We have succeeded in generating cw laser sidebands at wavelengths tunable from ∼5.5 to ∼6.5 μm. The behavior of the power output of the generated radiation is described quantitatively by using the equivalence between four-photon mixing and Raman scattering from coherent spin motion in a spin-flip Raman laser.
The conversion of a visible dye laser output into tunable infrared (IR) laser radiation via stimulated Raman scattering in Cs vapor was investigated. Small-signal gain, threshold intensity, and conversion efficiency measurements were obtained versus pump laser detuning. Fixed-frequency IR outputs at other wavelengths were also observed. One of these, the7P_{3/2}-5D_{5/2}transition, had a strong lasing component polarized perpendicular to the pump laser polarization. Lasing near the 8523-Å resonance line was attributed to a four-wave parametric interaction as a plausible generation mechanism.
The generation of a multifrequency continuous-wave laser through stimulated Raman scattering and phase-matched four-wave mixing in a medium-filled optical cavity is demonstrated. Three different quantum pathways for the four-wave mixing, two of them degenerate and one of them nondegenerate, can be excited independently by tuning the intracavity dispersion. The results suggest that phase-matched Raman sidebands were generated on the longer wavelength side as well as on the shorter wavelength side, which can be used for the Fourier synthesis of a train of ultrashort optical pulses.
We demonstrate the efficient generation of Raman sidebands in a medium coherently prepared in a dark state by continuous-wave low-intensity laser radiation. Our experiment is performed in sodium vapor excited in $\ensuremath{\Lambda}$ configuration on the D1 line by two laser fields of resonant frequencies ${\ensuremath{\omega}}_{1}$ and ${\ensuremath{\omega}}_{2},$ and probed by a third field ${\ensuremath{\omega}}_{3}.$ First-order sidebands for frequencies ${\ensuremath{\omega}}_{1},$ ${\ensuremath{\omega}}_{2}$ and up to the third-order sidebands for frequency ${\ensuremath{\omega}}_{3}$ are observed. The generation starts at a power as low as 10 \ensuremath{\mu}W for each input field. Dependences of the intensities of both input and generated waves on the frequency difference $({\ensuremath{\omega}}_{1}\ensuremath{-}{\ensuremath{\omega}}_{2}),$ on the frequency ${\ensuremath{\omega}}_{3},$ and on the optical density are investigated.
Four-wave mixing can be used to generate coherent output beams, with frequencies difficult to acquire in commercial lasers. Here, a single narrow external cavity diode laser locked to the two photon 5s-5d transition in rubidium is combined with a tapered amplifier system to produce a high power cw beam at 778 nm and used to generate coherent light at 420 nm through parametric four-wave mixing. This process is analyzed in terms of the intensity and frequency of the incoming beam as well as the atomic density of the sample. The efficiency of the process is currently limited when on resonance due to the absorption of the 420 nm beam, and modifications should allow a significant increase in output power.