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Injection locking performance of a 1 micro set XeF laser pulse and Raman converter scaling have been investigated. Narrowband ultraviolet radiation from a frequency-doubled dye laser has been used to control the linewidth and polarization of a long pulse-length electron beam-excited XeF laser. Linewidths of 0.004 nm have been achieved in the 353 nm band of the XeF (B yields X) Laser transition. Over 90% of the energy in the free-running laser pulse has been extracted in the narrowband injection-locked pulse. Ratios of injection signal power to output laser power on the order of .00001 are adequate for efficient injection-locking to occur. Efficient Raman conversion of microsecond-pulse, injection-locked XeF (353 nm) laser radiation into the blue-green region via the second Stokes shift in hydrogen has been demonstrated using a Raman oscillator- amplifier scheme. Strong depletion of the pump and the first Stokes radiation accompanied by a dominant second Stokes (500 nm) output was observed for the first time. Amplifier power conversion efficiency of 43% was achieved along with a blue-green output energy of 1.7 J at an energy efficiency of 34%. These data support Raman converter scaling analyses which predict feasibility of efficient XeF-to-blue-green conversion at higher energies.

The objective of this program is to demonstrate the scaling potential of efficient Raman frequency conversion techniques for ultraviolet lasers. Molecular hydrogen is used as the Raman medium and an oscillator-amplifier configuration is employed to maximize conversion efficiency and beam quality. At the present time, major program milestones have been successfully met. Injection locking has been demonstrated to be an efficient technique for laser bandwidth control. Good optical beam quality has been achieved on the XeF laser through the use of unstable resonator optics. Conversion of XeF laser radiation to blue- green wavelengths has been demonstrated in the Raman oscillator. Work is now in progress on assembly of the Raman oscillator-amplifier system to complete the final phase of the program. It is expected that 50% energy efficiency will be demonstrated for the shift of 353 nm XeF radiation to 498 nm.

A thorough study on the feasibility of efficient CO laser frequency tripling in molecular gases has been completed. Computer code calculations of nonlinear susceptibilities and detailed analysis of efficiency limitations have been carried out for nine candidate molecules belonging to three different resonant enhancement schemes. The results of the study show that direct frequency tripling would yield small efficiencies. However, a two-step conversion process involving an intermediate frequency shifting may provide large enhancement factors for efficient two-photon resonant sum frequency generation. (Author)

The CdHg excimer has received attention as a possible efficient visible laser medium. In the experiments described here, a pulsed, tunable laser was used to excite the Cd atomic state which forms CdHg excimers in three body collisions with Hg and Ar. Gain and absorption measurements were performed by using an argon-ion laser to probe several wavelengths within the 470 nm excimer emission band. Net absorption was observed at all wavelengths investigated. Acoustic and thermal disturbances which might mimic absorption have been carefully considered and it is determined that these are not important. We conclude that the CdHg excimer exhibits net absorption within its 470 nm emission band. These results cast considerable doubt on the possibility of efficient laser action in CdHg. (Author)

This report describes work performed under the Navy/DARPA Submarine Laser Communications Program. Phase I of this program calls for a laboratory demonstration of a 1 joule laser source emitting in the 450-510 nm region of the spectrum with an efficiency of 1%. IN order to meet these goals, Northrop Research and Technology Center has developed a Raman down-converted XeC1 laser. Results of this experimental/theoretical research are presented.

Considerable progress in two areas are discussed: generation of tunable coherent sources for spectroscopic applications, and the study of molecular Na2 and Hg2 using optical pumping spectroscopic techniques. The tunable source progress now allows the concept of a widely tunable coherent spectrometer to be seriously considered. As presently designed, the computer controlled spectrometer will tune the entire .22 to 30 micrometers spectral range using nonlinear optical methods. Spectroscopic studies have centered on the diatomic molecules Hg2 and Na2. The interest in the molecules stems from their potential use as coherent sources. In addition, by the use of coherent source optical pumping, quantitative spectroscopic factors can be accurately measured.