Electrooptic polarization modulation in [110]-oriented GaAs-InGaAs multiple quantum wells

An electrooptic modulator that is sensitive to the polarization state of transmitted light is demonstrated by using the intrinsic optical anisotropy of biaxially strained [110]-oriented GaAs-In_y Ga_1-xAs multiple quantum wells. The ellipticity and the direction of polarization of a linearly polarized input pulse are modulated by a change in the in-plane dichroism and birefringence produced by a change in the voltage applied across the p-i-n region containing the quantum wells. Sensitive ellipsometric measurements are used to directly measure the anisotropy in the complex index of refraction between the two principal in-plane axes of the sample as a function of wavelength for selected voltages. The latter information is then used to determine the operating wavelength, the contrast ratio, the optical bandwidth, and the tunability of the modulator. This structure requires only standard elementary post-growth processing