CN201054063Y - Optical parametric chirped pulse amplification laser system - Google Patents

Abstract

An optical parametric chirp amplifier-pulse laser system comprises a titanium stone femtosecond mode-locking pulse oscillator, a first sub-beam film, a CEP stable signal pulse source, an OPCPA synchronizing pump source, an OPCPA amplifier stage and a compressor. The first sub-beam film is in the output beam direction of the titanium stone femsecond mode-locking pulse oscillator. The first sub-beam divides a laser beam into a transmission beam and a reflection beam. The CEP stable signal pulse source, the OPCPA amplifier stage and the compressor are sequentially in the transmission beam direction. The CEP stable signal pulse source comprises a photon crystal optical fiber, a chirp mirror, a cycle polarization lithium niobium crystal and a stretcher. The OPCPA amplifier stage comprises a first two-color mirror, a first non-linear crystal, a second two-color mirror and the second non-linear crystal. The OPCPA synchronizing pump source comprises a Q-switched multiple frequency YAG laser, a narrow-band titanium stone regenerative amplifier, the second sub-beam and a full mirror. The utility model can achieve the output of the near infrared ultra short laser pulse, the pulse width is less than thirty femtosecond.

Description

Optical parameter chirp impulse amplification laser system

Technical field

The utility model relates to laser system, and particularly the stable optical parameter chirped pulse of a kind of carrier envelope phase of near-infrared band (being designated hereinafter simply as CEP) amplifies (being designated hereinafter simply as OPCPA) laser system.

Background technology

In recent years, the ultra-short pulse laser technology has obtained development at full speed, chirped pulse amplifies constantly improving of (being designated hereinafter simply as CPA) technology and OPCPA technology makes the pulsewidth of ultrashort laser pulse constantly narrow, and has successfully realized the output of the ultrashort superpower pulse of cycle magnitude.At present, the ultrashort pulse systematic research mainly is confined to 800nm wave band and 1064nm wave band.Application facet such as the generation of higher hamonic wave and ultra high-speed optical communication in inert gas, the ultrashort pulse that obtains near-infrared band has great importance.

The carrier envelope phase of ultrashort pulse (abbreviating CEP as) is defined as the relative phase between pulse envelope peak value and the peak electric field, and acting in the fields such as chirped pulse generation, optics atomic clock and quantum coherent control of CEP seems important unusually.CEP antihunt means in the ultra-short pulse laser system can be divided into initiatively and passive dual mode.Initiatively the CEP stationary mode is by (Nature Vol.421, No.6,611-616,2003) the carrier phase drift (CEO) of system measured and the mode of FEEDBACK CONTROL realizes.This mode is stable very effective to the CEP of femtosecond oscillator, but provides real-time measurement feedback to be difficult to realize under kHz repetition frequency high-energy amplification mode.The people such as A.Baltuska of Japan have proposed to utilize difference frequency (difference frequency) process to realize the stable method of passive CEP (Physical Review Letters, Vol.88, No.13,133901,2002).Based on this principle, people such as gondola C.Manzoni propose a kind of hollow optic fibre that uses and realize that as the difference frequency process in the spectrum widening combination of elements nonlinear crystal the stable optical parameter of CEP amplifies (abbreviating OPA as) pulse laser system (Optics Express, Vol.14, No.21,10109-10116), its light path arrangement as shown in Figure 1.Femto second titanium jewel chirped pulse amplifies (CPA) system 1 output center wavelength and is positioned at～the ultrashort, super strong laser pulse sequence of 800nm, single pulse energy～1.5mJ and pulse width～50fs.In the part of this pulse train (～250 μ J) the input CEP stabilization signal pulse generation part 6, another part (～1.25mJ) be divided into two parts through behind the beam splitting chip 8, be used separately as the pump light of two-stage OPA process.The pulse train that enters in the CEP stabilization signal pulse generation part 6 is at first carried out spectrum widening by the nonlinear interaction in the hollow optic fibre 3, and the pulse of broadening obtains the stable near infrared signal pulse of CEP through the II class phase matching difference frequency process in barium metaborate (the abbreviating BBO as) crystal 5 after being compressed by chirped mirror 4 time domains.The flashlight that the difference frequency process obtains is directly inputted in the OPA amplifier stage 14 and amplifies, and the CEP after obtaining amplifying through the femtosecond pulse pumping non-colinear OPA process in the two- stage bbo crystal 11,13 stablize femtosecond pulse and exports.

Because the spectrum widening in the hollow optic fibre is limited in one's ability, this system need export the femto second titanium jewel CPA laser system of high energy pulse as prime.And what adopt in the amplifier stage is that femtosecond pulse pumping non-colinear OPA process in the bbo crystal comes signal pulse is amplified, adjusted in concert accuracy requirement to system is very high, and it is also quite limited that the output power of system is subjected to the restriction of signal pulse width and pumping pulse energy.In addition, the tuning of wavelength realize by rotating the crystal angle, and be bigger to the influence of back light path, and be not easy accurate control.

Summary of the invention

The purpose of this utility model is the deficiency that exists in the above-mentioned technology formerly, and a kind of optical parameter chirp impulse amplification laser system is provided, near the laser of this system's output wavelength carrier envelope stable phase of adjustable ultrashort pulse 1.55 μ m.

Principle of the present utility model is to utilize non-linear photon crystal optical fiber (PCF) that the portion of energy of the femtosecond pulse of titanium jewel mode locking oscillator output is carried out the conversion of high-level efficiency spectrum, based on the accurate phase matching difference frequency of the conllinear in periodically poled lithium niobate crystal process, obtain the tunable CEP stabilization signal of near-infrared wavelength light then.Flashlight obtains amplifying by the mode of full phototiming arrowband pumping OPCPA.By the control of periodically poled lithium niobate crystal temperature effect being realized accurately tuning to signal wavelength.

Technical solution of the present utility model is as follows:

A kind of optical parameter chirp impulse amplification laser system, it is characterized in that comprising titanium jewel femtosecond mode locking pulse oscillator, first beam splitting chip, CEP stabilization signal impulse source, OPCPA synchronous pump source, OPCPA amplifier stage and compressor reducer, its position relation is as follows: the output beam direction at this titanium jewel femtosecond mode locking pulse oscillator is first beam splitting chip, this first beam splitting chip is divided into transmitted light beam and folded light beam with laser beam, in described transmitted light beam direction is described CEP stabilization signal impulse source successively, OPCPA amplifier stage and compressor reducer, described CEP stabilization signal impulse source is by the photonic crystal fiber with optical axis, chirped mirror, periodically poled lithium niobate crystal and stretcher constitute; Described OPCPA amplifier stage is made up of first dichroic mirror, first nonlinear crystal, second dichroic mirror and second nonlinear crystal successively along light path; Described OPCPA synchronous pump source is made up of q-multiplier YAG laser instrument, arrowband titanium jewel regenerative amplifier, second beam splitting chip and total reflective mirror successively along light path; The resonator cavity that described folded light beam is injected described arrowband titanium jewel regenerative amplifier amplifies, and amplifies after described second beam splitting chip and total reflective mirror inject described OPCPA amplifier stage through described first dichroic mirror and second dichroic mirror respectively and carries out synchronous pump.

The job step of the utility model laser system is as follows:

1) titanium jewel femtosecond mode locking pulse oscillator produces the ultrashort pulse sequence that centre wavelength is positioned at 800nm, single pulse energy～80nJ and pulse width＜50fs; This pulse train is injected into the signal pulse and the pumping pulse that are used to produce the OPCPA amplifier stage in CEP stabilization signal impulse source and the OPCPA synchronous pump source respectively by the first beam splitting chip separated into two parts.

2) inject the pulse of CEP stabilization signal impulse source through after the non-linear spectral transformation of photonic crystal fiber, energy is transferred to about 550nm greatly, pulse after the spectrum conversion is carried out the time domain compression with chirped mirror, difference frequency process by 550nm component in the periodically poled lithium niobate crystal and 850nm component obtains centre wavelength and is positioned near the 1550nm the stable broadband difference frequency signal of CEP then, again through obtaining the signal pulse of OPCPA amplifier stage behind the stretcher.In the difference frequency process, the temperature by control cycle poled lithium niobate crystal can realize thermal tuning within the specific limits to the centre wavelength of difference frequency signal.

3) pulse in the input OPCPA synchronous pump source is through being positioned at the arrowband high-energy long pulse sequence of 800nm by output center wavelength behind the narrow-band regenerative amplifier of q-multiplier YAG laser pumping, this pulse train is divided into two parts by second beam splitting chip, is used as the pump light that two-stage OPCPA amplifies respectively.

Direct incident of flashlight of 4) exporting from CEP stabilization signal impulse source and the pump light by dichroic mirror and 800nm incide and carry out high-gain in the nonlinear crystal and put in advance, and the flashlight after amplifying is for the first time restrainted pump light through another dichroic mirror and another and incided on the nonlinear crystal and fully amplified;

5) signal pulse after amplifying, is obtained the stable ultrashort pulse of near-infrared band CEP and exports to～30fs magnitude by compressor compresses.

In sum, compare, the utlity model has following outstanding feature with technology formerly:

1) adopts the non-linear photon crystal optical fiber paired pulses spectrum of special construction to change, and adopt the periodically poled lithium niobate crystal, thereby just can obtain the stable near infrared broadband signal light of CEP with the oscillator femtosecond pulse of nJ magnitude as the difference frequency device; And formerly needing the femtosecond light of hundred μ J magnitudes just can obtain the stable flashlight of CEP in the technology, conversion efficiency is low;

2) can realize easily within the specific limits exporting the tuning of pulse center wavelength by thermal tuning difference frequency periodically poled lithium niobate crystal;

3) adopted the amplification mode of full phototiming arrowband pumping OPCPA in the amplifier stage, can obtain high-gain effectively and amplify; And what adopt in the first technology is the amplification form of non-colinear Broadband Femtosecond optical pumping OPA in the bbo crystal, and the pulse energy that can obtain is limited.

Description of drawings

Fig. 1 stablizes OPA ultra-short pulse laser system structural representation for the tunable near infrared CEP of technology formerly.

Fig. 2 the utility model optical parameter chirp impulse amplification laser system structural representation.

Fig. 3 is the spectrum after the process photonic crystal fiber is changed among the utility model embodiment.

The CEP stable difference frequency signal spectrum of Fig. 4 for calculating among the utility model embodiment.

Fig. 5 is the gain spectral of first order OPCPA process among the utility model embodiment.

Embodiment

The utility model is described in further detail below in conjunction with embodiment and accompanying drawing.

See also Fig. 2 earlier, Fig. 2 the utility model optical parameter chirp impulse amplification laser system structural representation.As seen from the figure, the utility model optical parameter chirp impulse amplification laser system, by titanium jewel femtosecond mode locking pulse oscillator 15, first beam splitting chip 16, CEP stabilization signal impulse source 21, OPCPA synchronous pump source 24, OPCPA amplifier stage 30 and compressor reducer 32 are formed, its position relation is as follows: the output beam direction at this titanium jewel femtosecond mode locking pulse oscillator 15 is first beam splitting chip 16, this first beam splitting chip 16 is divided into transmitted light beam and folded light beam with laser beam, in described transmitted light beam direction is described CEP stabilization signal impulse source 21 successively, OPCPA amplifier stage 30 and compressor reducer 32, described CEP stabilization signal impulse source 21 is by the photonic crystal fiber 17 with optical axis, chirped mirror 18, periodically poled lithium niobate crystal 19 and stretcher 20 constitute; Described OPCPA amplifier stage 30 is made up of first dichroic mirror 26, first nonlinear crystal 27, second dichroic mirror 28 and second nonlinear crystal 29 successively along light path; Described OPCPA synchronous pump source 24 is made up of q-multiplier YAG laser instrument 22, arrowband titanium jewel regenerative amplifier 23, second beam splitting chip 25 and total reflective mirror 31 successively along light path; The resonator cavity that described folded light beam is injected described arrowband titanium jewel regenerative amplifier 23 amplifies, and amplifies after described second beam splitting chip 25 and total reflective mirror 31 carry out synchronous pump through described first dichroic mirror 26 and the described OPCPA amplifier stage 30 of second dichroic mirror, 28 injections respectively.

As mentioned above, this laser system mainly comprises with the lower part: titanium jewel femtosecond mode locking pulse oscillator 15, beam splitting chip 16, CEP stabilization signal impulse source 21, OPCPA synchronous pump source 24, OPCPA amplifier stage 30, compressor reducer 32.Titanium jewel femtosecond mode locking oscillator 15 output center wavelengths are positioned at the ultrashort pulse sequence of 800nm, single pulse energy～80nJ and pulse width＜50fs, this pulse train is injected into respectively in CEP stabilization signal impulse source 21 and the OPCPA synchronous pump source 24 by first beam splitting chip, 16 separated into two parts.CEP stabilization signal impulse source 21 produces centre wavelength and is positioned near the stable broadband OPCPA flashlight of CEP of 1.55 μ m.Wherein photonic crystal fiber 17 is transferred to the most of energy of the 800nm femtosecond pulse of input on the spectrum main peak that is positioned at 550nm; In periodically poled lithium niobate crystal 19, experience the difference frequency process by the pulse after the compression of chirped mirror 18 time domains, because the pump light and the flashlight of difference frequency process derive from same wideband pulse, then Shu Chu idle light phase will remain constant and realize that CEP is stable, when ignoring the pump light loss, the difference frequency process can be described with following coupled wave equation:

$\frac{{\mathrm{dA}}_s}{\mathrm{dz}}={\mathrm{i\κ}}_{\mathrm{DF}}{A}_p{A}_i^{*}\exp \left(\mathrm{iz\Δk}\right)---\left(1\right)$

$\frac{{\mathrm{dA}}_i}{\mathrm{dz}}={\mathrm{i\κ}}_{\mathrm{DF}}{A}_p{A}_s^{*}\exp \left(\mathrm{iz\Δk}\right)---\left(2\right)$

Subscript i wherein, s, p represent idle light, flashlight and pump light respectively, and A is the optical electric field variable, κ _DFBe difference frequency PROCESS COUPLING coefficient, Δ k is the phase misalignment dosage, and z is the distance that light is propagated in crystal.

Wideband pulse behind the difference frequency is input in the OPCPA amplifier stage 30 as signal pulse after through stretcher 20 broadenings amplifies.OPCPA synchronous pump source 24 produces the pulse laser that centre wavelength is positioned at the arrowband ps magnitude of 800nm, and wherein narrow-band regenerative amplifier 23 is to use 22 pumpings of q-multiplier YAG laser instrument.The laser pulse of narrow-band regenerative amplifier 23 outputs is divided into two parts through second beam splitting chip 25, is used as the pump light that two-stage OPCPA amplifies respectively.OPCPA amplifier stage 30 mainly is made up of nonlinear crystal 27 and 29, and the signal pulse after the amplification is compressed to～the 30fs magnitude by compressor reducer 32, obtains the stable ultrashort pulse output of near-infrared band CEP.Gain in the OPCPA amplifier stage can be described with following formula:

G＝1+(ξL) ²(sinh?B/B) ² (3)

Wherein: G is the flashlight gain, $B=\sqrt{{\left(\mathrm{\ξL}\right)}^2-{(\mathrm{\ΔkL}/2)}^2},$ ξ is a small-signal gain, and L is a crystal thickness, and Δ k is the phase misalignment dosage.

The structure of present embodiment as shown in Figure 2.Employing can output pulse width～50fs, the titanium jewel femtosecond mode locking pulse oscillator 15 of centre wavelength 800nm single pulse energy～80nJ, by first beam splitting chip 16 be divided into～10nJ and～70nJ two parts.The former is injected into as seed light and carries out the arrowband amplification in the OPCPA amplifier stage synchronous pump source 24, and the latter is injected in the OPCPA flashlight generation systems 21.Inject the 70nJ pulse behind the non-linear spectral change action of photonic crystal fiber 17, obtain the super continuous spectrums output as shown in Figure 3 of energy～10nJ spectral shape, obtain～9nJ (～10fs) ultrashort pulse after the compression through chirped mirror 18.By the difference frequency process in the thick periodically poled lithium niobate crystal 19 of 1mm, can obtain the stable pulse output of CEP that centre wavelength is positioned at 1550nm left and right sides energy～5pJ, through obtaining after the broadening effect of prism to stretcher 20～signal pulse of 5ps.The idle light spectral shape of the difference frequency process that calculates according to equation (1), (2) as shown in Figure 4.Adopt the q-multiplier YAG laser instrument 22 pumping arrowband titanium jewel regenerative amplifiers 23 of output wavelength 532nm in the OPCPA amplifier stage synchronous pump source 24, the 800nm narrow-band impulse of output～5mJ (10ps) incides in the OPCPA amplifier stage 30 as the pump light of OPCPA.Adopt two-stage to amplify in the OPCPA amplifier stage 30: to adopt the thick periodically poled lithium niobate crystal 27 of 3mm to obtain high-gain during the first order is amplified and amplify, under the pump energy of 100 μ J, can obtain～signal of 1 μ J amplifies output, and the gain spectral of the first order OPCPA process that calculates according to equation (3) is as shown in Figure 5; Thick three lithium borates (LBO) crystal 29 of 5mm amplify to be adopted in the second level, can obtain under the pump energy of 4.9mJ～the 1550nm broadband chirped pulse output of 0.5mJ.At last, through can obtain behind the compressor reducer 32 pulse energy＞0.2mJ, pulse width～30fs in the stable ultrashort pulse output of infrared CEP.

Claims (1)

1. optical parameter chirp impulse amplification laser system, it is characterized in that by titanium jewel femtosecond mode locking pulse oscillator (15), first beam splitting chip (16), CEP stabilization signal impulse source (21), OPCPA synchronous pump source (24), OPCPA amplifier stage (30) and compressor reducer (32) are formed, its position relation is as follows: the output beam direction at this titanium jewel femtosecond mode locking pulse oscillator (15) is first beam splitting chip (16), this first beam splitting chip (16) is divided into transmitted light beam and folded light beam with laser beam, in described transmitted light beam direction is described CEP stabilization signal impulse source (21) successively, OPCPA amplifier stage (30) and compressor reducer (32), described CEP stabilization signal impulse source (21) is by the photonic crystal fiber (17) with optical axis, chirped mirror (18), periodically poled lithium niobate crystal (19) and stretcher (20) constitute; Described OPCPA amplifier stage (30) is made up of first dichroic mirror (26), first nonlinear crystal (27), second dichroic mirror (28) and second nonlinear crystal (29) successively along light path; Described OPCPA synchronous pump source (24) is made up of q-multiplier YAG laser instrument (22), arrowband titanium jewel regenerative amplifier (23), second beam splitting chip (25) and total reflective mirror (31) successively along light path; The resonator cavity that described folded light beam is injected described arrowband titanium jewel regenerative amplifier (23) amplifies, and amplifies after described second beam splitting chip (25) and total reflective mirror (31) carry out synchronous pump through described first dichroic mirror (26) and second dichroic mirror (28) the described OPCPA amplifier stage of injection (30) respectively.

Images