Multi-Segment Waveguide Photodetectors For High Resolution Wavelength Monitoring Near 1.55 μm

Abstract

<p>This thesis documents the development of a new optoelectronic device capable of functioning as a high resolution wavelength monitor near 1.55 μm. The primary objective of this work was to devise a simple and potentially low cost approach to monitor wavelength shifts in wavelength division multiplexing (WDM) networks and fiber Bragg grating optical strain sensors. The presented technique utilizes in-line pairs of quantum well waveguide photodiodes fabricated in an InGaAsP /InP material system. The ratio of photocurrents produced between two consecutive waveguide detectors is taken as a sensitive measure of wavelength near the absorption band edge of the quantum wells. The device is shown to function over the conventional wavelength band with near pm wavelength sensitivity, while performing independently of the optical input power and signal polarization. The simultaneous monitoring of several incoming wavelengths is also demonstrated, where arrays of in-line detectors are utilized with a wavelength demultiplexer. In this thesis, several unique methods are presented to improve the performance of the devices, including the use of the quantum confined Stark effect to expand the wavelength operating range and to reduce the thermal sensitivity. Finally, as a practical demonstration, the in-line detectors are used to track the small wavelength shifts induced in various types of fiber Bragg grating optical strain sensors.</p>