We present a new dispersion-scan-based technique for the temporal characterization of ultrashort laser pulses directly on target and at full laser power. We demonstrate the technique by measuring intense 4-fs pulses in conditions optimized for HHG.
"High-power Lasers and Applications." Optica Acta: International Journal of Optics, 26(3), pp. 304–305
This paper presents reliable high power and high brightness 9xx-nm single emitter laser diodes, which have been designed for various multi-emitter fiber-coupled modules. Diode lasers from legend generation have been life-tested with currents up to 14A at heat-sink and junction temperatures of 50°C and 80°C respectively, and have accumulated more than 15,000 hours of life-test duration. In order to further improve reliable operational power and optimize beam quality, new generation devices have been developed. The new devices demonstrated more than 20W CW rollover power without catastrophic optical mirror damage (COMD). Near-field/far-field patterns have also been improved significantly. In addition to step-stress life-tests, a 7-level multi-cell life-test was designed to investigate acceleration factors relative to the operation conditions. Junction temperatures ranging from 60°C to 110°C and current from 14A to 18A were used in this multi-cell life-test. The ongoing multi-cell life-test has accumulated 1.3 million raw device hours and shown very few device failures in up to 7000 hours duration. Such a low failure rate doesn't allow a meaningful estimation of acceleration factors. When nominal acceleration factors are used, multi-cell life-test data supports ∼500 FIT, with 90% confidence, at 10W, 33°C/50°C heat-sink/junction temperatures.
In an inertial confinement fusion (ICF) system, wave-front aberrations existed in laser beam will enlarge the focal spot size and decrease power density at the target. Fortunately, an adaptive optical system (AO) could be employed in ICF system to correct the beam aberrations. As a powerful wave-front detector, Hartmann-Shack (H-S) sensor is often utilized as a wave-front sensor in AO. However, H-S sensor can not detect the aberrations after the sampling location. A new method is presented to measure the aberrations of entire ICF beam path in this paper. Based on the AO, a CCD is installed in the target chamber to detect the focal spot distribution. The deformable mirror's (DM) is yielded to different surface shapes; the extra different aberrations are modulated and added to ICF beam path, and then create their corresponding focal spots. The extra aberrations and the corresponding focal spots intensity could be recorded simultaneously by H-S sensor and CCD respectively. An amendatory phase-retrieval algorithm which is introduced can reconstruct the aberrations of entire ICF beam path from the pairs of extra aberrations and their corresponding focal spots intensity. The numerical simulation show that the AO can correct the aberrations of entire beam path of ICF successfully based on this method.
The X1 accelerator project at Sandia National Laboratory/New Mexico utilizes SF6 insulated, multi-stage, UV laser triggered gas switches. A 265 nm UV laser system was designed and built to generate eight simultaneous output pulses of 10 mJ each with a 13 nsec pulsewidth. A 1061 nm solid-state Nd:Cr:GSGG laser was frequency quadrupled using a two-stage doubling process. The 1061 nm fundamental laser energy was frequency doubled with a KTP crystal to 530 nm, achieving 65% conversion efficiency. The 530 nm output was frequency doubled with KD*P crystal to 265 nm, achieving conversion efficiency of 31%. The 265 nm beam pulse was split into eight parallel channels with a system of partially reflecting mirrors. Low timing jitter and stable energy output were achieved. The entire optical system was packaged into a rugged, o-ring sealed, aluminum structure 10" x 19" x 2.75". The size of the electronics was 12" x 8" x 8".Subsequent accelerator system requirements dictated a redesign of the triggering system for an output beam with less angular divergence. An unstable, crossed porro prism resonator was designed and incorporated into the system. The beam divergence of the redesigned system was successfully decreased to 0.97 mrad in the UV. The resulting frequency doubling efficiencies were 55% to 530 nm and 25% to 265 nm. The optical output remained at 10 mJ in each channel with an 11 nsec pulsewidth.
More than 30 years after the first use of high-power laser beams in metal working, continuous study of technology and systems is still being undertaken to improve the performance, reliability, and increase cost effectiveness of these processes. The papers in this volume cover the following subjects: welding; surface modification; laser machining and components for high power laser applications; components for high-power interaction and modeling; and emerging applications. Separate abstracts were prepared for most papers in this volume.
We have extended cw laser action down to 220 nm. This represents a 100 nm improvement to the state-of-the-art prior to our work. Moreover, we have obtained cw laser oscillation on twenty additional transitions in the spectral region between 220 and 320 nm.
DF and HCl lasers which emit in the 3.6 – 4μm region are well suited to laser applications which require high atmospheric transmission. Laser emission at 10.6μm may also be obtained by transfer from DFV or HClV to CO2. The DF laser system has received the most attention recently because of the greater ease in producing large flows of vibrationally excited DF. The straight chain reaction between D2 and F2 proceeds rapidly at room temperature through the “cold” reaction, F + D2 → DF(v≤4) + D, followed by the “hot” reaction D + F2 → DF(v≤14) + F. The analogous reaction between H2 and Cl2 is not sufficiently rapid at room temperature. Even at elevated temperatures the cold reaction, Cl + H2 → HCl + H, is nearly thermoneutral and produces mostly HCl(v=0). Consequently, another method of producing vibrationally excited HCl is desirable.
