CN103941515B - Optical frequency comb generation device and generation method with sweepable comb tooth frequency interval - Google Patents

Abstract

The invention provides a kind of comb frequency interval can the frequency comb generation device of frequency sweep, signal generator forms two-way output after microwave power divider, wherein, first via output is connected with electro-optic phase modulator after the first wide-band microwave power amplifier, second road output is connected with photoelectricity intensity modulator after sequentially passing through adjustable microwave delay line and the second wide-band microwave power amplifier, continuous-wave laser sequentially passes through electro-optic phase modulator and the output of photoelectricity intensity modulator of cascade, and photoelectricity intensity modulator is provided with direct current biasing.Additionally provide production method simultaneously.The present invention realizes the continuous frequency sweep in the broadband of comb frequency interval and accurately arbitrarily regulation；Produced frequency comb phase place, frequency stable；Produce frequency comb sufficient center wavelength accuracy, and tunable；Equipment scheme is simple, and cost is relatively low；Meet the application demand in the fields such as optical measurement, optical imagery, laser radar, laser spectroscopy, Fibre Optical Sensor, optic communication and Microwave photonics.

Description

Optical frequency comb generation device and generation method with sweepable comb tooth frequency interval

technical field

The invention relates to a method for generating an optical frequency comb whose comb-tooth interval frequency can be continuously swept by broadband phase in the technical field of optical communication and optical measurement, specifically, a method using a cascaded photoelectric phase modulator and a photoelectric intensity modulator An optical frequency comb generation device and method for realizing comb tooth interval frequency sweepable with broadband phase continuous frequency scanning, and comb tooth flatness of the optical frequency comb remains unchanged during the entire frequency sweep process.

Background technique

Optical frequency combs with precise and stable frequency intervals and coherent teeth are widely used in laser measurement, optical imaging, lidar, laser spectroscopy, optical fiber sensing, optical communication, and microwave photonics. An optical frequency comb with flat comb power, wide spectral range, phase coherence, and comb frequency interval can be continuously and arbitrarily controlled. There are pressing needs in signal generation, synchronization and phase-locking among multiple optical frequency combs, optical measurements, and generation of ultra-broadband continuum optical frequency combs.

At present, there are three main ways to generate optical frequency combs with tunable comb intervals: optical amplifier-based fiber loops, mode-locked lasers, and cascaded optoelectronic phase modulation driven by radio frequency signals.

The first is based on the optical fiber loop of the optical amplifier. The photoelectric modulator is placed inside the loop, and multiple comb teeth are generated by means of cyclic frequency offset, and the optical fiber amplifier and the optical bandpass filter inside the optical fiber loop are respectively Compensate for loop loss and control comb bandwidth. The comb tooth interval is related to the frequency of the modulator drive signal and the oscillation frequency of the fiber optic loop. When adjusting the comb tooth frequency interval, it is necessary to adjust the matching optical amplifier and optical filter. Therefore, the phase coherent continuous adjustment of the comb tooth interval frequency cannot be performed. ; and the optical amplifier in the optical fiber loop is cyclically amplified, and the frequency comb noise figure generated after multiple accumulations gradually increases.

The second is to use a nonlinear medium to broaden the spectrum of the mode-locked laser to generate a phase-coherent broadband supercontinuum. The frequency interval of the comb teeth can be tuned by adjusting the length of the oscillator cavity. After searching the prior art documents, it is found that there are mainly two existing methods for continuously sweeping and adjusting the comb-tooth interval frequency (ie repetition frequency) of the mode-locked laser. In the academic paper "Fiber-laser-based frequency comb with a tunable repetition rate" published in the academic journal "OpticsExpress" ("Optics Express") by Brian R.Washburn et al., A motor-controlled intracavity fiber delay line is proposed to change the cavity length of the mode-locked laser to achieve the purpose of frequency tuning. The adjustment range of the comb frequency interval is 49.34-50.12MHz, and the laser can maintain mode locking during the whole tuning process, that is, phase coherence. The academic paper "Stable sub-85fs passively mode-locked Erbiumfiber oscillator with tunable repetition rate" published in the academic journal "OpticsExpress" by Holger Hundermark et al. In Erbium Fiber Oscillator), it is proposed to change the cavity length by changing the position of the adjustable lens in the mode-locked laser cavity to achieve the purpose of frequency tuning. The adjustment range of the frequency interval is 1.1MHz, and the stable coherence between the comb teeth can be maintained during the whole tuning process. The above schemes can continuously and coherently tune the frequency interval of the comb teeth of the optical frequency comb. However, since the mode-locked laser requires complex and stable control of the cavity, the tunable range of the cavity length is limited, thereby limiting the frequency interval of the comb teeth. The tuning range is several MHz and requires complex cavity stability control mechanisms.

The third method, cascaded photoelectric phase modulation driven by radio frequency signals, can produce an optical frequency comb with phase coherence and flat comb power. The number of comb teeth produced by it is slightly less than the first two methods, but its structure is simple and stable. And the frequency interval of the comb teeth can be precisely adjusted directly by the driving radio frequency signal. However, in order to keep the generated frequency comb flat, the driving signals of the cascaded photoelectric phase and intensity modulators need to be controlled to match their phases, and the phase relationship of the driving signals needs to be recalibrated under different driving frequencies. Therefore, it is impossible to realize the wide-band continuous frequency sweep of the comb-tooth interval frequency while maintaining the flatness of the optical comb.

Contents of the invention

The object of the present invention is to overcome the deficiencies in the prior art, propose a kind of optical frequency comb generating device and generating method based on radio frequency signal driving cascaded photoelectric phase modulator and photoelectric intensity modulator comb tooth frequency interval sweepable frequency, The optical frequency comb generated by the generating device is phase-coherent, and the frequency interval of the comb teeth can be swept continuously in a wide-band range. The phase and frequency of the optical frequency comb generated by it are stable, and the implementation method is relatively simple, which can meet the needs of optical measurement and optical imaging. , laser radar, laser spectroscopy, fiber optic sensing, optical communication, and microwave photonics.

The present invention is achieved through the following technical solutions.

According to one aspect of the present invention, there is provided an optical frequency comb generation device with sweepable comb tooth frequency interval, including a signal generator, a continuous wave laser, a photoelectric phase modulator, a photoelectric intensity modulator, a microwave power divider, a A broadband microwave power amplifier, a second broadband microwave power amplifier and an adjustable microwave delay line, wherein the signal generator forms two output ports after passing through the microwave power divider, wherein the first output port passes through the first broadband microwave After the power amplifier is connected with the photoelectric phase modulator, the second output terminal is connected with the photoelectric intensity modulator after passing through the adjustable microwave delay line and the second broadband microwave power amplifier in turn, and the continuous wave laser is sequentially passed through the cascaded photoelectric Phase modulator and photointensity modulator output, the photointensity modulator is provided with a DC bias.

Preferably, it also includes a time-delay coherent instrument, a photoelectric receiver and a sampling oscilloscope, the output of the photoelectric intensity modulator is connected to the time-delay coherent instrument, the time-delay coherent instrument is connected to the photoelectric receiver, and the photoelectric intensity modulator is connected to the photoelectric receiver. The receiver is connected to a sampling oscilloscope.

Preferably, the signal generator is a microwave signal generator or a high-speed pulse signal generator.

According to another aspect of the present invention, there is provided a method for generating an optical frequency comb with a sweepable comb tooth frequency interval, comprising the following steps:

Step 1. The broadband frequency tunable signal generated by the signal generator is divided into two channels after passing through the microwave power divider. The first channel is amplified by the first broadband microwave power amplifier to drive the photoelectric phase modulator; the second channel passes through the adjustable microwave delay line After that, it is amplified by the second broadband microwave power amplifier to drive the photoelectric intensity modulator;

Step 2, the optical carrier signal output by the continuous wave laser passes through the cascaded photoelectric phase modulator and photoelectric intensity modulator, and adjusts the bias point of the photoelectric intensity modulator so that the output forms a flat optical frequency comb;

Step 3, adjust the adjustable delay line, so that the photoelectric delay difference is zero, to achieve broadband phase matching; at this time, the signal generator outputs a broadband sweep signal, correspondingly, the comb tooth interval of the optical frequency comb output by the photoelectric intensity modulator The frequency is also changed according to the frequency sweep, and an optical frequency comb with a comb tooth frequency interval that can be swept in a wide band is generated.

Preferably, in the step 2, the tooth interval frequency of the optical frequency comb is the same as the frequency of the signal generated by the signal generator.

Preferably, step 4 is also included, and the step 4 is specifically:

The optical frequency comb generated in step 3 with comb-tooth frequency intervals that can be swept in a wide band is displayed on a sampling oscilloscope after passing through a time-delay coherent instrument and a photoelectric receiver.

The optical frequency comb generation device and method provided by the present invention can sweep the frequency interval of the comb teeth, the flatness of the comb teeth of the output optical frequency comb does not change with the frequency of the signal generator output signal, that is, it does not change The frequency of the comb tooth interval changes, and the stable spectral flatness can be maintained during the whole broadband sweep process; the optical signal delay and the microwave driving signal delay are precisely matched between the cascaded optoelectronic phase modulator and the optoelectronic intensity modulation. A cascaded photoelectric phase modulator and a photoelectric intensity modulator are used, and the delay between the optical signal and the microwave drive signal between the two modulators is precisely adjusted to achieve broadband phase matching of the photoelectric delay difference. Through the microwave drive signal The broadband phase continuous frequency scanning realizes the method of scanning the optical frequency comb with the interval frequency of the comb tooth and the broadband phase continuous frequency, and the flatness of the comb teeth of the optical frequency comb remains unchanged during the whole frequency scanning process.

Compared with the prior art, the present invention has the following beneficial effects:

1. Breaking through the limitation of the traditional optical frequency comb generation method, because the frequency of the microwave signal generator is stable, accurate, and can be controlled and adjusted arbitrarily, it realizes the wide-band continuous frequency sweep and precise arbitrary adjustment of the comb tooth frequency interval;

2. The optical frequency comb generated by the microwave signal driven modulator has high stability, and the phase and frequency of the generated optical frequency comb are stable;

3. High stability or tunable continuous optical laser can be used as the optical carrier, so the central wavelength of the generated optical frequency comb is stable and tunable;

4. The equipment scheme is simple and the cost is low;

5. Breaking through the limitations of traditional optical frequency combs, it meets the application requirements of optical measurement, optical imaging, laser radar, laser spectroscopy, optical fiber sensing, optical communication, and microwave photonics.

Description of drawings

Other characteristics, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

Fig. 1 is the schematic diagram of the structure of the optical frequency comb generating device whose comb tooth frequency interval can be swept in the present invention;

Fig. 2 is the schematic diagram of the method of photoelectric delay difference broadband phase matching;

Fig. 3 is a schematic diagram of photoelectric time delay difference broadband phase matching, wherein, (a) is a schematic diagram when photoelectric time delay difference τ _S ≠ 0, (b) is a schematic diagram when photoelectric time delay difference τ _S =0;

Fig. 4 is the method flowchart of microwave drive signal broadband phase matching;

Fig. 5 is an effect diagram of wide-band frequency sweep of optical frequency comb tooth frequency interval generated in the embodiment of the present invention;

Fig. 6 is the spectrum of the optical frequency comb produced in the embodiment of the present invention, wherein, (a) is the spectrogram when the comb spacing frequency is the lowest 8.5GHz, and (b) is the spectrum when the comb spacing frequency is the highest 19.0GHz picture;

In the figure: 101 is a continuous wave semiconductor laser, 102 is a Mach-Zehnder photoelectric phase modulator, 103 is a Mach-Zehnder photoelectric intensity modulator, 104 is a 3-dB microwave power divider, and 105 is the first gain-adjustable broadband microwave power Amplifier, 106 is a second gain adjustable broadband microwave power amplifier, 107 is an adjustable microwave delay line, 108 is a microwave signal generator, 109 is a high-speed pulse signal generator, 110 is a Mach-Zehnder time-delay coherent instrument, 111 is a high-speed balanced photoelectric Receiver, 112 is a high-speed sampling oscilloscope, 113 is a DC bias.

detailed description

The following is a detailed description of the embodiments of the present invention: this embodiment is implemented on the premise of the technical solution of the present invention, and provides detailed implementation methods and specific operation processes. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention.

Please also refer to Figures 1 through 6.

This embodiment provides an optical frequency comb generating device with comb-tooth frequency intervals that can be swept, including a signal generator, a continuous wave laser, a photoelectric phase modulator, a photoelectric intensity modulator, a microwave power divider, a first broadband microwave power amplifier, a second broadband microwave power amplifier and an adjustable microwave delay line, wherein the signal generator forms two output terminals after passing through a microwave power divider, wherein the first output terminal is connected to the first broadband microwave power amplifier after passing through the first broadband microwave power amplifier The photoelectric phase modulator is connected, and the second output end is connected with the photoelectric intensity modulator after passing through the adjustable microwave delay line and the second broadband microwave power amplifier in sequence, and the continuous wave laser is sequentially passed through the cascaded photoelectric phase modulator and output of a photoelectric intensity modulator, and the photoelectric intensity modulator is provided with a DC bias.

Further, it also includes a time-delay coherent instrument, a photoelectric receiver, and a sampling oscilloscope. The receiver is connected to a sampling oscilloscope.

Further, the signal generator adopts a microwave signal generator or a high-speed pulse signal generator.

The present embodiment provides an optical frequency comb generating device with sweepable frequency intervals of comb teeth, and a method for generating an optical frequency comb includes the following steps:

Step 1. The broadband frequency tunable microwave signal generated by the signal generator is divided into two paths after passing through the microwave power divider. The first path is amplified by the first broadband microwave power amplifier to drive the photoelectric phase modulator; the second path is passed through the adjustable microwave delay After the line, it is amplified by the second broadband microwave power amplifier to drive the photoelectric intensity modulator;

Step 2, the optical carrier signal output by the continuous wave laser passes through the cascaded photoelectric phase modulator and photoelectric intensity modulator, and adjusts the bias point of the photoelectric intensity modulator so that the output forms a flat optical frequency comb;

Step 3, adjust the adjustable delay line, so that the photoelectric delay difference is zero, to achieve broadband phase matching; at this time, the signal generator outputs a broadband sweep signal, correspondingly, the comb tooth interval of the optical frequency comb output by the photoelectric intensity modulator The frequency is also changed according to the frequency sweep, and an optical frequency comb with a comb tooth frequency interval that can be swept in a wide band is generated.

Further, in the step 2, the tooth interval frequency of the optical frequency comb is the same as the frequency of the microwave signal generated by the signal generator.

Further, step 4 is also included, and the step 4 is specifically:

The optical frequency comb generated in step 3 with comb-tooth frequency intervals that can be swept in a wide band is displayed on a sampling oscilloscope after passing through a time-delay coherent instrument and a photoelectric receiver.

The present embodiment will be described in detail below in conjunction with the accompanying drawings.

In this example,

The continuous wave laser can use a continuous wave semiconductor laser;

The photoelectric phase modulator can be a Mach-Zehnder photoelectric phase modulator;

The photoelectric intensity modulator can be a Mach-Zehnder photoelectric intensity modulator;

The microwave power divider can use a 3-dB microwave power divider;

Both the first broadband microwave power amplifier and the second broadband microwave power amplifier may be gain-adjustable broadband microwave power amplifiers;

Mach-Zehnder time-delay coherer can be used as delay coherer;

The photoelectric receiver can use a high-speed balanced photoelectric receiver;

The sampling oscilloscope can use a high-speed sampling oscilloscope;

Fig. 1 is a functional block diagram of the present invention. The optical frequency comb generation device provided in this embodiment with comb-tooth frequency intervals that can be swept, mainly includes: a continuous wave semiconductor laser, a Mach-Zehnder photoelectric phase modulator, a Mach-Zehnder photoelectric intensity modulator, and a 3-dB microwave power divider , Broadband microwave power amplifier, adjustable microwave delay line, high-speed pulse signal generator or microwave signal generator, Mach-Zehnder delay coherent instrument, high-speed photoelectric receiver, high-speed sampling oscilloscope. First utilize high-speed pulse signal generator or microwave signal generator, Mach-Zehnder time-delay coherent instrument, high-speed photoelectric receiver, high-speed sampling oscilloscope to make the broadband phase matching of the photoelectric delay difference between cascaded modulators, that is to say τ _S =0, then use a microwave signal generator to generate the comb-tooth interval frequency broadband sweepable optical frequency comb.

Specifically:

1. Fig. 2 is a schematic diagram of the photoelectric delay difference broadband phase matching method: the high-speed pulse signal generator 109 generates a 10MHz square wave signal with a rise time of 30ps, which is divided into two paths after passing through the 3-dB microwave power divider 104, and one path is directly Input to the gain-adjustable broadband microwave power amplifier 105 and drive the Mach-Zehnder photoelectric phase modulator 102 after being amplified; Zender photoelectric intensity modulator 103 . The optical carrier output by the narrow-linewidth continuous wave semiconductor laser 101 is modulated by the cascaded Mach-Zehnder photoelectric phase modulator 102 and the Mach-Zehnder photoelectric intensity modulator 103, and then passed through the Mach-Zehnder time-delay coherent instrument with a delay of Δt=100ps After 110, it is input to a high-speed photoelectric receiver 111, and its output is observed through a high-speed sampling oscilloscope 112.

2. As shown in Figure 3(a), adjust the adjustable microwave delay line. When the photoelectric delay difference τ _S ≠ 0, the signals of the two arms of the Mach-Zehnder delay coherence instrument have a π phase shift in one cycle, so the output A narrow pulse of 100ps with the same period as the square wave signal is generated at the terminal. As shown in Figure 3(b), when the photoelectric delay difference is fully broadband phase-matched, that is, τ _S =0, there is no π phase shift in the two-arm signals of the Mach-Zehnder delay coherer, so there is no narrow pulse signal at the output. However, due to the limited square wave rise time and receiver bandwidth, the output pulse power decreases as τ _S decreases. The change trend of pulse power and τ _S relative to the broadband phase matching point is shown in Fig. 4. When the pulse power is minimum, further fine adjustment can be made to realize broadband phase matching of photoelectric delay difference.

Three, as shown in Figure 1, in the present embodiment, the drive signal that produces comb-tooth interval frequency broadband sweepable frequency comb is microwave signal generator 108, replaces the high-speed pulse signal generator in the first part (Fig. 2) 109, the broadband frequency tunable microwave signal produced by it is divided into two paths after being passed through a 3-dB power divider, and one path is amplified by the gain-adjustable broadband microwave power amplifier 105 until the peak-to-peak value is four times the voltage of the phase modulator V _π-PM The phase modulator 102 is then driven; the other path is amplified by the gain-adjustable microwave power amplifier 106 to a peak-to-peak value twice the voltage of the intensity modulator V _π-IM after passing through the tunable microwave delayer, and then the intensity modulator 103 is driven. Adjust the adjustable microwave delayer to the photoelectric delay broadband phase matching point described in step (2), and adjust the DC bias 113 of the intensity modulator at the same time to form a flat optical frequency comb output signal.

4. Adjust the microwave signal generator so that the output microwave signal sweeps in the range of 8.5 GHz to 19.0 GHz over an octave, and the output comb-tooth interval frequency broadband sweepable optical frequency comb is shown in Figure 5. Its comb flatness remains within 4dB over the entire sweep frequency range.

5. Figure 6(a) and (b) are the spectrum diagrams of the optical frequency comb when the comb-tooth spacing frequency is the lowest 8.5GHz and the highest 19.0GHz, respectively.

6. In this embodiment, when the photoelectric delay difference deviates from the broadband phase matching point, the flatness of the output optical frequency comb changes within the frequency sweep range of the entire comb interval frequency. When it is not at the best broadband phase matching point, the flatness of the output optical frequency comb changes drastically in the comb-tooth interval frequency sweep range. In practice, due to the limited rise time and receiver bandwidth described in step (2), the accuracy of the wideband phase matching point is limited, and the nonlinearity of the wideband power amplifier will introduce additional frequency harmonics, and the half-wave voltage of the modulator changes with the change of the driving frequency, resulting in a 4dB flatness change of the output optical frequency comb in the entire comb interval frequency sweep range.

7. Taking a microwave signal generator as an example, the method for generating an optical frequency comb with a sweepable comb tooth frequency interval provided in this embodiment is specifically:

Step 1, using the laser output by the continuous optical laser as the optical carrier, successively passing through the cascaded photoelectric phase modulator and photoelectric intensity modulator, and outputting the optical frequency comb signal; wherein, the cascaded photoelectric phase modulator and photoelectric intensity modulator The device is driven by the same microwave signal generator, and the driving frequency is exactly the same; the microwave signal generated by the microwave signal generator is amplified by the microwave power amplifier, and drives the photoelectric phase modulator and the photoelectric intensity modulator respectively;

The output optical frequency comb signal can be expressed as:

${\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; out</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; j\&pi;</span>}{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; PM</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; \{</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; j\&pi;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; DC</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; IM</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; \}</span>$

Among them, E _c is the strength of the optical carrier signal, j is the imaginary number unit, t is the time, π is the circumference ratio, ω _c is the angular frequency of the optical carrier signal, ω _s =2πf _s is the angular frequency of the driving signal, f _s is the driving The frequency of the signal, β _PM , β _IM and β _DC are the normalized modulation depth of the phase modulator, intensity modulator and intensity modulator DC bias relative to its half-wave voltage, τ _S =τ _O -τ _E is The delay difference between the optical signal delay τ _O and the microwave driving signal delay τ _E between the two cascaded modulators. The comb tooth frequency interval of the optical frequency comb signal is the frequency f _s of the driving microwave signal, and the comb tooth flatness of the optical frequency comb signal is related to the product ω _s τ _S of the driving signal frequency and the photoelectric delay difference.

Step 2, when the photoelectric delay difference τ _S =0 between the cascaded photoelectric phase modulator and the photoelectric intensity modulator, that is, when the broadband phase matching is realized for the photoelectric delay difference, the optical frequency comb signal for:

${\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; out</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; no</span>}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; ]</span>\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; \&infin;</span>}{\overset{<span\; class="notranslate">\; +</span><span\; class="notranslate">\; \&infin;</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}<span\; class="notranslate">\; \{</span>{\mathrm{<span\; class="notranslate">\; J</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&pi;</span>}{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; PM</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j\&pi;</span>}{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; DC</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; J</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; PM</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; IM</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; \}</span>$

Among them, n is the tooth number of the comb, and J _n (x) represents a Bessel function of order n. At this time, the flatness of the teeth of the optical frequency comb is only related to the modulation depth of the modulator and the DC bias of the intensity modulator, and has nothing to do with the frequency of the driving signal. By adjusting the modulation depth and DC bias, an optical frequency comb with flat teeth can be obtained.

Step 3, on the basis of step 1 and step 2, the frequency of the microwave signal generated by the microwave signal generator is continuously swept to generate an optical frequency comb with a continuous frequency interval of comb teeth, while maintaining the optical frequency The flatness of the teeth of the comb.

On the basis of the above-mentioned technical solution, the microwave signal generator can generate broadband frequency-sweeping microwave signals. The adjustment of the photoelectric delay difference between the cascaded modulators is realized through microwave delay lines.

Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims (6)

1. a comb frequency interval can the frequency comb generation device of frequency sweep, it is characterised in that include signal generator, Continuous-wave laser, electro-optic phase modulator, photoelectricity intensity modulator, microwave power divider, the first wide-band microwave work( Rate amplifier, the second wide-band microwave power amplifier and adjustable microwave delay line, wherein, described signal generator passes through Forming two-way output after microwave power divider, wherein, first via output is through the first wide-band microwave power amplifier Being connected with electro-optic phase modulator afterwards, the second road output sequentially passes through adjustable microwave delay line and the second wide-band microwave work( Being connected with photoelectricity intensity modulator after rate amplifier, described continuous-wave laser sequentially passes through the electro-optic phase modulation of cascade Device and the output of photoelectricity intensity modulator, described photoelectricity intensity modulator is provided with direct current biasing.

2. comb frequency interval according to claim 1 can the frequency comb generation device of frequency sweep, it is characterised in that Also include time delay correlator, optoelectronic receiver and sampling oscilloscope, the output of described photoelectricity intensity modulator with prolong When correlator be connected, described time delay correlator is connected with optoelectronic receiver, described optoelectronic receiver with sampling oscillography Device is connected.

3. comb frequency interval according to claim 1 and 2 can the frequency comb generation device of frequency sweep, its feature Being, described signal generator uses microwave signal generator or high-speed pulse signal generator.

4. a comb frequency interval can the frequency comb production method of frequency sweep, it is characterised in that comprise the following steps:

Step 1, signal generator produces wideband frequency tunable signal and is divided into two-way by after microwave power divider, the One tunnel the first wide-band microwave power amplifier amplifies rear drive electro-optic phase modulator；Second tunnel postpones through adjustable microwave After line, then amplify through the second wide-band microwave power amplifier, drive photoelectricity intensity modulator；

Step 2, the optical carrier of continuous-wave laser output is adjusted through electro-optic phase modulator and the light electric strength of cascade Device processed, the bias point of regulation photoelectricity intensity modulator makes output form smooth frequency comb；

Step 3, regulates variable delay line so that light electric delay difference is zero, it is achieved wideband phase mates；Now, signal The signal of generator output broadband frequency sweep, correspondingly, the comb spacing frequency of the frequency comb of photoelectricity intensity modulator output is also Frequency sweep change therewith, producing comb frequency interval can the frequency comb of broadband frequency sweep.

5. comb frequency interval according to claim 4 can the frequency comb production method of frequency sweep, its feature exists In, in described step 2, the comb spacing frequency of frequency comb is identical with the frequency of signal produced by signal generator.

6. the comb frequency interval according to claim 4 or 5 can the frequency comb production method of frequency sweep, its feature Be, also include step 4, described step 4 particularly as follows:

The comb frequency interval that step 3 produces can the frequency comb of broadband frequency sweep, through time delay correlator and optoelectronic receiver After, shown by sampling oscilloscope.