阅读说明：本技术 一种基于垂直腔面发射激光器的微波频率梳的产生方法 (Method for generating microwave frequency comb based on vertical cavity surface emitting laser ) 是由 庞海越 樊亚仙 陶智勇 李沼云 刘欢 邹梦强 马静 于 2019-10-21 设计创作，主要内容包括：本发明公开了一种基于垂直腔面发射激光器的微波频率梳的产生方法,该方法是利用在光电反馈作用下垂直腔面发射激光器呈现出的非线性动力学特性,通过调节光电反馈系统中的光电反馈强度和光电反馈时间,同时产生两路功率均衡、梳线纯净、超宽带、光信号和电信号两种形式、偏振方向正交的线性偏振微波频率梳；光电反馈系统由依次连接的垂直腔面发射激光器(VCSEL)、光隔离器(OI)、可变光衰减器(VOA)、光分束器(FC)、单模光纤(SMF)、光电探测器(PD)、电放大器(EA)和电耦合器(EC)组成；该方法获得微波频率梳具有功率均衡、梳线纯净、超宽带、偏振方向正交等优点,能够满足更多领域的应用需求。(The invention discloses a method for generating a microwave frequency comb based on a vertical cavity surface emitting laser, which utilizes the nonlinear dynamic characteristics of the vertical cavity surface emitting laser under the action of photoelectric feedback, and simultaneously generates two paths of linear polarization microwave frequency combs with balanced power, pure comb lines, ultra wide bands, two forms of optical signals and electric signals and orthogonal polarization directions by adjusting the photoelectric feedback intensity and the photoelectric feedback time in a photoelectric feedback system; the photoelectric feedback system consists of a Vertical Cavity Surface Emitting Laser (VCSEL), an Optical Isolator (OI), a Variable Optical Attenuator (VOA), an optical beam splitter (FC), a Single Mode Fiber (SMF), a Photoelectric Detector (PD), an Electric Amplifier (EA) and an Electric Coupler (EC) which are connected in sequence; the microwave frequency comb obtained by the method has the advantages of balanced power, pure comb lines, ultra wide band, orthogonal polarization direction and the like, and can meet application requirements of more fields.)

1. A method for generating a microwave frequency comb based on a vertical cavity surface emitting laser is characterized in that the method utilizes the nonlinear dynamic characteristics of the vertical cavity surface emitting laser under the photoelectric feedback effect, and simultaneously generates two paths of linear polarization microwave frequency combs with balanced power, pure comb lines, ultra wide bands, two forms of optical signals and electric signals and orthogonal polarization directions by adjusting the photoelectric feedback intensity and the photoelectric feedback time in a photoelectric feedback system;

the photoelectric feedback system is composed of a Vertical Cavity Surface Emitting Laser (VCSEL), an Optical Isolator (OI), a Variable Optical Attenuator (VOA), an optical beam splitter (FC), a Single Mode Fiber (SMF), a Photoelectric Detector (PD), an Electric Amplifier (EA) and an Electric Coupler (EC) which are connected in sequence.

2. The method as claimed in claim 1, wherein the optical-electrical feedback system is formed by sequentially passing laser light emitted from the VCSEL through OI, VOA, FC, taking 10% of the optical signal as output detection signal, and converting 90% of the optical signal into electrical signal after passing through SMF and PD; after the electric signal passes through the EC after being amplified by the EA, 20% of the electric signal is used as an output detection signal, and 80% of the electric signal is applied to the bias current of the VCSEL in the form of an irregular current disturbance signal, so that the gain coefficient of the VCSEL is irregularly changed, the VCSEL is promoted to present nonlinear dynamic behavior, and the MFC is generated.

3. The method as claimed in claim 1, wherein the electro-optical feedback is performed by applying a bias current to the VCSEL after converting the optical signal into an irregular current perturbation signal, so as to cause the gain coefficient of the VCSEL to change irregularly, thereby causing the VCSEL to exhibit nonlinear dynamic behavior.

4. The method as claimed in claim 1, wherein the ultra-wideband refers to a power of 180GHz or more within 10 dB.

5. The method for generating the vertical cavity surface emitting laser based microwave frequency comb according to claim 1, wherein the optical signal and the electrical signal are in the form of microwave frequency comb optical signal, 10% of the optical signal output by the beam splitter (FC) in the electro-optical feedback system; the 20% of the electrical signal output by the Electrical Coupler (EC) is in the form of a microwave frequency comb electrical signal.

6. The method as claimed in any one of claims 1, 2 and 3, wherein the VCSEL has a center wavelength of 1550nm, and the two orthogonal linear polarization directions of the 1550nm VCSEL output can be controlled by adjusting the temperature and bias current of the 1550nm VCSELxLP polarization mode andyLP polarization mode。

7. A method as claimed in any one of claims 1, 2 and 4, wherein said electro-optical feedback system is adapted to adjust OI to ensure unidirectional transmission of the optical path; regulating the photoelectric feedback intensity of the photoelectric feedback system by regulating the VOA; splitting the optical signal into two parts by FC; regulating and controlling photoelectric feedback time by regulating SMF; converting the optical signal into an electrical signal by using the PD; the intensity of an electric signal in photoelectric feedback is regulated and controlled by adopting EA; by dividing the electrical signal into two parts using the EC, 20% of the electrical signal is used as the output probe optical signal, and 80% of the electrical signal is applied to the bias current of the vcsel in the form of a current perturbation signal.

8. The method for generating the VCSEL-based microwave frequency comb according to any one of claims 1, 2, 5, and 7, wherein the FC outputs 10% of the optical signal as an output probe optical signal and 90% of the optical signal is used for electro-optical feedback.

9. The method as claimed in any one of claims 1, 2, 5 and 7, wherein the EC outputs 20% of the electrical signal as the output probing optical signal, and 80% of the electrical signal current disturbs the bias current applied to the vcsel.

Technical Field

The invention relates to the technical field of microwave photonics, in particular to a method for generating a microwave frequency comb based on a Vertical-cavity surface-emitting laser (VCSEL).

Background

A Microwave Frequency Comb (MFC) refers to a microwave signal in the frequency domain consisting of a series of frequency components equally spaced as a comb. Compared with single-frequency microwave signals, the MFC has the advantages of multiple spectral lines, wide frequency range, balanced spectral line intervals, capability of providing multi-frequency microwave signals and single-frequency microwave signals and the like, and therefore has wide application prospects in the fields of radar detection, optical fiber wireless hybrid communication, satellite communication, anti-interference testing, frequency and distance measurement and the like.

In recent years, scholars at home and abroad successively put forward a plurality of MFC generation technical schemes, which mainly comprise two main types of methods, namely electrical methods and optical methods. The traditional generation method of the electrical microwave frequency comb is limited by the bandwidth of an electronic device, and the generated MFC signal has the defects of sharply reduced higher harmonic amplitude, smaller bandwidth and the like. Therefore, it is difficult to obtain signals of power-balanced and ultra-wideband MFCs by electrical methods, and it is difficult to meet the requirements of some application fields. The MFC generated based on the optical method can overcome the bandwidth limitation of electronic devices in the electrical method, and can generate MFC signals with balanced power and ultra-wide band, so that the MFC has attracted extensive attention. The currently reported technical solutions for producing MFC by optical methods are mainly the following two: (1) MFC is obtained by utilizing the nonlinear effect of a tunnel junction of a scanning tunneling microscope. For example, in 2011, m.j.hagmann and a.efilmv et al, published on applied physics Letters in the article "Microwave frequency-comb generation in a tunneling junction by interface simulation of ultra fast lasers", a technical solution for using 15fs ultra fast pulses to excite the tunnel junction of a tunnel microscope was proposed, an MFC signal with a comb pitch of 74.25MHz and a bandwidth of about 1GHz was obtained through experiments, and a typical output power of a fundamental frequency signal in the MFC was-146 dBm. (2) The optical frequency comb is switched using a Photodetector (PD) to obtain the MFC. For example, in 2015, w.t.wang and j.g.liu et al, in optics communications publication, "Multi-band local microwave signal generation based on optical frequency comb generator", a technical solution for generating an MFC by PD conversion of an optical frequency comb under optical sideband injection locking was proposed, and an MFC with a comb pitch of 5GHz and a bandwidth of about 40GHz was obtained experimentally. The technical scheme of adopting the two optical methods to generate the microwave frequency comb has unique advantages, but the defects are more prominent, for example, the obtained microwave frequency comb has the defects of nonadjustable comb pitch, frequency jitter, larger phase noise and the like. In addition to the above two methods, in recent years, research on generating MFC signals by using nonlinear dynamics exhibited by semiconductor lasers under external disturbance has attracted much attention. As published in the book "Tunable and broadband microwave frequency comb based on a semiconductor device with an incoherent optical feedback" by m.r.zhao and z.m.wu et al in Chinese Physics B in 2015, an all-optical scheme for generating ultra-wideband MFC using the non-linear dynamics of an incoherent optical feedback semiconductor laser was proposed, and MFC with a bandwidth of 40GHz varying in the range of ± 5dB could theoretically be obtained. L.fan and g.q.xia et al, 2017, published on IEEE Access as "Tunable ultra-wideband and microwave frequency comb generation based on a current modulated microwave oscillator unit optical injection", and proposed a technical scheme for generating a Tunable ultra-wideband microwave frequency comb based on a current modulated distributed feedback semiconductor laser under light injection.

In addition, there are many patents for methods for generating microwave frequency combs in recent years, for example, in 2014, published by Zhang BaoFu et al, university of people's liberation military project, china, "a device and a method for generating optical frequency combs by using a photoelectric oscillator" (patent publication No. CN104092491A) proposes a device and a method for generating optical frequency combs by using a photoelectric oscillator. Published patent full-optical broadband microwave frequency comb generator (patent publication No. CN104577648A) by Duntao et al of southwest university in 2015, an full-optical broadband microwave frequency comb generator based on a distributed feedback semiconductor laser is provided. Fan li et al, university in southwest 2017, published a patent "tunable ultra-wideband microwave frequency comb generation method based on semiconductor lasers" (patent publication No. CN106981814A), and proposed a method in which continuous light output by an adjustable laser source is injected into a current-modulated semiconductor laser, and the semiconductor laser is prompted to generate a high-quality tunable ultra-wideband microwave frequency comb by using a bandwidth enhancement effect caused by light injection. The technical scheme and the device have the advantages and can be applied to various fields. However, the lasers used are all edge-emitting distributed feedback lasers, and there are few methods and devices for generating a microwave frequency comb using vertical cavity surface emitting lasers. Compared with an edge-emitting semiconductor laser, the vertical cavity surface-emitting laser has the unique advantages of low threshold current, high optical fiber coupling efficiency, dynamic single longitudinal mode output, low manufacturing cost, easiness in integrating a high-density two-dimensional array and the like. In recent years, patents have been reported for the generation of microwave frequency combs using vertical cavity surface emitting lasers. For example, in 2015, duntao et al published patent "a dual-path microwave frequency comb generator based on an optoelectronic feedback VCSEL" (CN 105006727B), the invention utilizes the optoelectronic feedback VCSEL to generate a dual-path microwave frequency comb, but the wavelength of the VCSEL is at the short wavelength of 850nm in the first loss window, and in addition, the optoelectronic feedback module adopts spatial optical elements such as an aspheric lens, a beam splitter, a half-wave plate, and a polarization beam splitter, which makes the adjustment of the optical path complicated.

Therefore, the research of a novel method and a device for generating a high-quality microwave frequency comb based on a vertical cavity surface emitting laser has important significance and practical value in meeting application requirements in more fields.

Disclosure of Invention

The invention aims to overcome the defects of the existing MFC generation technology and provide a method for generating a microwave frequency comb based on a vertical cavity surface emitting laser so as to obtain a linear polarization microwave frequency comb with the advantages of balanced power, pure comb lines, ultra wide band, orthogonal polarization direction and the like, so that the linear polarization microwave frequency comb can meet the application requirements of more fields.

The technical scheme for realizing the purpose of the invention is as follows:

a method for generating a microwave frequency comb based on a vertical cavity surface emitting laser comprises the steps of utilizing the nonlinear dynamic characteristics of the vertical cavity surface emitting laser under the photoelectric feedback effect, and simultaneously generating two paths of linear polarization microwave frequency combs with balanced power, pure comb lines, ultra wide bands, two forms of optical signals and electric signals and orthogonal polarization directions by adjusting the photoelectric feedback intensity and the photoelectric feedback time in a photoelectric feedback system;

the photoelectric feedback system is composed of a Vertical Cavity Surface Emitting Laser (VCSEL), an Optical Isolator (OI), a Variable Optical Attenuator (VOA), an optical beam splitter (FC), a Single Mode Fiber (SMF), a Photoelectric Detector (PD), an Electric Amplifier (EA) and an Electric Coupler (EC) which are connected in sequence.

The photoelectric feedback system is characterized in that after laser emitted by a VCSEL sequentially passes through OI, VOA and FC, 10% of optical signals serve as output detection signals, and 90% of the output optical signals are converted into electric signals after passing through SMF and PD; after the electric signal passes through the EC after being amplified by the EA, 20% of the electric signal is used as an output detection signal, and 80% of the electric signal is applied to the bias current of the VCSEL in the form of an irregular current disturbance signal, so that the gain coefficient of the VCSEL is irregularly changed, the VCSEL is promoted to present nonlinear dynamic behavior, and the MFC is generated.

The photoelectric feedback function is to convert an optical signal into an irregular current disturbance signal and apply the irregular current to the VCSEL to drive the gain coefficient of the VCSEL to change irregularly, so that the VCSEL presents abundant nonlinear dynamic behaviors.

The ultra-wideband refers to the power within the amplitude range of 10dB, and the bandwidth can reach more than 180 GHz.

The optical signal and the electric signal are in the form that 10% of optical signals output by a beam splitter (FC) in the photoelectric feedback system are microwave frequency comb optical signals; the 20% of the electrical signal output by the Electrical Coupler (EC) is in the form of a microwave frequency comb electrical signal.

The central wavelength of the VCSEL is 1550nm, and two linear x LP polarization modes and y LP polarization modes of the 1550nm VCSEL, which are orthogonal in output polarization direction, can be controlled by adjusting the temperature and the bias current of the 1550nm VCSEL.

The photoelectric feedback system ensures the unidirectional transmission of the optical path by adjusting OI; regulating the photoelectric feedback intensity of the photoelectric feedback system by regulating the VOA; splitting the optical signal into two parts by FC; regulating and controlling photoelectric feedback time by regulating SMF; converting the optical signal into an electrical signal by using the PD; the intensity of an electric signal in photoelectric feedback is regulated and controlled by adopting EA; by dividing the electrical signal into two parts using the EC, 20% of the electrical signal is used as the output probe optical signal, and 80% of the electrical signal is applied to the bias current of the vcsel in the form of a current perturbation signal.

And the FC outputs 10% of optical signals as output detection optical signals, and 90% of optical signals are used for photoelectric feedback.

In the EC, 20% of the output electrical signal is used as the output detection optical signal, and 80% of the electrical signal current is applied to the bias current of the vertical cavity surface emitting laser in the form of a disturbance signal.

Has the advantages that: according to the method for generating the microwave frequency comb based on the vertical cavity surface emitting laser, provided by the invention, as the photoelectric feedback belongs to incoherent feedback and is not influenced by the phase accumulation of a feedback external cavity, the method can be very conveniently and effectively regulated and controlled through the existing electronic technology, and is gradually one of effective modes for people to research the nonlinear dynamics of a semiconductor laser in recent years. By adjusting the photoelectric feedback intensity and the photoelectric feedback time, the invention can simultaneously generate the linear polarization microwave frequency combs (x LP MFC and y LP MFC) with balanced power, pure comb line, ultra-wideband, two forms of optical signals and electric signals and orthogonal polarization directions, and the method has the following advantages:

1. a microwave frequency comb is generated by combining a VCSEL (vertical cavity surface emitting laser) and a photoelectric feedback loop;

2. the structure is simple, the volume is small, and the regulation and control are easy;

3. the ultra-wideband microwave frequency comb can generate ultra-wideband microwave frequency comb with power within 10dB amplitude range and bandwidth of 180 GHz;

4. the microwave frequency comb can generate optical signals and electric signals;

5. can simultaneously generate two paths of linear polarization microwave frequency combs with orthogonal polarization directions.

Drawings

Figure 1 is a schematic diagram of the structure of an electro-optical feedback system,

in the figure: VCSEL is vertical cavity surface emitting laser, OI is optical isolator, VOA is variable optical attenuator, FC is optical beam splitter, SMF is single mode fiber, PD is photodetector, EA is electric amplifier, EC is electric coupler;

FIG. 2 is a graph of VCSEL output power as a function of normalized bias current μ at free-running, with the solid curve being the linear polarization mode in the x-direction (x LP) and the dashed curve being the linear polarization mode in the y-direction (y LP);

fig. 3 is a power spectrum of VCSEL output when normalized bias current μ is 7, photoelectric feedback time τ is 0.1ns, and photoelectric feedback coefficient ζ is 0.667; where graph (a) is a microwave frequency comb linearly polarized in the x-direction (x LP MFC) and graph (b) is a microwave frequency comb linearly polarized in the y-direction (y LP MFC).

Detailed Description

The invention will be further elucidated with reference to the drawings and examples, without however being limited thereto.