Efficient intracavity second-harmonic generation at 1.06 μm in a BiB3O6 (BIBO) crystal

We report, for the first time, efficient intracavity second-harmonic generation (SHG) at 1.06 μm in a non-linear optical crystal, BiB₃O₆ (BIBO), at a type-I phase-matching direction of (θ,ϕ)=(168.9°,90°), performed with a LD end-pumped cw Nd:YVO₄ laser. A cw SHG output power of 364 mW has been obtained using a 1.9-mm-thick BIBO crystal. The optical conversion efficiency was 12.2% and the corresponding effective intracavity SHG efficiency was determined to be 32.4%. It was found that the intracavity SHG efficiency is greater than that obtained with a type-II phase-matching KTiOPO₄ (KTP) crystal with a thickness of 3 mm. The effective non-linear optical coefficient (d_eff) ratio of BIBO to that of KTP, determined experimentally, is 1.23:1. Received: 7 May 2001 / Revised version: 6 July 2001 / Published online: 19 September 2001     

Intra-cavity second harmonic generation with Nd:YVO4/BIBO laser at 542 nm

We report, for the first time, an efficient intra-cavity second-harmonic generation (SHG) at 1084 nm in a nonlinear optical crystal, BiB₃O₆(BIBO) at the direction of (θ, ?) = (170.1°, 90°), performed with a LD end-pumped cw Nd:YVO₄ laser. With 590 mW diode pump power, a continuous-wave (cw) SHG output power of 19 mW at 542 nm yellow-green color has been obtained using a 1.5 mm-thick BIBO crystal. The optical conversion efficiency was 3.22%. It was found that the output wavelength could be 532 nm, 537 nm or 542 nm according to regulating the angle of BIBO.     

低对称性非线性光学晶体BIBO的倍频性质

测量了BIBO晶体的主轴折射率.对BIBO晶体在整个空间内的倍频性质进行了系统讨论.当基频 光为Nd:YAG激光时（λ=1064nm），发现最大的有效非线性光学系数位于（168.9°，90°） 的Ⅰ类相位匹配方向上.测量了BIBO晶体的容限角、容限温度、光损伤阈值，以及1064nm的 腔外、腔内倍频性质.实验中，最大腔外倍频转换效率达到68%，腔内倍频输出达到1.06W. 关键词： 低对称性 BIBO晶体 倍频     

低对称性非线性光学晶体硼酸铋(BIBO)的1064nm三倍频性质

采用高温溶液法成功生长出高光学质量的硼酸铋 (BIBO)晶体 ,尺寸达到 2 4mm× 19mm× 35mm ,质量为4 8g。对BIBO晶体进行了定向 ,并测量了该晶体的主轴折射率。讨论了BIBO晶体的 10 6 4nm三倍频性质 ,包括相位匹配角、有效非线性光学系数deff、容限角、走离角等。结果表明 ,BIBO晶体的最佳三倍频方向为 (137.7°,130°) ,其有效非线性光学系数值达到 3.6 0 pm/V ,属I类相位匹配。就主平面内的相位匹配方向而言 ,(14 6 .4°,90°)具有最大的有效非线性光学系数值 ,为 3.16pm/V。在 10 6 4nm的腔外三倍频实验中 ,(14 6 .4° ,90°)BIBO晶体的转换效率达到 39.5 % ,角度容限半宽为 0 .2 2mrad·cm ,该数值与 0 .175mrad·cm的计算值基本符合。由于(33.6°,90°)BIBO晶体的有效非线性光学系数较小 (0 .31pm/V) ,其三倍频转换效率小于 5 %。     

Second harmonic generation in zinc oxide nanorods

Second-order optical nonlinearities of zinc oxide (ZnO) nanorods grown on quartz substrate were determined by optical second harmonic generation (SHG) measurements at 1064 nm fundamental wavelength. The average length of the zinc oxide nanorods ranged from 50 nm to 700 nm. By employing the Maker fringes technique, we obtained the second-order nonlinear optical coefficients d₃₃₃ and d₃₁₁. Their magnitudes and ratio are compared with that of zinc oxide thin film fabricated by different techniques. We see variations of the second-order nonlinear optical coefficients with respect to the aspect ratio of the nanorods. This is attributed to local field effects. PACS 42.65.Ky; 78.67.-n; 81.07.-b     

The growth,thermal and nonlinear optical properties of single-crystal GdAl3(BO3)4

The nonlinear optical single-crystals GdAl₃(BO₃)₄ (GAB), space group R32, were grown by the top-seed solution growth (TSSG) method. The thermal properties and the nonlinear optical characteristics have been investigated. The two principal coefficients of thermal expansion along (100) and (001) were measured to be 5.30 × 10⁻⁶, 1.88 × 10⁻⁵ K⁻¹. The transmission spectrum was measured and the second-harmonic generation (SHG) was presented. By way of our designed cross superimposed laser crystal multiplier, the frequency doubling laser at wavelength 457.5 nm was measured to be 18.2 mW and the facular properties indicated the multiplier contributed to the improvement of the frequency doubling conversion efficiency.     

Characterization of optical and nonlinear properties of periodically-poled RbTiOAsO4 in the mid-infrared range via difference-frequency generation

Tunable mid-infrared coherent radiation (3.25- 3.7 μm) is generated by quasi-phase-matched difference frequency generation in a multi-grating periodically-poled RbTiOAsO₄ crystal. The spontaneous polarization and coercive field of flux-grown RbTiOAsO₄ are determined by polarization switching measurements. The nonlinear interaction enables us to explore the optical and nonlinear properties of this material in the mid-infrared range, where data is scarce. The measurements are used to derive a mid- infrared corrected dispersion equation for n_z in RbTiOAsO₄. This equation is in excellent agreement with previously published measurements of nonlinear interactions in periodically-poled RbTiOAsO₄. The measured wavelength and temperature bandwidths are ≈48 nm cm and ≈29 °C cm, respectively. A relatively high temperature tuning slope of the phase-matched idler wavelength, -1.27 nm/°C, is measured. This may be useful for realizing temperature-tuned nonlinear devices. Received: 30 March 2000 / Revised version: 9 May 2000 / Published online: 30 June 2000     

基于BiB3O6晶体的飞秒光参量变换特性

对基于新型非线性晶体BiB₃O₆(BIBO)的飞秒光参量变换过程的参量特性进行了研究. 计算了BIBO晶体三个光学主平面内的相位匹配条件和有效非线性系数,确定了克尔透镜锁模钛宝石激光器的基频光与倍频光抽运时最佳的光学主平面和相位匹配方式,并分析了三波的时间走离和空间走离,以及信号光的参量增益和带宽. 为利用基于BIBO晶体的飞秒光参量技术获得高能量、宽调谐、窄脉宽的光源提供理论依据和实验指导. 关键词： 3O₆')" href="#">BiB₃O₆ 光参量变换 共线相位匹配 光学主平面     

Low- and high-order nonlinear optical characterization of C60-containing media

Third- and higher-order nonlinear optical processes in fullerenes were studies to define the influence of low-order nonlinearities on the high-order harmonic generation in these media. We measured the nonlinear absorption coefficients of the C₆₀:toluene solution using the 532 and 1064 nm, 50 ps pulses. The high-order harmonic generation was studied during propagation of the 790 nm, 150 fs pulses through the plasmas produced on surfaces containing fullerene powder. These studies have shown that the low-order nonlinearities of fullerenes have no impact on the generation of harmonics in such mediums in the vacuum ultraviolet range at optimal intensity of laser radiation.     

Intracavity second-harmonic generation of 1.06 μm in GdCa4O(BO3)3 crystals

The characteristics of intracavity second-harmonic generation (SHG) at 1.06 μm in GdCa₄O(BO₃)₃ (GdCOB) crystals cut for different type I phase-matching (PM) directions of (θ,φ)=(66.8°, 132.3°); (19.4°, 0°); (90°, 46°) have been investigated. It was found that the intracavity SHG was significantly efficient in the PM direction of (66.8°, 132.3°), and that the intrinsic lower effective nonlinear coefficient (d_eff) was responsible for the less-efficient SHG in the other two directions. A maximum CW SHG output power of 2.81 W was obtained with an optical conversion efficiency of 18.7%, while the corresponding effective intracavity SHG efficiency was determined to be 41.3%. The intracavity SHG efficiency of GdCOB has been found to reach two-thirds of that obtained with type II phase-matching KTiOPO₄ (KTP). Received: 26 April 2000 / Revised version: 3 July 2000 / Published online: 5 October 2000     

Linear and nonlinear optical properties of yttrium formate dihydrate,Y(HCOO)<Subscript>3</Subscript>·2H<Subscript>2</Subscript>O

Yttrium formate dihydrate, Y(HCOO)₃·2H₂O (point group 222), a promising new material for Raman laser frequency converters, has been reinvestigated with respect to the linear and nonlinear optical (second-harmonic generation, SHG) properties. High-precision data of refractive indices and their dispersion in the wavelength range 365–1083 nm are given, together with the three independent components of the tensor of nonlinear optical susceptibility (SHG) [d_ijk ^SHG]. A calculation of the macroscopic nonlinear optical susceptibility from the hyperpolarizabilities of the formate groups results in good agreement with the experimental values. This signals that the nonlinear optical interaction in Y(HCOO)₃·2H₂O can mainly be attributed to the formate groups. PACS 42.65.Ky; 42.70.Mp; 78.20.Ci     

Laser diode array pumped Yb:YAG/BIBO 515 nm thin disc laser with four-pass optical coupling system

We presented a new simple flat-concave cavity system to produce compact and low-cost 515 nm laser, and the validity has been demonstrated. The Yb:YAG crystal with 10% concentration was 300 μm thickness and 10 mm in diameter. The four-pass optical coupling system was well designed with two spherical imaging mirrors (ϕ = 30 mm, R = 50 mm). Taking into account mode matching, the pump-spot radius in the laser crystal was calculated by LightTools software. The 2 × 2 × 1.5 mm³ BIBO crystal cutting at a type-I phase-matching direction of (θ, φ) = (166.8°, 90°) was employed. With 4.4 W incident power, the maximum output power of 14.3 mW at 515 nm was obtained without optimization of soldering technique, and the single-frequency phenomenon was first observed when the output power was 3 mW.     

Nonlinear optical absorption and refraction in Ru, Pd, and Au nanoparticle suspensions

We present the results of studies of the nonlinear optical properties of Pd, Ru, and Au nanoparticles. We studied the nonlinear refraction and nonlinear absorption of suspensions of these nanoparticles at 1064-nm wavelength. A relatively strong nonlinear absorption of the Pd nanoparticles was observed in the case of 1064-nm, 50-ps pulses (β=2×10⁻⁹ m W⁻¹). The Ru and Pd nanoparticles showed weak negative nonlinear refraction (γ∼−(6–8)×10⁻¹⁶ m² W⁻¹) in this spectral range. In the case of the Au nanoparticles, a saturated absorption at 532 nm dominated over other nonlinear optical processes.     

Nonlinear optical properties of an azo-based dye irradiated by picosecond and nanosecond laser pulses

The nonlinear optical properties of an azo-based dye were investigated using Z-scan technique employing 38 ps pulses at 532 and 1064 nm, and 6 ns laser pulses at 532 nm. Large nonlinear absorption and nonlinear refraction were observed at both ps and ns 532 nm in the azoic dye. When excited at ps 1064 nm, this dye displayed a large two-photon absorption cross-section (σ₂=1810 GM). Meanwhile, the optical nonlinearity mechanism was discussed in terms of molecular structure, excitation wavelength, and pulse width.     

Studies of the second-order nonlinear optical properties of cubic boron nitride

Cubic boron nitride (cBN) is a kind of artificial wide-energy-gap semiconductor crystal, which has zinc blende structure with Td symmetry. The second-order nonlinear optical properties of cBN single crystal were investigated for the first time. Using a Q-switching Nd:YAG laser, the optical rectification and the second-harmonic generation at 532 nm from cBN single crystal were observed. In order to determine the nonlinear optical coefficient of a minute-size cBN sample, a simple method based on modified transverse linear electro-optic modulation was also introduced. This approach is convenient because it is unnecessary to know the absolute intensity of a probing beam for measuring the half-wave voltage of a cBN sample. Finally, cBN’s linear electro-optic coefficient γ₄₁=1.07×10^-14 m/V and nonlinear optical coefficient d₁₄(0,ω,-ω)=1.07×10^-13 m/V were obtained. PACS 42.65.An; 42.65.Ky; 78.20.Jq     

Customizing optical and dielectric traits of ammonium dihydrogen phosphate (ADP) crystal exploiting Zn2+ ion for photonic device applications

Current investigation is aimed to explore the influence of Zn²⁺ ion on structural, optical and dielectric characteristics of ammonium dihydrogen phosphate (ADP) crystal to explore its widespread suitability for photonic device applications. The slow solvent evaporation technique has been adopted to grow the Zn²⁺ ion influenced ADP (Zn-ADP) crystal. The energy dispersive spectroscopic technique has been employed to determine the constituent elements of Zn-ADP crystal. The optical transmittance of pure and Zn-ADP crystal has been examined within 200–1100 nm by means of UV–visible spectral analysis. The Kurtz–Perry test has been employed to determine the enhancement in second harmonic generation (SHG) efficiency of ADP crystal due to presence of Zn²⁺ ion. The SHG efficiency of Zn-ADP crystal is found to be 3.15 times greater than potassium dihydrogen phosphate (KDP) and 1.79 times higher than ADP. The Z-scan analysis has been performed at 632.8 nm to study the third order nonlinear optical attributes (such as nonlinear refraction (n₂), absorption (β) and cubic susceptibility (χ³)) of Zn-ADP crystal. Dielectric analysis has been carried out within the temperature range of 30 to 90 °C to evaluate the effect of Zn²⁺ ion on dielectric constant and dielectric loss of ADP crystal. The thermal stability of the grown crystal has been investigated within the temperature range of 40–500 °C. The application of developed Zn-ADP crystal for photonic devices has been discussed in vision of obtained results.     

Photoinduced second harmonic generation studies on Tris(thiourea)copper(I) perchlorate Cu(SC(NH2)2)3(ClO4)

We have established a possibility to obtain the photoinduced optical second harmonic generation in the initially centrosymmetric single crystals of tris(thiourea)copper(I) perchlorate crystallized in the monoclinic system with the space group P2₁/c. The second‐order susceptibility of the investigated crystal was measured by inducing the crystal by external laser field. The results obtained are interesting and discussed in detail. We have established that the optical second harmonic generation achieves its maximum (about 0.84 pm/V) at photoinducing power density about 1430 kW/cm² for the fundamental wavelength 1064 nm. The maximal output second harmonic generation (SHG) was achieved at an angle of about 35° between the pumping and fundamental power beam's polarizations. Such maximum may be a consequence of a competition between the so formed anharmonic photothermal expansions and the thermal destruction that occurred because of the heating of the crystal surfaces. Our independent verifications have shown that the photoinduced surfaces were heated up to 8–12° C. This may cause occurrence of photothermal relaxation processes. The output SHG exists only immediately after the act of photoinduction. The obtained dependences are caused by specific features of the Raman spectra of the investigated crystals. Copyright © 2008 John Wiley & Sons, Ltd.     

Generation of femtosecond laser pulses at 396 nm in K_3B_6O_(10)Cl crystal

K_3B_6O_(10)Cl(KBOC), a new nonlinear optical crystal, shows potential advantages for the generation of deep ultraviolet(UV) light compared with other borate crystals. In this paper we study for the first time the second harmonic generation(SHG) of a femtosecond Ti:sapphire amplifier with this crystal. Laser power is obtained to be as high as 220 m W at the central wavelength of 396 nm with a 1-mm-long crystal, and the maximum SHG conversion efficiency reaches 39.3%. The typical pulse duration is 83 fs. The results show that second harmonic(SH) conversion efficiency has the room to be further improved and that the new nonlinear crystal is very suited to generate the high efficiency deep ultraviolet laser radiation below 266 nm.     

Harmonic generation in bismuth triborate (BiB3O6)

We report a study of second- and third-harmonic generation in BiB₃O₆ (BiBO). The effective nonlinearity, phase-matching angle, acceptance bandwidth, and walk-off are calculated and analyzed within the principal planes of the optical indicatrix. In the experiment, the phase-matched harmonic generation is investigated within the xz and yz planes. Also, the temperature dependence of the noncritical phase matching for laser radiation propagating along the z axis is measured for second-harmonic generation (SHG) at crystal temperatures of 25–265^∘C. The corresponding wavelengths of the laser radiation are in the range of 1.16 to 1.34μm. In addition, SHG of 1342-nm radiation of a q-switched Nd:YVO₄ laser system is investigated for noncritical and critical phase matching. The achieved conversion efficiencies are 59% and 20%, respectively. Besides SHG, third-harmonic generation (THG) of 1064-nm, ns laser pulses is investigated. The measured conversion efficiency is as high as 34%. For THG the properties of BiBO are compared with those of BBO and LBO.     

Frequency doubling of Nd:YAG- and GaAs-lasers by KNbO3: Ta crystals

Abstract

For KNb_1-xTa_xO₃ crystals the influence of the Ta-concentration on the phase-matching properties for optical second harmonic generation (SHG) was measured. For non-critical phase matched SHG of the Nd:YAG-laser (1064nm) the coefficient d₃₁ of the tensor of the nonlinear susceptibility was applied, while for the GaAs-laser (905 nm) the coefficient d₃₂ was used. For both laser wavelengths the phase-matching temperature decreases with increasing Ta-concentration. Non-critical phase-matching at room temperature can be reached with the GaAs-laser for a Ta-concentration of ≈9%. The corresponding value for the Nd:YAG-laser is ≈14%.