PhD Defense: "Heterogeneous Integration for Reduced Phase Noise and Improved Reliability of Semiconductor Lasers"

Sudharsanan Srinivasan

March 12th (Thursday), 10:00am
Engineering Science Building (ESB), Room 2001

In this talk, we show four laser demonstrations that use the hybrid silicon platform to lower phase noise due to spontaneous emission, based on the following two techniques, viz. confinement factor reduction and negative optical feedback. The first two demonstrations are of mode-locked lasers and the next two are of tunable lasers. Some of the key results include; (a) 14dB white frequency noise reduction of a 20GHz radio-frequency (RF) signal from a harmonically mode-locked long cavity laser with greater than 55dB supermode noise suppression, (b) 8dB white frequency noise reduction from a colliding pulse mode-locked laser by reducing the number of quantum wells and a further 6dB noise reduction using coherent photon seeding from long on-chip coupled cavity, (c) linewidth reduction of a tunable laser down to 160kHz using negative optical feedback from coupled ring resonator mirrors, and (d) linewidth reduction of a widely tunable laser down to 50kHz using on-chip coupled cavity feedback effect.

Next, we present the results of a reliability study conducted to investigate the influence of molecular wafer bonding between Si and InP on the lifetime of distributed feedback lasers, a common laser source used in optical communication. No degradation in lasing threshold or slope efficiency was observed after aging the lasers for 5000hrs at 70°C and 2500hrs at 85°C. However, among the three chosen bonding interface layer options, the devices with an interface superlattice layer showed a higher yield for lasers and lower dark current values in the on-chip monitor photodiodes after aging.

About Sudharsanan Srinivasan:

photo of Sudharsanan Srinivasan Sudharsanan Srinivasan received his Bachelors degree with specialization in Engineering Physics from Indian Institute of Technology, Madras, India in 2009 and Masters in Electrical and Computer Engineering from University of California Santa Barbara in 2010. His research interests are in Silicon Photonics.

Hosted by: Prof. John Bowers