Pulsed xenon and krypton flashlamps and D.C. krypton arc lamps are universally used as pump sources for solid state lasers. This paper details the electrical, mechanical, and optical design parameters that must be understood to allow optimization of these light sources for specific solid state laser applications of interest. The spectral output characteristics, cooling requirements, and electrical behavior of arc discharge tubes are discussed. Guidelines for the proper choice of lamp seal type, envelope material and size, electrode style, power density, gas, and fill pressure are offerred. Finally, structural and operational parameters that strongly influence lamp lifetime are identified, categorized, and explained.
The lamps used for pumping lasers represent electrical loads which are difficult to drive due to the wide range of impedance presented by the lamp to the driving source. The power conditioning systems used to interface between the lamp and the primary power source are reviewed with an eye toward current practice and trends for the future. We examine a wide range of operating requirements and attempt to characterize various power conditioning systems with regard to the difficulties associated with these requirements.
Cavity designs are grouped according to the mean power dissipated in them. Specific models for specular and diffuse cavities are presented and reflector materials compared. The determination of flow tube dimensions and prediction of laser rod temperature is given. Rod and lamp mounting techniques are discussed.
Disk amplifier design for inertial fusion lasers has evolved with changing fusion-driver requirements from a primary emphasis on gain to a primary emphasis on efficiency. In this paper we compare Shiva and Nova amplifiers to a developmental amplifier (SSA) and show greater than a two-fold improvement in efficiency over past designs under all operating conditions. Experiments to optimize the efficiency of the SSA show that preionization of the flashlamps produces significant benefits and that the packing fraction of lamps is more important than the flashlamp reflector shape. They also show that the optimized flashlamp pulselength and reflector geometry depend on the desired stored energy in the laser medium. We have demonstrated a 7% storage efficiency at a stored fluence per disk of 0.5 J/cm2 (stored energy density of 0.06 J/cm3) and 4% at 2.0 J/cm2 (0.25 J/cm3). Comparison of SSA measurements with storage-efficiency calculations show that our flashlamp model accurately predicts the single-pass pumping of disk amplifiers.
A review of current state of the art high energy and high average power flashlamp excited dye lasers is presented. Coaxial flashlamp dye laser designs have not changed significantly since they were first developed in 1968. However, there is now a better understanding on how to optimize operating parameters. New high brightness coaxial flashlamp excited dye laser systems can produce tunable ultraviolet radiation by means of second harmonic generation with high efficiency and output. Energy conversion efficiency over 16 percent has been measured at one joule input levels, and over one joule of ultraviolet light has been produced at a conversion efficiency exceeding ten percent. For high average power outputs greater than a 100 watts, the linear flashlamp excited dye laser is the preferred approach. Linear lamp dye lasers are intrinsically more efficient than coaxial lamp lasers,and pulsed electrical to laser output efficiency over 1.6 percent has been observed without the use of high dye concentrations. Except in a true waveguide dye laser, high concentration of the dye solution increases efficiency at the expense of beam quality. Design and performance parameters of a high brightness capillary cell, dye laser in terms of a beam quality figure of merit number R is described.
We review the application of flashlamps to the optical pumping of slab laser devices. In particular, pumping configurations, operating regimes, and the impact of well-known flashlamp performance limitations will be reviewed. The operation of slab laser devices in the stress-limited and pump-limited regimes will be delineated. We also present for the first time a theory of flashlamp failure based upon Wiebull fracture statistics and derive expressions for the thermally induced and hoop stress components in the wall of flashlamps.
Current military laser rangfinders and designators are typically of Nd:YAG, are Q-switched, and operate at an output of 50 to 150 m.j. over the frequency range of 1 to 25 Hz. A great deal of emphasis is placed upon efficiency. In this context, a compilation is made of experimental data from various sources concerning the familiar topics of lamp gas, fill pressure, size, envelope material and spectra. Some hypotheses are made to explain the high efficiency typical of operation in the preignited mode and at high pressures. Experimental and analytical determination of the lamp temperature in a conductive cooling mode of operation are presented, and a scheme for reduction of laser pulse jitter in dye Q-switched operation is evaluated.
Continuously-pumped (CW or Continuous Wave) Nd:YAG lasers have now been used in industry for more than 15 years. The diversity of industrial laser applications and operating environments which have developed over the years has dictated the design criteria of lasers which are expected by the user to operate flawlessly, in many instances 24 hours per day, 7 days per week continuously. The pressures of laser performance, reliability, ease of maintenance, and price in a competitive market strongly influence the design considerations of these lasers.
A critical review of technology related to flashlamp pumping of solid-state lasers used in industry is presented within a systematic theoretical and experimental framework appropriate to a broad range of industrial applications from drilling to heat treating. A general overview of system considerations leads to general lamp performance requirements. These are then considered in perspective to current cost analysis considerations and operations research data. Recent developments in flashlamp pumped lasers are discussed and general comments on future trends in technology that affect industrial pulsed lasers are presented.
We give a review of the wide field of high power pulsed Nd:YAG lasers and of their main scientific applications. We describe the high repetition rate (3kHz) Q-switched laser developed in our laboratory, as an example of a new generation of YAG lasers.
Optical pump sources for lasers include not only flashlamps and arc lamps but other sources as well. These sources can be divided into four catagories. First, when new laser materials are invented, most often the first laser operation is achieved by pumping them with another laser. However, there are too many possible combinations of laser pumped lasers to discuss adequately in a single paper. This paper will mention only one of these sources, the laser diode array. The second class of optical pump sources can only be described as "unconventional" optical sources since this includes many different approaches to the pulsed generation of light. The third class is conventional noble gas flashlamps. The fourth category is additive lamps or lamps with radiation enhancing dopants.
Ater the initial introduction of the first solid-state laser, there was a flurry of research directed toward the discovery of new lasers. Activity during this period of time produced the Cr:Al2O3 laser and the Nd:YAG laser. For a relatively long time after this, research directed toward the discovery of new solid-state lasers appeared to subside. Over the past several years, this trend seemed to reverse itself. Cr:BeAl2O4 was one of the first of the new lasers to be introduced. Rather than concentrate either on this laser or on Nd-based lasers, this talk will be directed toward other new solid-state lasers. New lasers, or rediscovery of old lasers, has concentrated on two groups of elements, the lanthanide series elements and the transition metal elements. A substantial difference exists between the solid-state lasers depending on the group of elements of which the active atom is a member. Differences and similarities will be highlighted as the methods used in solid-state laser engineering to meet new objectives are explored.