Wavelength and Intensity Tracking System

Abstract

An optical-electrical-mechanical servosystem has been developed that can track a spectral line the wavelength of which is changing as a function of time (or position on the emitting surface in the case of a luminescing sample). The system is based on an automatic continuous measurement of the wavelength derivative of the spectral line. The wavelength derivative is obtained through a “wavelength wobbler” modification of a monochromator. In this paper the system is demonstrated in the spatially continuous analysis of III-V alloy materials with respect to alloy composition and photoluminescence (PL) efficiency. Spatial resolution of the system in the analysis of composition and PL efficiency in the growth direction of graded alloy composition GaAs_1−xP _x is demonstrated to be less than 1 µm for angle-lapped samples. Further, use of the system in spectral line shape analysis is demonstrated. Suggestions for the use of the system in the automated testing of light emitting products are made. Extension of the system to other modes (than luminescence) is proposed.