Tunable Stimulated Raman Scattering from Mobile Carriers in Semiconductors

Abstract

In this paper we discuss the recent results of stimulated Raman scattering (SRS) from mobile carriers in semiconductors. Single-particle as well as collective excitations of the electron gas in semiconductors can lead to tunable Raman scattering, which is of considerable interest. We show that some of the possible scattering mechanisms have Raman gain large enough to obtain tunable SRS. The specific case is our recent report of the first observation of tunable SRS in the infrared. This SRS process involves the spin flip of conduction electrons in InSb. Its frequency ${\ensuremath{\omega}}_{s}$ is tunable by varying a dc magnetic field $B$ as ${\ensuremath{\omega}}_{s}={\ensuremath{\omega}}_{0}\ensuremath{-}g{\ensuremath{\mu}}_{B}B$, where ${\ensuremath{\omega}}_{0}$ is the frequency of the pump, $g$ is the $g$ value of electrons, and ${\ensuremath{\mu}}_{B}$ is the Bohr magneton. With $Q$-switched C${\mathrm{O}}_{2}$ laser at 10.6 \ensuremath{\mu} as the pump, the spin-flip Raman laser is tunable from 10.9 to 13.0 \ensuremath{\mu} ($B\ensuremath{\approx}15\ensuremath{-}100$ kG). The tunable coherent power is \ensuremath{\sim} 10 W for an input power of 1.0 kW. The tunable SRS has a linewidth of $\ensuremath{\lesssim}0.03$ ${\mathrm{cm}}^{\ensuremath{-}1}$ at ${\ensuremath{\omega}}_{s}\ensuremath{\approx}800$ ${\mathrm{cm}}^{\ensuremath{-}1}$ and its tuning linearity and resettability exceeds 1: 3 \ifmmode\times\else\texttimes\fi{} ${10}^{4}$. We will discuss in detail the physics underlying the tunable SRS and describe the possible applications of such a tunable coherent radiation.