waveguide.
6. An integrated optical device as claimed in any preceding claim in which the waveguide is a silicon waveguide.
7. An integrated optical device as claimed in claim 6 in which the waveguide is formed on a silicon-on-insulator chip comprising a silicon layer separated from a supporting substrate by an optical confinement layer.
8. An integrated optical device as claimed in claims 3 and 5 in which the rib waveguide comprises a rib projecting from a slab region, the doped regions being formed in the slab region on opposite sides of the rib.
9. An integrated optical device as claimed in any preceding claim in which the diode is located within 1000 microns of said source of stray charge carriers.
10. An integrated optical device as claimed in claim 9 in which the diode is located adjacent said source of stray charge carriers.
11. An integrated optical device as claimed in claim 9 or 10 in which the source of stray charge carriers is a variable optical attenuator.
12. An integrated optical device as claimed in claim 11 in which the diode and the variable optical attenuator are formed on the same waveguide.
13. An integrated optical device as claimed in claim 12 in which said diode is electrically connected to the attenuator.
14. An integrated optical device as claimed in any preceding claim in which the diode is located so as to help shield a device susceptible to electrical cross-talk from stray charge carriers.
15. An integrated optical device as claimed in claim 14 in which said device is an optical monitor.
16. An integrated optical device as claimed in claims 12 and 15 in which the diode is located between a variable optical attenuator and an optical monitor formed in the same waveguide.
17. An integrated optical device as claimed in any preceding claim in which the diode is used in conjunction with other electrical isolation means.
18. An integrated optical device as claimed in claim 17 in which said other electrical isolation means comprises trenches and/or n-i-p-i-n (or p-i-n-i-p) structures.
19. An integrated optical device in which the waveguide is one of an array of waveguides each of which has a diode as described in any of the preceding claims.
20. An integrated optical device as claimed in claim 19 in which additional doped regions are provided between adjacent waveguides so as to form additional diodes therebetween.
21.An integrated optical device substantially as hereinbefore described with reference to and/or as shown in one or more of the accompanying drawings.
22. A method of reducing the number of stray charge carriers within an optical waveguide comprising the provision of a diode arranged to sweep said stray charge carriers out of the waveguide.
23. A method of reducing the number of stray charge carriers within an optical waveguide substantially as hereinbefore described with reference to one or more of the accompanying drawings.
GB0224954A 2002-10-26 2002-10-26 Reducing the number of stray charge carriers within an optical waveguide Withdrawn GB2394598A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB0224954A GB2394598A (en) 2002-10-26 2002-10-26 Reducing the number of stray charge carriers within an optical waveguide

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Application Number Priority Date Filing Date Title
GB0224954A GB2394598A (en) 2002-10-26 2002-10-26 Reducing the number of stray charge carriers within an optical waveguide

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GB0224954D0 GB0224954D0 (en) 2002-12-04
GB2394598A true GB2394598A (en) 2004-04-28

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007248850A (en) * 2006-03-16 2007-09-27 Oki Electric Ind Co Ltd Mach-zehnder type semiconductor element and control method thereof
WO2016094808A1 (en) * 2014-12-12 2016-06-16 Cisco Technology, Inc. Electro-optic modulator termination
WO2019130021A1 (en) * 2017-12-29 2019-07-04 Oclaro Technology Limited Negative bias to improve phase noise
WO2021015981A1 (en) * 2019-07-19 2021-01-28 Ciena Corporation Multi-pass free-carrier absorption variable optical attenuators and multi-pass thermal phase shifters
WO2022197875A1 (en) * 2021-03-17 2022-09-22 Ayar Labs, Inc. Low non-linear loss silicon waveguides with sweep-out diodes

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Publication number Priority date Publication date Assignee Title
US4904039A (en) * 1988-11-18 1990-02-27 The United States Of America As Represented By The Secretary Of The Air Force Electro-optic devices utilizing a sapphire substrate
EP0433552A2 (en) * 1989-12-21 1991-06-26 International Business Machines Corporation Silicon-based rib waveguide optical modulator
US5191630A (en) * 1990-04-20 1993-03-02 Nec Corporation Nonlinear optical device for controlling a signal light by a control light
US5351317A (en) * 1992-08-14 1994-09-27 Telefonaktiebolaget L M Ericsson Interferometric tunable optical filter
US5550939A (en) * 1992-04-13 1996-08-27 British Telecommunications Public Limited Company High speed optical switching device including a capacitance structure

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4904039A (en) * 1988-11-18 1990-02-27 The United States Of America As Represented By The Secretary Of The Air Force Electro-optic devices utilizing a sapphire substrate
EP0433552A2 (en) * 1989-12-21 1991-06-26 International Business Machines Corporation Silicon-based rib waveguide optical modulator
US5191630A (en) * 1990-04-20 1993-03-02 Nec Corporation Nonlinear optical device for controlling a signal light by a control light
US5550939A (en) * 1992-04-13 1996-08-27 British Telecommunications Public Limited Company High speed optical switching device including a capacitance structure
US5351317A (en) * 1992-08-14 1994-09-27 Telefonaktiebolaget L M Ericsson Interferometric tunable optical filter

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007248850A (en) * 2006-03-16 2007-09-27 Oki Electric Ind Co Ltd Mach-zehnder type semiconductor element and control method thereof
WO2016094808A1 (en) * 2014-12-12 2016-06-16 Cisco Technology, Inc. Electro-optic modulator termination
US9575337B2 (en) 2014-12-12 2017-02-21 Cisco Technology, Inc. Electro-optic modulator termination
WO2019130021A1 (en) * 2017-12-29 2019-07-04 Oclaro Technology Limited Negative bias to improve phase noise
US11901698B2 (en) 2017-12-29 2024-02-13 Lumentum Technology Uk Limited Negative bias to improve phase noise
WO2021015981A1 (en) * 2019-07-19 2021-01-28 Ciena Corporation Multi-pass free-carrier absorption variable optical attenuators and multi-pass thermal phase shifters
US11226504B2 (en) 2019-07-19 2022-01-18 Ciena Corporation Free-carrier absorption variable optical attenuators and thermal phase shifters formed by an optical waveguide having multiple passes in an intrinsic region
WO2022197875A1 (en) * 2021-03-17 2022-09-22 Ayar Labs, Inc. Low non-linear loss silicon waveguides with sweep-out diodes
US11733554B2 (en) 2021-03-17 2023-08-22 Ayar Labs, Inc. Low non-linear loss silicon waveguides with sweep-out diodes
US20230393424A1 (en) * 2021-03-17 2023-12-07 Ayar Labs, Inc. Low Non-Linear Loss Silicon Waveguides with Sweep-Out Diodes

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