Multifrequency Raman amplifiers

Enhanced strong-coupling stimulated Brillouin amplification assisted by Raman amplification

Higher intensity of strong-coupling stimulated Brillouin scattering (SC-SBS) amplification is achieved by supplementary Raman amplification. In this scheme, a Raman pump laser first amplifies the seed pulse in the homogeneous plasma, and then a SC-SBS pump laser continues the amplification in the inhomogeneous plasma in order to suppress the spontaneous instability of pump lasers. The intensity of the seed laser gets higher and the duration of the seed laser gets shorter than that in the pure SC-SBS scheme with the same incident energy, while the energy conversion efficiency is not significantly reduced. We also found that the SC-SBS amplification is seeded by the leading pulse of Raman amplification. The results obtained from envelope coupling equations, Vlasov simulations, and two-dimensional particle-in-cell simulations agree with each other. This scheme offers a possible way to improve the SC-SBS amplification in experiments.

Optical phase conjugation in backward Raman amplification

Compression of an intense laser pulse using backward Raman amplification (BRA) in plasma, followed by vacuum focusing to a small spot size, can produce unprecedented ultrarelativistic laser intensities. The plasma density inhomogeneity during BRA, however, causes laser phase and amplitude distortions, limiting the pulse focusability. To solve the issue of distortion, we investigate the use of optical phase conjugation as the seed pulse for BRA. We show that the phase conjugated laser pulses can retain focusability in the nonlinear pump depletion regime of BRA, but not so easily in the linear amplification regime. This somewhat counterintuitive result is because the nonlinear pump depletion regime features a shorter amplification distance, and hence less phase distortion due to wave-wave interaction, than the linear amplification regime.

A Comprehensive Study on EDFA Characteristics: Temperature Impact

In this paper, a comprehensive study on erbium-doped fiber amplifier (EDFA) characteristics under temperature variation has been performed. The rate and propagation equations that characterize EDFA performance pumped at 980 nm and 1480 nm in the forward direction are solved numerically. The Boltzmann distribution between the pump and the gain wavelength is taken into account, and is found to be effective when pumping only at 1480 nm. In addition, a full comparison between the effect of temperature on some of the EDFA characteristics such as the maximum peak gain, optimum fiber length, saturation input power, and saturation output power has been carried out. The temperature variation in the range from −40 °C to +80 °C is taken into account.