A kind of optical microcavity frequency comb based on broach feedback regulation produces system
Technical field
The present invention relates to integrated photonics and non-linear optical field.Be particularly related to a kind of optical microcavity frequency comb based on broach feedback regulation and produce system.
Background technology
A kind of new type light source that frequency comb is made up of the coherent light waves of a series of equifrequents interval, narrow linewidth.It seems similarly to be the broach of proper alignment on frequency spectrum, so gain the name.Be widely used in that the synchronous and calibration of metering, the clock of accurate spectrum, time and frequency, long distance are relevant, high-performance satellite navigation, optical communication and Network Synchronization, high precision tracking and range finding etc.
Traditional larger mode-locked laser of frequency comb Technology Need volume, not only cost costliness is also higher to the requirement of applied environment.And compact conformation, be easy to the integrated optical microcavity frequency comb technology based on optical non-linear effect and obtained increasing attention, just in fast development.Pump light enters after optical microcavity, and due to the enhanced intensity effect of optical microcavity, compared with outside pumping light intensity, the light intensity in optical microcavity can increase doubly a lot.Strong like this light intensity can excite Kerr effect, and produces new frequency component by nonlinear effects such as four-wave mixings.Difference on the frequency between frequency component, i.e. the broach interval of frequency comb, just in time equals the free spectral range (FreeSpectralRange, FSR) of optical microcavity, so new frequency just in time also resonates with optical microcavity.This resonance is also enhanced new frequency, and produces with original frequency the resonant frequency upgrading by four-wave mixing.So repeatedly, thus can produce a lot of equifrequent spacing frequency component form frequency comb.
The generation of optical microcavity frequency comb has two kinds of different paths.When wherein a kind of frequency comb that is called I class generates, from pump light, generate frequency comb with one times of FSR to both sides expansion.Another kind be called II class frequency comb generate time from pump light, first expand to both sides with many times of FSR, along with the increase of pumping light power, the broach of one times of FSR is filled gradually, becomes the frequency comb with one times of FSR.Research shows that I class frequency comb has good coherence, can obtain being close to by shaping pulse the femtosecond pulse of theoretical limit; II class frequency comb only has partial coherence, although can compress time-domain signal by shaping pulse, cannot obtain being close to the femtosecond pulse of theoretical limit, and application will be seriously limited.
The generation system of optical microcavity frequency comb, is that single pumping laser directly enters into optical microcavity at present.System composition is comparatively simple, and the performance of optical microcavity but the generation threshold value of frequency comb almost places one's entire reliance upon proposes very high requirement to pumping laser power conventionally, is unfavorable for the miniaturization of system and the reduction of cost.And lack Optimization Mechanism initiatively, and can not realize coherence and broach interval is controlled, hinder the universal and application of optical microcavity frequency comb.
This area is needed the optical microcavity frequency comb that a kind of high-performance easily realizes badly and is produced system, reduces threshold value that frequency comb produces, improves coherence, realizes controlled broach interval, and improve the tolerance to pumping condition.
Summary of the invention
The invention provides a kind of optical microcavity frequency comb based on broach feedback regulation and produce system.
System of the present invention is made up of pumping laser, bundling device 1, optical microcavity, bundling device 2, wave filter, amplification/regenerator, wherein the output of pumping laser enters optical microcavity through bundling device 1, the output of optical microcavity is after bundling device 2, a part becomes the output of system, a part becomes feedback regulation signal, the feedback regulation signal feedback regulation circuit that device, amplification/regenerator form is after filtering got back to bundling device 1, is injected among optical microcavity together with pumping laser.
Pumping laser comprises it being the combination of semiconductor light sources, dyestuff light source, solid light source, gas lamp and above-mentioned light source and fiber amplifier, solid image intensifer, semiconductor optical amplifier.Pumping laser is the high coherent light of single-frequency normally, for the non-linear process in optical microcavity provides light source.
Optical microcavity comprises micro-ring, micro-dish, the microballoon with optical nonlinearity gain.Optical microcavity is strapped in light in small region, has greatly strengthened the interaction of light and material.
Bundling device 1 and bundling device 2 comprise fiber coupler, integrated waveguide coupling mechanism, optics light splitting piece, wavelength division multiplexer, bandpass filter and light top and bottom path multiplexer.
Wave filter and the coefficient effect of bundling device 2 are to allow the one or more broach wavelength except the wavelength of pumping laser place to see through, and can change amplitude, phase place, the delay of one or more broach that can see through, and do not allow the wavelength transmission of pumping laser place.
Wave filter comprises optical filter, optical fiber filter, grating filter, integral wave guide filter, the variable self-tracking filter of saturated absorption material formation and their combination.
The effect of amplification/regenerator is the signal that generation is relevant to one or more broach that can see through after wave filter and bundling device 2 actings in conjunction, generates signal after amplification, the live width compression of one or more broach that can see through after wave filter and bundling device 2 actings in conjunction or frequency shifts; Amplification/regenerator comprises fiber amplifier, solid image intensifer, semiconductor optical amplifier, the laser instrument that is fed adjustment signal injection locking and their combination.
Compared with producing frequency comb with single pumping laser, the present invention increases Liao Yi road feedback regulation signal, and the dynamic process that can produce frequency comb be intervened, thereby affects telling on that optical frequency goes out.
Select one or more broach outside pump light as feedback regulation signal, and it is amplified, be injected into optical microcavity together with pump light, realize the low threshold value of frequency comb and produce.In frequency comb generation system based on broach feedback, feedback regulation circuit and pumping light power sum, by required pump power under single pumping condition.
Improve frequency comb coherence, suppress the appearance of II class frequency comb, the generation of induction I class frequency comb.Select the broach of the distance pump light 1 × FSR being produced by pump light as feedback regulation signal, and the four-wave mixing composition that stops other broach to produce enters into feedback regulation circuit, induction frequency comb develops to I class, thereby reduces the RF noise of frequency comb, the coherence who improves frequency comb.
Select apart from pump light n × FSR(n=1,2,3 ...) broach carry out feedback regulation, realize broach and be spaced apart the frequency comb output of n × FSR.
Compared with the system that produces frequency comb with existing single pumping laser, this system can reduce threshold value that frequency comb produces, improves coherence, realize controlled broach interval, and improves the tolerance to pumping condition.The present invention is simple in structure, repeatability is strong, and the effect that system performance is improved is remarkable.
Explanation below and accompanying drawing describe some illustrative aspects of the present invention in detail, are only to use some modes in each mode in the principle of the invention; The present invention is intended to comprise all these aspects and their equivalent.
Brief description of the drawings
Fig. 1 is that a kind of optical microcavity frequency comb based on broach feedback regulation produces system schematic.
Fig. 2 is first embodiment of the present invention, Qi Zhongyou: tunable single frequency laser 201, high power light amplifier 202, bundling device 203, optical microcavity 204, bundling device 205, wave filter 206, amplifier 207, output terminal 208.
Fig. 3 is second embodiment of the present invention, Qi Zhongyou: tunable single frequency laser 301, high power light amplifier 302, bundling device 303, optical microcavity 304, bundling device 305, wave filter 306, amplifier 307, output terminal 308.
Fig. 4 is the 3rd embodiment of the present invention, wherein have: tunable single frequency laser 401, high power light amplifier 402, bundling device 403, optical microcavity 404, bundling device 405, wave filter 406, amplifier 407, output terminal 408, loop device 410,3dB bundling device 411, saturated absorbing body 412, Polarization Controller 413, and 410,411,412,413 formed variable self-tracking filter 409.
Fig. 5 is the 4th embodiment of the present invention, Qi Zhongyou: tunable single frequency laser 501, high power light amplifier 502, bundling device 503, optical microcavity 504, bundling device 505, wave filter 506, output terminal 508, regenerator 514.
Fig. 6 is a kind of structure of regenerator in the 4th embodiment of the present invention, wherein have: bundling device 601, loop device 603,3dB bundling device 604, saturated absorbing body 605, Polarization Controller 606, amplifier 607, wave filter 608, bundling device 609, and 603,604,605,606 formed variable self-tracking filter 602.
Fig. 7 is the spectrum of embodiment in Fig. 2, is respectively the frequency comb spectral line of feedback broach while being positioned near 1 × FSR, 2 × FSR pump light, 3 × FSR and single pumping, corresponding diagram (a) and (b), (c), (d).
Fig. 8 is the pumping condition relation of embodiment in Fig. 2, and when comprising feedback broach and being positioned near 1 × FSR, 2 × FSR pump light, 3 × FSR and single pumping, frequency comb produces the requirement to pumping wavelength and pump intensity;
Fig. 9 is the spectrum of embodiment in Fig. 4, is respectively single pumping and the frequency comb spectral line that has feedback regulation circuit, corresponding diagram (a) and (b).
Figure 10 is the RF spectrum of embodiment in Fig. 4, has single pumping and have the RF spectrum of feedback regulation circuit in figure.
Embodiment
Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is described, obviously, described embodiment is only the embodiment of a part of the present invention, instead of whole embodiment.
(1) first embodiment:
Shown in Fig. 2,201 single-frequency lasers that provide, 202 amplify luminous power, for system provides pumping laser.Pumping laser enters 204,204 output through 205 through 203, and a part becomes the output access 208 of system, and a part becomes feedback regulation signal.Feedback regulation signal is selected a broach through 206, then gets back to 203 after being amplified by 207, is injected in 204 together with pumping laser.208 access spectrometers, measure the frequency comb spectral line under different condition.
206 centre wavelength is first placed near 1 × FSR, 2 × FSR pumping wavelength, 3 × FSR position, realizes the frequency comb that broach is spaced apart 1 × FSR, 2 × FSR, 3 × FSR and produces, as Fig. 7 (a), (b), (c).Visible, utilize system of the present invention, the broach interval of having realized frequency comb is controlled.
202 output power is 26dBm, and 207 output power is 18dBm, and 203 splitting ratio is 2:8, enters into 204 pumping laser power 26dBm × 80%=320mW, feedback light power 18dBm × 20%=12mW, general power 332mW.Close 207, i.e. single pumping, cannot produce frequency comb.Until 202 output power is elevated to 30dBm, just realize the generation of frequency comb, as Fig. 7 (d).Now, enter into pumping laser power 30dBm × 80%=800mW of 204, far above the 332mW based on feedback regulation circuit.Visible, utilize system of the present invention, realize the reduction that frequency comb produces threshold value.
After frequency comb produces, fine setting pumping wavelength and pump power, measurement can maintain the pumping wavelength of frequency comb generation and the critical value range of pump power, i.e. and pumping condition tolerance, as Fig. 8.Visible, utilize system of the present invention, improve the tolerance to pumping condition.
(2) second embodiment:
Shown in Fig. 3, first embodiment as shown in Figure 2 develops, and the feedback regulation signal intensity that the difference of effect is to enter optical microcavity is larger.Feedback regulation signal becomes a road and pump light has the new pump light that fixed frequency is poor and power approaches, and can apply larger impact to frequency comb production process.
(3) the 3rd embodiment:
Shown in Fig. 4, on the basis of first embodiment as shown in Figure 2, increase variable self-tracking filter 409, by 408 access spectrometers and RF spectrum instrument.In the time of single pumping, realize the generation of frequency comb, spectrum is as Fig. 9 (a), and RF spectrum is as Figure 10.Although the broach of frequency comb is spaced apart 1 × FSR, its RF noise is stronger at 200MHz, 400MHz, 600MHz, only has partial coherence, belongs to II class frequency comb.
Access feedback regulation circuit, 406 centre wavelength is positioned near the 1 × FSR of pumping laser wavelength position, leaches near broach.409 further filtering, the broach that only allows pump light to produce passes through, and as feedback regulation signal, after amplification, through 403 injections 404, the output spectrum of frequency comb changes little, as Fig. 9 (b).RF noise significantly reduces, as Figure 10.
In the present embodiment, why feedback regulation can reduce RF noise, be because 409 filterings near the four-wave mixing composition being produced by other broach 1 × FSR, only allow the broach of pump light generation to pass through, induced the generation of I class frequency comb.
(4) the 4th embodiment:
Shown in Fig. 5,501 single-frequency lasers that provide, 502 amplify luminous power, for system provides pumping laser.Pumping laser enters 504,504 output through 505 through 503, and a part becomes the output access 508 of system, and a part becomes feedback regulation signal.Feedback regulation signal is selected a broach through 506, then is got back to 503 by 514 amplifying, after linewidth narrowing, is injected in 504 together with pumping laser.
Shown in Fig. 6, be in the present embodiment, a kind of implementation of regenerator, it has the effect of amplification and narrow-band filtering simultaneously.