The relevant synthetic multiplying arrangement of a kind of frequency division multiplexing spectrum
Technical field
The present invention proposes the relevant synthetic multiplying arrangement of a kind of frequency division multiplexing spectrum.
Background technology
The high power optical fibre laser pulse has important application in fields such as basic scientific research, industrial processes, laser radar, inertial confinement fusion, precision measurement, laser remote sensings.But due to the restriction that is subject to thermo-optic effect, nonlinear effect, gain media damage threshold, separate unit ultrashort pulse fiber laser average power generally is limited in hectowatt grade, and its peak power is generally the gigawatt magnitude.
For the limited defective of single channel amplifying power, adopt multimode blocking structure, the phase place of controlling each road optical-fiber laser reaches phase-locked output, realizes the relevant synthetic of pulse, can make the Output of laser average power obtain decades of times, and the lifting of hundreds of times of peak power densities.Realize that effective pulse laser is relevant synthetic, must satisfy simultaneously the locking of impulsive synchronization and phase place.Realize that at present the pulse coherence synthetic method mainly contains three kinds, a kind of is the polarized combination method, it is to utilize polarization beam apparatus the linear polarization seed light source to be divided into several Shu Guang of different polarization direction, after being amplified respectively, each polarized light component carries out again polarization coupling, the method shortcoming need to be the optical path difference of fine adjustment unit light beam, and the phase place of polarized light component is difficult to locked simultaneously.The 2nd, passive relevant synthetic method, thus it is to realize that by certain Energy Coupling mechanism or nonlinear interaction the auto-compensation that each road laser phase rises and falls reaches the phase place locking, and the method locking precision is low, and device stability is poor.The 3rd, the synthetic method that initiatively is concerned with, it can realize very high locking precision, but required electrical feedback apparatus structure is complicated, usually exists larger random time to postpone.
In addition, high power pulse is in amplification process, and the impact of the effects such as, GVD (Group Velocity Dispersion) non-linear owing to being subject to makes the short pulse of high-peak power after the fiber amplifier transmission is amplified, and time waveform and spectrum produce serious distortion, can not satisfy actual demand.Avoid the time and frequency zone noise in amplification process, the accurate high-power fiber transmission amplification process of controlling need to overcome following defective:
1, gain narrowing effect.According to Fourier's variation relation, the gain spectra narrowed width will directly cause achieved pulse width to increase.
2, intensity-phase noise.This noise can make each spectrum component phase place random fluctuation, spectrum both sides appearance concussion structure.
3, high-order dispersion and nonlinear phase shift accumulation non-linear chirp.Non-linear chirp can not be compensated by the chirp management device, will make the division of pulse time domain, and limiting peak power promotes.
4, medium gain limit bandwidth.For the optical-fiber laser medium, same gain media can only realize that limited spectrum signal amplifies, and the ultrashort even Few-cycle pulse of restriction high power is realized.Based on above-mentioned factor, single multiplying arrangement is difficult to further realize that the high power of paired pulses light amplifies.
In sum, although have at present the multiple technology and method of realizing that high power pulse amplifies, all exist various shortcomings and deficiencies.
Summary of the invention
The present invention is directed to the deficiency in above-mentioned traditional laser pulse amplifying technique, the relevant synthetic multiplying arrangement of a kind of frequency division multiplexing spectrum has been proposed, the method organically combines frequency multiplexing technique and relevant synthetic technology, solves impulsive synchronization and the relevant difficult problem of frequency spectrum in the relevant building-up process of ultrashort pulse optical-fiber laser.
For achieving the above object, the present invention by the following technical solutions:
the relevant synthetic multiplying arrangement of a kind of frequency division multiplexing spectrum, comprise ultra-short pulse oscillator, Pre-power amplifier, the spectrum widening device, the wavelength-division multiplex beam splitter, the multistage multiplying arrangement of phase noise precompensation and time synchronized, the wavelength-division multiplex bundling device, compressor reducer, the laser pulse that ultra-short pulse oscillator produces passes through Pre-power amplifier in turn, the spectrum widening device, the wavelength-division multiplex beam splitter, the multistage multiplying arrangement of phase noise precompensation and time synchronized, the wavelength-division multiplex bundling device, compressor reducer, the ultrashort pulse of compressor reducer output high-peak power, the multistage multiplying arrangement of described phase noise precompensation and time synchronized comprises a plurality of phase noise compensation multiplying arrangements, a plurality of delay controllers, beam splitter, measure each road and amplify the balanced type optics simple crosscorrelation time jitter measurement mechanism of the relative time shake of pulse, described phase noise compensation multiplying arrangement comprises acousto-optic frequency shifters, multi-stage fiber amplifier, beam splitting chip, self-reference zero-frequency sniffer, filter amplifier, the seed light of wavelength-division multiplex beam splitter output is passed through acousto-optic frequency shifters, multi-stage fiber amplifier, beam splitting chip, self-reference zero-frequency sniffer in turn.
Described ultra-short pulse oscillator adopts Yb dosed optical fiber light comb, and its centre wavelength is 1030nm, and pulse repetition rate is 80MHz, locking precision<1mHz, and pulse carrier envelope phase locking precision<10mHz, pulse output average power is 50mW.
Described power adopts the forward pumping formula amplifier of ytterbium-doped double-cladded-layer photonic crystal fiber through Pre-power amplifier, its output average pulse power is greater than 1W.
Described spectrum widening device is one section photonic crystal fiber, the ultrashort light pulse of ultra-short pulse oscillator output is coupled into this section photonic crystal fiber, utilize the high nonlinear coefficient of photonic crystal fiber, make pulse spectrum produce new frequency content in the nonlinear optical processs such as phase-modulation and four-wave mixing, and making pulse spectrum obtain effective broadening.
Between the centre wavelength 900nm of described wavelength-division multiplex beam splitter~1100nm, bandwidth is 5nm.
Described multi-stage fiber amplifier is formed by connecting from beginning to end by two or more ytterbium-doped double-clad fiber amplifier, wherein places an optoisolator between adjacent two ytterbium-doped double-clad fiber amplifiers.
Described self-reference zero-frequency detector comprises photonic crystal fiber, and first, second lens are arranged on two phase matching periodically poled lithium niobate nonlinear crystal and photodetectors between lens; Described multi-stage fiber amplifier output optically-coupled enters photonic crystal fiber, first, second lens focus on and collimation by light beam, on phase matching periodically poled lithium niobate nonlinear crystal, two kinds of different spectral composition difference frequencies produce new frequency content, and the low-frequency component in this new spectrum component and stretched-out spectrum produces beat signal on photodetector.
described balanced type optics simple crosscorrelation time jitter measurement mechanism comprises polarization beam apparatus, the first dichroic mirror, the 3rd lens, the first detector, frequency-doubling crystal, the 4th lens, the second dichroic mirror, the second detector and differential amplifier, input the amplification light of reference light and multi-stage fiber amplifier output at two input ends of polarization beam apparatus, the amplification light of reference light and multi-stage fiber amplifier output is orthogonal in the polarization direction, polarization beam apparatus is combined into one the tunnel with two-beam, polarization beam apparatus output fairing is inferior to the first dichroic mirror, the 3rd lens, frequency-doubling crystal, the 4th lens, focus in frequency-doubling crystal after the second dichroic mirror, and at frequency-doubling crystal two ends generation frequency-doubled signal, with these two frequency-doubled signals respectively through first, after the second detector, ask difference can obtain the simple crosscorrelation output signal of FEEDBACK CONTROL piezoelectric ceramics by differential amplifier.
Described balanced type optics simple crosscorrelation time jitter measurement mechanism also includes catoptron, and the position of accommodation reflex mirror can change the initial position of two input light.
Compared with prior art, the invention has the beneficial effects as follows: 1, by multiplex pulse wavelength-division multiplex formula amplifying technique and the relevant synthetic technology of pulse spectrum, efficiently solve the single amplifier gain effect that narrows, can realize that wideband pulse light is carried out high power to be amplified.2, the phase noise reduction technology has effectively reduced the intensity-phase noise in the amplification process.3, combine pulse simple crosscorrelation time jitter measuring technique, greatly improved the burst length synchronization accuracy, thereby make the relevant possibility that becomes of pulse spectrum.4, can be used for realizing more high-power ultrashort pulse output.In addition, the method also has the advantages such as compact conformation, good stability, expansibility be strong.
Description of drawings
Fig. 1 is the structured flowchart of the relevant combining amplifier of frequency division multiplexing;
Fig. 2 is the structural drawing of the multistage amplification of phase noise compensation formula and delay controller;
Fig. 3 is the structural drawing of multi-stage fiber amplifier;
Fig. 4 is the structural drawing of self-reference zero-frequency detector;
Fig. 5 is the structural drawing of balanced type optics simple crosscorrelation time jitter measurement mechanism;
Fig. 6 is the structural drawing that multi-stage fiber amplifier is delayed time and controlled;
Fig. 7 is the structural drawing of compressor reducer.
Embodiment
The present invention is described in further detail by embodiment below in conjunction with accompanying drawing:
as Fig. 1-7, the relevant synthetic multiplying arrangement of a kind of frequency division multiplexing spectrum, this device comprises ultra-short pulse oscillator 1, Pre-power amplifier 2, spectrum widening device 3, wavelength-division multiplex beam splitter 4, the multistage multiplying arrangement 5 of phase noise precompensation and time synchronized, wavelength-division multiplex bundling device 6, compressor reducer 9, the laser pulse that ultra-short pulse oscillator 1 produces is in turn by Pre-power amplifier 2, spectrum widening device 3, wavelength-division multiplex beam splitter 4, the multistage multiplying arrangement 5 of phase noise precompensation and time synchronized, wavelength-division multiplex bundling device 6, compressor reducer 9, the ultrashort pulse of compressor reducer 9 output high-peak powers.
The power of the laser pulse that described ultra-short pulse oscillator 1 produces is increased to a watt magnitude through Pre-power amplifier 2, is then ultra-continuous wideband spectrum by spectrum widening device 3 laser pulse stretchings with watt magnitude.Described ultra-short pulse oscillator 1 adopts Yb dosed optical fiber light comb, and its centre wavelength is 1030nm, and pulse repetition rate is 80MHz, locking precision<1mHz, and pulse carrier envelope phase locking precision<10mHz, pulse output average power is 50mW.
Described power adopts the forward pumping formula amplifier of ytterbium-doped double-cladded-layer photonic crystal fiber through Pre-power amplifier 2, its output average pulse power is greater than 1W.
Described spectrum widening device 3 is one section photonic crystal fiber, the ultrashort light pulse of ultra-short pulse oscillator 1 output is coupled into this section photonic crystal fiber, utilize the high nonlinear coefficient of photonic crystal fiber, make pulse spectrum produce new frequency content in the nonlinear optical processs such as phase-modulation and four-wave mixing, and making pulse spectrum obtain effective broadening greater than the wide range pulsed light of 100nm.The preferred 10cm of described photonic crystal fiber length.
4 pairs of ultra-continuous wideband spectrum of described wavelength-division multiplex beam splitter carry out frequency spectrum to be cut apart, and it is divided into the light pulse that multichannel has different centre wavelengths, and after each road beam splitting, light pulse is as seed light; Between the centre wavelength 900nm of described wavelength-division multiplex beam splitter 4~1100nm, bandwidth is 5nm.
The multistage multiplying arrangement 5 of described phase noise precompensation and time synchronized with every road seed light by carrying out the Pulse Power Magnification of carrier envelope stable phase and time precise synchronization.As Fig. 2, the multistage multiplying arrangement 5 of described phase noise precompensation and time synchronized comprises a plurality of phase noise compensation multiplying arrangements 50, a plurality of delay controller T, beam splitter 7, balanced type optics simple crosscorrelation time jitter measurement mechanism 8.
As Fig. 3, described phase noise compensation multiplying arrangement 50 comprises acousto-optic frequency shifters 51, multi-stage fiber amplifier 52, beam splitting chip 53, self-reference zero-frequency sniffer 54, filter amplifier 55.The seed light of wavelength-division multiplex beam splitter 4 outputs is passed through acousto-optic frequency shifters 51, multi-stage fiber amplifier 52, beam splitting chip 53, self-reference zero-frequency sniffer 54, filter amplifier 55 in turn.Described multi-stage fiber amplifier 52 is formed by connecting from beginning to end by two or more ytterbium-doped double-clad fiber amplifier, wherein places an optoisolator between adjacent two ytterbium-doped double-clad fiber amplifiers.
Every road seed light is successively through after acousto-optic frequency shifters 51 shift frequencies, delay controller T time-delay, amplified by multi-stage fiber amplifier 52, a seed light part after amplifying with beam splitting chip 53 is defeated by self-reference zero-frequency sniffer 54, the beat signal of self-reference zero-frequency sniffer 54 output through after filter and amplification as the driving frequency of acousto-optic frequency shifters 51, adopt feed-forward to compensate each road phase noise, realize low noise amplification and the phase place locking of multiplex pulse light; Measure by balanced type optics simple crosscorrelation time jitter measurement mechanism 8 the relative time shake that pulse is amplified on each road simultaneously, and FEEDBACK CONTROL delay controller T realizes the exact time synchronization to multiplex pulse.
Described beat signal, i.e. the carrier envelope phase zero frequency signal f0+ Δ of pulse, wherein f0 is the zero frequency signal of pulse, Δ is the additive phase noise of amplifier, after amplifying through circuit filtering, is used for driving acousto-optic frequency shifters 51, i.e. fx=f0+ Δ.
As Fig. 4, described self-reference zero-frequency detector 54 comprises photonic crystal fiber 541, and first, second lens 542,544 are arranged on two phase matching periodically poled lithium niobate nonlinear crystal 543 and photodetectors 545 between lens; Described multi-stage fiber amplifier 52 output optically-coupled enter photonic crystal fiber 541, and first, second lens 542,544 allow light beam focus on and collimation, on phase matching periodically poled lithium niobate nonlinear crystal 543, and two kinds of different spectral composition ω
1=mf+f
0, ω
2=nf+f
0, n, m are positive integer, and f is pulse repetition rate, and f0 is that pulse carrier phase zero frequency difference produces new frequency content ω frequently
3=ω
1-ω
2=(m-n) f.Low-frequency component (m-n) f+f in this new spectrum component and stretched-out spectrum
0Produce beat signal (m-n) f+f on photodetector 20
0-m-n) f=f
0, i.e. the zero frequency signal f of pulse
0
as Fig. 5, described balanced type optics simple crosscorrelation time jitter measurement mechanism 8 comprises polarization beam apparatus 81, the first dichroic mirror 82, the 3rd lens 83, the first detector 84, frequency-doubling crystal 85, the 4th lens 86, the second dichroic mirror 87, the second detector 88 and differential amplifier 89, input the amplification light of reference light and multi-stage fiber amplifier 52 outputs at two input ends of polarization beam apparatus 81, the amplification light of reference light and multi-stage fiber amplifier 52 outputs is orthogonal in the polarization direction, polarization beam apparatus 81 is combined into one the tunnel with two-beam, polarization beam apparatus 81 output fairing are inferior to the first dichroic mirror 82, the 3rd lens 83, frequency-doubling crystal 85, the 4th lens 86, focus in frequency-doubling crystal 85 after the second dichroic mirror 87, and at frequency-doubling crystal 85 two ends generation frequency-doubled signals, with these two frequency-doubled signals respectively through first, the second detector 84, after 88, ask difference can obtain the simple crosscorrelation output signal of FEEDBACK CONTROL piezoelectric ceramics by differential amplifier 89.
Described balanced type optics simple crosscorrelation time jitter measurement mechanism 8 also includes catoptron 80, the position of accommodation reflex mirror can change the initial position of two input light, thereby can guarantee in certain relative time delay scope the approximate time jitter size that is proportional to of the frequency-doubled signal of balance cross-correlator output.Wherein the output light of amplifier is as amplifying light, and utilizes coupling mechanism to export 10% light signal as reference light from oscillator stage.
As Fig. 6, described delay controller T is one section optical fiber that is wrapped on piezoelectric ceramics, be connected by one section optical fiber that is wrapped on piezoelectric ceramics between the acousto-optic frequency shifters 51 of each phase noise compensation multiplying arrangement 50 and wavelength-division multiplex beam splitter 4, the branch road seed light of wavelength division multiplexer output is introduced into one section optical fiber that is wrapped on piezoelectric ceramics, and then enter acousto-optic frequency shifters 51 and multi-stage fiber amplifier 52, enter at last bundling device.Simultaneously, after being amplified, the simple crosscorrelation output signal process of balanced type optics simple crosscorrelation time jitter measurement mechanism 8 outputs directly drives piezoelectric ceramics, by the real-time control of stroke to realize the burst length in optical fiber is postponed of FEEDBACK CONTROL piezoelectric ceramics, and then realize the multiple beam exact time synchronization.
D) the amplification pulse of each road multi-stage fiber amplifier 52 outputs under the condition of the accurate locking of relative carrier envelope phase and time precise synchronization, is carried out the relevant synthetic of multiplex pulse by wavelength-division multiplex bundling device 6;
Wavelength-division multiplex bundling device 6 adopts the pulsed light after the high power light coupling mechanism amplifies multichannel to close bundle.
E) carry out dispersion compensation and Pulse Compression with 9 pairs of pulses that are concerned with after synthesizing of compressor reducer, thereby obtain the ultrashort pulse output of high-peak power.
Compressor reducer 9 comprises two transmission-type gratings 91 and two catoptrons 92, as shown in Figure 7, can realize effective compression of involutory bundle afterpulse by adjusting two distances between grating 91.