基于硅波导的喇曼光放大器

在硅波导上添加反向偏压的PIN结构,当波导产生受激喇曼散射时,可以将波导中双光子吸收(TPA)产生的光生自由载流子扫出波导,降低了波导的非线性损失,极大地提高了硅波导中泵浦光对信号光的喇曼增益。为了应用已经非常成熟的硅工艺,并且应用硅波导使器件小型化,根据法布里-帕罗(F-P)腔和行波放大器理论,在硅波导两端的解理面蒸镀增透膜,应用这种波导的喇曼效应设计了一种光放大器,即基于硅波导的喇曼光放大器。建立了计算放大器增益的方程,给出了不同波导长度和输入功率情况下的放大器增益,得出适当增加波导长度和泵浦光功率可以得到较高喇曼增益的结论。基于硅的光放大器有较高的饱和功率且没有泵浦源的限制,通过调整泵浦激光的波长可以放大不同波长的信号光。

A Raman Laser Amplifier Based on Silicon Waveguide

The first demonstration of light amplification in silicon represents a significant milestone towards producing fully integrated monolithic photonic chips. Stimulated Raman scattering has been used to demonstrate light amplification and lasing in silicon. The nonlinear optical loss associated with two-photon absorption (TPA)-induced free carrier absorption (FCA) is the main limitation to amplify the laser. With introducing a reverse-biased p-i-n diode embedded in a ridge silicon waveguide, when a reverse bias voltage is applied to the p-i-n diode, the TPA-generated electron-hole pairs can be swept out of the silicon waveguide by the electric field between the p- and n-doped regions. Thus the effective carrier lifetime, representing the lifetime of the free carrier's interaction with the optical mode in the waveguide region, reduces with increasing bias voltage. Because the technics on silicon has been very mature and apparatus made in silicon is very smart, it is a good method to apply the silicon as the waveguide to reduce the volume of laser amplifier. There is no restrict of pump power resource for the Raman laser amplifier based on silicon waveguide. It also possess further higher saturate power. We design a new type of Raman laser amplifier based on silicon waveguide by coating the transmissive film to the cleavage of silicon waveguide according to the Fabry-Perot resonance technique and traveling wave amplifier theory. The Raman gain coefficient can be controlled by the reverse bias voltage on the silicon waveguide, and the amplified signal light wavelength responses to the pump light wavelength in the Raman laser amplifier. The lifetime of photo-generated carriers in silicon-on-insulator rib waveguides is studied in connection with the optical loss produced via nonlinear absorption. We present an analytical model about the Raman gain by using the conclusion that effective carrier lifetimes of 1 ns can be obtained in waveguides resulting in negligible nonlinear absorption. The Raman gain and output power of the amplifier is calculated by the equation we constructed. For a 4.8 cm long waveguide with an effective core area of ~1.6μm² and a reverse bias voltage of 25 V, we obtained a net gain of 2.6 dB with a pump laser wavelength of 1536 nm and a pump power of 600 mW inside the waveguide. Raman gain can be raised by increasing the waveguide length and pump power properly.