Cascaded carbon monoxide laser frequency conversion into the 4.3-4.9 μm range in a single ZnGeP2 crystal

Collinear cascaded mid-IR frequency conversion in a single nonlinear optical crystal was accomplished. Concurrent collinear generation of the sum frequency of multiline fundamental band carbon monoxide laser radiation as a first frequency conversion cascade resulted in collinear difference frequency generation within the 4.3 to 4.9 μm spectral range when mixing this sum frequency radiation with the fundamental one as the second cascade in the same ZnGeP(2) nonlinear optical crystal.     

Calculation of the stationary generation power of a solid-state raman laser with intracavity second harmonic generation and sum frequency mixing

Analytical equations for the power of second-harmonic stationary generation or sum frequency mixing in a Raman laser with an intracavity nonlinear medium are developed and analyzed as functions of pumping mode and other parameters of the laser system. Parameter relationships providing the maximum output power and conditions for suppression of both stimulated Raman scattering by sum frequency mixing and; consequently, of sum frequency mixing itself are found.     

Chiral discrimination in dispersion interactions and sum frequency generation

It is shown that the orientation averaged dispersion interaction which exhibits chiral discrimination is proportional to a double frequency integral of the product of two complex sum frequency generation responses.     

高功率,红光至中红外可调谐腔内和频光学参量振荡器

本文利用高重复频率,高平均功率大模场面积飞秒光纤激光器作为同步抽运源,抽运以多周期极化掺氧化镁铌酸锂为非线性晶体的单共振光学参量振荡器,获得了高功率可调谐红光至中红外光,信号光调谐范围为1450—2200 nm,闲频光调谐范围为2250—4000 nm,在2 W的抽运功率下,信号光输出波长为1502 nm时获得最大输出功率374 mW,转换效率为18.7%,脉冲宽度为144 fs,此时中红外输出中心波长为3.4μm,平均功率为166 mW.再利用BBO晶体对信号光进行腔内和频,获得和频光输出波长调谐范围为610—668 nm,在4.1 W抽运的情况下,最高平均功率为615 nm处的694 mW,转换效率达16.9%.     

基于混频效应的宽带激光谐波转换理论

提出了一种新的宽带激光谐波转换理论,指出实际宽带激光谐波转换不能简单应用倍频理论,提出同时存在不同波长之间满足和频相位匹配情况,因而宽带谐波转换应该是一个倍频加和频的混合转换过程.在合理设计下,不同波长之间的和频效应可以在整个谐波转换中占主导地位,突破了传统允许波长的限制,这种理论和方法不仅适合二倍频,同时适合三倍频等高次谐波转换 关键词： 宽带激光 谐波转换 混频     

Intra-cavity second-harmonic and sum-frequency generation in a diode-pumped broadband Yb-doped fibre laser

Intra-cavity nonlinear frequency mixing in a diode-pumped, broadband Yb-doped fibre laser has been investigated. Second-harmonic generation of the fibre output, second-harmonic generation of the residual pump beam and sum frequency mixing between the two was achieved simultaneously, resulting in three colour operation in the blue-green region. Including the nonlinear crystal inside the cavity is also shown to be effective in reducing fluctuations in the output power.     

Sum and difference frequency generation of white light continuum with the ps pulses of Nd:YAG laser in a thick BBO crystal

The white light continuum (WLC) generated in water/D₂O mixture by pumping with the fundamental of ps Nd⁺³:YAG laser has been used as a variable frequency source for the sum frequency generation as well as for its amplification. 35 ps long pulses with 8 mJ energy at 1064 nm were mixed collinearly with the WLC generated by the same laser beam in a 20 mm thick BBO crystal. The obtained tunable output has been identified as the sum frequency between the fundamental and a portion of the WLC with the required phase matching. Theoretical simulations are also given along with a few initial experiments to use this combination for the difference frequency generation (optical parametric amplification) under non-collinear geometry.     

Efficient yellow beam generation by intracavity sum frequency mixing in DPSS Nd:YVO4 laser

We present our studies on dual wavelength operation using a single Nd:YVO₄ crystal and its intracavity sum frequency generation by considering the influence of the thermal lensing effect on the performance of the laser. A KTP crystal cut for type-II phase matching was used for intracavity sum frequency generation in the cavity at an appropriate location for efficient and stable yellow output power. More than 550 mW of stable CW yellow-orange beam at 593.5 nm with beam quality parameter (M ²) ～4. 3 was obtained. The total pump to yellow beam conversion efficiency was estimated to be 3.83%.     

New trends in high-order harmonics generation using the mid-infrared pulses propagating through the laser-produced plasmas

Various recently emerged applications of mid-infrared pulses for high-order harmonic generation in laser plasmas produced on the surfaces of various materials are reviewed. Among them are (a) the highorder harmonic generation in Ag, Sn, fullerene, and graphene nanoparticle-containing plasmas using tunable two-color mid-infrared pulses, (b) efficiency dependence on the generating particle properties in the case of two-color high-harmonic generation of the longer-wavelength radiation in the plasmas, and (c) high-order sum and difference frequency generation using tunable two- and three-color commensurate and incommensurate mid-infrared pumps of graphite plasma. These studies demonstrate the perspectives of the frequency conversion of mid-infrared radiation in the extended laser-produced plasmas.     

Phase effects during parametric conversion in layer structures

Coupled-wave equations that describe the parametric amplification and generation of a sum frequency in a three-layer structure are studied theoretically in the constant-intensity approximation taking into account the inverse effect of the excited wave on the phase of the pumping wave. For this purpose, the approximation of constant intensity of the fundamental radiation is applied not to the layer structure as a whole but to each separately taken layer. In this case, the complex amplitudes of the interacting waves at the output of each layer are the input values of the corresponding complex amplitudes for the next layer. Analytical expressions obtained in the constant-intensity approximation for the efficiency of conversion to the sum frequency were analyzed numerically for different parameters of the problem. The efficiency of parametric amplification at a high frequency was found to depend on the intensity of the signal wave at a low frequency.     

在BBO中获得230.8—223.2nm高功率和频输出

用Q-YAG泵浦的Rh·6G染料激光在一块45°切割的β-BaB₂O₄(BBO)晶体中倍频,产生294.8—282.5nm范围的连续调谐输出,其能量为8mJ(在285nm处)。用这个倍频光与泵浦染料后剩余基波(1064nm)在另一块45°切割的BBO中和频,已获得230.8—223.2nm范围的连续调谐输出,其能量为120μJ,相应的峰值功率为12kW。还简述了获得高功率和频输出的关键技术。     

周期性极化铌酸锂波导全光开关特性分析

从理论方面研究了基于和频与差频级联二阶非线性效应的周期性极化铌酸锂波导全光开关的特性,给出了耦合模方程在满足相位匹配条件下小信号近似的解析表达式.用数值方法求解耦合模方程,讨论了相位失配情况下输出的信号光功率与控制光功率的关系.分析了全光开关器件的极化反转光栅周期、晶体温度、控制光波长等参量的容差特性与相互作用长度和晶体温度的关系 关键词： 级联二阶非线性 光开关 准相位匹配 周期性极化铌酸锂     

Tunable third-harmonic probe for non-degenerate ultrafast pump–probe measurements

In this article, we report a method to achieve a precisely tunable highly stable probe beam generation for performing pump–probe experiment around a given wavelength by tilting a sum frequency generation (SFG) crystal angle. The width of the generated third-harmonic beam is of the order of 2 nm throughout the tunable range. This method of probe beam generation has its application in isolating contributions from closely separated excitation states.     

基于角色散的非共线匹配宽带三倍频技术

宽带光打靶可以有效降低激光等离子体相互作用过程中非线性效应。提出一种基于角色散的非共线匹配宽带三倍频方案,利用宽带基频与窄带二倍频的非共线和频产生宽带三倍频,和频过程中通过特殊设计的渐变光栅实现不同频率的基频光束以特定角度入射,补偿了波长差异引入的位相失配使得全波段满足位相匹配条件。理论模拟表明,采用KDP晶体Ⅱ类位相匹配,将中心波长为1058 nm、带宽10 nm的宽带基频光与526.5 nm的二倍频光进行非共线匹配和频,可以实现高效宽带三倍频转换。     

Theoretical Analyzing of Optical Parametric Oscillation with Intracavity Sum Frequency Generation

1IntroduCionThe0Pticalparametricoscillator(OPO)provideSameansofgeneratingawideytUnablecohrentlight.Inordert0extendthetunablewavelengthtowardshorterrange,thetwootePprocessmustbeemPhad.Thereareseveralmethodsbeingused.Oneisthe0Pticalparametricoscillationfolowdbythesumfrempygeneration(0POSFG)ofthesignal(cos)andreSdualp~(eq),thefrequencydesiredcod=cos eq'AnalternativeistheOPOfolDWdbysecondhaImnicgeneration(OPChSHG),wherethesecondharmOnicgenerati0doubesthesignal0ftheOPO,cod=2co,'Anothe…     

Theoretical Analyzing of Optical Parametric Oscillation with Intracavity Sum Frequency Generation

A new scheme of optical parametric oscillator with intracavity sum frequency generation is proposed,and the operation characters such as threshold,conversion efficiency,etc.,are theoretically studied. The factor affecting conversion efficiency is discussed.     

Broadband supercontinuum generation in a single potassium di-hydrogen phosphate (KDP) crystal achieved in tandem with sum frequency generation

We present here an enhanced broadband supercontinuum generation in a potassium di-hydrogen phosphate (KDP) crystal. The enhancement in the bandwidth of the white light is obtained towards the shorter wavelength regime (<400 nm) by employing supercontinuum generation and sum frequency generation in tandem. The tunability in the blue region of the spectrum with angle is demonstrated. The bandwidth of supercontinuum achieved spans from 350 nm to 1300 nm. Further, we show the excellent polarization maintenance of continuum generated in KDP in comparison to that generated in water and BK-7 glass. PACS 42.65.Ky; 42.65.Jx; 42.65.Re; 42.25.Ja     

Vacuum ultraviolet generation in phase matched carbon monoxide

Resonantly enhanced four-wave sum frequency mixing in phase matched carbon monoxide leads to the generation of continuously tunable over 1200 cm^-1 coherent VUV radiation in the 1150 Å range. Experiments allow to determine the VUV absorption cross sections and indices of refraction of CO. Multiphoton photolysis of CO has been observed and confirmed by the VUV absorption in atomic carbon.     

Rapid vibrational imaging with sum frequency generation microscopy

We demonstrate rapid vibrational imaging based on sum frequency generation (SFG) microscopy with a collinear excitation geometry. Using the tunable picosecond pulses from a high-repetition-rate optical parametric oscillator, vibrationally selective imaging of collagen fibers is achieved with submicrometer lateral resolution. We furthermore show simultaneous SFG and second harmonic generation imaging to emphasize the compatibility of the microscope with other nonlinear optical modalities.     

非线性光学五十年

文章简要回顾了非线性光学的诞生以及早期的发展,包括二次谐波,激光和频和差频现象,受激拉曼散射,以及激光的一些自作用行为等,介绍了非线性光学的一些重要研究成果和应用,包括非线性光谱学,位相共轭和自适应光学,相干非线性光学以及高次谐波等,最后对非线性光学当前和未来研究热点作了总结和展望.