J.K. Mittal

A generalized diffraction filtered resonator with a copper vapor laser

Abstract The diffraction filtered resonator (DFR) offers large volume utilization while maintaining the diffraction limited nature of the output. Large active volume utilization demands a DFR with large resonator length and/or very small pinhole diameter. Increase in the resonator length results in lesser number of transits through the gain medium. Reducing the diameter of the pinhole, on the other hand, would reduce the feedback and hence increase the amplified spontaneous emission. In this paper a generalized DFR scheme is proposed, in which the mode volume is increased without either increasing the resonator length or reducing the pinhole diameter. The performance of these resonators with a high-gain, self-terminating laser like copper vapor laser is studied and compared with an equivalent semiconfocal DFR.

Asymmetry in the characteristics of collimated and uncollimated outputs from a copper vapor laser with a confocal positive branch unstable resonator

Abstract In a confocal positive branch unstable resonator, collimated output is extracted by placing a scraper mirror near the shorter focal length mirror. The output from the other end is generally not preferred because it has geometrical divergence in addition to the natural divergence. Recent experiments with noncavity lasers have indicated that asymmetry in the emission characteristics in the two counter directions could exist because of the fact that the radiation sees different radii of curvature mirrors during the first transit. Such behavior is particularly expected in high gain short inversion lifetime lasers like copper vapor lasers. In this paper, spatial and temporal characteristics of the output from the two ends of a PBUR CVL are studied. The results establish that significant asymmetry in the divergence of the two outputs exists. The temporal evolution of the divergence of the two outputs are different. The uncollimated output has better divergence compared to the collimated output.

Amplification of short (4 ns) copper vapor laser pulses

Abstract Generation of short duration (≈4 ns full width at half maximum) copper vapor laser pulses of high peak power, using an oscillator-amplifier setup is described. It is observed that the amplifier output is nearly constant for 40 ns delay variation between oscillator and amplifier.

A copper vapor laser with a positive branch self-filtering unstable resonator

Abstract We report the use of a positive branch self-filtering unstable resonator (PB/SFUR) with a copper vapor laser (CVL). The performance of this resonator is compared with that of a positive branch unstable resonator (PBUR) CVL. In the case of the PB/ SFUR CVL about 70% of the output power is contained in the diffraction limited divergence angle as compared to only about 10% for PBUR CVL. The analysis of the temporal behaviour of the output pulses indicates that the PB/SFUR starts influencing the laser pulse characteristics very early during the pulse.