Energy Scavenging in Silicon Raman Amplifiers

Continuous-wave Raman amplification in silicon waveguides with negative electrical power dissipation is reported. It is shown that a p-n junction can simultaneously achieve carrier sweep-out leading to net continuous-wave gain, and electrical power generation. The approach is also applicable to silicon Raman lasers and other third-order nonlinear optical devices. 1 Silicon-on-Insulator (SOI) has been long recognized as a preferred platform for the realization of both electronic and photonic devices. 1 One of the most attractive features of the SOI material system is the prospect of full integration of optical and electronic devices on the same substrate. Much progress has been made in Si-based photonics towards low-loss waveg-uides, photodetectors, electro-optic modulators, light sources and optical amplifiers. 2 However, little or no attention has been made to the power dissipation of photonic devices. At the same time, the problem of power dissipation in silicon VLSI is so severe that it threatens to bring to halt the continued advance of the technology, as described by the Moore's law. 3 This fact is highlighted by the recent momentous shift of the microprocessor industry away from increasing the clock speed and in favor of multi-core processors. 4 Evidently, realization of low-power silicon photonic devices is essential for opto-electronic integration. Typically, lasers are the most power-hungry photonic devices. However, the lack of an electrically-pumped Si laser, to the date, dictates an architecture where the light source remains off-chip. In such architecture, an off-chip source empowers the chip, whereas modulators, amplifiers, photodetectors, and perhaps wavelength converters, are integrated on the chip. Among these 2 devices the optical amplifier has the highest power dissipation. To the date, Raman amplification has been the most successful approach for achieving both amplification and lasing in silicon. 5−12 The main limitation of the silicon Raman amplifier is the optical loss caused by scattering from free carriers that are generated when the high intensity pump causes two photon absorption (TPA). 10,13 To achieve net continuous-wave gain, a reverse biased p-n junction can be used to sweep the carriers out of the waveguide core. 10−13 However, this comes at the expense of significant electrical power dissipation. 14 The present work addresses this power dissipation in silicon Raman amplifiers. It is shown that at moderate gain levels, it is not only possible to avoid the power dissipation, but also to extract net electrical power from the device. The net electrical power generation is achieved by …