Second-harmonic generation in strongly scattering porous gallium phosphide

Second-harmonic generation in a strongly scattering macroporous GaP layer with typical sizes of GaP nanocrystals ranging from 200 to 500 nm is studied using nanosecond pulses of an optical parametric oscillator. As the pump wavelength decreases from 1.6 to 1.0 m the second-harmonic yield from porous GaP increases more than one order of magnitude relative to the second-harmonic yield from crystalline GaP. This enhancement of the second-harmonic generation for shorter wavelengths correlates with the increase in the efficiency of light scattering, indicating the importance of scattering effects in nonlinear-optical processes in strongly scattering random media . PACS 42.25.Fx; 42.65.Ky     

Disorder-correlated enhancement of second-harmonic generation in strongly photonic porous gallium phosphide

We report an order of magnitude enhancement of second-harmonic generation (SHG) from porous gallium phosphide relative to SHG in crystalline gallium phosphide. Optical heterodyning measurements of photon free-path length reveal a correlation between SHG enhancement and disorder of the porous material.     

Raman scattering from surface optical phonon mode in gallium phosphide nanomaterials

The Raman scattering from gallium phosphide (GaP) nanoparticles (~53 nm) and nanosolids has been investigated. By means of Lorentzian fitting of the Raman scattering spectra, a surface optical phonon (SO) peak located between the transverse optical (TO) phonon and longitudinal optical (LO) phonon frequencies became observable. It has been proved by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) that a core-shell heterostructure is characteristic of the structure of GaP nanoparticles. According to electromagnetic theory, the SO frequency of the piezoelectric/semiconductor heterostructural nanomaterials was calculated.     

Efficient second-harmonic generation in nonlinear plasmonic waveguide

We theoretically studied a nonlinear optical process in a hybrid plasmonic waveguide composed of a nonlinear dielectric waveguide and a metal film with a separation of a thin air gap. Owing to the hybridization effect of guided mode and surface plasmon polariton mode, this particular waveguide is able to confine the optical-field in a deep subwavelength scale together with low propagation loss. Based on this, efficient second-harmonic generations (SHG) were revealed at the fundamental wavelength of λ=1.55?μm with good field confinement. The SHG efficiency, as well as the coupling coefficient and mode area, were analyzed and discussed in detail with respect to the structural parameters.     

Phase matching of second-harmonic generation in birefringent porous silicon

Optical second-harmonic generation is investigated in free-standing (110) porous silicon films having strong in-plane birefringence. Based on the measured values of the refractive indices, the conditions of phase matching are calculated and verified in the experiments on angular and polarization dependences of second-harmonic generation. Filling pores with a transparent dielectric liquid allows phase matching to be achieved and the second-harmonic signal to be increased by two orders of magnitude. The results of these experiments suggest an opportunity to form new-type nonlinear-optical media consisting of birefringent porous silicon as a phase-matching matrix for the materials embedded in the pores. Received: 30 April 2001 / Published online: 7 June 2001     

Efficient broadband second-harmonic generation by dispersive achromatic nonlinear conversion using only prisms

Using a lossless dispersive apparatus consisting of six prisms, optimized to match a second-harmonic crystal phase-matching angle versus wavelength to second order, we efficiently doubled tunable fundamental light near 660 nm over a range of 80 nm, using a 4-mm-long type I beta -barium borate crystal without tuning the crystal angle. Another set of six prisms after the crystal realigned the propagation directions of the various second-harmonic frequencies to be collinear to within 1/4 spot diameter in position and 200microrad in angle. The measured conversion efficiency of a 40-mJ, 5-ns fundamental pulse was 10%.     

Microdefects in lec gallium phosphide and generation of dislocations in homoepitaxial layers

Acta physica Academiae Scientiarum Hungaricae - GaP LEC substrates doped with sulphur (N D−N A≈(3−7)×1017 cm−3) were characterized by transmission electron microscopy...     

Surface states on gallium phosphide

Ultraviolet photoelectron spectroscopy shows that the surface Fermi level of clean cleaved GaP (10) is pinned 1.50 eV above the valence band maximum of empty surface states. Synchrotron radiation-excited photo-emission partial yield spectroscopy supports this conclusion.     

Heat treatment of gallium phosphide

Annealing effect of GaP depends on the phosphorus pressure observed by Hall effect, X-ray diffraction and photoluminescence. The phosphorus pressure for the peaks of the lattice constant after annealing coincide with that for the high resistivity in the Hall measurement.     

Many-quantum absorption in gallium phosphide

A study has been made of photoconductivity in GaP induced by 1.78 and 1.17 eV photons from Q-switched ruby or neodymium lasers. Many-quantum processes were observed with 2 to 7 photons participating simultaneously. Double-photon absorption with a phonon participating has also been investigated. The observed many-quantum transitions confirm the recent ideas about GaP zone structure.Based on a generating function method, the theory of many-quantum transitions is developed which takes into account the peculiarities of crystal zone structure. The experimental data are in satisfactory agreement with the theory.Both the many-quantum theory and the experimental method reported in the present paper permit one to study the zone structure of various crystals and to obtain new or supplementary information on fundamental optical constants of solids.     

Magneto-optical transitions in gallium phosphide

The structure of the magnetic levels of the GaP valence band has been calculated within the framework of the effective-mass method. We have determined the effective masses of holes in the direction of a fieldH[001], the probabilities of magneto-optical transitions, and their dependence on the reduced wave vector. The distinctive features of the magneto-optical spectra of GaP are discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 66–70, July, 1987.     

Quasi-phase-matched second-harmonic generation by use of a total-internal-reflection phase shift in gallium arsenide and zinc selenide plates

We fabricated a novel quasi-phase-matched frequency converter, using a zigzag optical beam path in a thin, polished parallel plate. Second-harmonic generation experiments demonstrated angle-tuned output at 4.6 to 5.3mum in GaAs and 1.7 to 2.0mum in ZnSe crystals when pulsed infrared laser sources were used.     

Angle-resolved second-harmonic light scattering from colloidal particles

We report angle-resolved second-harmonic generation (SHG) measurements from suspensions of centrosymmetric micron-size polystyrene spheres with surface-adsorbed dye (malachite green). The second-harmonic scattering profiles differ qualitatively from linear light scattering profiles of the same particles. We investigated these radiation patterns using several polarization configurations and particle diameters. We introduce a simple Rayleigh-Gans-Debye model to account for the SHG scattering anisotropy. The model compares favorably with our experimental data. Our measurements suggest scattering anisotropy may be used to isolate particle nonlinear optics from other bulk nonlinear optical effects in suspension.     

Three-photon non-linear cross-section of gallium phosphide

The luminescence of GaP which follows non-linear optical excitation has been studied by using three- and two-photon optical pumping by a neodymium and a ruby laser, respectively. By comparing the intensities of the excitonic A-line emission in the two spectra, the three-photon cross section is obtained. This result is compared with previous experimental and theoretical values.     

Efficient intracavity second-harmonic generation at 1063 nm in a GdCOB crystal

We report an efficient intracavity second-harmonic generation (SHG) at 1063 nm in a non-linear optical crystal, GdCa₄O(BO₃)₃ (GdCOB), performed with a diode end pumped continuous-wave (CW) Nd:GdVO₄ laser. In the case of a laser with an a-cut 0.4 at % Nd:GdVO₄ crystal frequency-doubled with a GdCOB crystal cut for Type I frequency doubling. A CW SHG output power of 2.25 W has been obtained using a 15 mm long GCOB crystal. The optical conversion efficiency with respect to the incident pump power was 12.4%.     

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.