Be used for improving the Q-switched laser of output stability
Technical field
The present invention relates to laser technology field, be specially for the Q-switched laser that improves output stability.
Background technology
Pulse laser plays an important role in fields such as industrial processes, laser radar, remote sensing, nonlinear frequency transformations.Especially the pulse laser of high repetition frequency, high-peak power, narrow pulsewidth and compact is applied to a lot of aspects, such as Laser Micro-Machining, environmental monitoring, medical diagnosis etc.At present, passive Q-adjusted technology is one of effective method of the generation high repetition frequency relatively commonly used, the output of high-peak power laser pulse, therefore is widely adopted.
Passive Q-regulaitng laser only needs to insert saturable absorber in the chamber, need not external drive source control, it is little to have volume, simple in structure, the advantages such as cost of manufacture is low, but adopt the pulse laser of passive Q-adjusted technology in industry and Military Application, usually to have following problem: one, passive Q-regulaitng laser generally has higher amplitude stability and repetition rate stability at Near Threshold, but the raising along with repetition rate, because pump power is unstable, cause output pulse amplitude stability and repetition rate stability decrease (W.J.Mandeville, K.M.Dinndorf, et.al, Characterization of passively Q-switched microchip lasers for laser radar, Proceedings of SPIE, Vol.2748,358-366); Two, in the passive Q-regulaitng laser because the anisotropic absorption characteristic of saturable absorber, cause the pulse signal of two cross-polarizations to be exported at random, be unfavorable for the laser steady operation, greatly limited extensive use (the Y. Wang of passive Q-regulaitng laser, M. Gong, P. Yan, et al. Stable polarization short pulse passively Q-switched monolithic microchip laser with [110] cut Cr
4+: YAG[J]. Laser Phys. Lett, 2009,6 (11), 788 – 790; R. Bhandari and T. Taira, " Megawatt level UV output from [110] Cr4+:YAG passively Q-switched microchip laser; " Opt. Express19 (23), 22510 – 22514 (2011) .).
Technical investigation according to the inventor, first problem for the passive Q-regulaitng laser existence, be that output amplitude is unstable and repetition rate is unstable, existing documents and materials report can improve to a great extent the range stability of output pulse and repetition rate stability by the Pre-pumping technology and (see following information for details: Weiyu Wang, Mali Gong, et al. Pulse control of passively Q-switched microchip laser with CW pumping modulation, Proceedings of SPIE, Vol.3899,455-460; Chinese patent, publication number: CN 1265528A, the Pre-pumping method of passive Q-regulaitng laser is stablized in acquisition); Second Problem for the passive Q-regulaitng laser existence, be that the output polarization direction is unstable, thereby existing documents and materials report is realized stable polarized adjusting Q pulse laser output (H. Sakai by the cut direction that changes saturable absorber, A. Sone, H. Kan, and T. Taira, in:Technical Digest of the 20th Anniversary Meeting Advanced Solid-State Photonics, Incline Village, NV, USA, January 29 – February 1,2006 (ASSP 2006), paper MD2.; Y. Wang, M. Gong, P. Yan, et al. Stable polarization short pulse passively Q-switched monolithic microchip laser with [110] cut Cr
4+: YAG[J]. Laser Phys. Lett, 2009,6 (11), 788 – 790; R. Bhandari and T. Taira, " Megawatt level UV output from [110] Cr4+:YAG passively Q-switched microchip laser; " Opt. Express19 (23), 22510 – 22514 (2011) .).Below all do not relate to and utilize Pre-pumping technology and polarized pump technology to solve simultaneously the unsettled problem of output in the passive Q-regulaitng laser, comprise that amplitude is unstable, repetition rate is unstable and the unsettled problem in polarization direction.
The present invention adopts the polarised light pumping, adopts simultaneously the Pre-pumping technology to obtain the stable output of Q-switched laser, has low cost, simply effective, applied widely, the reliable application prospect of working stability.
Summary of the invention
The object of the present invention is to provide for the Q-switched laser that improves output stability, this laser has compact conformation, simple effective, reliable, the practical advantage of working stability.
The present invention is characterised in that, at least comprise: pumping source, pumping drive system, gain medium, saturable absorber, chamber mirror, described pumping source is semiconductor laser, the pump light that sends is linearly polarized light, can be directly or by inciding in the gain medium emission spectra of pumping source and the absorption spectra of gain medium coupling behind the coupled lens; The Pre-pumping technology realizes by the pumping drive system; Gain medium produces Laser output; Described gain medium and saturable absorber are two discrete crystal, perhaps be combined into a kind of composite crystal by technique, that its combined process adopts is diffusion interlinked, one of liquid phase epitaxy, vapour phase epitaxy, four kinds of techniques of metal organic chemical vapor deposition, or in gain medium, mix simultaneously laser gain ion and saturable absorption ion, consist of the laser medium that self-saturation absorbs; Described chamber mirror comprises an Effect of Back-Cavity Mirror and an output coupling mirror; Effect of Back-Cavity Mirror is to be coated with anti-reflection to the pumping source emission wavelength and to the laser wave of the gain medium emission anti-blooming that grows tall, the reflectivity of its high-reflecting film is greater than 99%; Output coupling mirror is coated with the blooming that optical maser wavelength is partly seen through.
Described pumping drive system is at first before Laser output, apply a pre-pumping current that is lower than the laser pumping threshold value, carry out the inverted population accumulation, after pre-pumping, the pulse pump electric current that stack is higher than pumping threshold causes Output of laser, so loops driving.
Described Effect of Back-Cavity Mirror is plated in gain medium on the end face of pumping source with the form of optical medium film, anti-reflection to pump light, to the laser wave reflection of growing tall, the reflectivity of its high-reflecting film is greater than 99%, and this gain medium is coated with the anti-reflection blooming of optical maser wavelength on the logical light face of output.
Described laser adopts the various cavity structures that comprise straight chamber, refrative cavity, annular chamber.
The present invention compared with prior art, have the following advantages and the high-lighting effect: the present invention proposes pass through employing polarised light pumping and Pre-pumping technology, thereby be used for improving the Q-switched laser of output stability, have simply effective, practical, applied widely, the reliable advantage of working stability, solved that the output amplitude that exists in traditional industry and the Military Application is unstable, repetition rate is unstable and the unsettled problem of output polarization direction.
Description of drawings
Fig. 1 is the structural representation of first embodiment of Q-switched laser for improving output stability provided by the invention.
Fig. 2 is the structural representation of second embodiment of Q-switched laser for improving output stability provided by the invention.
Among Fig. 1 ~ Fig. 2,1-semiconductor laser, 2-pumping drive system, 3-coupled lens, 4-Effect of Back-Cavity Mirror, 5-gain medium, 6-saturable absorber, 7-output coupling mirror.
Embodiment
The invention will be further described below in conjunction with accompanying drawing 1:
Fig. 1 is first embodiment of the Q-switched laser for improving output stability provided by the invention.Thought of the present invention can be applied to the laser of various chambeies type, such as straight chamber, refrative cavity etc.; Described gain medium and saturable absorber are two discrete crystal, perhaps be combined into a kind of composite crystal by technique, that its combined process adopts is diffusion interlinked, one of liquid phase epitaxy, vapour phase epitaxy, four kinds of techniques of metal organic chemical vapor deposition, or in gain medium, mix simultaneously laser gain ion and saturable absorption ion, consist of the laser medium that self-saturation absorbs.Here select the diffusion interlinked composite crystal that is integrated of straight chamber, gain media and saturable absorber as the embodiment of a convenient explanation of the present invention.
Adopt semiconductor laser 1 as pumping source among first embodiment, carry out Pre-pumping by pumping drive system 2, the pump light of launching is linearly polarized light, incides in the gain medium 5 after focusing on by coupled lens 3.The absorption spectra coupling of the emission spectra of semiconductor laser 1 and gain media 5.4 pairs of pump lights of Effect of Back-Cavity Mirror are anti-reflection, and high anti-to laser, the reflectivity of its high-reflecting film is greater than 99%.Effect of Back-Cavity Mirror 4 is plated in gain media 4 on the end face of pumping with the form of optical medium film in this embodiment.Gain medium 5 is for can produce solid-state laser operation material Laser output and that saturable absorber 6 has the saturable absorption characteristic to its emission wavelength, such as Nd:YAG, Nd:YVO
4, Nd:glass etc.Gain medium 5 is coated with the anti-reflection blooming of optical maser wavelength on the logical light face of output.Output coupling mirror 7 is coated with the blooming that optical maser wavelength is had certain transmitance.
Saturable absorber is widely used in the passive Q-regulaitng laser, and it absorbs electric dipole and has definite direction, and this effect makes the laser polarization light output usually.In first embodiment, utilized the anisotropic properties of saturable absorber, adopt the polarised light pumping, make along the orientation preferentially absorptive pumping light that absorbs electric dipole in the saturable absorber by control pumping polarisation of light characteristic, strengthened the anisotropic absorption loss, thereby make the linearly polarized light of laser stable output, improved thus the polarization stability of output pulse; Realize Pre-pumping by pumping drive system 2 simultaneously, at first apply a pre-pumping current that is lower than the laser pumping threshold value, make inverted population in the gain media run up to the threshold region of primary inverted population, can not open at this stage Q switching, be the enough inverted populations of unlatching accumulation of next stage Q switching simultaneously, pressure is before each Q switching is opened, make the laser system inverted population run up to threshold region near the primary inverted population, it is slow to have overcome the saturable absorber reaction speed, the residue inverted population inconsistent so that cause output unsettled problem, after pre-pumping, cause Output of laser by stack far above the pumping pulse electric current of pumping threshold, afterwards, pumping recovers to be lower than the pre-pumping current of threshold value, for transfer Q ready next time, so circulation, and then improved range stability and the repetition rate stability of output pulse.
Fig. 2 is the structural representation of second embodiment of Q-switched laser for improving output stability provided by the invention, it is characterized in that, gain medium 5 and saturable absorber 6 are two discrete crystal, and its enforcement principle and first embodiment of the present invention are basic identical.