An InGaAsP/InP Twin-Guide Laser Diode with Rectangular Ring Cavity

Abstract

A twin-guide laser diode, which consists of an active waveguide with rectangular ring cavity and a transparent output waveguide coupled to each other as a directional coupler, has been fabricated and its performance has been investigated. Four straight waveguides and total internal reflection (TIR) mirrors conceptually construct the ring cavity. which enhances the traveling wave characteristics such as mode purity. Lasing light is coupled to the transparent passive output waveguide by vertical evanescent coupling. The cavity mirrors were fabricated by Ar/Cl-2/H-2 reactive ion beam etching (RIBE) at the elevated process temperature to enhance the desorption rate of InClx for a smooth etching surface. The threshold current was measured to he 230 mA corresponding to a threshold current density of 4 kA/cm(2). The emission peak wavelength is approximately, 1.56 mum. The fabricated device shows single mode operation at current levels up to 1.4 times the threshold current.