Efficient second-harmonic generation by scattering from porous gallium phosphide

We experimentally study second-harmonic generation by femtosecond Cr: forsterite-laser radiation scattered on the surface of porous gallium phosphide with characteristic pore sizes and distances between the pores comparable with the second-harmonic wavelength. The intensity of the second-harmonic signal from samples with initial crystallographic surface orientations (110) and (111) is more than an order of magnitude higher than the intensity of the second harmonic generated in reflection from single-crystal gallium phosphide. The efficiency of second-harmonic generation by macroporous gallium phosphide substantially increases as the pump wave-length becomes shorter. The influence of light localization and scattering effects on the enhancement of second-harmonic generation and polarization properties of the second-harmonic is discussed.     

Methods for increasing the efficiency of nonlinear optical interactions in nanostructured semiconductors

Methods for increasing the efficiency of the optical second-and third-harmonic generation in gallium phosphide and silicon nanostructures formed by electrochemical etching of crystalline semiconductors are discussed. The efficiency of nonlinear optical interactions can be increased by using phase matching in anisotropic nanostructured semiconductors that exhibit form birefringence or by increasing the local field, as in scattering in macroporous semiconductors. The efficiencies of third-harmonic generation in porous silicon and of second-harmonic generation in porous gallium phosphide are found to increase by more than an order of magnitude.     

Optical phonons of circular wires in porous GaP

The reflection spectra of porous gallium phosphide samples are investigated in the far infrared region of wave numbers (10–700 cm^?1). In addition of the longitudinal and transverse optical phonon modes corresponding to the bulk material, additional vibrational modes are detected. Their number and spectral position are correctly described by a model of a dispersive dielectric medium under the assumption that porous gallium phosphide is formed by crystallites whose shape is close to cylindrical. It is concluded that such vibrational modes are optical phonons confined by the volume of the quantum wire. The experimental optical reflection spectra are used to obtain estimates of the average diameter of nanocrystallites forming the porous GaP layer.     

High power 4.65 μm single-wavelength laser by second-harmonic generation of pulsed TEA CO2 laser in AgGaSe2 and ZnGeP2

A high power 4.65 ??m single-wavelength laser by second-harmonic generation (SHG) of TEA CO₂ laser pulses in silver gallium selenide (AgGaSe₂) and zinc germanium phosphide (ZnGeP₂) crystals is reported. Experimental results show that the average output power of SHG laser is not only restricted by the damage threshold of the nonlinear crystals, but also limited by the irradiated power of fundamental-wave laser depending on the operating repetition-rate. It is found that ZnGeP₂ can withstand higher 9.3 ??m laser irradiation intensity than AgGaSe₂. As a result, using a parallel array stacked by seven ZnGeP₂ crystals, an average power of 20.3 W 4.65 ??m laser is obtained at 250 Hz. To the best of our knowledge, it is the highest output power for SHG of CO₂ laser by far.     

Spatial extent of random laser modes

We have experimentally studied the distribution of the spatial extent of modes and the crossover from essentially single-mode to distinctly multimode behavior inside a porous gallium phosphide random laser. This system serves as a paragon for random lasers due to its exemplary high index contrast. In the multimode regime, we observed mode competition. We have measured the distribution of spectral mode spacings in our emission spectra and found level repulsion that is well described by the Gaussian orthogonal ensemble of random-matrix theory.     

Dynamically phase-matched terahertz generation

We present the generation of intense terahertz pulses by optical rectification of 780 nm pulses in a large area gallium phosphide crystal. The velocity mismatch between optical and terahertz pulses thereby limits the bandwidth of the terahertz pulses. We show that this limitation can be overcome by a dynamic modification of the refractive index of the gallium phosphide crystal through generation of hot phonons. This is confirmed by excellent agreement between experimental results and model calculations.     

Forbidden band width and optical properties of thin gallium phosphide films

The temperature dependence of the forbidden band width of gallium phosphide films deposited by a discrete method on various substrates has been investigated in the present work. The influence of the material and temperature of the substrate on the forbidden band width and its change with thickness, are determined. This latter is treated as the appearance of a quantum dimensional effect. The dispersion of gallium phosphide films is measured in the visible band of the spectrum.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 9, pp. 88–92, September, 1971.     

Defect formation processes and their influence on mechanical stresses in green glow gallium phosphide structures

Defect formation and their influence on internal mechanical stresses in epitaxial gallium phosphide layers grown from a gallium melt with the addition of finely-dispersed gallium nitride particles in an atmosphere of hydrogen with ammonia are investigated in this paper. It is established that an increase from 0.04 to 0.1 vol. % in the ammonia content in the gas mixture will result in growth in the quantity of defects, in particular, inclusions of the second phase, as well as internal mechanical stresses, while for an NH₃ content greater than 0.1 vol. % – in the formation of shallow cracks and stress relaxation. The dependence between the internal mechanical stresses, the volume fraction, and the dispersion of the GaN inclusions in gallium phosphide is shown. The results obtained are discussed within the framework of the proposed model.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 23–27, January, 1991.     

Laser spectroscopy of GaP grown by the Czochralski method

A method of laser modulation spectroscopy using impurity-band absorption associated with deep impurity centers is suggested for studying the second-kind of critical points in the Brillouin zone of gallium phosphide.     

磷砷化镓黄色发光二极管

采用掺氨砷压法在磷化镓衬底上外延生长掺碲n型的GaAs0.15P0.85:N/GaP材料,制成磷砷化镓黄色发光二极管,测量了其光学和电学性能.讨论了影响器件发光效率的因素.     

Angular Dependences of the Intensity of the Raman Light Scattering on Polaritons in a Gallium Phosphide Crystal

Optics and Spectroscopy - Raman light scattering on phonons and polaritons is measured in a gallium phosphide sample. An unfocused beam of a 532-nm single-mode laser was used for excitation. A...     

Electrical and optical properties of gallium phosphide films

The electrical and optical properties of gallium phosphide films, prepared by the explosive evaporation and three-temperature methods, are studied. It is shown that film properties are strongly dependent on method of preparation and substrate temperature. Gallium phosphide films prepared by explosive evaporation having perfect structure possess the best electrical and optical properties.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 6, pp. 54–58, June, 1971.     

Absorption saturation of n-type gallium phosphide

The absorption of n-type gallium phosphide at 2.8 μm wavelength decreases at high light intensity. The saturation intensity is found to be 10 MW cm^?2.     

Growth kinetics of epitaxial layers of gallium phosphide by temperature-gradient zone recrystallization

A study is made of the dependence of the growth rate of epitaxial layers of gallium phosphide under conditions of temperature-gradient zone recrystallizatton on the thickness of the zone and the temperature. The coefficient of diffusion of phosphorus into gallium is calculated, and also the rate of change of the phosphorus concentration in the zone due to vaporization, the activation energies of the diffusion and vaporization processes, and also the atomickinetic coefficients of the crystallization process.     

Narrowband optical parametric gain in slow mode engineered GaInP photonic crystal waveguides

We predict narrowband parametric amplification in dispersion-tailored photonic crystal waveguides made of gallium indium phosphide. We use a full-vectorial model including the dispersive nature both of the nonlinear response and of the propagation losses. An analytical formula for the gain is also derived.     

Compact and cost-effective scheme for THz generation via optical rectification in GaP and GaAs using novel fs laser oscillators

We demonstrate a compact and cost-effective setup to generate broadband THz radiation. As pump source we use a diode-pumped solid-state femtosecond oscillator or a femtosecond fiber laser system, partially in combination with an optical parametric oscillator. For the THz generation we utilize optical rectification in gallium phosphide (GaP) and gallium arsenide (GaAs). The THz power is on the order of 1 μW and we demonstrate imaging and spectral measurements with this setup.     

ENDOR investigations of Ge doped GaP

ENDOR measurements of germanium doped gallium phosphide show a SHF-interaction with one neighbour shell strong enough to resolve the splitting of lines caused by the mutual interaction of the different nuclei of the same shell. The symmetry and hyperfine parameters of four other neighbour shells have also been determined.     

Enhanced second-harmonic generation from individual metallic nanoapertures

We demonstrate the ability of single-subwavelength-size nanoapertures fabricated in a gold metal thin film to enhance second-harmonic generation (SHG) as compared to a bare metal film. Nonlinear microscopy imaging with polarization resolution is used to quantify the SHG enhancement in circular and triangular nanoaperture shapes. The dependence of the measured SHG enhancement on circular aperture diameters is seen to originate from both phase retardation effects and field enhancements at the nanoaperture edge. Triangular nanoapertures exhibit superior SHG enhancement compared with circular ones, as expected from their noncentrosymmetric shape.     

纳米GaP粉体反射光谱的测量及其分析

通过测量纳米磷化镓(GaP)粉体在紫外可见光波段(200-800nm)的反射光谱,运用三流理论由反射光谱计算出纳米GaP粉体的吸收系数(Ea)和散射系数(Es)的比值(Ea/Es)。纳米GaP粉体的反射光谱的形状主要受吸收的影响,即GaP禁带结构的影响。     

A mild reduction-phosphidation approach to nanocrystalline GaP

Nanocrystalline gallium phosphide (GaP) has been prepared through a reduction-phosphidation by using Ga, PCl₃ as gallium and phosphorus sources and metallic sodium as reductant at 350 °C. The XRD pattern can be indexed as cublic GaP with the lattice constant of a=5.446 Å. The TEM image shows particle-like polycrystals and flake-like single crystals. The PL spectrum exhibits one peak at 330 nm for the as-prepared nanocrystalline GaP.