CN116125686A - Optical and electric double-resonance enhanced electro-optical comb generator - Google Patents
Optical and electric double-resonance enhanced electro-optical comb generator Download PDFInfo
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- CN116125686A CN116125686A CN202310139869.3A CN202310139869A CN116125686A CN 116125686 A CN116125686 A CN 116125686A CN 202310139869 A CN202310139869 A CN 202310139869A CN 116125686 A CN116125686 A CN 116125686A
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- 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
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Abstract
The invention discloses an optical and electric double-resonance enhanced electro-optical comb generator, which is applied to the technical field of electro-optical modulation and comprises the following components: an optical resonance enhanced electro-optic comb generator and an electrical modulation structure; the light in the optical resonance enhanced electro-optic comb generator passes through the electrical modulation structure, and an equidistant electro-optic comb is generated due to electro-optic modulation; the electrical modulation structure introduces a short-circuit electrode at the incident end and the emergent end of the traveling wave electrode, the discontinuity of the incident end short-circuit electrode and the reflecting end short-circuit electrode provides specific reflectivity to form an electrical resonant cavity, and electrical resonance enhancement is realized; wherein the characteristic frequency of the electric resonant cavity is equal to the free spectral range of the optical resonant cavity of the optical resonance enhanced electro-optic comb generator. The optical and electric double-resonance enhanced electro-optical frequency comb generator provided by the invention has the advantages of optical and electric double-resonance enhancement, large modulation depth, high comb tooth power, large spectrum bandwidth, flat spectrum and the like.
Description
Technical Field
The invention relates to the technical field of electro-optic modulation, in particular to an optical and electric double-resonance enhanced electro-optic comb generator.
Background
Optical frequency combs are used in a wide range of applications, from precision metrology and clocking to spectroscopy and optical communications. In optical communications, frequency combs are required to have an adjustable comb tooth spacing (free spectral range: FSR), a flat and broad-band spectrum. FSRs of optical frequency combs and microcavity optical frequency combs based on mode-locked lasers are related to structural parameters of the optical frequency combs, and complex control techniques are required to obtain soliton combs with stable amplitude and phase. The electro-optical frequency comb has the advantages of flexible adjustment of comb tooth spacing, high comb tooth power, flat frequency spectrum and the like.
In a conventional electro-optic frequency comb, an intensity modulator and a phase modulator are cascaded to realize the electro-optic comb, and a continuous wave signal is modulated by one or more radio frequency signals loaded on the electro-optic modulator to generate a plurality of sidebands. The comb spacing may be adjusted by controlling the frequency of the radio frequency signal, while the number of comb lines may be adjusted by the number of modulators used and the corresponding driving conditions. By selecting the appropriate modulator, the radio frequency signal and bias voltage are finely controlled, a flat spectrum with high signal-to-noise ratio can be obtained, but the system is complex and is not beneficial to integration. Thus, there has been proposed a resonance enhanced electro-optic frequency comb (T.Kobayashi, T.Sueta, Y.Cho, andY.Matsuo, "High-repetition-rate optical pulse modulator," appl. Phys. Lett.,1972, 21 (8): 341-343), in which an optical resonator is introduced in phase modulation, light can be modulated by passing through the modulator a plurality of times before being coupled out of the resonator, and when the modulation frequency is equal to the FSR of the resonator, an optical sideband generated by the phase modulator is enhanced by resonating in the cavity, and a plurality of generated comb lines are spread at intervals of the modulation frequency. Because of the existence of the optical resonant cavity, the intensity of electro-optic interaction is enhanced, the consumption of electrical frequency is reduced, and high-efficiency modulation can be realized. However, early electro-optic frequency combs with resonance enhancement were implemented in bulky high-loss free-space resonators, and were therefore very sensitive to fluctuations in the input optical frequency and modulation frequency, and the modulation of the light was weak, with practical comb widths being limited to around tens of nanometers. These have made the search for low-loss, miniaturized integrated resonance enhanced electro-optic frequency combs urgent. Therefore, an electro-optical comb (Nature, 2019, 568:378-381) combining a micro-ring resonator and an electro-optical phase modulator has been proposed, which effectively widens the frequency spectrum range and meets the requirements of miniaturization and easy integration of devices, but the dependence of the frequency spectrum width on the manufacturing process of the optical resonator is extremely high, and the manufacturing difficulty of the electro-optical comb is increased and is difficult to control because lithium niobate materials are difficult to etch. The transmission loss of microwaves affects the electro-optic modulation, thereby affecting the bandwidth and flatness of the electro-optic comb, so that the modulation depth of the structure can be increased by reducing the transmission loss of microwaves. Thus, the present-day electro-optic comb generators need to improve both optical and electrical performance, improve electrical modulation depth and resonant enhancement of intracavity light, reduce transmission loss of microwaves and light, and realize flat and broadband electro-optic combs.
Disclosure of Invention
In view of this, the present invention provides an optical and electrical dual resonance enhanced electro-optical comb generator, which reduces the transmission loss of microwave modulation signals and improves the modulation depth of the electro-optical comb structure.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
an optical and electrical dual resonance enhanced electro-optic comb generator comprising:
an optical resonance enhanced electro-optic comb generator and an electrical modulation structure; the optical comb generated by the optical resonance enhanced electro-optic comb generator is modulated in the electrical modulation area;
the electrical modulation structure introduces a short-circuit electrode at the incident end and the emergent end of the traveling wave electrode, the discontinuity of the incident end short-circuit electrode and the reflecting end short-circuit electrode provides specific reflectivity to form an electrical resonant cavity, and electrical resonance enhancement is realized;
wherein the characteristic frequency of the electric resonant cavity is equal to the free spectral range of the optical resonant cavity of the optical resonance enhanced electro-optic comb generator.
Through the technical scheme, the invention has the technical effects that: the microwave reflection surface is formed by adopting the short-circuit electrode structure, so that the standing wave electrode structure of the microwave FP cavity is formed, and the resonance enhancement of the microwave is realized, thereby enhancing the modulation effect of light.
Preferably, in the above-mentioned optical and electrical double-resonance enhanced electro-optical comb generator, the optical resonance enhanced electro-optical comb generator includes an optical resonant cavity and a coupling waveguide; pump light is coupled into the optical resonant cavity through the coupling waveguide; the pump light is modulated in the optical resonant cavity, equidistant optical combs taking the pump light as a center and the frequency of the modulated signals as intervals are generated in the optical resonant cavity, and the equidistant optical combs meet the resonance enhancement condition of the optical resonant cavity and are coupled into the coupling waveguide from the optical resonant cavity.
Preferably, in the optical and electrical dual resonance enhanced electro-optical comb generator, the optical resonant cavity includes an electro-optical modulation region and a non-electro-optical modulation region;
wherein the non-electro-optical modulation area adopts SiO 2 The layer is used as a buffer cover layer to separate the optical waveguide of the non-electro-optical modulation area from the upper metal electrode, reduce microwave loss and protect the optical waveguide; on the other hand, since the dielectric constant of the microwave in the optical waveguide is much larger than that of the optical waveguide, the electrode and the optical waveguide pass through SiO in the non-modulation area to realize the speed matching of the microwave and the optical waveguide 2 Isolated by microwaves at SiO with low relative dielectric constant 2 The propagation portion of the distribution to reduce the effective refractive index of the microwaves.
The metal electrode is in the same plane with the optical waveguide in the electro-optical modulation area and has a certain interval.
Preferably, in the optical and electrical dual-resonance enhanced electro-optical comb generator, the electrical modulation structure includes an electrical resonant cavity, a signal electrode, a ground electrode, an incident end hollowed-out portion, and a reflective end hollowed-out portion, the electrical resonant cavity includes an incident end shorting electrode and a reflective end shorting electrode, the incident end hollowed-out portion isolates the incident end shorting electrode from the ground electrode, and the reflective end hollowed-out portion isolates the reflective end shorting electrode from the ground electrode; the incident end short-circuit electrode and the reflecting end short-circuit electrode are connected with the signal electrode and the grounding electrode.
Preferably, in the optical and electrical dual resonance enhanced electro-optical comb generator, thicknesses of the signal electrode, the ground electrode, the incident end short-circuit electrode, and the reflective end short-circuit electrode are all the same.
Preferably, in the optical and electrical dual resonance enhanced electro-optical comb generator, the modulation depth and the optical comb spectral width are adjusted according to the distance between the signal electrode and the ground electrode and the specification of the signal electrode.
Preferably, in the optical and electrical dual resonance enhanced electro-optical comb generator, an electric field is applied through the electric resonant cavity to enable materials of the optical resonant cavity to generate electro-optical effect, and refractive index of light in the optical resonant cavity is changed to generate optical combs with modulation frequency as intervals.
Preferably, in the optical and electrical dual resonance enhanced electro-optical comb generator, the optical resonant cavity is an annular traveling wave cavity or an whispering gallery cavity.
Preferably, in the optical and electrical dual resonance enhanced electro-optical comb generator, the pump light is coupled from the coupling waveguide into the optical resonant cavity in an evanescent coupling mode.
Preferably, in the optical and electrical dual resonance enhanced electro-optical comb generator, the electric field reflection coefficient of the standing wave electrode is adjusted by adjusting the lengths and widths of the incident end short-circuit electrode, the reflection end short-circuit electrode, the incident end hollowed-out portion and the reflection end hollowed-out portion.
Compared with the prior art, the invention discloses an optical and electrical double-resonance enhanced electro-optical comb generator, which adopts a short-circuit electrode structure to form a microwave reflection surface to form a microwave FP cavity type standing wave electrode structure, thereby enhancing the resonance of microwaves and further enhancing the modulation effect of light. By designing the width and etching depth of the micro-ring resonant cavity, the electrode spacing of the standing wave electrode, the width and thickness of the signal electrode, the lengths of the incident end short circuit electrode and the reflecting end short circuit electrode of the standing wave electrode, the length and width of the hollowed-out part, the thickness and other parameters of the buffer layer SiO2, the optical loss and the microwave loss are lower, the effective refractive index of the microwaves is matched with the group velocity of the light waves, the electric field reflection coefficient and the modulation depth of the standing wave electrode are as large as possible, and therefore the spectrum bandwidth of the electro-optic comb is effectively widened.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present invention, and that other drawings can be obtained according to the provided drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of an optical and electrical dual resonance enhanced electro-optic comb generator according to the present invention.
FIG. 2 is a schematic diagram of an optical resonance enhanced electro-optic comb generator for comparison in accordance with an embodiment of the present invention.
FIG. 3 is a schematic cross-sectional view of the effective modulation area of an optical and electrical dual resonance enhanced electro-optic comb generator in accordance with an embodiment of the present invention.
FIG. 4 shows S of an electrical resonator in accordance with an embodiment of the invention 11 Test results of amplitude as a function of microwave frequency.
FIG. 5 shows S of an electrical resonator in accordance with an embodiment of the invention 11 And testing the phase change along with the microwave frequency.
Fig. 6 is a graph showing the results of a test of the modulation enhancement factor B of an electric resonator according to the variation of microwave frequency in example one of the present invention.
FIG. 7 is a simulation result of an electro-optical comb generator with enhanced optical resonance to generate an electro-optical frequency comb in accordance with an embodiment of the present invention.
FIG. 8 is a graph showing the test results of an electro-optic comb generated by an optical resonance enhanced electro-optic comb generator in accordance with one embodiment of the present invention.
FIG. 9 is a simulation result of an electro-optical frequency comb generated by an optical and electrical dual resonance enhanced electro-optical comb generator in accordance with an embodiment of the present invention.
FIG. 10 shows the test results of an electro-optical comb generated by an optical and electrical dual resonance enhanced electro-optical comb generator in accordance with one embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The embodiment of the invention discloses an optical and electrical double-resonance enhanced electro-optical comb generator, which adopts a short-circuit electrode structure to form a microwave reflecting surface to form a microwave FP cavity type standing wave electrode structure, thereby enhancing the resonance of microwaves and further enhancing the modulation effect of light. Through designing the width and the etching depth of micro-ring resonant cavity, the width of signal electrode, the thickness of electrode, the length of the incident end short-circuit electrode and the reflecting end short-circuit electrode of standing wave electrode, the width, the distance and the length and the width of the hollowed-out part, the thickness and other parameters of buffer layer SiO2 make optical loss and microwave loss lower, the effective refractive index of microwave matches with the group velocity of light wave, the reflection coefficient and the modulation depth of standing wave electrode electric field are as large as possible, thereby effectively widening the spectrum bandwidth of the electro-optic comb.
As shown in FIG. 1, the structure of the optical and electrical dual resonance enhancement type electro-optical comb generator is schematically shown, on the basis of only optical resonance enhancement, a short-circuit electrode is introduced into the incident end and the emergent end of a row wave electrode, the discontinuity of the electrode incident end and the emergent end electrode provides specific reflectivity, and a reflecting surface of an FP cavity is formed, namely the electro-resonance cavity. The microwave with specific frequency is resonated and enhanced in the electric resonant cavity, the structural size of the electric resonant cavity is designed to ensure that the modulation frequency of the electro-optical comb meets the resonance enhancing condition of the electric resonant cavity, the externally applied modulation electric field is enhanced, the modulation depth of the modulator and the power corresponding to the frequency of the teeth of the electro-optical comb are increased, and the spectrum bandwidth of the electro-optical comb is widened. The FP electric resonant cavity electrode is applied to a micro-ring cavity to realize an optical and electric double-resonance enhanced electro-optic frequency comb generator, and resonance enhancement is realized in optical and electric dimensions, so that a wider-band electro-optic frequency comb is obtained.
Fig. 1 is a schematic diagram of an optical and electrical dual-resonance enhanced electro-optical comb generator, which comprises a grounding electrode 1, a modulation area upper arm waveguide 2 of an optical resonant cavity, a signal electrode 3, a first incident end hollowed-out part 4, a second incident end hollowed-out part 5, a first grounding electrode pad6, a signal electrode pad7, a second grounding electrode pad8, an incident end short-circuit electrode 9, a modulation area lower arm waveguide 10 of the optical resonant cavity, a short-circuit electrode 11 of a reflecting end, a slab waveguide 12 and a reflecting end hollowed-out part 13.
FIG. 2 is a schematic diagram of an optical resonance enhanced type electro-optical comb generator for comparison in the present invention, which is a conventional electro-optical comb generator with a traveling wave electrode structure. Compared to fig. 1, both have optical resonators, except that the optical resonance enhanced electro-optical comb generator of fig. 2 does not introduce a shorting electrode, and thus does not achieve electrical resonance enhancement, only optical resonance enhancement.
FIG. 3 is a schematic cross-sectional view of an effective modulation region of an optical and electrical dual resonance enhanced electro-optic comb generator based on Lithium Niobate (LN) material, 14 being SiO, in an application example 2 The upper cover layer, 1 is a grounding electrode, 12 is a slab waveguide made of lithium niobate material, 15 is SiO 2 The substrate 16 is a Si substrate, 2 is a modulation area upper arm waveguide of the lithium niobate optical resonant cavity, 3 is a signal electrode, and 10 is a modulation area lower arm waveguide of the lithium niobate optical resonant cavity.
In this embodiment, pump light is coupled into the optical cavity through the coupling waveguide, the pump light is modulated by an electrical signal in the electrical resonant cavity in the optical cavity, equidistant optical combs with the pump light as a center and the modulated signal frequency as intervals are generated in the optical cavity, and the optical combs meet the resonance enhancement condition of the optical cavity and are coupled into the coupling waveguide from the optical cavity.
In this embodiment, the electrical resonant cavity structure is a short-circuit electrode of the incident end and a short-circuit electrode of the reflecting end are respectively introduced into the incident end and the emergent end of the row wave electrode, and the discontinuity of the electrodes is introduced, and the impedance of the short-circuit electrode of the incident end and the impedance of the short-circuit electrode of the reflecting end are not matched, so as to form a reflecting surface of the microwave FP cavity, and realize electrical resonance enhancement.
In this embodiment, the incident end short-circuit electrode and the reflection end short-circuit electrode both connect the signal electrode and the ground electrode, so as to realize short-circuit.
In this embodiment, the electrode around the short-circuit electrode is hollowed out, so as to reduce the reflectivity of the incident end of the electrode modulation structure.
In this embodiment, the optical resonant cavity is a ring traveling wave cavity or whispering gallery cavity.
In this embodiment, the optical comb generated in the optical cavity is coupled from the optical cavity to the coupling waveguide in an evanescent coupling manner.
In this embodiment, the pump light is coupled from the coupling waveguide into the optical cavity in an evanescent coupling.
In this embodiment, the pump light enters the optical cavity from the coupling waveguide, and the optical comb generated in the optical cavity is output from the same coupling waveguide.
In this embodiment, the optical resonator is made of a material having an electro-optical effect, and an electric field is applied through the optical resonator to make the material of the optical resonator generate the electro-optical effect, so as to change the refractive index of light in the optical resonator and generate an optical comb with a modulation frequency as an interval.
In this embodiment, the characteristic frequency of the electrical resonator is equal to the FSR of the optical resonator.
In this embodiment, in order to achieve non-contact between the optical waveguide of the non-modulation region and the metal electrode, microwave loss is reduced, and at the same time, the optical waveguide is protected by using SiO 2 A buffer layer separating the optical waveguide of the non-modulated region from the metal electrode, a buffer layer SiO 2 The thickness influences the microwave refractive index.
In the present embodiment, the distance G between the signal electrode and the ground electrode s Can influence the absorption loss of metal, the electric field loss of microwave and V π L, where V π Is half-wave voltage, L is the length of the modulation device, thereby affecting the optical sumModulation depth and optical comb spectrum width of the electric double-resonance enhanced type electro-optical comb generator.
In the present embodiment, the thickness H of the signal electrode s And signal electrode width W s Affecting the electric field loss of the microwaves.
In this embodiment, the thicknesses of the signal electrode, the ground electrode, the incident end short-circuit electrode, and the reflective end short-circuit electrode are all the same.
In the present embodiment, the lengths and widths of the incident-side shorting electrode and the reflective-side shorting electrode affect the electric field reflectance r 1 。
In the present embodiment, the length of the hollowed-out portion affects the electric field reflection coefficient r1.
In this embodiment, the widths of the incident-side shorting electrode and the reflective-side shorting electrode need to be continuously optimized so that the characteristic frequency of the electrical resonator is equal to the FSR of the optical resonator.
The optical resonators in fig. 1 and 2 are identical, with only the electrode structure being different. The optical resonator in the example is composed of dumbbell-shaped racetrack waveguides, the annular ring and the straight waveguide are connected by sin-shaped waveguides with gradual curvature, the FSR of the optical resonator is 20.42GHz, the coupling waveguide and the optical resonator are in point coupling, the core layer waveguide is ridge waveguide, the thickness is 0.6 μm, the etching depth is 0.3 μm, the width is 1.4 μm, and the waveguide substrate and the cover layer are SiO 2 The incident wavelength is 1550nm. An x-cut Lithium Niobate (LN) wafer is selected, and TE polarization of the waveguide is excited by an upper arm and a lower wall waveguide of a modulation region of the optical resonant cavity along the y direction of the LN. The direction of the electric field applied by the electrodes is along the z direction of LN, and the incident end short-circuits the width L of the electrode ref Is 5 μm. The width of the signal electrode is 15.8 μm, the electrode spacing is 7.2 μm, the electrode thickness is 0.84 μm, and the buffer layer is SiO 2 The thickness of (2) was 0.8. Mu.m.
Continuous light is transmitted from the coupling waveguide to the coupling region, part of the light is coupled into the optical resonant cavity, passes through the right circular ring part, the lower arm waveguide 10 of the modulation region, the left circular ring part and the upper arm waveguide 2 of the modulation region respectively, the power of the optical frequency meeting the condition of enhancing the resonance in the cavity is enhanced, the light component enhanced in the resonance in the cavity is partially coupled into the output waveguide in the coupling region, and part of the light component is modulated again by continuing to pass through the modulation region of the optical resonant cavity. The microwave modulation signal is loaded on the signal electrode 3 and the grounding electrode 1 through the first grounding electrode pad6, the signal electrode pad7 and the second grounding electrode pad8, and light in the upper arm 2 of a modulation area in the optical resonant cavity and the lower arm 10 of the modulation area in the optical resonant cavity is modulated. Light in the optical resonant cavity is coupled into the output waveguide again, and is output as equidistant electro-optical modulation comb teeth.
The metal electrode is in the same plane with the optical waveguide in the electro-optical modulation area and has a certain interval. Since the dielectric constant of the microwave in the optical waveguide is much larger than that of the light wave, in order to realize the speed matching of the microwave and the light wave, the electrode and the optical waveguide pass through SiO in the non-modulation area 2 Isolated by microwaves at SiO with low relative dielectric constant 2 The propagation portion of the distribution to reduce the effective refractive index of the microwaves.
To more intuitively demonstrate the advantages of the optical and electrical dual resonance enhanced electro-optic comb generators of the present invention, examples also make an optical resonance enhanced electro-optic comb generator as a reference, which does not contain an electrical resonator. As shown in fig. 2, the optical resonance enhanced electro-optical comb generator adopts traveling wave electrodes, which include a first input ground electrode pad17, a second ground electrode 18, a second signal electrode 19, a first output ground electrode pad20, a first output signal electrode pad21, an optical resonant cavity 22, a second output ground electrode pad23, a third ground electrode 24, a second input ground electrode pad25, a second slab waveguide 26, and a first input signal electrode pad27.
It is to be understood that: in an electro-optical modulation device, the electrode structure affects the applied intensity of the modulation electric field, which is an important factor in determining the modulation depth β. In order to integrate the modulation structure with the waveguide microcavity, the invention preferably selects an electrode structure of a coplanar waveguide type. The Signal electrode (S) and the Ground electrode (G) of the electro-optical comb modulated by the microstrip line GSG electrode structure are on the same plane, and the electro-optical comb is easy to integrate. When the loads of the input port and the output port are matched, the structure of the classical microstrip line GSG traveling wave electrode is obtained, and a schematic diagram is shown in figure 2; when the loads of the input port and the output port are not matched, the electrode provides certain microwave reflection, so that an electric resonant cavity is formed, coherent phase correlation of a microwave modulation electric field is realized, and the electrode is defined as a GSG standing wave electrode, and the schematic diagram is shown in figure 1.
In the row-wave electrode, the phase shift is modulated
Satisfies the following formula
Where a is the transmission loss of the microwave and the effective modulation region length is L. Generally aL is small, so the above formula can also be approximated as:
in the standing wave electrode, the initial phase of the modulation signal is ignored and aL is smaller, the modulation phase shift
The following formula can be approximated:
wherein the microwave transmittance of the incident end electrode is t 1 Reflectivity r 1 The transmittance and reflectance of the reflective end are t respectively 2 And r 2 。
It can be seen that the standing wave electrode promotes the overall modulation depth beta, and B is the modulation enhancement factor of the standing wave electrode relative to the traveling wave electrode.
Firstly, measuring S parameters and S of an FP cavity type electric resonant cavity electrode 11 Is the reverse of the incident port of the electrodeThe radio coefficient, S due to the resonance effect of the FP cavity 11 The amplitude measurement curve of (a) is Lorentz curve, S as shown in FIG. 4 11 The phase results of the parameters are shown in FIG. 5, in which abrupt changes occur near the resonant frequency, and the resonant frequency of the FP-cavity type electric resonant cavity electrode is 20.76GHz. The variation of the enhancement factor B of the modulation depth with the modulation frequency is shown in fig. 6, and the value of B at the electrode resonance frequency is 2.34, which proves that the modulation depth of the FP cavity type electric resonator electrode is 2.34 times that of the traveling wave electrode.
The optical parameters of the electro-optical comb were then measured as: the micro-cavity FSR=20.42 GHz, the power coupling coefficient k= 0.1751, the power attenuation constant a= 0.5822, the pumping power is 0.16mW in actual test, the peak voltage of an additional modulation signal is 2V, the modulation depth of the electrode structure calculated through simulation is 0.11 pi, the comb teeth generation result of the optical resonance enhanced electro-optic comb generator can be simulated first, as shown in fig. 7, the calculation shows that the optical resonance enhanced electro-optic comb generator is expected to generate 6 pairs of sidebands, and the attenuation slope of a modulation comb line from the center to two sides can be calculated to be 54dB/nm.
The actual test results of the frequency comb of the optical resonance enhanced electro-optic comb generator are shown in FIG. 8, when the frequency f is modulated m F at 20.3 to 20.5GHz m The modulation comb line generated at the moment is most 5 pairs and the attenuation slope of the comb line is 55dB/nm, which is consistent with the simulation result. As can be seen from FIG. 8, the maximum bandwidth of the electro-optic comb generator with enhanced optical resonance is 1.64nm.
By using the basic simulation parameters of the traveling wave electrode, only the enhancement of the modulation depth by the electric resonant cavity structure is considered, and the electro-optic frequency comb generation result of the electro-optic comb generator with optical and electric double resonance enhancement can be simulated, as shown in fig. 9, compared with the electro-optic comb generator with optical resonance enhancement, the electro-optic comb generator with optical resonance enhancement has the advantages that the number of the modulated comb lines is increased to 13 pairs, and the attenuation slope of the modulated comb lines from the center to two sides is 24.1dB/nm.
The practical test result of the electro-optical frequency comb of the electro-optical comb generator with enhanced optical and electrical double resonance is shown in FIG. 10, when the modulation frequency f m At 20.4 and 20.6GHzThe frequency spectrums of the micro-ring FSR and the FP cavity are the widest and 2.79nm respectively, 9 pairs of modulation sideband lines are generated, the attenuation slope of the sideband comb teeth is obviously reduced to 35.7dB/nm, and the simulation result is similar.
The results in the examples fully show the improvement of the modulation depth by the electric resonant cavity structure, and prove the advantages of the optical and electric double-resonance enhanced electro-optical comb generator that resonance enhancement is carried out simultaneously in the aspects of optics and electricity, the modulation intensity of microwaves is improved, the transmission loss of the microwaves is reduced, the comb tooth power of the electro-optical comb is directly and indirectly improved, the spectrum bandwidth of the electro-optical frequency comb is effectively widened, and the like.
In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant points refer to the description of the method section.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. An optical and electrical dual resonance enhanced electro-optic comb generator comprising:
an optical resonance enhanced electro-optic comb generator and an electrical modulation structure; the light in the optical resonance enhanced electro-optic comb generator passes through the electrical modulation structure, and an equidistant electro-optic comb is generated due to electro-optic modulation;
the electrical modulation structure introduces a short-circuit electrode at the incident end and the emergent end of the traveling wave electrode, the discontinuity of the incident end short-circuit electrode and the reflecting end short-circuit electrode provides specific reflectivity, an electrical resonant cavity is formed, and electrical resonance enhancement is realized;
wherein the characteristic frequency of the electric resonant cavity is equal to the free spectral range of the optical resonant cavity of the optical resonance enhanced electro-optic comb generator.
2. An optical and electrical dual resonance enhanced electro-optic comb generator as claimed in claim 1, wherein the optical resonance enhanced electro-optic comb generator comprises an optical resonant cavity and a coupling waveguide; the coupling waveguide couples pump light into the optical cavity; the pump light is modulated in the optical resonant cavity, equidistant optical combs taking the pump light as a center and the modulation signal frequency as an interval are generated in the optical resonant cavity, the equidistant optical combs meet the resonance enhancement condition of the optical resonant cavity, and the equidistant optical combs are coupled into the coupling waveguide from the optical resonant cavity to realize the output of the equidistant optical combs.
3. An optical and electrical dual resonance enhanced electro-optic comb generator as claimed in claim 2, wherein the optical cavity comprises an electro-optic modulation region and a non-electro-optic modulation region;
wherein the non-electro-optical modulation area adopts SiO 2 A layer as a buffer cap layer separating the optical waveguide of the non-electro-optic modulation region from the metal electrode above the crossover waveguide; the metal electrode is in the same plane with the optical waveguide in the electro-optical modulation area and has a certain interval.
4. The electro-optical comb generator of claim 1, wherein the electrical modulation structure comprises an electrical resonant cavity, a signal electrode, a ground electrode, an incident end hollowed-out portion, and a reflective end hollowed-out portion, the electrical resonant cavity comprising an incident end shorting electrode, a reflective end shorting electrode, the incident end hollowed-out portion separating the incident end shorting electrode from the ground electrode, the reflective end hollowed-out portion separating the reflective end shorting electrode from the ground electrode; the incident end short-circuit electrode and the reflecting end short-circuit electrode are connected with the signal electrode and the grounding electrode.
5. The electro-optical comb generator of claim 4, wherein said signal electrode, said ground electrode, said incident side shorting electrode, and said reflective side shorting electrode are all the same thickness.
6. An optical and electrical dual resonance enhanced electro-optic comb generator as claimed in claim 4 or 5, wherein the modulation depth and the optical comb spectral width are adjusted in accordance with the spacing of the signal electrode and the ground electrode and the structural parameters of the signal electrode.
7. An optical and electrical dual resonance enhanced electro-optic comb generator as set forth in claim 4 wherein application of an electric field through said electrical resonator causes the electro-optic effect of the material of said optical resonator to change the refractive index of light in said optical resonator to produce optical combs at modulation frequency intervals.
8. An optical and electrical dual resonance enhanced electro-optic comb generator as claimed in claim 2 or claim 3 wherein the optical cavity is a ring traveling wave cavity or whispering gallery cavity.
9. An optical and electrical dual resonance enhanced electro-optic comb generator as claimed in claim 8 wherein pump light is coupled from the coupling waveguide into the optical cavity in the form of evanescent coupling.
10. The electro-optic comb generator of claim 4 wherein the electric field reflectance of the electrodes is adjusted by adjusting the length and width of the incident end shorting electrode, the reflective end shorting electrode, the incident end hollowed out portion, and the reflective end hollowed out portion.
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| CN202310139869.3A CN116125686A (en) | 2023-02-21 | 2023-02-21 | Optical and electric double-resonance enhanced electro-optical comb generator |
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| CN202310139869.3A CN116125686A (en) | 2023-02-21 | 2023-02-21 | Optical and electric double-resonance enhanced electro-optical comb generator |
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