Monolithically integrated mode-locked ring lasers and Mach-Zehnder interferometers in AlGaInAs

Abstract

In this thesis, monolithically integrated photonic devices for next generation optical telecommunications networks were investigated, namely semiconductor modelocked ring lasers and Mach-Zehnder interferometers operating at 1550 nm. Fabricated on the aluminium quaternary, the 2.3mm long passively mode-locked ring devices produced 1 ps pulses at a repetition rate of around 36GHz. It was found that the symmetrically placed dual saturable absorber configuration lead to the largest area of stable mode-locking, agreeing well with theoretical predictions in the literature. Optical harmonic injection mode-locking was found to improve the pulse timing stability, with a reduction in the radio frequency 3 dB linewidth from 1.4MHz down to 108 kHz, indicating a vast improvement in timing jitter. The sputtered SiO2 quantum-well intermixing technique allowed for the realisation of both symmetric and asymmetric arm length Mach-Zehnder interferometers, which were demonstrated as an electro-optic switch, tunable wavelength filter and optical code division multiple access encoder/decoder. The work concluded with the monolithic integration of a mode-locked ring laser and asymmetric Mach-Zehnder interferometer to demonstrate a simple, yet effective, photonic integrated circuit