Third-harmonic generation in a general two-component quasi-periodic optical superlattice

The quasi-periodic optical superlattice is a promising material for use in optical frequency conversion. We propose a method for designing a quasi-periodic structure for efficient third-harmonic generation (THG) at any given wavelength. With this method we have made a LiTaO(3) sample in which 27% THG at 0.48microm was achieved, together with a series of highly efficient multiwavelength second-harmonic generation outputs. The result is in good agreement with the theoretical prediction.     

局域表面等离激元诱导的三次谐波增强效应

本文研究了二维金三角形纳米颗粒阵列的三次谐波非线性光学效应. 金三 角纳米颗粒阵列是基于微球刻印技术制成. 采用反射式光学系统, 观察到该纳米结构在光谱分辨的飞秒激光照射下产生明显的三次谐波. 研究表明, 当激光抽运频率接近金纳米颗粒的局域表面等离激元共振位置时, 三次谐波信号得到增强; 三次谐波辐射方向满足动量匹配条件. 关键词： 微球刻印 三次谐波产生 表面等离激元     

High-power picoseconds 355 nm laser by third harmonic generation based on CsB3O5 crystal

We report on the high average power third harmonic generation (THG) of a mode-locked picosecond laser in a CsB₃O₅ (CBO) crystal. The picosecond laser beam at 1064 nm is produced by a home-made 30 W master oscillator power-amplifier (MOPA) Nd:YVO₄ laser system. The maximum THG output at 355 nm is up to 5.4 W. We also investigate the phase matching angle at different temperatures. During high power operation, the temperature of the CBO crystal is set at a high temperature of more than 100 °C. The THG system has shown a fine long-term stability for more than two months of operation. PACS 42.55.Px; 42.55.Rz; 42.70.Mp; 42.70.Nq; 42.65.Ky     

Noncritically phase-matched frequency conversion in Gd(x)Y(1-x)Ca(4)O(BO(3))(3) crystal

A nonlinear optical crystal YCa(4)O(BO(3))(3) (YCOB) is phase matchable for third-harmonic generation (THG) of a Nd:YAG laser by type I mixing between 1.064 and 0.532mum . By partial substitution of Gd for Y in YCOB, a solid solution Gd(x)Y(1-x)Ca(4)O(BO(3))(3) gradually changes the phase-matching angles of THG to (theta, ?)=(90( degrees ), 90 ( degrees )) . We present the properties of noncritically phase-matched THG in Gd(x) Y(1-x)Ca(4)O(BO(3))(3) (x=0.28) .     

Design of the Seed Source for High Power KrF Excimer Laser System

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基于单块周期极化铌酸锂晶体级联三倍频的440 nm蓝光固体激光器

阐述了一种基于单块周期极化铌酸锂晶体级联三倍频实现440 nm蓝光输出的实验方案。根据周期极化铌酸锂晶体的Sellmeier方程以及倍频与和频的相位匹配条件,在一块周期极化铌酸锂晶体上设计了两段不同的极化周期,使其在同一工作温度下能分别实现倍频与和频,在先后经过倍频与和频后,实现级联三倍频输出。实验采用Nd: YAG产生的1319 nm光作为基频光,重频400 Hz,脉宽110 ns,横向和纵向光束质量因子分别为1.81和2.65。耦合进周期极化铌酸锂晶体后,出射光中检测到660 nm的红光和440 nm的蓝光。通过调整工作温度和入射基频光功率,得到2.4 mW的最大蓝光输出,此时工作温度55.5 ℃,基频光功率530 mW。实验结果验证了单块晶体实现级联三倍频440 nm蓝光输出的可行性。     

Electronic and Optical Properties of a Lens Shaped Quantum Dot under Magnetic Field：Second and Third-Harmonic Generation

In the present work, we have studied electronic and optical properties of a lens-shaped quantum dot under an external magnetic field. For this goal, we have calculated the energy levels and wave functions using the finite element method (FEM) for different values of magnetic field. We have also studied effect of magnetic field on second harmonic generation (SHG) and third-harmonic generation (THG) in the lens-shaped quantum dot. In this regard, we have obtained an analytic expression for the SHG and THG by a compact density matrix approach and an iterative procedure. According to the obtained results, it is found that the presence of the magnetic field affects the symmetry of the system. The SHG and THG are decreased with increasing the magnetic field. The magnetic field has a great influence on the energy levels, wave functions, the SHG and THG in a lens shaped quantum dot.     

Broadband Third-Harmonic Generation with a Composite KD*P Crystal

We predict that broadband efficient third-harmonic generation (THG) can be achieved with a frequency-doubling crystal and a novel composite KD*P tripler. The composite KD*P tripler is made of two partially deuterated KDP crystals with different deuteration levels by using the thermal bonding technique. The deuteration level of a partially deuterated KDP crystal is used as a degree of freedom to alter the phase-matching (PM) wavelength. Simulations show that the composite KD*P tripler can improve third-harmonic conversion efficiencies over a very wide band of input fundamental frequencies. In terms of robustness, alignment and stability, this THG scheme should be more promising than other broadband THG approaches because the composite KD*P tripler is a monolithic device.     

Electronic and Optical Properties of a Lens Shaped Quantum Dot under Magnetic Field: Second and Third-Harmonic Generation

In the present work, we have studied electronic and optical properties of a lens-shaped quantum dot under an external magnetic field. For this goal, we have calculated the energy levels and wave functions using the finite element method(FEM) for different values of magnetic field. We have also studied effect of magnetic field on second harmonic generation(SHG) and third-harmonic generation(THG) in the lens-shaped quantum dot. In this regard, we have obtained an analytic expression for the SHG and THG by a compact density matrix approach and an iterative procedure. According to the obtained results, it is found that the presence of the magnetic field affects the symmetry of the system. The SHG and THG are decreased with increasing the magnetic field. The magnetic field has a great influence on the energy levels, wave functions, the SHG and THG in a lens shaped quantum dot.     

Power scaling of blue and red light based on frequency mixing inside adhesive-free bond composite Nd:YAG laser cavity

We report our results on effective third-harmonic generation (THG) by cascading quasi-phase-matched second-harmonic and sum-frequency generation in a dual-period-periodically-poled KTP crystal. Significant improvement of the output powers were achieved for the 440 nm blue light and 660 nm red light based on Q-switched frequency-tripling and frequency-doubling 1319-nm radiation inside an adhesive-free bond composite Nd:YAG laser. The highest output powers of 197 mW and 1.19 W were achieved for the blue and red light at the corresponding input powers of 12.9 and 17.1 W for the diode laser.     

Characterization of third-harmonic generation from femtosecond laser-excited silicon

Third-harmonic generation (THG) from silicon crystals excited by femtosecond pulses has been studied. THG as a function of probe pulse delay from linear and circularly polarized probe pulses was examined. Both polarizations exhibit a fast, 300 fs drop in THG when the Si is pumped by pulses with fluence above the melting threshold. This drop for both polarizations indicates that electronic effects dominate THG in laser-melted Si since structural effects should principally influence THG from linearly polarized probes, suggesting that care needs to be exercised in interpreting THG signal as an ultrafast probe of crystalline structure in semiconductors.     

Optical properties of a GaAs cone-like quantum dot: Second and third-harmonic generation

In the present work, we have studied numerically the second harmonic generation (SHG) and third harmonic generation (THG) in a cone-like quantum dot. For this purpose, we firstly obtained the energy levels and wave functions of this system. Then, we have used an expression for the SHG and THG by a compact density matrix approach and an iterative procedure. The SHG and THG enhance and shift toward lower energy by increasing the height h and vertex angle α. According to the results it is found that the structural parameters have great influence on the THG in this system.     

Third-harmonic generation from ZnO films deposited by MOCVD

Third-harmonic generation (THG) was studied from ZnO thin film deposited by the metalorganic chemical vapor deposition (MOCVD) technique on sapphire substrates at different temperatures. A strong THG signal was obtained from the film deposited at an appropriate temperature. The dependence of THG on the deposition temperatures was discussed. A third-order susceptibility ⁽³⁾=3.77×10^-12 esu was deduced for a film deposited at 250 °C. This value is similar to that observed from ZnO nanocrystalline films fabricated by pulse-laser deposition (PLD). We conclude that film structure and the crystalline quality is main factors determined the THG in the film. PACS 42.55. Sa; 77.80.-e; 42.55.Px     

Highly efficient third-harmonic generation with electro-optically Q-switched diode-end-pumped Nd:YVO4 slab laser

We have achieved efficient third-harmonic generation (THG) with an electro-optically Q-switched diode-end-pumped slab laser by cascading second-harmonic and sum-frequency generation in a lithium triborate (LBO) crystal. The high conversion efficiency, short pulse length and high pulse energy is the characteristic of the output 355 nm light. An average power of 11.1 W at a repetition rate of 10 kHz was achieved. The pulse energy is 1.1 mJ and the pulse length is 5 ns. The peak power of pulse is 0.22 MW. The conversion efficiency from 1064 nm to 355 nm reached 44.4% which is to our knowledge the highest conversion efficiency. Furthermore, the 355 nm light is near TEM₀₀ mode. The beam quality is M² < 1.5. In this paper, the experimental setup, results and the factors which can affect the conversion efficiency are discussed.     

Three-dimensional optical data storage using third-harmonic generation in silver zinc phosphate glass

We demonstrate the possibility of three-dimensional optical data storage inside a specific zinc phosphate glass containing silver by using third-harmonic generation (THG) imaging. Information is stored inside the glass with femtosecond laser irradiation below the refractive index modification threshold. We use the same laser for THG readout. The capability of storage with this technique is discussed.     

Parity-forbidden excitations of Sr(2)CuO(2)Cl(2) revealed by optical third-harmonic spectroscopy

We present the first study of nonlinear optical third-harmonic generation (THG) in the strongly correlated charge-transfer insulator Sr(2)CuO(2)Cl(2). For fundamental excitation in the near infrared, the THG spectrum reveals a strongly resonant response for photon energies near 0.7 eV. Polarization analysis reveals this novel resonance to be only partially accounted for by three-photon excitation to the optical charge-transfer exciton, and indicates that an even-parity state at 2 eV, with a(1g) symmetry, participates in the third-harmonic susceptibility.     

Simultaneously phase-matched second- and third-harmonic generation from 1.55 microm radiation in annealed proton-exchanged periodically poled lithium niobate waveguides

Third-harmonic generation (THG) in the cw regime from C-band radiation was achieved in annealed proton-exchanged periodically poled lithium niobate (PPLN) waveguides. By suitable design of fabrication parameters and operating conditions, quasi-phase-matching (QPM) is obtained simultaneously for the second-harmonic generation process (omega-->2omega, first-order QPM) and for the sum-frequency-generation process (omega+2omega-->3omega, third-order QPM), which provides the third harmonic of the pump field. The high overlap between the field profiles of the interacting modes--TM00 at omega and TM10 at 2omega and 3omega--results in what is believed to be the highest ever reported normalized conversion efficiency for THG from telecommunication wavelengths, equal to 0.72%W(-2) cm(-4).     

In vivo imaging of cell morphology and cellular processes in Caenorhabditis elegans, using non-linear phenomena

We present the detailed imaging of structures and processes of the nematode Caenorhabditis elegans (C. elegans) using non-linear microscopy. Complementary information about the anatomy of the nematode was collected by implementing a combination of two photon excitation fluorescence (TPEF), second and third harmonic generation (SHG and THG) image contrast modes on the same microscope. Three-dimensional (3D) reconstructions of TPEF, SHG and THG images were also performed. Moreover, THG imaging technique has been tested as a potential, novel, non-destructive diagnostic tool for monitoring cellular processes in vivo, such as neuronal degeneration.     

Third-harmonic generation in two-dimensional pseudo-dot system with an applied magnetic field

Third-harmonic generation (THG) in a two-dimensional quantum pseudo-dot system with an applied magnetic field is theoretically investigated. THG coefficient is obtained by using the compact-density matrix approach and an iterative method. Numerical results are presented for typical GaAs/AlGaAs pseudo-parabolic quantum dots. The results show that the external magnetic field and the geometrical size of the pseudo-dot system have evidently influences on the THG, whereas their influences are different.