Abstract: A backward-wave Raman amplifier or pulse compressor for compressing laser pulses. A laser pulse, or pump beam, of relatively long duration enters one end of the compressor. A short, initiating Stokes-Raman pulse enters the other end of the compressor and absorbs energy from the pump beam as the Stokes-Raman pulse traverses the compressor. The cross-sectional area of the Stokes-Raman pulse within the compressor increases linearly with distance traversed through the compressor so that the energy density within the pulse remains substantially constant as the pulse traverses the compressor and receives energy from the pump beam which traverses the compressor in the opposite direction. The cross section of the pump beam also varies linearly with distance within the compressor so as to coincide substantially with the cross section of the Stokes-Raman pulse and thus achieve efficient compression.

Abstract: A device for translating the frequency of the energy contained in a laser beam. Higher order Raman scattering is utilized to convert the energy in a laser beam into a collimated beam of radiation at a frequency removed from that of the original beam by an amount corresponding to the frequency shift exhibited by higher order Raman scattering processes. A Raman cell is utilized as a saturated amplifier at power density levels below that required for oscillation, so as to obtain efficient conversion. By selecting the path length within the Raman cell, nearly all of the energy exiting the cell is caused to appear in a single, higher order Stokes wave.

Abstract: A laser which utilizes a saturable absorber within a second resonator to obtain mode-locking for the production of short pulses. A second resonator which contains the saturable absorber and operates at the lasing frequency of the absorber intensifies the radiation from the absorber. The intensified radiation interacts with the absorber to reduce its effective lifetime and thus shorten its recovery time following saturation. The reduced lifetime absorber interacts with a laser amplifier to mode-lock the amplifier, thus producing short pulses of laser energy.

Abstract: The frequency of the output beam of a high power krypton fluoride laser is shifted by a plurality of Raman cells arranged successively in the path of the laser beams. These cells each contain a gas selected from the following gases: H.sub.2, HD, D.sub.2 and CH.sub.4, the combination of the gases used being chosen to provide a frequency shift of the beam so as to produce an output in the 330-355 nm range, which is suitable for use in photopredissociation of formaldehyde (HDCO) so as to produce heavy water (D.sub.2 O).