CN116594204A - Optical frequency comb generating device and method based on thin film lithium niobate - Google Patents
Optical frequency comb generating device and method based on thin film lithium niobate Download PDFInfo
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- 230000003287 optical effect Effects 0.000 title claims abstract description 160
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 title claims abstract description 84
- 238000000034 method Methods 0.000 title claims abstract description 18
- 239000010409 thin film Substances 0.000 title claims description 37
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- 238000005086 pumping Methods 0.000 claims abstract description 35
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- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 claims description 4
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- 229910002601 GaN Inorganic materials 0.000 description 4
- 229910005540 GaP Inorganic materials 0.000 description 4
- 229910001218 Gallium arsenide Inorganic materials 0.000 description 4
- GPXJNWSHGFTCBW-UHFFFAOYSA-N Indium phosphide Chemical compound [In]#P GPXJNWSHGFTCBW-UHFFFAOYSA-N 0.000 description 4
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- JMASRVWKEDWRBT-UHFFFAOYSA-N Gallium nitride Chemical compound [Ga]#N JMASRVWKEDWRBT-UHFFFAOYSA-N 0.000 description 2
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- HZXMRANICFIONG-UHFFFAOYSA-N gallium phosphide Chemical compound [Ga]#P HZXMRANICFIONG-UHFFFAOYSA-N 0.000 description 2
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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
- G02F1/01—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
- G02F1/03—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 ceramics or electro-optical crystals, e.g. exhibiting Pockels effect or Kerr effect
- G02F1/035—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 ceramics or electro-optical crystals, e.g. exhibiting Pockels effect or Kerr effect in an optical waveguide structure
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Abstract
The invention provides an optical frequency comb generating device and method based on film lithium niobate, which belongs to the technical field of optical frequency combs, and comprises a pumping unit for providing single-frequency/multi-frequency laser; the microwave modulation unit is used for carrying out electro-optic modulation on the normal dispersion double micro-ring resonant cavity unit to generate modulation sidebands; the normal dispersion double micro-ring resonant cavity unit generates an optical frequency comb by utilizing normal dispersion, an electro-optic effect and a third-order nonlinear effect. According to the invention, single-frequency/multi-frequency laser is coupled to a normal dispersion double micro-ring resonant cavity unit based on film lithium niobate, and the spectrum widening and spectrum envelope flattening of the optical frequency comb are realized through the combined action of normal dispersion, an electro-optic effect and a third-order nonlinear effect.
Description
Technical Field
The invention relates to the technical field of optical frequency combs, in particular to an optical frequency comb generating device and method based on film lithium niobate.
Background
The optical frequency comb has important application in the fields of wavelength division multiplexing passive optical network, ultra-large capacity high-speed coherent optical communication, optical signal processing, laser radar, microwave photonics and the like. The current methods for generating optical frequency combs can be roughly divided into a mode-locked laser generating optical frequency combs, an electro-optical modulation generating optical frequency combs, a pulse pumping cavity-free optical waveguide generating optical frequency combs based on super-continuous spectrum broadening and a Kerr micro-ring resonant cavity generating optical frequency combs.
Mian Zhang proposed the use of electro-optic effect in lithium niobate micro-ring resonators to create optical frequency combs (Mian Zhang, et al, broadband electro-optic frequency comb generation in a lithium niobate microring resonator [ J ]. Nature, 2019), which achieve electro-optically modulated optical frequency combs with a spectral span that exceeds the entire L-band, but such single-cavity structures, where most of the light is transmitted through a common straight waveguide without coupling into the resonator, have optical frequency comb energy conversion efficiencies limited to only 0.3%, and have triangular optical frequency comb spectral envelopes. The Yaowen Hu proposes to improve the pump conversion efficiency of the integrated electro-optic modulation frequency comb by 100 times by using two coupled micro-ring resonators (Yaowen Hu, et al high-efficiency and broadband electro-optic frequency combs enabled by coupled micro-relators [ J ]. Nature Photonics, 2022), but the generated spectral envelope of the optical frequency comb is still triangular due to the near-zero dispersion, and the envelope flatness is still not ideal. Many practical application-oriented scenes have certain requirements on the flatness of the spectral envelope of the optical frequency comb, so that the improvement of the flatness of the spectral envelope of the optical frequency comb is an urgent problem to be solved.
When generating an electro-optical modulation optical frequency comb based on a thin film lithium niobate micro-ring resonator by utilizing an electro-optical effect, an electro-optical phase modulator is realized on a straight waveguide of a runway type microcavity. However, the thin film lithium niobate optical waveguide is a multimode optical waveguide, and the common circular bending can cause the problems of complex cross coupling between modes and high-order mode excitation in the multimode microcavity, so that the loss of a fundamental mode is increased and the Q value of the microcavity is reduced.
The optical frequency comb can be generated by utilizing the third-order Kerr nonlinear effect in the normal dispersion or anomalous dispersion micro-ring resonant cavity. The generation of optical frequency combs in the normal dispersion region is of great interest because of their higher pump conversion efficiency, but the normal dispersion region has no modulation instability effect similar to the anomalous dispersion region, requiring mode cross coupling to provide local anomalous dispersion to generate four-wave mixed sidebands or multi-frequency sideband pump assisted start-up. In the normal dispersion region, various implementations have been made for generating an optical frequency comb by single-frequency laser pumping, xue Xiaoxiao and the like, in which a single microcavity is pumped by single-frequency laser to generate an optical frequency comb by forming four-wave mixing sidebands by locally introducing anomalous dispersion based on the cross coupling of a fundamental mode and a high-order mode (Xiaoxiao Xue, et al mode-locked dark pulse Kerr combs in normal-dispersion microresonators [ J ]. Nature Photonics, 2015); elham Nazemosadat and the like generate optical frequency combs (Elham Nazemosadat, et al switching dynamics of dark-pulse Kerr frequency comb states in optical microresonators [ J ]. Phys.Rev.A, 2021) using mode splitting to form sidebands by cross-coupling of the fundamental mode and the higher-order mode; warren Jin et al use light propagating forward and reverse in the micro-ring to generate mode splitting to form sidebands to produce an optical frequency comb (Warren Jin et al Hertzlinewidth semiconductor lasers using CMOS-ready ultra high Q microresonators [ J ]. Nature Photonics, 2021). The method has the advantages that local anomalous dispersion is generated by using the cross coupling of the fundamental mode and the high-order mode to form sidebands, so that single-frequency laser generates optical frequency combs in a normal dispersion area, but the method has a serious disadvantage that the position where mode splitting or mode cross coupling occurs is not easy to control, and complicated regulation and control are needed. In addition, input dual-frequency laser or high repetition rate pulsed laser pumping can be utilized, but high repetition rate pulsed light sources often require cascaded electro-optic modulators and pulse compression units, which are bulky and complex to control.
Disclosure of Invention
The invention aims to provide an optical frequency comb generating device and method based on film lithium niobate, which are used for solving at least one technical problem in the background technology.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
in one aspect, the invention provides an optical frequency comb generating device based on film lithium niobate, which comprises a pumping unit, a microwave modulating unit and a normal dispersion double micro-ring resonant cavity unit, wherein:
the pumping unit is used for providing laser pumping;
the microwave modulation unit is a coplanar waveguide traveling wave type electrode electro-optical modulator and consists of an electrode, a driving signal and a load resistor; the signal output port of the driving signal is connected with the outer electrode of the runway type lithium niobate microcavity, and the common ground wire port of the driving signal is connected with the inner electrode of the runway type lithium niobate microcavity; the traveling wave electrode structure enables light waves and microwaves to propagate along the same direction of the coplanar electrode, signals are added to the thin film lithium niobate crystal in a traveling wave mode, so that a high-frequency electric field fully interacts with the light waves in the traveling wave mode, and electro-optic modulation of the runway type lithium niobate microcavity unit is realized;
the normal dispersion double micro-ring resonant cavity unit is a thin film lithium niobate micro-cavity, and consists of an input-output coupling waveguide and two annular runway type micro-cavity waveguides which are integrated by a single chip, wherein the input-output coupling waveguide and the two annular runway type micro-cavity waveguides adopt a pulley coupling structure to realize effective excitation of a fundamental mode.
Optionally, the input coupling waveguide is used for inputting pump laser, and the output coupling waveguide is used for outputting generated optical frequency comb; the laser pumping device comprises a first annular microcavity and a second annular microcavity based on Euler bending, wherein the first annular microcavity is smaller than the circumference of the second annular microcavity, and the first annular microcavity is used for improving the coupling efficiency of pumping laser.
Optionally, the second annular microcavity is a runway-type microcavity based on Euler bending, and is used for enabling a fundamental mode to smoothly transition from a straight waveguide to a curved waveguide, and inhibiting high-order mode excitation, so that mode cross coupling of the fundamental mode and the high-order mode is inhibited, and the Q value of the microcavity is improved; the direct waveguide part of the runway type microcavity carries out electro-optic modulation on a fundamental mode transmitted in the waveguide, firstly, the electro-optic modulation generates sidebands, and along with the multi-time surrounding transmission of a fundamental mode optical field in the microcavity, the optical frequency comb spectrum broadening and spectrum envelope flattening are realized through the combined action of normal dispersion, an electro-optic effect and a third-order nonlinear effect.
Optionally, the pumping unit is used for providing single-frequency laser/multi-frequency laser pumping into the waveguide, and the pumping power range is 1 mW-10W.
Optionally, the microwave modulation unit is a coplanar waveguide traveling wave type electrode electro-optical modulator, and the electrode material is gold.
Optionally, the normal dispersion double micro-ring resonant cavity unit is a single-chip integrated normal dispersion film lithium niobate micro-cavity optical waveguide or an optical waveguide formed by materials with an electro-optic effect and a third-order nonlinear effect; the normal dispersion double micro-ring resonant cavity unit comprises an input coupling waveguide and an output coupling waveguide, and a double micro-ring resonant cavity waveguide, wherein the nonlinear coefficient is about 0.3W -1 m -1 To 500W -1 m -1 。
Optionally, the normal dispersion film lithium niobate microcavity is realized by adopting a micro-ring resonant cavity based on Euler bending and/or similar Euler bending; a pulley coupling structure is adopted between the double micro-ring resonant cavity and the input-output coupling waveguide; a metal heating electrode is arranged above the cladding of the micro-ring resonant cavity and is used for tuning the resonant wavelength of the micro-cavity.
Optionally, the normal dispersion film lithium niobate microcavity optical waveguide is a ridge-structured multimode film lithium niobate optical waveguide.
Optionally, the optical frequency comb generating device is used for generating a tunable flat coherent optical frequency comb in 1550nm wave band.
In a second aspect, the present invention provides a method of optical frequency comb generation using an apparatus as described above, comprising the steps of:
the pumping unit is used for making single-frequency/multi-frequency laser pumping be incident into the input coupling film lithium niobate waveguide;
coupling single-frequency/multi-frequency laser to the smaller perimeter annular microcavity based on Euler bending through the input coupling waveguide, and further coupling the single-frequency/multi-frequency laser to the longer perimeter runway microcavity based on Euler bending, so that the power conversion efficiency of the optical frequency comb pump is improved;
in a runway type microcavity based on Euler bending, a coplanar waveguide traveling wave type electrode electro-optic modulation unit is utilized to realize optical frequency comb spectrum broadening and spectrum envelope flattening through the combined action of normal dispersion, electro-optic effect and third-order nonlinear effect.
The invention has the beneficial effects that: the single-frequency/multi-frequency laser pump is incident into an input coupling film lithium niobate waveguide and then is coupled to a normal dispersion double micro-ring resonant cavity unit, so that the effective excitation of a fundamental mode is ensured based on Euler bending, a high-order mode is restrained, sidebands are generated by electro-optic modulation, multi-frequency laser is generated, and the spectrum broadening and spectrum envelope flattening of the optical frequency comb are realized through the combined action of normal dispersion, electro-optic effect and third-order nonlinear effect; complex mode cross coupling regulation and control are avoided, and the generation of a relatively flat high-efficiency optical frequency comb in a normal dispersion area is realized.
Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic diagram of an electro-optic effect and a third-order nonlinear effect based on a thin film lithium niobate in an optical frequency comb device according to an embodiment of the present invention.
FIG. 2 is a schematic diagram of an electro-optic effect and a third order nonlinear effect based on thin film lithium niobate in 1550nm band to generate an optical frequency comb in a normal dispersion region according to an embodiment of the present invention.
Fig. 3 is a schematic diagram of a time domain and a frequency domain correspondence of an optical frequency comb with optical pulses being fourier transform limit according to an embodiment of the present invention.
Fig. 4 is a schematic diagram of a normal dispersion flat film lithium niobate ridge structure optical waveguide according to an embodiment of the present invention.
Fig. 5 is a schematic cross-sectional view of an electro-optic modulator according to an embodiment of the present invention.
Fig. 6 is a schematic diagram of a 180 ° euler bending structure in a racetrack microcavity according to an embodiment of the present invention.
FIG. 7 is a graph of the normal dispersion flat film lithium niobate ridge structured curved waveguide (radius of curvature 212.31 μm) quasi-transverse electric Transverse Electric (TE) fundamental mode second order dispersion according to an embodiment of the present invention.
FIG. 8 shows a normal dispersion flat film lithium niobate ridge structured curved waveguide quasi-transverse electric Transverse Electric (TE) fundamental mode micro-ring dispersion D according to an embodiment of the present invention 2 D (D) 3 A graph; wherein FIG. 8 (a) is a fundamental mode micro-ring dispersion D 2 FIG. 8 (b) is a graph showing fundamental mode micro-ring dispersion D 3 Graph diagram.
Fig. 9 is a diagram showing time and frequency spectrum evolution of an optical frequency comb generated in a micro-ring resonator according to an embodiment of the present invention under different pump detuning (detuning). Wherein fig. 9 (a) is the intra-cavity spectral evolution; fig. 9 (b) is the intra-cavity time domain evolution.
FIG. 10 is a graph showing the pulse time domain and spectral envelope of a typical micro-ring cavity and the evolution of average power in the typical cavity according to the detanning, which are generated by the laser in the micro-ring resonant cavity after multiple cyclic transmission according to the embodiment of the present invention; fig. 10 (a) is a pulse time domain diagram, fig. 10 (b) is a spectrum envelope diagram, and fig. 10 (c) is a graph of evolution of typical intra-cavity average power with detanning.
FIG. 11 is a graph showing pulse time domain and spectrum envelope in a micro-ring cavity corresponding to an optical frequency comb generated by multiple cyclic transmission of laser in the micro-ring cavity under different detanning conditions according to an embodiment of the present invention; fig. 11 (a) is a pulse time domain diagram, and fig. 11 (b) is a spectrum envelope diagram.
Fig. 12 is a graph showing the multiple relationship between modulation frequency Ω and FSR according to an embodiment of the present invention, where laser generates a pulse time domain envelope in the micro-ring cavity corresponding to an optical frequency comb after multiple cyclic transmission in the micro-ring cavity.
FIG. 13 is a graph showing the pulse spectrum in the micro-ring cavity corresponding to the optical frequency comb generated by the laser after multiple cyclic transmission in the micro-ring resonant cavity by changing the multiple relationship between the modulation frequency Ω and the FSR according to the embodiment of the present invention.
FIG. 14 is a graph of pulse time and frequency spectrum envelopes in a micro-ring cavity corresponding to an optical frequency comb generated by laser after multiple times of cyclic transmission in the micro-ring resonant cavity and a graph of evolution of average power in the cavity along with detanning under different pump input powers according to the embodiment of the present invention; where fig. 14 (a) is a pulse time domain diagram, fig. 14 (b) is a spectrum envelope diagram, and fig. 14 (c) is a graph of evolution of intra-cavity average power following cluttering.
Fig. 15 is a graph showing the evolution of the average power of pulses in the micro-ring resonator according to the detanning under different normal dispersion values according to the embodiment of the present invention, and a time domain and a spectrum envelope of pulses in the micro-ring resonator corresponding to an optical frequency comb generated after the laser is circularly transmitted in the micro-ring resonator for multiple times.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements throughout or elements having like or similar functionality. The embodiments described below by way of the drawings are exemplary only and should not be construed as limiting the invention.
It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless expressly stated otherwise, as understood by those skilled in the art. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, and/or groups thereof.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
In the description of this specification, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present invention, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.
In the description of the present specification, the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like indicate an orientation or positional relationship based on that shown in the drawings, merely for convenience of description and to simplify the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present technology.
The terms "mounted," "connected," and "disposed" are to be construed broadly, and may be, for example, fixedly connected, disposed, detachably connected, or integrally connected, disposed, unless otherwise specifically defined and limited. The specific meaning of the above terms in the present technology can be understood by those of ordinary skill in the art according to the specific circumstances.
In order that the invention may be readily understood, a further description of the invention will be rendered by reference to specific embodiments that are illustrated in the appended drawings and are not to be construed as limiting embodiments of the invention.
It will be appreciated by those skilled in the art that the drawings are merely schematic representations of examples and that the elements of the drawings are not necessarily required to practice the invention.
Example 1
In this embodiment 1, first, an optical frequency comb generating device and method based on thin film lithium niobate are provided, where single frequency laser/multi-frequency laser is coupled to a normal dispersion thin film lithium niobate dual micro-ring resonant cavity, and optical frequency comb spectrum broadening and spectrum envelope flattening are achieved through combined actions of normal dispersion, electro-optic effect and third-order nonlinear effect, and flatness is also good.
The optical frequency comb generating device in the embodiment comprises a pumping unit, a modulating unit and a double micro-ring resonant cavity unit, wherein: the pumping unit is used for providing single-frequency laser/multi-frequency laser pumping; the modulating unit is a coplanar waveguide traveling wave type electrode electro-optical modulator and consists of an electrode, a driving signal and a load resistor. The signal output port of the driving signal is connected with the outer electrode of the runway type lithium niobate microcavity, and the common ground wire port of the driving signal is connected with the inner electrode of the runway type lithium niobate microcavity; the traveling wave electrode structure enables light waves and microwaves to propagate along the same direction of the coplanar electrode, signals are added to the thin film lithium niobate crystal in a traveling wave mode, so that a high-frequency electric field fully interacts with the light waves in the traveling wave mode, and electro-optic modulation of the runway type lithium niobate microcavity unit is realized.
The normal dispersion double micro-ring resonant cavity unit is a thin film lithium niobate micro-ring resonant cavity and consists of an input-output coupling waveguide and two annular runway type micro-cavity waveguides which are integrated by a single chip, wherein the input-output coupling waveguide and the two annular runway type micro-cavity waveguides adopt pulley coupling to realize fundamental mode excitation; the input coupling waveguide is used for inputting pump laser, and the output coupling waveguide is used for outputting generated optical frequency comb; the smaller perimeter annular Euler microcavity is used for improving the coupling efficiency of the pump laser; the other ring-shaped runway microcavity with longer perimeter is a runway microcavity based on Euler bending or similar Euler bending, compared with the common circular bending, the bending radius of the ring-shaped runway microcavity is gradually changed, the bending radius of the ring-shaped runway microcavity is larger at the joint of the ring-shaped runway microcavity and the straight waveguide, so that a fundamental mode can be smoothly transited from the straight waveguide to the bent waveguide, high-order mode excitation is restrained, mode cross coupling of the fundamental mode and the high-order mode is restrained, the Q value of the microcavity is improved, the straight waveguide part of the runway microcavity is combined with the modulation unit to carry out electro-optic modulation on a fundamental mode light field transmitted in the waveguide, firstly, sidebands are generated by the electro-optic modulation, multi-frequency laser is generated, the fundamental mode light field is transmitted in the microcavity in a multi-circle mode, and the spectral broadening and spectral envelope flattening of the optical frequency are realized through the combined actions of normal dispersion, electro-optic effect and three-order nonlinear effect.
The modulating unit is a coplanar waveguide traveling wave type electrode electro-optic modulator, and the electrode material is gold.
The normal dispersion double micro-ring resonant cavity unit is a single-chip integrated normal dispersion film lithium niobate micro-cavity optical waveguide (optical waveguides formed by materials with electro-optical modulation effect and third-order nonlinear effect, such as lithium tantalate LiTaO) 3 Silicon carbide SiC, aluminum nitride AlN, gallium nitride GaN, gallium arsenide GaAs, gallium phosphide GaP, indium phosphide InP and the like), comprises an input-output coupling waveguide and a double micro-ring resonant cavity waveguide, and has a nonlinear coefficient range of 0.3W -1 m -1 To 500W -1 m -1 (appropriate normal dispersion values are achieved depending on the width and height of the waveguide).
The normal dispersion film lithium niobate microcavity optical waveguide is realized by adopting a micro-ring resonant cavity based on Euler bending and/or similar Euler bending. And a pulley coupling structure is adopted between the double micro-ring resonant cavity and the input-output coupling waveguide, so that the effective excitation of a fundamental mode is ensured, and a high-order mode is restrained. And a heating electrode is arranged in a partial area above the double micro-ring resonant cavity cladding and is used for tuning the resonant wavelength of the micro-cavity. The dual micro-ring resonators have different circumferences, and the circumference length of the dual micro-ring resonators is in the order of tens of micrometers to several centimeters.
The normal dispersion film lithium niobate microcavity optical waveguide is a ridge-structure multimode film lithium niobate optical waveguide, and the ridge-structure multimode film lithium niobate optical waveguide ridge has a top width of several micrometers, a ridge thickness and a film thickness below the ridge of several hundred nanometers, and an inclination angle of between 50 and 80 degrees.
The optical frequency comb generating device is used for generating a tunable flat coherent optical frequency comb in 1550nm wave band.
In this embodiment 1, the optical frequency comb generating method is implemented by using the apparatus described above, and includes the following steps:
the single-frequency/multi-frequency laser emitted by the pumping unit is incident into the lithium niobate optical waveguide of the input coupling film;
in order to improve the power conversion efficiency of the optical frequency comb, the single-frequency laser is coupled to the smaller circumference annular Euler bending microcavity waveguide through the input coupling film lithium niobate optical waveguide, and further coupled to the longer circumference annular runway microcavity waveguide based on Euler bending and/or similar Euler bending.
In the long perimeter annular runway type microcavity waveguide based on Euler bending, a coplanar waveguide traveling wave type electrode electro-optic modulation unit is utilized to realize optical frequency comb spectrum broadening and spectrum envelope flattening through the combined action of normal dispersion, electro-optic effect and third-order nonlinear effect.
In summary, in this embodiment, single-frequency/multi-frequency laser meeting the conditions is incident into the input coupling thin film lithium niobate waveguide, the conversion efficiency of optical frequency comb pumping is improved by utilizing a double-ring microcavity structure, and mode cross coupling is well suppressed in a runway microcavity based on euler bending and/or euler-like bending structures, so that a fundamental mode can be smoothly transited from a straight waveguide to a bent waveguide, the straight waveguide portion is combined with the modulation unit to perform electro-optical modulation on a fundamental mode optical field transmitted in the waveguide, first, sidebands are generated by the electro-optical modulation, multi-frequency laser is generated, and along with the repeated surrounding transmission of the fundamental mode optical field in the microcavity, optical frequency comb spectrum broadening and spectrum envelope flattening are realized through normal dispersion, electro-optical effect and third-order nonlinear effect. Normal dispersion maintains the coherence of the optical frequency comb, producing an optical frequency comb with tunable frequency spacing, coherence and spectral envelope flatness.
Changing the modulation frequency Ω of the modulation signal and the multiple of the microcavity FSR can be seen to change the modulation frequency to be a multiple of FSR, and a plurality of pulses occur in one time domain period of the microcavity, i.e. a plurality of pulses occur within one week around the microcavity.
Example 2
In this embodiment 2, an optical frequency comb generating device is provided, which aims to obtain a high-efficiency broadband coherent optical frequency comb with tunable frequency intervals. Referring to fig. 1 and 2, the optical frequency comb generating device includes a pumping unit, a normal dispersion dual micro-ring resonator unit, and a modulation unit thereof, which are sequentially connected, wherein:
the pumping unit is used for providing single-frequency/multi-frequency pumping laser; the modulating unit is a coplanar waveguide traveling wave type electrode electro-optical modulator and consists of an electrode, a driving signal and a load resistor. The signal output port of the driving signal is connected with the outer electrode of the lithium niobate microcavity, and the common ground wire port of the driving signal is connected with the inner electrode of the lithium niobate microcavity; the traveling wave electrode structure enables light waves and microwaves to propagate along the same direction of the coplanar electrode, and signals are applied to the crystal in the form of traveling waves, so that a high-frequency electric field fully interacts with the light waves in the form of traveling waves, and electro-optic modulation of the microcavity unit is realized. The normal dispersion double micro-ring resonant cavity unit is a thin film lithium niobate micro-cavity and consists of an input-output coupling waveguide and two annular runway type micro-cavity waveguides which are integrated by a single chip, and the input-output coupling waveguide and the two annular runway type micro-cavity waveguides adopt a pulley coupling structure to realize effective excitation of a fundamental mode; the input coupling waveguide is used for inputting pump laser, and the output coupling waveguide is used for outputting generated optical frequency comb; a small perimeter annular microcavity based on Euler bending is used for improving the coupling efficiency of pump laser; the other long perimeter annular runway microcavity is a runway type microcavity based on Euler bending or similar Euler bending, compared with the common circular bending, the Euler bending can enable a fundamental mode to be smoothly transited from a straight waveguide to a bent waveguide, inhibit high-order mode excitation, inhibit mode cross coupling of the fundamental mode and the high-order mode, improve the Q value of the microcavity, the straight waveguide part of the runway type microcavity is combined with the modulation unit to carry out electro-optic modulation on a fundamental mode light field transmitted in the waveguide, firstly, the electro-optic modulation generates sidebands to generate multi-frequency laser, and the multi-frequency laser is transmitted in the microcavity in a surrounding mode for multiple times along with the fundamental mode, and the optical frequency comb spectrum broadening and the spectrum envelope flattening are realized through normal dispersion, electro-optic effect and third-order nonlinear effect.
In the embodiment, a novel architecture and a novel method are adopted, single-frequency/multi-frequency laser is coupled to the double micro-ring resonant cavity unit, and the spectrum widening and spectrum envelope flattening of the optical frequency comb are realized through the combined action of normal dispersion, an electro-optic effect and a third-order nonlinear effect.
The embodiment 2 also provides a method for generating an optical frequency comb, which comprises the following steps: the single-frequency pump laser emitted by the pump unit is incident into the input coupling film lithium niobate optical waveguide; in order to improve the power conversion efficiency of the optical frequency comb pump, the single-frequency laser is coupled to the smaller circumference annular Euler bending microcavity waveguide through the input coupling film lithium niobate optical waveguide, and then is coupled to the longer circumference annular runway type microcavity waveguide based on Euler bending and/or similar Euler bending; in a long-circumference annular runway type microcavity waveguide, a coplanar waveguide traveling wave type electrode electro-optic modulation unit is utilized, and the shaped pulse is subjected to time domain broadening and spectrum envelope flattening through the combined action of normal dispersion, electro-optic effect and third-order nonlinear effect.
The pumping unit inputs single-frequency laser, and the input peak power is 0.1W-1W. In addition, a plurality of frequency lasers with far interval frequencies (interval frequency is more than 100 nm) can be input, parameters of each laser are the same as the parameters of the laser, and the generated optical frequency comb can form a plurality of optical frequency combs in a frequency domain, and the input laser frequency is taken as a center wavelength.
The modulating unit is a coplanar waveguide traveling wave type electrode electro-optic modulator, the traveling wave type electrode electro-optic modulator, single-frequency laser is transmitted in a thin film lithium niobate waveguide, microwave modulating signals are transmitted in electrodes, the speeds of the two signals are consistent, and the transmission is in the same direction, so that interaction (electro-optic modulation) is completed, but light waves and microwaves can have a certain degree of walk-off (speed mismatch) along with the increase of transmission length, so that the coplanar waveguide traveling wave electrode structure has important influence on characteristic parameters of the electro-optic modulator due to the width of the electrodes, the thickness of the electrodes, the distance between the electrodes and the thickness of upper and lower cladding layers, and preferably, the electrode material in the embodiment is gold, the width of the electrodes is 10 mu m, the thickness of the electrodes is 0.9 mu m, and the distance between the electrodes is 7 mu m, so that the electro-optic modulator meeting the conditions is achieved.
The normal dispersion double micro-ring resonant cavity unit is a film lithium niobate micro-cavity, and is composed of an input-output coupling waveguide and two annular runway micro-cavity waveguides which are integrated by a single chip, wherein the width of the top of a film lithium niobate optical waveguide ridge is in the order of several micrometers, the thickness of the ridge and the thickness of a film below the ridge are in the order of several hundred nanometers, and the inclination angle is 50-80 degrees.
In this embodiment, an optical frequency comb generating device may be specifically implemented by the following procedure:
the pump unit emits single-frequency laser which is higher than threshold conditions of electro-optic effect and third-order nonlinearity, the single-frequency laser is incident into the input coupling film lithium niobate optical waveguide, then the laser is coupled to the normal dispersion double micro-ring resonant cavity unit, the two micro-cavities keep a critical coupling state, pumping conversion efficiency is improved, the single-frequency laser generates modulation sidebands through electro-optic modulation in the runway type micro-cavity based on Euler bending, the self-phase modulation in the normal dispersion film lithium niobate optical waveguide is utilized to lead to frequency domain broadening of the laser, the third-order nonlinearity effect and normal dispersion interaction exist simultaneously in the transmission process, and further strengthening of phase modulation is realized by matching with electro-optic phase modulation, so that the spectral broadening and spectral envelope flattening of the optical frequency are realized, the flatness can be improved to within 10dB, and the pumping conversion efficiency is higher.
Specifically, the thin film lithium niobate microcavity waveguide is a ridge-structure thin film lithium niobate optical waveguide, and the ridge-structure thin film lithium niobate optical waveguide can obtain flat normal dispersion with proper size by adjusting the width and the height of the optical waveguide.
Through the optimization design of the geometric structure, in the embodiment, the top width of the thin film lithium niobate optical waveguide ridge is 3000nm, the ridge thickness is 450nm, the thickness of the thin film below the ridge is 200nm, the inclination angle is 80 degrees, and the thin film lithium niobate optical waveguide is a high-power limiting factor optical waveguide, the periphery of the lithium niobate optical waveguide is surrounded by a silicon dioxide material, and the refractive index equation of the silicon dioxide material is shown as the following formula (1):
the nonlinear index of refraction of the silica material at 1550nm is calculated according to the following formula (2):
n 2 ＝2.2×10 -20 m 2 /W (2)
the refractive index equation of the lithium niobate material is shown in the following formula (3):
the nonlinear index of refraction of the thin film lithium niobate material at 1550nm is calculated according to the following formula (4):
n 2 ＝1.8×10 -19 m 2 /W (4)
simulation calculation is carried out to obtain second-order dispersion beta of quasi-TE fundamental mode of ridge-structure film lithium niobate optical waveguide with bending radius of 212.31 mu m at 1550nm 2 226.6ps 2 The nonlinear coefficient gamma is about 0.540547W/km -1 m -1 The waveguide loss of the quasi-TE fundamental mode is considered to be 3dB/m, and the ridge structure film lithium niobate optical waveguide quasi-TE fundamental mode second-order dispersion beta 2 The graph is shown in fig. 7. D (D) k Representing the k-th order dispersion parameter in the micro-ring, D at 1550nm 2 /2 pi and D 3 The values of/2 pi are-0.695319 MHz and 848.9Hz respectively, and the fundamental mode micro-ring dispersion D 2 D (D) 3 The curve is shown in fig. 8.
In this embodiment, the ridge-type structured thin film lithium niobate is actually a multimode optical waveguide, and in practical application, mode coupling in the multimode optical waveguide is mostly present in the bending process of the waveguide, and in this embodiment, a 180 degree euler bending structure is adopted in the track-running microcavity, so that the fundamental mode can smoothly transit from a straight waveguide to a bent waveguide, and mode cross coupling can be well inhibited, high-order mode excitation is inhibited, and only the TE fundamental mode is ensured to be effectively excited and propagated. The curvature of the euler curve varies linearly with its length. In this example, a mathematical model of euler bending at an angle θ=180° is constructed as follows, the linear coefficient of euler bending is a, we need to specify the bending radius R min The corresponding euler bending length s is defined by s=2r min θ, for a given euler curve,it is certain that each point on the curve can be characterized by a and length s, as follows equation (5):
where L' =as,equation (5) is fresnel integral, and the drawing of the euler curve is realized by writing codes in python language, and specifically we choose the diameter 2R of the euler curve with θ=180° min The euler bending length s calculated according to the formula was 188.49 μm at 60 μm as shown in fig. 6.
In this example, the Free Spectral Range (FSR) of the microring resonator is 100GHz, the group index n of the microring at a wavelength of 1550nm g 1.93144. According to the formulaCalculated R of racetrack microcavity 0 For 246.89 μm, the length of the entire microcavity l=2pi R 0 The racetrack microcavity straight waveguide length is (L-2 s)/2= 587.135 μm, = 1551.25 μm.
The single-frequency laser is incident to an input coupling film lithium niobate optical waveguide and then coupled to a first annular microcavity with smaller circumference based on Euler bending, and is aimed at improving the pump conversion efficiency, under the critical coupling condition, the single-frequency laser is coupled to a longer circumference runway type microcavity with an electro-optic modulation unit based on Euler bending, the modulation unit adopts a traveling wave electrode structure, the modulated microwaves and the light waves are transmitted in the same direction in the electrode and the waveguide in parallel, the high-speed electro-optic modulation is realized, the electro-optic modulation generates modulation sidebands at the initial stage of transmission, the multi-frequency laser is generated, and then the equation of the electric field envelope in the resonant cavity under the combined actions of the electro-optic modulation, normal dispersion and third-order nonlinear effect is shown as the following formula (6):
wherein J s ＝Jcos(sD 1 t+θ) is a signal of a radio frequency signal source of the modulation unit, J is called modulation intensity, s is a modulation frequency related parameter (s=1 indicates that the modulation frequency is the same as the microcavity FSR). If the modulation intensity J=0, the formula is a common LLE equation, and the electric effect can be seenIt should be possible to enhance the phase modulation within the cavity and create modulation sidebands (frequency components).
Therefore, with further increase of transmission distance, under normal dispersion condition, the combined action of electro-optic effect and third-order nonlinear effect causes the time domain waveform to be shaped like rectangle, the frequency spectrum is widened, the flatness is further optimized, and the broadband optical frequency comb with better flatness is generated. The whole time domain and frequency domain evolution process of generating the optical frequency comb in the microcavity can be solved by using the formula (6).
Pump detuning (detuning) is defined as the center frequency of the pump laser and the micro-ring resonance frequency omega 0 Can produce stable optical frequency combs within a certain range of detanning. Definition xi 0 =2δω/κ represents pump detuning (δω represents the difference between the pump center angular frequency and the micro-ring resonance angular frequency, and κ represents the sum of the internal and external losses. Due to the thermal effect and non-linearity of the micro-ring itself, the resonance frequency ω of the micro-ring is caused when the pump frequency is changed from high frequency to low frequency 0 Drift occurs at the effective resonant frequency omega eff The expression is
Wherein alpha is L Representing the coefficient of thermal expansion, alpha N The index of refraction and the temperature difference of the micro-ring are represented by n, P cav Representing power in the micro-loop, n 2 Representing a non-linear refractive index coefficient, A eff Is the effective mode field area.
A typical time-domain and spectral envelope plot corresponding to an optical frequency comb within a micro-ring cavity is shown in fig. 10. The parameters for generating the optical frequency comb are set as follows: the FSR of the runway type microcavity is 100GHz, the pumping power is 100mW, the waveguide loss in the cavity is 8dB/m, and the dispersion D of the microcavity 2 /2 pi and D 3 And (2) pi is-0.695319 MHz and 848.9Hz respectively, the modulation intensity J=6 and s=1 of the electro-optic modulator, and the micro-ring resonator and the output coupling waveguide are in critical coupling. Within a certain pump detuning (detuning) range, stable optical frequency combs can be generated, fig. 9 b) shows the intracavity power with detuningThe changing evolution process can be seen that in a certain range of detinning, the spectrum gradually widens (fig. 9 a)) as detinning increases, and when detinning increases to a certain value, beyond the effective zero detuning region, the power in the cavity rapidly decreases to 0, and the brighter the color in the figure indicates the higher the power. Fig. 10 a) and b) show typical time and frequency domain diagrams of an optical frequency comb generated at a detouring=20, respectively, and fig. 10 c) shows the evolution of the intra-cavity average power (Intracavity power) as the detouring changes, where the intra-cavity average power refers to the power superposition at each position in the cavity averaged at a certain detouring position. Fig. 11 shows a comparison of the time and spectral envelopes of the optical frequency combs in the micro-ring cavity for 17, 20, and 23, respectively, it can be seen that as the detuling increases, the corresponding spectrum widens and the intra-cavity pulse duration becomes shorter.
Changing the multiple relationship(s) between the modulation frequency Ω and the FSR, it can be seen that multiple pulses (corresponding to an increase in the spectral spacing of the optical frequency comb) occur in one time domain period of the microcavity by changing the FSR multiple, as shown in fig. 12 and 13.
Changing the pump input power, as the pump power increases, the evolution of the average power in the cavity along with the detinning is shown in fig. 14 c), and it can be seen that as the pump power increases from 0.03W to 0.16W, the detinning tuning range increases continuously; fig. 14 a) and 14 b) are time-domain and frequency-domain envelopes of the optical frequency comb when the detuning approaches the effective zero detuning region (with the same pulse time-domain duty cycle) respectively at different pump powers, it can be concluded that the frequency spectrum of the corresponding optical frequency comb becomes wider when the pump power increases.
By changing the geometric structure size of the thin film lithium niobate optical waveguide, the quasi-TE fundamental mode second-order dispersion beta can be changed 2 The change in the normal dispersion has some effect on the generation of the optical frequency comb, the result of which is shown in fig. 15. FIG. 15 a) shows the corresponding beta for ridge top width, ridge total thickness of 3000nm×650nm, 2200nm×650nm, 3000nm×600nm, respectively (where the film thickness under the ridge is 200 nm) 2 Dispersion curve graph. FIG. 15 b) shows the evolution of average power in the cavity with detanning for different thin film lithium niobate optical waveguide geometries, seen at a wide heightBeta at 2200nm by 650nm 2 The value is small, the tuning range of the tuning device is maximum, and the tuning range is basically equivalent when the width is 3000nm multiplied by 600nm and the width is 3000nm multiplied by 650 nm. From FIGS. 15 c) and d) it can be seen that at the same pulse time domain duty cycle, the time domain pulse power is substantially equivalent at a width of 3000nm by 650nm and at a width of 3000nm by 600nm, whereas the time domain pulse power is highest at a width of 2200nm by 650nm, while beta 2 The closer the dispersion value is to the near-zero dispersion region, the wider the spectral width.
In practical application, the flatness of the optical frequency comb can be further improved by optimizing the micro-ring resonant cavity structure and loss, dispersion or pulse shaping again.
It will be appreciated by those skilled in the art that the number of various elements shown in fig. 1 for simplicity only may be less than the number of an actual optical frequency comb generating system, but such omission is certainly not premised on a clear and thorough disclosure of embodiments of the invention.
In summary, aiming at the problems of mode cross coupling and high-order mode excitation in multimode optical waveguides, the invention proposes to realize bending by adopting a 90-degree/180-degree Euler bending structure in a microcavity, so that a fundamental mode can smoothly transit from a straight waveguide to a bent waveguide, the mode cross coupling can be well restrained, the high-order mode excitation is restrained, only a quasi-TE fundamental mode is ensured to be effectively excited and propagated, and the Q value of the microcavity is improved. Aiming at the problem that a normal dispersion area needs multi-frequency sideband pumping auxiliary starting to generate an optical frequency comb, the invention provides that an electro-optical modulator is utilized to firstly form a modulation sideband to generate multi-frequency laser, then the multi-frequency laser is transmitted in a normal dispersion microcavity in a multi-time surrounding manner, and the optical frequency comb spectrum widening and spectrum envelope flattening are realized through the combined action of normal dispersion, an electro-optical effect and a third-order nonlinear effect.
The optical frequency comb generating device provided by the embodiment of the invention is mainly used for realizing the high-efficiency broadband coherent flat optical frequency comb with controllable tuning of the frequency interval in 1550nm wave bands, and is beneficial to the fields of ultra-high-speed coherent optical communication, microwave photonics and the like.
The above description is of the preferred embodiments of the invention, but the scope of the invention is not limited theretoIn this regard, various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention. Such as selecting other materials with electro-optic effect and higher third order nonlinearity, such as lithium tantalate LiTaO 3 Silicon carbide SiC, aluminum nitride AlN, gallium nitride GaN, gallium arsenide GaAs, gallium phosphide GaP, indium phosphide InP, and the like as optical waveguides, operate in a normal dispersion region. The working band can also select other bands such as visible light band, 1300nm band, etc.
While the foregoing description of the embodiments of the present invention has been presented in conjunction with the drawings, it should be understood that it is not intended to limit the scope of the invention, but rather, it should be understood that various changes and modifications could be made by one skilled in the art without the need for inventive faculty, which would fall within the scope of the invention.
Claims (10)
1. The optical frequency comb generating device based on the film lithium niobate is characterized by comprising a pumping unit, a microwave modulating unit and a normal dispersion double micro-ring resonant cavity unit, wherein:
the pumping unit is used for providing laser pumping;
the microwave modulation unit is a coplanar waveguide traveling wave type electrode electro-optical modulator and consists of an electrode, a driving signal and a load resistor; the signal output port of the driving signal is connected with the outer electrode of the runway type lithium niobate microcavity, and the common ground wire port of the driving signal is connected with the inner electrode of the runway type lithium niobate microcavity; the traveling wave electrode structure enables light waves and microwaves to propagate along the same direction of the coplanar electrode, signals are added to the thin film lithium niobate crystal in a traveling wave mode, so that a high-frequency electric field fully interacts with the light waves in the traveling wave mode, and electro-optic modulation of the runway type lithium niobate microcavity unit is realized;
the normal dispersion double micro-ring resonant cavity unit is a thin film lithium niobate micro-cavity, and consists of an input-output coupling waveguide and two annular runway type micro-cavity waveguides which are integrated by a single chip, wherein the input-output coupling waveguide and the two annular runway type micro-cavity waveguides adopt a pulley coupling structure to realize effective excitation of a fundamental mode.
2. The thin film lithium niobate based optical frequency comb generating device of claim 1, wherein the input coupling waveguide is used for inputting pump laser light, and the output coupling waveguide is used for outputting the generated optical frequency comb; the double-microring resonant cavity unit comprises a first annular microcavity and a second annular microcavity based on Euler bending, wherein the first annular microcavity is smaller than the circumference of the second annular microcavity, and the first annular microcavity is used for improving the coupling efficiency of pump laser.
3. The optical frequency comb generating device based on the thin film lithium niobate according to claim 2, wherein the second annular microcavity is a racetrack microcavity based on euler bending, and is used for smoothly transiting a fundamental mode from a straight waveguide to a curved waveguide, and suppressing high-order mode excitation, so that mode cross coupling of the fundamental mode and the high-order mode is suppressed, and the Q value of the microcavity is improved; the direct waveguide part of the runway type microcavity carries out electro-optic modulation on a fundamental mode transmitted in the waveguide, firstly, the electro-optic modulation generates sidebands, and along with the multi-time surrounding transmission of a fundamental mode optical field in the microcavity, the optical frequency comb spectrum broadening and spectrum envelope flattening are realized through the combined action of normal dispersion, an electro-optic effect and a third-order nonlinear effect.
4. The optical frequency comb generating device based on thin film lithium niobate according to claim 1, wherein the pumping unit is configured to provide single frequency laser/multi-frequency laser pumping into the waveguide, and the pumping power ranges from 1mW to 10W.
5. The optical frequency comb generating device based on the thin film lithium niobate according to claim 1, wherein the microwave modulating unit is a coplanar waveguide traveling wave type electrode electro-optical modulator, and the electrode material is gold.
6. The optical frequency comb generating device based on thin film lithium niobate according to claim 1, wherein the normal dispersion double micro-ring resonator unit is a single chip integrated normal dispersion thin film niobateLithium microcavity optical waveguides, or optical waveguides formed of materials having an electro-optic effect and a third-order nonlinear effect; the normal dispersion double micro-ring resonant cavity unit comprises an input coupling waveguide and an output coupling waveguide, and a double micro-ring resonant cavity waveguide, wherein the nonlinear coefficient is about 0.3W -1 m -1 To 500W -1 m -1 。
7. The optical frequency comb generating device based on film lithium niobate according to claim 1, wherein the normal dispersion film lithium niobate microcavity is realized by using a micro-ring resonant cavity based on euler bending; a pulley coupling structure is adopted between the double micro-ring resonant cavity and the input-output coupling waveguide; a metal heating electrode is arranged above the cladding of the micro-ring resonant cavity and is used for tuning the resonant wavelength of the micro-cavity.
8. The optical frequency comb generating device based on thin film lithium niobate according to claim 1, wherein the normally dispersive thin film lithium niobate microcavity optical waveguide is a ridge-structured multimode thin film lithium niobate optical waveguide.
9. The thin film lithium niobate based optical frequency comb generation device of any of claims 1 to 8, wherein the optical frequency comb generation device is used to generate tunable flat coherent optical frequency combs in the 1550nm band.
10. A method of generating an optical frequency comb using the apparatus of any one of claims 1-9, comprising the steps of:
the pumping unit is used for making single-frequency/multi-frequency laser pumping be incident into the input coupling film lithium niobate waveguide;
coupling single-frequency/multi-frequency laser to the smaller perimeter annular microcavity based on Euler bending through the input coupling waveguide, and further coupling the single-frequency/multi-frequency laser to the longer perimeter runway microcavity based on Euler bending, so that the power conversion efficiency of the optical frequency comb pump is improved;
in a runway type microcavity based on Euler bending, a coplanar waveguide traveling wave type electrode electro-optic modulation unit is utilized to realize optical frequency comb spectrum broadening and spectrum envelope flattening through the combined action of normal dispersion, electro-optic effect and third-order nonlinear effect.
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| CN117856759A (en) * | 2024-03-07 | 2024-04-09 | 山东大学 | Method and apparatus for achieving frequency tuning and spectral broadening of cantilever microresonators |
| CN117896010A (en) * | 2024-03-14 | 2024-04-16 | 华中科技大学 | Optical wavelength multicast device and system |
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| CN117856759A (en) * | 2024-03-07 | 2024-04-09 | 山东大学 | Method and apparatus for achieving frequency tuning and spectral broadening of cantilever microresonators |
| CN117856759B (en) * | 2024-03-07 | 2024-05-24 | 山东大学 | Method and apparatus for achieving frequency tuning and spectral broadening of cantilever microresonators |
| CN117896010A (en) * | 2024-03-14 | 2024-04-16 | 华中科技大学 | Optical wavelength multicast device and system |
| CN117896010B (en) * | 2024-03-14 | 2024-06-11 | 华中科技大学 | Optical wavelength multicast device and system |
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