QUANTUM WELLS IN OPTOELECTRONICS: Polarisation dependence of refractive index of MQW waveguides

Abstract

The polarisation dependence of the refractive index of a multiple quantum well wave-guide has been investigated using the grating coupler technique. The use of a layer of anti-reflection coating during the holographic definition of the gratings allows high contrast ratios to be routinely achieved, and by defining the grating coupler in a low-index material on top of the semiconductor and simplifying the measurement procedure, the precision of the results is enhanced and the timefactor of the measurements is reduced. Over the range of wavelengths from 840 to 880 nm, the refractive index of the multiple quantum well material was observed to change by 8 × 10−2 and 6.7 × 10−2 for the transverse electric and transverse magnetic polarisations, respectively. The birefringence of the material was observed to increase from 1.4 × 10−2 at 880 nm to 2.7 × 10−2 at 840 nm.