CN117311055A - On-chip multi-wavelength light source based on optical frequency comb - Google Patents
On-chip multi-wavelength light source based on optical frequency comb Download PDFInfo
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- CN117311055A CN117311055A CN202311266484.XA CN202311266484A CN117311055A CN 117311055 A CN117311055 A CN 117311055A CN 202311266484 A CN202311266484 A CN 202311266484A CN 117311055 A CN117311055 A CN 117311055A
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- 230000003287 optical effect Effects 0.000 title claims abstract description 146
- 230000010287 polarization Effects 0.000 claims abstract description 37
- 238000005253 cladding Methods 0.000 claims abstract description 28
- 239000012792 core layer Substances 0.000 claims abstract description 22
- 239000010410 layer Substances 0.000 claims abstract description 19
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 6
- 238000006243 chemical reaction Methods 0.000 claims description 6
- 229910052581 Si3N4 Inorganic materials 0.000 claims description 4
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- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims description 4
- 150000001875 compounds Chemical class 0.000 claims description 3
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 claims description 3
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
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- 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
- G02F1/35—Non-linear optics
- G02F1/353—Frequency conversion, i.e. wherein a light beam is generated with frequency components different from those of the incident light beams
- G02F1/3536—Four-wave interaction
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- Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
Abstract
An on-chip multi-wavelength light source based on an optical frequency comb, a pumping light source, a light source module and a light source module, wherein the pumping light source module is suitable for emitting pumping light; an optical waveguide chip comprising: a substrate; a lower cladding layer disposed on the substrate; the sandwich layer, set up on the lower cladding, the sandwich layer includes: the polarization beam splitter is formed on the lower cladding and is suitable for obtaining target linearly polarized light with the electric field or magnetic field vector direction parallel to the cross section of the waveguide according to the pumping light; the micro-resonant cavity is formed on the lower cladding, and the target linearly polarized light resonates in the micro-resonant cavity, wherein under the condition that the optical power in the micro-resonant cavity reaches a preset threshold value, a four-wave mixing phenomenon is generated in the micro-resonant cavity, and an optical frequency comb is obtained, wherein the optical frequency comb comprises a plurality of lights with different wavelengths, and the lights with different wavelengths are arranged at equal intervals; the wavelength division multiplexer is formed on the lower cladding and comprises a plurality of channels, and light with different wavelengths from the download port output by the micro resonant cavity is output through different channels; and the upper cladding layer is arranged on the core layer.
Description
Technical Field
The invention relates to the field of optical communication light sources, in particular to an on-chip multi-wavelength light source based on an optical frequency comb.
Background
With the development of the information age, the demands for communication capacity and communication rate have been increasing, and data transmission at a single wavelength cannot meet the increasing demands for communication. The wavelength division multiplexing technology is an effective method and a common means for improving the communication capacity, the multi-wavelength light source is an important component part in a wavelength division multiplexing system, and most of the current multi-wavelength light sources adopt an array structure consisting of a plurality of lasers with different output wavelengths, namely a single-wavelength laser array. However, the multi-wavelength light source generated by the method has no coherence among light waves with different wavelengths, and the wavelength of the output light waves is difficult to realize strict equidistant arrangement in a frequency domain; furthermore, the laser array is generally large in size and requires multiple drives, limiting its further application in coherent communication systems.
Disclosure of Invention
In view of this, the present invention provides an on-chip multi-wavelength light source based on an optical frequency comb, in which the frequency interval between any two adjacent light beams is uniform.
As a first aspect of the present invention, there is provided an on-chip multi-wavelength light source based on an optical frequency comb, comprising:
the pumping light source is suitable for emitting pumping light;
an optical waveguide chip comprising:
a substrate;
a lower cladding layer disposed on the substrate;
a core layer disposed on the lower cladding layer, the core layer comprising:
the polarization beam splitter is formed on the lower cladding and is suitable for obtaining target linearly polarized light with an electric field or magnetic field vector direction parallel to the cross section of the waveguide according to the pump light;
the micro-resonant cavity is formed on the lower cladding, and the target linearly polarized light resonates in the micro-resonant cavity, wherein under the condition that the optical power in the micro-resonant cavity reaches a preset threshold value, a four-wave mixing phenomenon is generated in the micro-resonant cavity, and an optical frequency comb is obtained, wherein the optical frequency comb comprises a plurality of lights with different wavelengths, and the lights with different wavelengths are arranged at equal intervals;
a wavelength division multiplexer formed on the lower cladding layer, the wavelength division multiplexer including a plurality of channels, light of different wavelengths from the download port of the micro resonant cavity being output through different channels;
and the upper cladding layer is arranged on the core layer.
According to an embodiment of the invention, the core layer further comprises:
and a plurality of variable optical attenuators formed on the lower cladding, the variable optical attenuators being adapted to adjust optical powers of the light of the corresponding wavelengths outputted from the wavelength division demultiplexers in a one-to-one correspondence so that the optical powers of the adjusted light of the respective wavelengths are the same.
According to an embodiment of the present invention, the on-chip multi-wavelength light source further includes:
a beam splitter adapted to split light output from an output port of the micro-resonator into a first beam and a second beam;
the optical power meter is suitable for detecting the power of the first light beam;
and the spectrometer is suitable for detecting the wavelength of the second light beam.
According to an embodiment of the present invention, the on-chip multi-wavelength light source further comprises,
the optical amplifier is suitable for amplifying the power of the pump light emitted by the pump light source and inputting the pump light with amplified power to the polarization beam splitter.
According to an embodiment of the present invention, the on-chip multi-wavelength light source further comprises,
and the heating module is suitable for heating the micro-resonant cavity so as to keep the frequency of the optical frequency comb output by the micro-resonant cavity stable.
According to an embodiment of the invention, the polarizing beam splitter comprises a multimode interferometer, a Mach-Zehnder interferometer, a directional coupler type polarizing beam splitter.
According to an embodiment of the present invention, the directional coupling type polarization beam splitter includes a first waveguide, a second waveguide, and a third waveguide;
the pump light is input from a first waveguide, in the transmission process, first linearly polarized light in the pump light is coupled into a second waveguide from the first waveguide, mode conversion occurs in the second waveguide, the mode-converted first linearly polarized light is coupled into a third waveguide, mode conversion occurs, the first linearly polarized light is obtained, second linearly polarized light in the pump light is transmitted in the first waveguide, and the polarization direction of the first linearly polarized light is perpendicular to the polarization direction of the second linearly polarized light;
the target linearly polarized light is first linearly polarized light or second linearly polarized light.
According to an embodiment of the present invention, the core layer further includes a transmission waveguide between the polarization beam splitter and the micro-resonant cavity, between the micro-resonant cavity and the wavelength division demultiplexer, and between the wavelength division demultiplexer and the variable optical attenuator array, connected by the transmission waveguide.
According to an embodiment of the invention, the material of the core layer comprises silicon dioxide, silicon nitride, lithium niobate or a III V semiconductor compound or polymer.
According to an embodiment of the present invention, the variable optical attenuator array comprises two or more symmetrical or asymmetrical mach-zehnder variable optical attenuators.
According to the embodiment of the invention, in the optical frequency comb generated by the micro-resonant cavity, the distance between any two adjacent wavelengths is equal, and the distance between any two adjacent wavelengths is an integral multiple of the cavity length of the micro-resonant cavity, so that the optical frequency comb in the embodiment of the invention is equidistant.
According to the embodiment of the invention, because the light with different wavelengths in the optical frequency comb is generated in the same micro resonant cavity, the light with different wavelengths is generated in accordance with the resonance condition of the micro resonant cavity, so that the coherence between the light with different wavelengths generated by the embodiment of the invention is better.
Drawings
FIG. 1 shows a schematic diagram of an on-chip multi-wavelength light source based on an optical frequency comb according to an embodiment of the present invention;
fig. 2 shows a symmetrical mach-zehnder variable optical attenuator structure provided in accordance with an embodiment of the present invention;
FIG. 3 shows a schematic diagram of a micro-ring provided in accordance with an embodiment of the present invention;
fig. 4 shows a schematic diagram of a polarizing beam splitter provided according to an embodiment of the invention.
Description of the reference numerals
1: a pump light source;
2: an optical waveguide chip;
21 core layer
211: a polarizing beam splitter;
2111: a first waveguide;
2111-1: a second straight waveguide;
2111-2: bending the waveguide;
2112: a second waveguide;
2113: a third waveguide;
212: a micro-resonant cavity;
2121: a first straight waveguide;
2122: a circular ring waveguide;
213: a wave-division multiplexer;
214: a variable optical attenuator;
2141: a first 3dB directional coupler;
2142: second 3dB directional coupler
2143: an upper modulating wall;
2144: down to the wall;
215: a transmission waveguide;
3: a beam splitter;
4: an optical power meter;
5: a spectrometer;
6: an optical amplifier;
7: and a heating module.
Detailed Description
In the process of realizing the invention, the traditional multi-light source system based on the laser arrays with different output wavelengths has large size, light waves with different wavelengths have no coherence, and the output light wave wavelengths are difficult to realize strict equidistant arrangement in the frequency domain, so that the application of the system in the field of high-speed coherent communication is limited.
An optical frequency comb (optical frequency comb for short) is a spectrum consisting of a series of frequency components uniformly spaced apart with a stable coherent phase relationship in the frequency domain, and is an effective solution for providing an on-chip multi-wavelength light source. The Kerr optical frequency comb has the advantages of small volume, on-chip integration, low power consumption, high stability, simple structure and the like, and draws great attention. The Kerr optical frequency comb generating process is that the input pump light continuously resonates and enhances in the microcavity, when the optical power in the cavity exceeds the threshold power, the nonlinear Kerr effect of the material generates optical parametric oscillation to realize the generation of a primary main comb, and the cascade four-wave mixing effect expands the range of the main comb to form a coherent spectrum along with the increase of the power in the cavity. The optical frequency comb is produced in various nonlinear dynamic states, such as a 'Turing ring' state, a modulation unstable state, a chaotic state, a soliton state and the like. The optical frequency comb in the 'Turing ring' state has smaller pump light power, large comb teeth on the frequency spectrum and better stability, and is suitable for on-chip multi-wavelength light sources.
The present invention will be further described in detail below with reference to specific embodiments and with reference to the accompanying drawings, in order to make the objects, technical solutions and advantages of the present invention more apparent.
Fig. 1 shows a schematic diagram of an on-chip multi-wavelength light source based on an optical frequency comb according to an embodiment of the present invention.
As shown in fig. 1, an on-chip multi-wavelength light source based on an optical frequency comb includes: a pump light source 1 and an optical waveguide chip 2. The pump light source 1 is adapted to emit pump light. The optical waveguide chip 2 includes: a substrate (not shown), a lower cladding layer (not shown), a core layer 21, and an upper cladding layer (not shown). The lower cladding layer is provided on the substrate, the core layer 21 is provided on the lower cladding layer, and the upper cladding layer is provided on the core layer 21.
The core layer 21 includes: a polarizing beam splitter 211, a micro-resonator 212, a wavelength-division demultiplexer 213, a variable optical attenuator 214. The polarizing beam splitter 211 is adapted to obtain the target linearly polarized light from the pump light. The micro-resonant cavity 212 is formed on the lower cladding layer, and the target linearly polarized light resonates in the micro-resonant cavity 212, wherein under the condition that the optical power in the micro-resonant cavity 212 reaches a preset threshold value, a four-wave mixing phenomenon is generated in the micro-resonant cavity 212, and an optical frequency comb is obtained, wherein the optical frequency comb comprises a plurality of light with different wavelengths, and the light with different wavelengths are arranged at equal intervals. The wavelength division demultiplexer 213 is formed on the lower cladding layer, and the wavelength division demultiplexer 213 includes a plurality of channels, and light of different wavelengths from the download port of the micro resonator 212 is output through different channels.
According to an embodiment of the present invention, the pump light is inputted into the optical waveguide chip 2, and the polarization beam splitter 211 converts the pump light into a target linearly polarized light matched with the micro resonator 212, and then inputted into the micro resonator 212. The pump light source 1 is adjusted to adjust the light intensity and the light wavelength of the pump light, and in the adjusting process, the wavelength of the pump light gradually approaches to the resonance wavelength of the micro-resonant cavity 212 from small to large, and as the light power in the micro-resonant cavity 212 gradually increases, the temperature in the cavity rises to generate a thermal effect, and the thermal effect causes the wavelength of the light in the micro-resonant cavity 212 to be red shifted. The increasing wavelength of the pump light "pushes" the resonant wavelength of the light within the micro-resonator 212 from the cold cavity resonant wavelength to the maximum resonant wavelength, at which time the wavelength of the pump light is slightly smaller than the maximum resonant wavelength, and the amount of heat generated by the micro-resonator 212 and the dissipation are equal to reach a steady state. The micro-resonant cavity 212 is made of a high nonlinear material, when the pump light power exceeds the parametric oscillation threshold, the interaction of a high-intensity light field in the micro-resonant cavity 212 and a waveguide excites a four-wave mixing process, wherein paired pump photons annihilate, and signals and idler photons are generated at higher and lower frequencies to form a primary main comb. As the power of the light within the micro-cavity 212 increases, the cascaded four-wave mixing process further expands the main comb range, and the sub-combs begin to generate adjacent to the resonant frequencies of the main comb until each resonant frequency within the bandwidth of the optical frequency comb is occupied. Thus obtaining the optical frequency comb with uniform frequency interval. The wavelength division demultiplexer 213 separates light of different wavelengths in the optical frequency comb. The wavelength division multiplexer 213 is an input/output arrayed waveguide grating, which separates light with different wavelengths from one waveguide according to the grating diffraction principle, and outputs the light respectively, wherein the wavelength interval of the output end is 100GHz.
According to an embodiment of the present invention, the polarization beam splitter 211, the micro resonator 212, and the wavelength division demultiplexer 213 are integrated on one optical waveguide chip 2, and the optical waveguide chip 2 can obtain an optical frequency comb using pump light generated from one pump light source 1. Therefore, the light source in the embodiment of the invention only needs to drive one pumping light source, and the application of the light source in a coherent communication system is increased compared with a device for generating an optical frequency comb by adopting a plurality of pumping light sources.
According to an embodiment of the present invention, since the micro-resonant cavity 212 has wavelength selectivity, only light satisfying the resonance condition (specific wavelength) of the micro-resonant cavity 212 can be output, and the resonance condition of the micro-resonant cavity 212 is: m×λ=n×l, where λ is the wavelength of light, n is the refractive index of the micro-resonant cavity 212, L is the cavity length of the micro-resonant cavity 212, and m is the positive integers 1, 2, and 3 …, so that the intervals between the wavelengths output in the embodiment of the present invention are equal, and the wavelength difference between two adjacent light beams is: lambda (lambda) 0 2 /(n×L), where λ 0 Is the resonant wavelength.
According to an embodiment of the present invention, the core layer 21 further includes: the plurality of variable optical attenuators 214, the plurality of variable optical attenuators 214 forming a variable optical attenuator array, the plurality of variable optical attenuators 214 being formed on the lower cladding, the variable optical attenuators 214 being adapted to adjust the optical power of the light of the corresponding wavelength outputted from the wavelength division demultiplexer 213 in one-to-one correspondence so that the optical power of the adjusted light of each wavelength is the same. The input end of each variable optical attenuator 214 in the variable optical attenuator array is connected to the output end of the corresponding wavelength division demultiplexer 213, so as to adjust the light intensities of the light beams with different wavelengths, and equalize the light intensities of the light beams with different wavelengths. The variable optical attenuator 214 in this embodiment is embodied as a symmetrical mach-zehnder variable optical attenuator. In the optical frequency comb generated by the micro-resonant cavity 212, the light intensity of each wavelength is gaussian distributed with the pump wavelength as the center, the power difference of the optical signals between the channels in the coherent optical communication system can increase the optical signal to noise ratio and the optical error rate, and the variable optical attenuator array is added after the wavelength demultiplexer 213 to ensure the uniform power of the optical signals of each wavelength.
Fig. 2 shows a symmetrical mach-zehnder variable optical attenuator structure provided according to an embodiment of the present invention.
As shown in fig. 2, the symmetrical mach-zehnder variable optical attenuator consists of two 3dB directional couplers and two thermally modulated walls. The input optical signal is divided into two beams with equal power after passing through the first 3dB directional coupler 2141, and the two beams are respectively transmitted by the modulation arm 2144 under the upper modulation wall 2143, one of the arms is heated by using a metal electrode, and the refractive index of the heated arm is increased according to the thermo-optical effect, and the optical path length of the optical signal transmitted therein is prolonged, so that the optical path difference is generated between the two optical signals of the upper and lower arms. At the second 3dB directional coupler 2142, the two light signals are interfered and recombined, and the final output light intensity depends on the phase difference of the two light beams, and the output light intensity is maximum when the phase difference is 0, and minimum when the phase difference of the two light beams is pi, so that the adjustment of the signal light intensity is focused. Furthermore, the variable optical attenuator array can control the switch of each path of optical signals according to the need, when the optical network communication need is reduced and certain wavelength light sources are not needed, the corresponding variable optical attenuators can be adjusted to minimize the output light intensity of the path, and the requirement of switching off one path of optical signals is met.
According to an embodiment of the present invention, the download port of microresonator 212 is connected to the input port of wavelength demultiplexer 213; each output port of the wavelength demultiplexer 213 is connected to each input port of the variable optical attenuator array.
According to an embodiment of the present invention, referring to fig. 1, the core layer 21 further includes a transmission waveguide 215, between the polarization beam splitter 211 and the micro-resonator 212, between the micro-resonator 212 and the wavelength division demultiplexer 213, between the wavelength division demultiplexer 213 and the variable optical attenuator 214 are connected through the transmission waveguide 215, and materials of the polarization beam splitter 211, the micro-resonator 212 and the transmission waveguide 215 are the same. Since the polarization beam splitter 211 and the micro-resonant cavity 212 are connected by the transmission waveguide 215, the polarization state of the target linearly polarized light is not changed in the process of transmitting the polarization beam splitter 211 to the micro-resonant cavity 212. According to an embodiment of the present invention, the electric or magnetic field vector direction of the target linearly polarized light is parallel to the cross section of the transmission waveguide 215. The transmission waveguide 215 is a rectangular waveguide.
Because each light of the optical frequency comb is generated in the same micro resonant cavity 212, each light of the frequency comb meets the resonance condition and the phase matching condition of the micro resonant cavity 212, and is output after passing through the transmission waveguide 215, each wavelength light has stable phase and good coherence during output, and therefore, each light of the optical frequency comb generated by the embodiment of the invention has better coherence.
According to an embodiment of the present invention, the above-mentioned multi-wavelength light source further includes: a beam splitter 3, an optical power meter 4 and a spectrometer 5. The optical beam splitter 3, the optical power meter 4 and the spectrometer 5 form a microcavity detection unit. The output port of the micro-resonant cavity 212 is connected to a microcavity monitoring unit. The beam splitter 3 is adapted to split the light output from the output port of the micro-resonator 212 into a first beam and a second beam. The optical power meter 4 is adapted to detect the power of the first light beam. The spectrometer 5 is adapted to detect the wavelength of the second light beam.
According to an embodiment of the present invention, the splitting ratio of the optical splitter 3 may be, for example, 50:50, and the input end of the optical splitter 3 is connected to the output end of the micro-resonant cavity 212, one output end of the optical splitter 3 is connected to the optical power meter 4, and the other output end is connected to the spectrometer 5. The light output by the output end of the micro-resonant cavity 212 can monitor the condition of the light field in the micro-resonant cavity 212, and the light output by the light beam splitter 3 is split into two light beams with equal intensity by the light beam splitter 3 and is respectively input into the optical power meter 4 and the spectrometer 5. The energy from the micro-resonant cavity 22 to the cavity can be obtained by observing the indication change of the optical power meter 4, and the optical frequency comb generation condition in the micro-resonant cavity 22 can be known in real time by observing the spectrometer 5, so that the micro-cavity can be regulated and controlled conveniently.
The multi-wavelength light source according to an embodiment of the present invention further includes, an optical amplifier 6. The output end of the optical amplifier 6 is connected with the input end of the polarization beam splitter 211, and the pump light source 1 is connected with the input end of the optical amplifier 6. The optical amplifier 6 is adapted to amplify the power of the pump light emitted from the pump light source 1 and to input the power-amplified pump light to the polarization beam splitter 211. The optical power input into the optical waveguide chip 2 can be improved by adding the optical amplifier 6 after the pumping light source 1, so that the threshold power generated by the optical frequency comb can be more easily achieved, and the optical amplifier 6 is an erbium-doped optical fiber amplifier or a semiconductor optical amplifier. The beam splitter 211 is polarized after the optical amplifier 6 so that the pump light is converted into a single polarization state matched with the micro-resonant cavity 212, and crosstalk generated by simultaneous resonance of different polarization states in the micro-resonant cavity is avoided.
With continued reference to FIG. 1, the microresonator includes: and a heating module 25. The heating module 25 is housed outside the microresonator 22. The heating module 7 heats the micro-resonant cavity 212 under the driving of the electric signal, so that the frequency of the optical frequency comb output by the micro-resonant cavity 212 is kept stable.
In accordance with an embodiment of the present invention, microresonator 212 is a microring, microdisk, or photonic crystal microcavity.
Fig. 3 shows a schematic diagram of a micro-ring provided according to an embodiment of the invention.
As shown in fig. 3, the micro-ring includes two first straight waveguides 2121 and one circular ring waveguide 2122, which has four ports, an input port at the top left, an output port at the top right, a download port at the bottom left, and an upload port at the bottom right. In order to make the free spectral range of the microring at the wavelength 1550nm be 100GHz, the microring radius is designed to be 232.6 μm. Single-frequency continuous pump light is input from an output port and is guided and coupled into the circular ring waveguide 2122 through the first straight wave 2121, the distance between the first straight wave 2121 and the circular ring waveguide 2122 meets the critical coupling condition, the pump light is continuously input into the circular ring waveguide 2122 and resonates and is enhanced in the circular ring waveguide 2122, and finally the input optical power reaches the maximum optical intensity in the circular ring waveguide 222 when the optical loss in the circular ring waveguide 2122 is equal.
According to an embodiment of the present invention, the pump light is divided into two polarized light beams with polarization states perpendicular to each other by the polarization beam splitter 211, the two polarized light beams are respectively TE and TM modes, and the polarized light beams of the TE and TM modes respectively output the directional coupling type polarization beam splitter from two output ports, and the directional coupling type polarization beam splitter includes a first waveguide 2111, a second waveguide 2112 and a third waveguide 2113. The pump light is input from the first waveguide 2111, during the transmission process, the first linearly polarized light in the pump light is coupled into the second waveguide 2112 from the first waveguide 2111, and mode conversion occurs in the second waveguide 2112, the mode-converted light with the first linearly polarized light is coupled into the third waveguide 2113, and mode conversion occurs, so that the first linearly polarized light is obtained, the second linearly polarized light in the pump light is transmitted in the first waveguide 2111, and the polarization direction of the first linearly polarized light is perpendicular to the polarization direction of the second linearly polarized light. The target linearly polarized light is either the first linearly polarized light or the second linearly polarized light. An output of polarizing beam splitter 211 is coupled to an input port of microresonator 212 for inputting either the first polarization or the second polarization to microresonator 212.
According to an embodiment of the present invention, polarizing beamsplitter 211 comprises a multimode interferometer, a Mach-Zehnder interferometer, or a directional coupler type polarizing beamsplitter. The polarization beam splitter 211 converts the pump light into a single polarization state that matches the microresonator 212, avoiding cross-talk that would occur if different polarization states were simultaneously resonating in the microresonator 22.
Fig. 4 shows a schematic diagram of a polarizing beam splitter provided according to an embodiment of the invention.
As shown in fig. 4, the polarization beam splitter 211 is an asymmetric directional coupling-based polarization beam splitter. The asymmetric directionally coupled polarization beam splitter is composed of three waveguides, a first waveguide 2111, a second straight waveguide 2112, and a third waveguide 2133, respectively. The first waveguide 2111 is constituted by a second straight waveguide 2111-1 and a curved waveguide 2111-2. The pump light is input from the first waveguide 2111, and the first polarized light of TM0 mode in the pump light is gradually coupled into the second waveguide 2112, converted into a higher order mode TM1 during transmission and transmitted in the second waveguide 2112 due to the phase matching condition being satisfied. When the first polarized light of the TM0 mode in the first waveguide 2111 is all converted to the TM1 mode in the second waveguide 2112, the curved waveguide portion through which the first waveguide 2111 passes is separated from the second waveguide 2112, thereby preventing the TM1 mode in the second waveguide 2112 from being re-coupled into the first waveguide 2111. Meanwhile, since the phase matching condition is satisfied, the polarized light of the TM1 mode transmitted in the second waveguide 2112 is coupled into the third waveguide 2113 and reconverted into the first polarized light of the TM0 mode. Due to the phase mismatch, the cross coupling of the second polarized light of the TE0 mode transmitted in the first waveguide 2111 is strongly restrained, and the second polarized light is kept in the first waveguide 2111 for transmission, so that the purpose of polarization beam splitting is achieved.
According to an embodiment of the present invention, the polarization beam splitter 211, the variable optical attenuator 214, the transmission waveguide 215, the wavelength division demultiplexer 213, and the micro resonator 212 are all etched on the core layer 2.
According to an embodiment of the present invention, the material of the core layer 21 comprises silicon dioxide, silicon nitride, lithium niobate, or a group III-V semiconductor compound or polymer.
According to an embodiment of the present invention, the variable optical attenuator array comprises two or more symmetrical or asymmetrical Mach-Zehnder variable optical attenuators.
According to an embodiment of the invention, the pump light source is a wavelength tunable continuous laser source, the wavelength is adjustable in the range of 1530nm to 1560nm, and the adjustment precision is 0.1pm. The optical amplifier used was an erbium-doped fiber amplifier with a maximum output power of 37dBm. The tunable laser is connected with the erbium-doped fiber amplifier by an optical fiber, the light intensity of continuous light output by the laser is amplified after passing through the erbium-doped fiber amplifier, then the light is input into the chip in an end-face coupling mode, and the optical field in the optical fiber is matched with the optical field transmitted in the waveguide by adding the mode spot converter on the chip, so that the coupling loss is reduced, wherein the material of the adopted optical waveguide chip is silicon-based silicon nitride.
Compared with the traditional multi-wavelength light source based on laser arrays with different output wavelengths, the multi-wavelength light source provided by the embodiment of the invention has the advantages that the structure is more compact and concise, the cost and the power consumption of the system are reduced, and the application field of the system is widened.
Compared with the traditional multi-wavelength light source, the on-chip multi-wavelength light source provided by the embodiment of the invention has good consistency of frequency intervals and coherence among different frequency lights; the on-chip integrated variable optical attenuator array can adjust the light intensity of each path of light, so that the output optical signal has good uniformity and can be directly used for a coherent optical communication system; the variable optical attenuator array can control the light on each path of optical signal according to the requirement, so that the quantity of the output light of the multi-wavelength light source is controllable, and the variable optical attenuator array has stronger use flexibility.
While the foregoing embodiments have been described in some detail for purposes of clarity of understanding, it will be understood that the invention is not limited to the details of construction and the embodiments described, but is capable of modification in various other respects, all without departing from the spirit and principles of the present invention.
Claims (10)
1. An on-chip multi-wavelength light source based on an optical frequency comb, comprising:
the pumping light source is suitable for emitting pumping light;
an optical waveguide chip comprising:
a substrate;
a lower cladding layer disposed on the substrate;
a core layer disposed on the lower cladding layer, the core layer comprising:
the polarizing beam splitter is formed on the lower cladding and is suitable for obtaining target linearly polarized light according to the pump light;
the micro-resonant cavity is formed on the lower cladding, and the target linearly polarized light resonates in the micro-resonant cavity, wherein under the condition that the optical power in the micro-resonant cavity reaches a preset threshold value, a four-wave mixing phenomenon is generated in the micro-resonant cavity, and an optical frequency comb is obtained, wherein the optical frequency comb comprises a plurality of lights with different wavelengths, and the lights with different wavelengths are arranged at equal intervals;
a wavelength division multiplexer formed on the lower cladding layer, the wavelength division multiplexer including a plurality of channels, light of different wavelengths from the download port of the micro resonant cavity being output through different channels;
and the upper cladding layer is arranged on the core layer.
2. The on-chip multi-wavelength light source of claim 1, wherein the core layer further comprises:
and a plurality of variable optical attenuators formed on the lower cladding, the variable optical attenuators being adapted to adjust optical powers of the light of the corresponding wavelengths outputted from the wavelength division demultiplexers in a one-to-one correspondence so that the optical powers of the adjusted light of the respective wavelengths are the same.
3. The on-chip multi-wavelength light source of claim 1, further comprising:
a beam splitter adapted to split light output from an output port of the micro-resonator into a first beam and a second beam;
the optical power meter is suitable for detecting the power of the first light beam;
and the spectrometer is suitable for detecting the wavelength of the second light beam.
4. The on-chip multi-wavelength light source of claim 1, further comprising,
the optical amplifier is suitable for amplifying the power of the pump light emitted by the pump light source and inputting the pump light with amplified power to the polarization beam splitter.
5. The on-chip multi-wavelength light source of claim 1, further comprising,
and the heating module is suitable for heating the micro-resonant cavity so as to keep the frequency of the optical frequency comb output by the micro-resonant cavity stable.
6. The on-chip multi-wavelength light source of claim 1, wherein the polarizing beam splitter comprises a multimode interferometer, a mach-zehnder interferometer, a directional coupler type polarizing beam splitter.
7. The on-chip multi-wavelength light source of claim 1, wherein the directionally coupled polarizing beam splitter comprises a first waveguide, a second waveguide, and a third waveguide;
the pump light is input from a first waveguide, in the transmission process, first linearly polarized light in the pump light is coupled into a second waveguide from the first waveguide, mode conversion occurs in the second waveguide, the mode-converted first linearly polarized light is coupled into a third waveguide, mode conversion occurs, the first linearly polarized light is obtained, second linearly polarized light in the pump light is transmitted in the first waveguide, and the polarization direction of the first linearly polarized light is perpendicular to the polarization direction of the second linearly polarized light;
the target linearly polarized light is first linearly polarized light or second linearly polarized light.
8. The on-chip multi-wavelength light source of claim 1, wherein the core layer further comprises a transmission waveguide between the polarizing beam splitter and the micro-resonant cavity, between the micro-resonant cavity and the wavelength-splitting multiplexer, between the wavelength-splitting multiplexer and the variable optical attenuator array, through the transmission waveguide.
9. The on-chip multi-wavelength light source of claim 1, wherein the material of the core layer comprises silicon dioxide, silicon nitride, lithium niobate, or a group III-V semiconductor compound or polymer.
10. The on-chip multi-wavelength light source of claim 1, wherein the variable optical attenuator array comprises two or more symmetrical or asymmetrical mach-zehnder variable optical attenuators.
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