CN205452778U - Linear frequency modulation narrow linewidth fiber laser in broadband - Google Patents
Linear frequency modulation narrow linewidth fiber laser in broadband Download PDFInfo
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- CN205452778U CN205452778U CN201620101893.3U CN201620101893U CN205452778U CN 205452778 U CN205452778 U CN 205452778U CN 201620101893 U CN201620101893 U CN 201620101893U CN 205452778 U CN205452778 U CN 205452778U
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Abstract
The utility model discloses a linear frequency modulation narrow linewidth fiber laser in broadband, include 1.5 micron waves of the narrow linewidth seed source follower continuous laser of polarization in excess supply, radio -frequency signal source produces linear frequency modulated signal, sends into the modulator driver, and the modulator driver is with linear frequency modulated signal and offset voltage loading to double -parallel phase modulator, narrow linewidth seed source follower end and double -parallel phase modulator link to each other, and laser takes place linear frequency modulation at double -parallel phase modulator, and the double -parallel phase modulator output links to each other with fiber splitter, and fiber splitter output output unit modulation back laser links to each other with phase modulator 0 as radar local oscillator light, fiber splitter output, enlargies back laser from phase modulator 0 output. The utility model discloses have narrow linewidth, modulation bandwidth big, satisfy synthetic aperture laser radar and linear frequency modulation continuous wave laser radar operation requirement, the modulation is fast, the frequency modulation linearity high.
Description
Technical field
This utility model belongs to laser radar technique field, particularly relates to a kind of wide-band linearity frequency modulation(PFM) narrow cable and wide optical fiber laser.
Background technology
The wide-band linearity frequency modulating technology of narrow-linewidth laser is the key technology in Synthetic Aperture Laser Radar and linear frequency modulated CW lidar, but the wide-band linearity frequency modulating technology slower development of solid state laser, seriously constrains the development of laser radar technique.Laser instrument is carried out the methods such as the method main acousto-optic modulation of linear frequency modulation, thermal tuning, piezoelectric ceramics, Electro-optical Modulation.The transition time being passed light beam by crystal Bragg diffraction bandwidth and sound wave due to acousto-optic modulator performance is limited, the frequency of sound field can only arrive the magnitude of 100MHz, the acousto-optic modulator of high modulation bandwidth, its modulation bandwidth is only 200MHz, and modulation bandwidth is restricted.The mode being inserted into piezoelectric ceramic device or employing temperature control to laser cavity is all the most relatively common method.But the shortcoming impacts such as lagging characteristics, creep properties and the temperature characterisitic thereof due to piezoelectric ceramics, modulating frequency is low, and frequency instability is bigger；And when utilizing change temperature to realize laser frequency is modulated, although wide-band tuning can be realized, reach the tuning bandwidth of hundred GHz, but fast modulation cannot be realized, and frequency modulation precision is relatively low.The intracavity electro-optic crystal modulation of solid state laser is the method realizing the warbled relative optimization of fast linear.The Lincoln laboratory of masschusetts, U.S.A Polytechnics uses microplate short bore configurations Nd:YAG laser instrument in nineteen ninety, lithium tantalate electro-optic crystal intracavity modulation scheme can realize the linear frequency modulation of maximum 12GHz, and it is 1GHz that laser stably exports the tuning range that the linearity is good simultaneously；2008, University Of Shanxi used LiNbO3Etalon combines the method for Lithium metaniobate electro-optic crystal, and opposite end pump Nd:YVO4 laser realizes quickly tuning, it is achieved tuning range is 17.2GHz；2014, Harbin Institute of Technology's design a kind of LD pumping Nd:YVO4 linear frequency modulation laser instrument, utilize the electrooptic effect of electro-optic crystal RTP, this laser instrument is carried out linear frequency preparation test, obtaining maximum tuning range is 2.08GHz.But the electrooptic modulator that laser cavity internal modulation uses is the discrete device with larger volume size, commonly referred to as " body manipulator ", its shortcoming is to apply external electric field, the optical property of crystal to be changed to whole crystal, need to load the highest voltage, so that the light wave passed through is modulated." body manipulator " is all to realize big modulating bandwidth with high modulation rate.If wanting to realize wide-band linearity frequency modulated signal, then need the biggest applied voltage.The modulating speed that Lincoln laboratory, University Of Shanxi, Harbin Institute of Technology realize is respectively 12MHz/V, 8.6MHz/V and 9.5MHz/V.But electronic device is limited by slew rate, it is difficult to meet the body manipulator wide-band linearity frequency modulation(PFM) requirement to the linearity that upper kilovolt high pressure proposes, the excellent fm linearity that in fact can not realize.Although as Lincoln laboratory can realize the linear frequency modulation of maximum 12GHz in micro-slice laser, but the good tuning range of the linearity is only 1GHz.In addition to laser chamber internal modulation, the modulation of laser rays resistant frequency can also use external modulation mode.2015, the patent of Shanghai Optics and Precision Mechanics institute, Chinese Academy of Sciences's application proposes sawtooth signal by directly driving quadratic electro-optical effect phase-modulator to realize large-scale narrow-linewidth laser fast linear frequency modulation [application number: 2015103403174] after high voltage amplifier.In this patent application and do not take into account electronic device and limited by slew rate the most simultaneously, it is difficult to realizing the situation with good linearity, additionally the device of this patent application can not realize the single sideband modulation of laser frequency, it is difficult to directly applies in laser radar.Owing to waveguide modulator substantially simply applies external electric field to the least thin membrane regions, electric field is limited near thin film region, therefore its required driving power than body manipulator little one to two orders of magnitude, apply relatively low modulation voltage and be achieved with bigger modulation bandwidth.The fm linearity of electrooptic waveguide modulator is not limited by electronic devices and components slew rate, easily realizes, and therefore using electro-optical transducer phase-modulator that laser carries out external modulation can the broadband fast linear frequency modulation of narrow-linewidth laser.The many narrow-linewidth lasers comprising multiple effective frequency composition, the integral multiple that frequency interval is frequency modulating signal between each effective frequency content is produced after narrow-linewidth laser is phase modulated.Laser is by needing output single sideband singal after phase-modulator, it is necessary to suppression light carrier, high-order harmonic wave and another side band signal.Common practice is narrow-band filtering, but can be directly realized by the single sideband modulation of upper sideband rejection ratio by electric light ripple Lithium metaniobate double flat line phase manipulator.Calendar year 2001, Osaka, Japan Sumitomo new industrial research laboratory proposes the method that the integrated Lithium metaniobate double flat line phase manipulator of 2 × 2 Mach-Zender interferometer (MZI) structure realizes optical carrier suppression single sideband modulation.2013, astronomical and astrophysics institute and Japanese national observatory the scholar of TaiWan, China Academia Sinica uses double flat row MZI modulator external modulation to realize the frequency tuning of 120GHz in 0.2s, but owing to sideband and optical carrier suppression are poor, scheme use optical filter obtain single sideband singal.PHOTLINE company of France report in 2013 uses double flat line phase manipulator to realize sideband rejection ratio 35dB as frequency shifter, can shift frequency scope 1-18GHz.
The method using phase-modulator that laser external modulation realizes light frequency tuning at present is suggested, but utilize 2 × 2MZI structure double flat line phase manipulator to be directly realized by optical carrier suppression single-side belt, produce the performance of optical wavelength shift frequency, realizing wide-band linearity frequency modulating technology, the scheme developing 1.5 micron wave length rapid wideband linear frequency modulation narrow cable and wide optical fiber lasers has no report.
Utility model content
The purpose of this utility model is to provide a kind of wide-band linearity frequency modulation(PFM) narrow cable and wide optical fiber laser, it is desirable to provide a kind of modulation bandwidth is big, modulating speed is fast, fm linearity is high, 1.5 microns of wide-band linearity frequency modulation(PFM) narrow cable and wide optical fiber lasers of all optical fibre structure of simple in construction, all-fiber, eye-safe, linear polarization output.
This utility model is realized in, a kind of wide-band linearity frequency modulation(PFM) narrow cable and wide optical fiber laser, described wide-band linearity frequency modulation(PFM) narrow cable and wide optical fiber laser includes: narrow linewidth seed source, double flat line phase manipulator, radio-frequency signal source, modulator driver, fiber optic splitter, fiber amplifier, fiber optic splitter outfan and fiber amplifier outfan, wherein said narrow linewidth seed source outfan is connected with double flat line phase manipulator, laser is modulated at double flat line phase manipulator generation linear frequency, double flat line phase manipulator outfan is connected with fiber optic splitter, laser after fiber optic splitter outfan output partial modulation is as Radar Local-oscillator light, fiber optic splitter output is connected with fiber amplifier, laser after amplification exports from fiber amplifier outfan.
Further, described radio-frequency signal source is for producing the sine wave signal of the linear frequency modulation being applied on double flat line phase manipulator, signal bandwidth scope 1GHz-18GHz.
Further, described double flat line phase manipulator uses dual Parallel Design, and in Mach-Zender interferometer MZI, nested two sub-MZI, form 2 × 2MZI structure, and operation principle is as follows:
MZI1And MZI2It is Δ φ respectively that the light phase introduced by each self-bias voltage postpones1With Δ φ2, MZI3By direct current biasing at MZI1With MZI2Output between produce light phase postpone Δ φ3, when this situation, the output electric field of manipulator uses first kind Bessel series to launch to obtain:
Wherein, Ω and ω0Being radiofrequency signal and the angular frequency of light field of input, β is the index of modulation, E0It it is the optical field amplitude of input；
When the bias voltage on two sub-MZI is identical, i.e. Δ φ1=Δ φ2=Δ φ0, formula (1) becomes:
From formula (2), if MZI1And MZI2The electric Phase delay of input and MZI3The light phase introduced between postpones appropriate synthesis, and some harmonic wave sideband of output will be cancelled, in particular cases, it is achieved carrier-suppressed SSB；
Consider the least situation of β, i.e. J3(β)<<J2(β)<<J1(β),J0(β), formula (2) is reduced to:
As Δ φ0=π, if radiofrequency signal input phase postpones φe=± pi/2, light phase postpones Δ φ simultaneously3=± pi/2.The output light field being derived different phase combination generations by formula (3) is distributed as:
a)φe=pi/2, Δ φ3=pi/2, Δ φ0=π
Power spectral density is simultaneouslyIn power spectrum, only frequency is (ω0+ Ω) harmonic wave exist, be referred to as upper single-side belt carrier wave suppression；
b)φe=pi/2, Δ φ3=-pi/2, Δ φ0=π
Power spectral density is simultaneouslyIn power spectrum, only frequency is (ω0-Ω) harmonic wave exist, be referred to as the sideband carrier suppression that places an order；
c)φe=-pi/2, Δ φ3=pi/2, Δ φ0=π
Power spectral density is simultaneouslyAgain only having frequency in power spectrum is (ω0-Ω) harmonic wave exist, be referred to as the sideband carrier suppression that places an order.
d)φe=-pi/2, Δ φ3=-pi/2, Δ φ0=π
Power spectral density is simultaneouslyAgain only having frequency in power spectrum is (ω0+ Ω) harmonic wave exist, be referred to as upper single-side belt carrier wave suppression.
Therefore, as long as MZI1, MZI2, MZI3 are applied specific bias voltage, driving the radiofrequency signal of MZI1, MZI2 to have particular phases and postpone, double flat line phase manipulator just can realize the suppression of single-side belt carrier wave.Double flat line phase manipulator achieves the function to light wave shift frequency.It is capable of exporting light shift frequency amount radio frequency signal intensity with the radio frequency signals drive double flat line phase manipulator of linear frequency modulation, it is achieved the linear frequency modulation of light frequency.
Further, described fiber amplifier be single-mode optical fiber amplifier, double-cladding fiber amplifier or both combine the multi-stage fiber amplifier of composition.
The wide-band linearity frequency modulation(PFM) narrow cable and wide optical fiber laser that this utility model provides, has the feature of narrow linewidth；Outside narrow linewidth seed source laser cavity, realize frequency modulation(PFM), frequency-modulating process retains the narrow linewidth characteristic of seed source.This utility model has the advantages that modulation bandwidth is big；Modulation bandwidth is determined by the modulation bandwidth of double flat line phase manipulator, the modulation of 1～18GHz bandwidth range can be realized at present, Synthetic Aperture Laser Radar can be met and linear frequency modulated CW lidar uses requirement, exceed the linear FM bandwidth of the solid state laser reported simultaneously；This utility model has the advantages that modulating speed is fast, realizes frequency modulation(PFM) outside narrow linewidth seed source laser cavity, and modulating speed is determined by radio-frequency signal source output waveform rate of change；This utility model has the advantages that fm linearity is high, double flat line phase manipulator is waveguide optical devices, bias voltage is less than 13V, and fm linearity is not limited by electronic devices and components slew rate, and fm linearity is far above the solid state laser using electro-optic crystal internal modulation scheme.This utility model has the feature of simple in construction, double flat line phase manipulator realize linear frequency modulation, directly export, from double flat line phase manipulator, the single sideband singal that light carrier is suppressed at high proportion with other sideband, it is not necessary to carry out optically filtering；This utility model Output of laser wavelength is 1.5 microns, has the feature of eye-safe；Optical component whole band tail optical fiber output that this utility model uses, laser structure has the feature of all-fiber；The all polarizers of optical component that this utility model uses, Laser Output Beam has the feature of output lead polarization.
Accompanying drawing explanation
Fig. 1 is the wide-band linearity frequency modulation(PFM) narrow cable and wide optical fiber laser structural representation that this utility model embodiment provides；
In figure: 1, narrow linewidth seed source；2, double flat line phase manipulator；3, radio-frequency signal source；4, modulator driver；5, fiber optic splitter；6, fiber amplifier；7, fiber optic splitter outfan；8, fiber amplifier outfan.
Fig. 2 is the principle assumption diagram of the double flat line phase manipulator that this utility model embodiment provides.
Detailed description of the invention
In order to make the purpose of this utility model, technical scheme and advantage clearer, below in conjunction with embodiment, this utility model is further elaborated.Should be appreciated that specific embodiment described herein, only in order to explain this utility model, is not used to limit this utility model.
Below in conjunction with the accompanying drawings application principle of the present utility model is explained in detail.
Refering to Fig. 1,1.5 microns of wide-band linearity frequency modulation(PFM) narrow cable and wide optical fiber lasers compositions include: narrow linewidth seed source 1, double flat line phase manipulator 2, radio-frequency signal source 3, modulator driver 4, fiber optic splitter 5, fiber amplifier 6, fiber optic splitter outfan 7, fiber amplifier outfan 8.Wherein:
Narrow linewidth seed source 1 exports 1.5 micron wave length linear polarization continuous lasers.Radio-frequency signal source 3 produces linear frequency modulation signal, is sent to modulator driver 4, and linear frequency modulation signal and bias voltage are loaded into double flat line phase manipulator 2 by modulator driver 4.Narrow linewidth seed source 1 outfan is connected with double flat line phase manipulator 2, and laser occurs linear frequency to modulate at double flat line phase manipulator 2.Double flat line phase manipulator 2 outfan is connected with fiber optic splitter 5, and fiber optic splitter outfan 7 exports the laser after partial modulation as Radar Local-oscillator light.Fiber optic splitter 5 exports and is connected with fiber amplifier 6, and the laser after amplification exports from fiber amplifier outfan 8.
The key components in embodiment used be presented herein below:
Narrow linewidth seed source 1 can be 1.5 micron wavebands output the narrow linewidth semiconductor laser of continuous laser, DBR/DFB optical fiber laser, solid state lasers in any one, spectral line width is less than 200kHz, polarization state is linear polarization, and single-mode polarization maintaining fiber exports, Output optical power 1～100mW.
Double flat line phase manipulator 2 is the waveguide optical electrooptic modulator of 2 × 2MZI structure, and Electrooptic crystal material can be Lithium metaniobate, potassium tantalate-niobate etc..
Radio-frequency signal source 3 is for producing the sine wave signal of the linear frequency modulation being applied on double flat line phase manipulator 2, signal bandwidth scope 1GHz-18GHz.
After modulator driver 4 receives radiofrequency signal, it is converted into the two paths of signals with enough power and fixed skew, two paths of signals and 3 road bias voltages are loaded into double flat line phase manipulator 2.The phase contrast of two paths of signals and 3 roads polarization voltage are accomplished that the suppression of up or down single-side belt carrier wave supplies as required.
Fiber amplifier can be single-mode optical fiber amplifier, double-cladding fiber amplifier or both combine the multi-stage fiber amplifier of composition.The linear frequency modulation amplified output of laser can improve the measurement distance of laser radar.
This utility model utilizes 2 × 2MZI structure double flat line phase manipulator can be directly realized by optical carrier suppression single-side belt, produce the performance of optical wavelength shift frequency, by loading linear frequency modulation signal, it is achieved 1.5 micron wave length rapid wideband linear frequency modulation narrow-linewidth laser outputs.This utility model has that modulation bandwidth is big, modulating speed is fast, fm linearity is high, the feature of simple in construction, all-fiber, eye-safe, linear polarization output, it is possible to meet Synthetic Aperture Laser Radar and linear frequency modulation laser radar application requirement.
In this utility model, described double flat line phase manipulator is core devices, and structure refers to Fig. 2.Manipulator uses dual Parallel Design, and in Mach-Zender interferometer (MZI), nested two sub-MZI, form 2 × 2MZI structure.According to the operation principle of double flat line phase manipulator, as long as to MZI1、MZI2、MZI3Apply specific bias voltage, drive MZI1、MZI2Radiofrequency signal have particular phases postpone, double flat line phase manipulator just can realize single-side belt carrier wave suppresses.Double flat line phase manipulator achieves the function to light wave shift frequency.It is capable of exporting light shift frequency amount radio frequency signal intensity with the radio frequency signals drive double flat line phase manipulator of linear frequency modulation, it is achieved the linear frequency modulation of light frequency.
The foregoing is only preferred embodiment of the present utility model, not in order to limit this utility model, all any amendment, equivalent and improvement etc. made within spirit of the present utility model and principle, within should be included in protection domain of the present utility model.
Claims (3)
1. a wide-band linearity frequency modulation(PFM) narrow cable and wide optical fiber laser, it is characterized in that, described wide-band linearity frequency modulation(PFM) narrow cable and wide optical fiber laser includes: narrow linewidth seed source, double flat line phase manipulator, radio-frequency signal source, modulator driver, fiber optic splitter, fiber amplifier, fiber optic splitter outfan and fiber amplifier outfan, wherein said narrow linewidth seed source outfan is connected with double flat line phase manipulator, laser is modulated at double flat line phase manipulator generation linear frequency, double flat line phase manipulator outfan is connected with fiber optic splitter, laser after fiber optic splitter outfan output partial modulation is as Radar Local-oscillator light, fiber optic splitter output is connected with fiber amplifier, laser after amplification exports from fiber amplifier outfan.
2. wide-band linearity frequency modulation(PFM) narrow cable and wide optical fiber laser as claimed in claim 1, it is characterised in that described radio-frequency signal source is for producing the sine wave signal of the linear frequency modulation being applied on double flat line phase manipulator, signal bandwidth scope 1GHz-18GHz.
3. wide-band linearity frequency modulation(PFM) narrow cable and wide optical fiber laser as claimed in claim 1, it is characterised in that described double flat line phase manipulator uses dual Parallel Design, in Mach-Zender interferometer MZI, nested two sub-MZI, form 2 × 2MZI structure.
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