Improvement of oscillation characteristics of ring oscillator through photoconductivity and dielectric constant of photorefractive materials

Abstract

The intensity of oscillation and the oscillation frequency shift are two most important parameters that characterize the performance of a photorefractive ring oscillator. In this paper, the effect of photoconductivity and dielectric constant of photorefractive (PR) materials on these parameters has been studied in case of non-degenerate two-wave mixing in PR materials. It has been found that for a given value of photoconductivity of PR material, the highly reflecting ($R > 90\%$) cavity mirrors are much effective parameter as compared to the other parameters (frequency detuning, absorption strength, energy beam coupling strength and dielectric constant) for the enhancement of the intensity of oscillation in the oscillator. Also, the magnitude of oscillation frequency of the photorefractive ring oscillator (PRO) can be increased by inserting PR crystal of lower dielectric constant ($\varepsilon < 7.0$), higher photoconductivity ($\sigma_{\text{p}} > 500\,{\text{pS/cm}}$) and highly reflectivity ($R > 90\%$) cavity mirrors provided that the cavity-length detuning $\left( {\frac{\Delta \varGamma }{\pi } > 1.0} \right)$ of the oscillator is higher. This means that the intensity and frequency of the PRO could be controlled by the dielectric constant and photoconductivity of a PR crystal which would greatly improve performance of a PRO and their applications based on these photorefractive ring oscillators such as wave front color conversion, optical limiting, optical computing and beam cleanup.