Spin-Flip Raman Lasers SFRL

The cross section for this light-induced spin-flip process may become very large because the Thomson cross section of an electron in a semiconductor 

The most widely used pumping sources for InSb-SFR lasers are the CO laser at A = 5 ym or the CO2 laser at A = 9-10 pm. Since the 5 ym pump radiation is close to the band gap, the resonance enhancement of the SFR cross section allows cw operation of InSb lasers with output powers of about 1 W. For Hgp. 77%. 23Te the band gap is at 9.4 ym which favors the CO2 laser as pumping source, while InAs can be pumped with an HF laser. In favorable cases threshold pump powers as low as 5 mW have been observed in CO laser-pumped InSb lasers. The tuning range of InSb-SFR lasers extends from 5.0 to 6.5 ym when pumped by a CO laser and from 9.0 to about 14 ym when a CO2 laser is used as pumping source. 

The linewidth of the SFR laser depends on the free carrier concentration and on local temperature variations in the crystal, on the properties of the cavity, and on the stabilities of pump frequency and magnetic field strength. Note that at tuning rates of 2 cm KG a relative change Al/I = 10 of the magnet current already causes a shift Av = lO Hz of the SRL frequency v. With 

Numerous applications of SFR lasers to high-resolution infrared spectroscopy have demonstrated the capabilities of this tunable laser type regarding spectral resolution and achievable signal-to-noise ratio (see Sect.8.5 and [7.12,14]). 

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Radiation from infrared spectrometer source. SFRL Spin flip Raman laser. 

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