Proceedings Article | 7 July 2005
Proc. SPIE. 5840, Photonic Materials, Devices, and Applications
KEYWORDS: Optical amplifiers, Modulation, Waveguides, Scattering, Silicon, Fiber lasers, Semiconductor lasers, Raman spectroscopy, Phonons, Raman scattering
In silicon, direct electronic transitions leading to light emission have a low probability of occurrence due to the momentum mismatch between upper and lower electronic levels. Until recently, this had prevented the realization of the long waited silicon optical amplifier and laser. Raman scattering, which describes the interactions of light with vibrational levels, can be used as a way to bypass the indirect band structure of silicon and to obtain amplification and lasing. The Raman approach is very appealing because device can be made in pure silicon with a spectrum that is widely tuneable though the pump laser wavelength. While a new research topic, amplifiers with pulsed gain of 20dB and CW gain of 3 dB have already been demonstrated. Using parametric Raman coupling, wavelength conversion from 1550nm to 1300nm has been achieved. A distinguishing feature of silicon Raman devices, compared to fiber devices, is the electronic modulation capability. By integrating a p-n junction with the silicon gain medium, electrically switched lasers and amplifiers have already been demonstrated. These have many exciting applications. For example, the laser can be directly modulated to transmit data, and can be part of a silicon optoelectronic integrated circuit. At the same time, electrically switched amplifiers represent loss-less optical modulators.
