Monolithically integrated mode-locked ring lasers and
Mach-Zehnder interferometers in AlGaInAs.
PhD thesis, University of Glasgow.
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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.
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