You're going to hit Stokes law if you try to pump in the IR.. IR would not pump the 694 transition, the pump light for a three or four level system needs to be shorter in wavelength then the lasing wavelength. The process Has to comply with the laws of Thermodynamics. You may see long wavelength IR fluoresce from a Chromium line if you pump at 976, if you could detect 1.5 to 3.5 microns.
Steve
Qui habet Christos, habet Vitam!
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When I still could have...