Band-edge photorefractivity in semiconductors: Theory and experiment

Abstract

At wavelengths close to the band edge, strong photorefractive gratings using the Franz–Keldysh electrorefractive effect can be written in semiconductors. Two-beam-coupling exponential gain coefficients as high as Γ=16.3 cm−1 have been obtained in GaAs by combining the electrorefractive photorefractive grating with the conventional electro-optic photorefractive grating and using the moving grating technique to enhance the photorefractive space-charge field. A method for calculation of the gain coefficient near the band edge of materials is presented. The method is applied to GaAs and the results are compared to the experimental data. Reasonable agreement with experiment has been achieved. An optimal spectral range (910 nm<λ<930 nm) for near-band-edge photorefractivity in GaAs has been found. Conventional theories of photorefractivity based on Kukhtarev’s equations are found to be sufficient for calculation of the photorefractive space-charge field near the band edge. Predictions of the gain coefficient near the band edge using the moving grating technique are presented. Other methods of increasing the photorefractive gain such as the temperature-dependent resonance in InP:Fe are also discussed.

On formula for natural linewidth in Fabry-Perot lasers; simulation of experiments

“…At the same time, we take into account the phase and amplitude components of the natural linewidth. (10), (16) and Ke14 in Fig.1) in Fig. A1 and the bridge function T((mW)/P) (see (A2)) in Fig.…”

“…In an early paper [9], when using nonlinear photorefractivity [10], n = n 0 +n 1 (ω) E +n 2 (ω)E 2 .…”

Simulation of natural linewidth and line form for semiconductor lasers; Interpretation of experiments

“…We consider a laser model distributed in space (in this model the emission power and natural linewidth depend on spatial variable). We use an experimentally measured dependence of the refractive index of the laser active zone on the electric field intensity E. From the experimental paper [15] it follows that n = n 0 +n 1 ()…”

Overview of Nonlinear Optics

“…The largest effects require kilovolts to be applied to the crystal, but kilohertz response can be achieved. If the wavelength is near the band edge of the semiconductor, the local resonant nonlinear refractive index can add to the non-local electro-optic refractive index change to enhance the photorefractivity (Partovi, 1991). Wave-mixing can be observed with mW of incident power (Nolte, 1999).…”