摘要:

The aim of this work is to study gray tracking during type II second-harmonic-generation 1064→532 nm in halide flux grownKTiOPO4crystals. The repetition rate of the laser varies from 1 to 20 kHz. We experimentally demonstrate that the gray-tracking threshold, expressed by the harmonic peak power density, is a decreasing exponential function of theQ-switch frequency. The corresponding 532 nm average power density, however, remains constant. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118391

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Beryllium chalcogenides have a much higher degree of covalency than other II–VI compounds. Be containing ZnSe based mixed crystals show a significant lattice hardening effect. In addition, they introduce substantial additional degrees of freedom for the design of wide gap II–VI heterostructures due to their band gaps, lattice constants, and doping behavior. Therefore, these compounds seem to be very interesting materials for short wavelength laser diodes. Here, we report on the first fabrication of laser diodes based on the wide band gap II–VI semiconductor compound BeMgZnSe. The laser diodes emit at a wavelength of 507 nm under pulsed current injection at 77 K, with a threshold current of 80 mA, corresponding to 240A/cm2. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118422

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Type I phase matched second harmonic generation (SHG) in the organic crystal ortho-Dicyanovinyl-anisole (DIVA) has been measured for a range of near infrared fundamental wavelengths (855–960 nm). Turning curves for type I phase matched SHG were derived from measured refractive index values and show noncritical phase matching at 860. Measured type I phase matched SHG is in close agreement with the calculated results and gives effective SHG coefficients ranging from 1.9 to 5.9 times as large asd32of potassium niobate. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118393

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The response of GaAs metal-semiconductor-metal photodetectors (MSM-PD) is simulated using a phenomenological model of transport equations, which takes into account the electron intervalley transfer. Calculations are performed for intrinsic devices with 1 &mgr;m and 0.5 &mgr;m interdigital spacing with the corresponding equivalent (parasitic) circuit of the photodetector. It is pointed out that parasitic effects may induce a significant distortion, a delay of intrinsic response, and increase bit error rate. Analysis of the equivalent or parasitic circuit of the MSM-PD transfer function shows that the distortion and delay of the intrinsic signal can be minimized by choosing the optimal photodetector capacitance. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118394

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We present a study of the transmission coefficients of two-dimensional photonic band gap materials consisting of dielectric cylinders in graphite arrangement. By the study of the attenuation versus slab thickness, we determine the most efficient graphite configuration. We show how uncoupled modes create opaque regions for plane waves propagating along the &Ggr;-P direction and widen the gap originating from the existence of forbidden photonic bands. Our results demonstrate that graphite structure is a promising geometry yielding an attenuation as strong as triangular structure with greater convenience in the fabrication at the submicronic scale. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118395

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report on the synthesis and the optical characterization of a photorefractive sol-gel material which contains nonlinear azo chromophore and carbazole charge transporting molecules. Both of these functional groups are covalently attached to the silica based backbone. Thin sol-gel films exhibit stable optically nonlinear properties: the electro-optic coefficientr13measured at 633 nm is found to be 17 pm/V one day after corona poling and 15 pm/V after three weeks and over a period of several months. Photorefractivity is demonstrated by two beam coupling experiments without external applied electric field. Sol-gel films present a stable photorefractive memory effect with a net internal gain of 200cm−1. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118396

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Strain effects in a strained SiGe/Si quantum well induced by self-assembled Ge islands have been studied by varying the Ge coverage. The strain by the Ge islands induces a complicated behavior in photoluminescence spectra depending on the Ge coverage. The Ge islands give the enhanced local strain to the underlying structures with the increase of the Ge coverage, at the early stage of the growth. However, as the Ge coverage increases the enhanced local strain does not continue being reinforced but is limited after once being retrogressed. These results are discussed in terms of elastic deformation due to the lattice mismatch between Si and Ge and the lattice relaxation in Ge islands. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118397

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Optical and electroluminescent properties of a new poly(p-phenylene)-type polymer, poly(benzoyl-1, 4-phenylene) (PBP) were studied. PBP is soluble in common organic solvents, has high thermal stability and shows bright blue photoluminescence. Light-emitting diodes fabricated with PBP as the active layer emit blue electroluminescence with a peak wavelength at 446 nm and a brightness of about 100cd/m2. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118398

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

In the photoluminescence (PL) of BaFBr:Eu2+,Eu3+,the emissions of Eu2+,carrier electron-hole (e-h) recombination, andEu3+are observed, while in the photostimulated luminescence (PSL) only the emission ofEu2+is exhibited. This disappearance of e-h recombination in PSL is considered to be caused by carrier migration during photo-stimulation. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118204

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report the fabrication of a near-infrared avalanche photodetector with a gain-bandwidth product of over 300 GHz. The detector uses a Si multiplication layer and an InGaAs absorption layer. A 3 dB bandwidth of over 9 GHz was measured for current gains as high as 35. Photocurrent measurements using 1.3&mgr;m light indicate a quantum efficiency for the detector of 0.60, near the limit expected based on the absorber thickness. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118399

出版商:AIP    

年代:1997

数据来源: AIP