Single frequency laser sources, which also provide tunability, have wide use in spectroscopy and remote sensing as well as for other applications such as optical pumping. Optical parametric oscillators (OPOs) offer the potential for broadly tunable output in spectral regions inaccessible by conventional laser sources. We report here on the design and use ot an OPO architecture developed to produce pulsed, tunable, single-frequency output in the mid-infrared spectral region and used for optical pumping of gas. Design information about two separate OPOs that were developed will be presented along with experimental details of the optical pumping of CO on the (3-0) band around 1.57 μm and on the (2-0) band around 2.3 μm.
Practical meaningful mono-energetic laser accelerator requires the electron bunch to be within a small proportion of the period of the accelerating field. By two laser accelerator schemes, we exemplify how the emerging picosecond terawatt (ps-TW) CO<SUB>2</SUB> laser technology helps to satisfy this requirement. These include: a staged electron laser accelerator (STELLA) experiment, which is being conducted at the Brookhaven Accelerator Test Facility (ATF), and a prospective laser wakefield accelerator (LWFA), where ps-TW CO<SUB>2</SUB> laser may offer noticeable advantages over more conventional T<SUP>3</SUP> solid-state lasers.
The cleaning of mirrors in large, remote telescopes is essential if these telescopes are to meet their performance goals, including low (2%) thermal emissivity in the infrared. Aluminum- coated mirror samples which were naturally or artificially contaminated with materials representative of those at observatories, were cleaned with a UV laser beam or CO<SUB>2</SUB> snow. Cleaning effectiveness was determined from studies of residual particle densities and size distributions (measured from low-magnification optical imaging). For exposures under two weeks both laser and CO<SUB>2</SUB> cleaning yield comparable results; however, for longer exposures (up to three months) UV laser cleaning is about twice as effective in our tests. At the laser energy densities required for effective cleaning, no surface changes or damage was observed even after cleaning the same spot 200 times. For 8-m class telescopes, the annual consumption cost of sufficiently pure CO<SUB>2</SUB> is comparable to the capital cost of a UV laser. Both methods clean such surfaces in less than one day. Two attractive features of laser cleaning are that the method can be fully automated and run frequently without significant cost of manpower or expendables, and that by focusing the laser beam tighter it can be used to strip old surface coatings prior to recoating.
A radially polarized laser beam is useful for applications such as laser particle acceleration. The issues of transporting and focusing (with an axicon) a radially polarized beam that was generated in the laboratory are examined. Problems of preserving the polarization while directing the beam are solved by using a compound 90-deg-fold out-of-plane pair of mirrors. When focused by an axicon, the radially polarized beam produces a diffraction-free Bessel beam. The transverse intensity distribution agrees with theory.
The amount of fluorine consumed during e-beam excitation of KrF laser mixtures is measured under lasing and nonlasing conditions. At a specific energy loading of approximately 145 J/l for a mixture of Ar/Kr/F2 = 859/142/2.8 Torr, an F2 loss of approximately 80% under lasing conditions is observed. During nonlasing conditions the loss is approximately 60%. This difference in the amount of F2 consumption between lasing and nonlasing conditions is unexpected. Additional work is suggested to verify that this is a true effect.