Silicon Photonics - Raman amplification, two-photon absorption and their applications

by Dr. LIANG Tak Keung, Photonic Information Technology Group, Basic and Advanced Research Department, National Institute of Information and Communications Technology (NICT), Tokyo, Japan

 :  23 Nov 2005 (Wed)
 :  4:00pm - 5:00 pm
Venue  :  Room 3311, 3/F (Lift 17-18), HKUST

Silicon photonics technology has attracted immense research interest because it offers low cost optoelectronics solutions for applications such as telecommunications, chip-to-chip interconnects and integrated bio-medical sensors. In silicon-on-insulator optical waveguides, light is confined in a single-crystal silicon layer separated from the substrate by a thin layer of buried silicon dioxide. The large step in refractive index enables a tight confinement of light in a small waveguide area, which can be exploited to achieve high optical intensity propagation. Thus many practical nonlinear optical devices can be realized in these waveguides.

In this talk, the fabrication and characterization of functional elements in silicon-based passive planar lightwave circuits will be described. The seminar will explain the inter-relationship between nonlinear absorption processes (including two-photon absorption and free-carrier absorption) and stimulated Raman scattering in silicon waveguides, and how this knowledge led to the recent breakthrough in using silicon waveguides for optical amplifiers/lasers based on the stimulated Raman scattering effect. The two-photon absorption (TPA) in silicon is intrinsically an ultrafast process, thus making it of potential interest for wideband high speed photonic signal processing applications. An ultrafast all-optical switch based on cross-absorption modulation scheme in nanoscale silicon wire waveguides has been demonstrated. The results showed that the direct use of TPA allows switching speeds which are not limited by the slow effective carrier lifetime in the waveguides. Finally, the technology challenges and prospects of these wire waveguides will be discussed.

Dr. Liang Tak Keung received his B.Eng, M.Phil and Ph.D degrees from the Department of Electronic Engineering of the Chinese University of Hong Kong in 2000, 2002 and 2004 respectively. He is currently working in the National Institute of Information and communications Technology (NICT) in Tokyo, Japan (known as the Communications Research Laboratory before 2004). His research interests include Raman amplification in silicon, nonlinear optical properties and applications of silicon optical waveguides, ultrafast photonic signal processing in nanoscale silicon wire waveguides and SOI planar lightwave circuits. He regularly serves as the reviewer for international journals including Applied Physics Letters, Optics Letters, Photonic Technology Letters and Journal of Lightwave Technology.

Dr. Liang has authored and co-authored over 36 papers in international refereed journals and conference proceedings. He won the Outstanding Thesis Award 2004 of CUHK Engineering Faculty for his thesis entitled "Silicon Planar Lightwave Circuits: Raman Amplification and Polarization Processing". He is also one of the recipients of the Award for the Best Research Output by Research Postgraduate Students 2004, CUHK. Recently, he has received the 2005 Young Scientist Awards in Engineering Science from the Hong Kong Institute of Science. He is the member of the Institute of Electrical and Electronics Engineers (IEEE) and the Optical Society of America (OSA).


*** All are Welcome ***