Nonlinear Absorption Changes Research Articles

Nonlinear optical pulse propagation in a semiconductor medium in the transient regime. II. Interferometric sampling

For pt.I see ibid., vol.26, no.4, p.760-9 (1990). A numerical model of pulse propagation in a semiconductor is used to simulate the technique of interferometric sampling of the semiconductor response to an optical pulse. Interferometric sampling is a form of time-resolved interferometry which combines elements of classical interferometry and pump-probe techniques to obtain the transient response of nonlinear refractive index and absorption changes in a material. The technique is shown to accurately measure saturated changes in phase and transmittance, as well as the interband recombination time. >

Pump-pulse induced chirp production in semiconductors

Nonlinear absorption and refractive index changes in wide-gap semiconductors (CdS, CdSSe, and GaSe) after ps light irradiation are determined with an excite-and-probebeam spectrometer. Based on a simple model pump-pulse induced chirp parameters on a signal pulse of different wavelength are calculated. Possible applications are discussed.

Analysis of nonlinear absorption changes in reaction centers of photosynthetic bacteria as a result of selective excitation with high-power laser pulses

A theoretical analysis is made of nonlinear changes in the optical density of reaction centers of photosynthetic bacteria after excitation with high-power picosecond laser pulses. A simplified four-level model is used to show that changes in the optical density of such a system are independent of the phase memory parameter at very high excitation intensities. The results of numerical calculations of nonlinear changes in the optical density of reaction centers are in qualitative agreement with the experimental data. These results are sensitive to variation of both the phase relaxation time and of the dipole moments of optical transitions in the molecules which absorb the exciting radiation. The feasibility of determination of these parameters is demonstrated.