Examination Committee

Prof Long QUAN, CSE/HKUST (Chairperson)
Prof Andrew W O POON, ECE/HKUST (Thesis Supervisor)
Prof Shayan MOOKHERJEA, Department of Electrical and Computer Engineering, University of California (External Examiner)
Prof Kei May LAU, ECE/HKUST
Prof Hoi Sing KWOK, ECE/HKUST
Prof Kam Sing WONG, PHYS/HKUST

Abstract

Leveraging the mature silicon complementary metal-oxide-semiconductor (CMOS) fabrication technology, silicon photonics offers a unique potential platform to build low-cost, high-speed, energy-efficient, compact devices and modules for intra-datacenter optical interconnects which requires link distance up to ~10 km.  One of the key building blocks for such photonics link is the on-chip light source emitting at Telecom/Datacom wavelengths. 
 
In this thesis, we demonstrate and propose a number of on-chip light sources including (i) direct-modulated waveguide-integrated microspiral disk lasers on III-V substrate, (ii) hybrid silicon waveguide-integrated microspiral disk lasers and (iii) a 2-channel hybrid silicon transmitter using microspiral disk laser as single element.
 
We investigate direct-modulated waveguide-coupled microspiral disk lasers on InP substrate.  We employ spatially selective injection by means of a ring-shaped p-contact on top of the microdisk rim region to selectively inject current to the whispering-gallery-like modes.  We report room-temperature continuous-wave (cw) electrically injected lasers with an estimated laser output power of at least 200 mW.  We realize small-signal modulation with a 3dB bandwidth exceeding 10 GHz and demonstrate an open eye diagram at 15 Gbit/s.  We study the laser emission characteristics using an angle-resolved, spatial- and spectral-resolved spectroscopy, respectively.
 
We develop the hybrid silicon microspiral disk lasers using benzocyclobutene (BCB) die-to-die bonding and oxide multiple-dies-to-wafer bonding.  We numerically and experimentally investigate different silicon microspiral disk cavities directly coupled with an output-waveguide, with III-V gain mediums of different circular microdisk geometries vertically coupled on the top.  We demonstrate around or below 10 mA threshold with a maximum output power in the level of 100 mW in the waveguide under pulsed injection.  A 2-channel laser array with 12.9nm spacing multiplexed into a single waveguide output is also demonstrated under pulsed injection.  Upon room-temperature cw injection, we demonstrate a device with lasing threshold ~10mA.