Alexander E. Mandl

KrF laser studies at high krypton density

Measurements were made of the intrinsic laser efficiency of the KrF excimer laser system as a function of increasing krypton buffer gas at pump rates up to 0.17 MW/cm/sup 3/. The results show that the laser efficiency monotonically increases with increased krypton concentration to a maximum value of 12% for a pure krypton buffer gas. Code calculation shows very good agreement with experiment.

Improvements in long‐pulse, electron‐beam‐pumped XeF(C→A) laser performance

The performance of the XeF(C→A) laser, pumped at a rate of 290 kW/cm3 with a 600‐ns electron‐beam pulse, has been improved through the optimization of the laser gas mixture and resonator output coupler reflectivity. An intrinsic efficiency of 1.1% and a specific output energy of 2 J/l have been demonstrated. A uniformly pumped region of the gain medium was selected for diagnosis in these measurements. In a separate experiment with larger diameter mirrors, a total output energy of 4 J was recorded. These are the highest specific and total output energies reported thus far for a directly electrically excited XeF(C→A) laser. The laser pulse duration was 350 ns (FWHM), and the laser bandwidth was 160 A. The small‐signal net gain was measured during the electron‐beam pulse at various wavelengths, and a peak gain of 0.4%/cm was observed. The sidelight fluorescence spectrum was also recorded.

Multipulse operation of a high average power, good beam quality zig-zag dye laser

A laser pumped zig-zag dye laser operating at 568 nm with a pulse length /spl sim/2 /spl mu/s has been sealed to high power using a MOPA configuration. Pulse energies in excess of 7 J with beam quality <2 XDL have been achieved under repetitively pulsed, 10 Hz operation. RMS jitter was measured as 0.12 of a 1 XDL spot. The device has operated with over 70 W output for runs up to 5 s. Substantially longer run times and output powers are possible. This device represents an advance in dye laser capabilities. Improvement in pointing accuracy of better than an order of magnitude have been demonstrated. In addition, an improvement in beam quality by about an order of magnitude has been achieved compared to other dye lasers operating in this power range.

Single-mode operation of a zigzag dye laser

We report single-mode operation of a laser pumped zigzag dye laser for pulse lengths >1 /spl mu/s with beam quality close to the diffraction limit. A unique linear optical cavity using counter-propagating orthogonally polarized waves was used. Laser efficiency measurements performed with a stable cavity had outputs of greater than 1.7 J at 568 mn using Pyrromethene-567 dye. The intrinsic laser efficiency was 55% with a slope efficiency of 77%. Single-mode operation was achieved using an unstable resonator with intra-cavity etalons to control the free running modes of the cavity and seeding with a single-mode Kr-ion laser operating at 568 nm. Heterodyne measurements were used to determine that the bandwidth was near the transform limit with the frequency chirping at a rate /spl sim/60 MHz/Ms. Far-field measurements of the beam quality indicated close to diffraction limited output. >

Compact diode-pumped Yb:YAG slab laser

We have developed a diode end-pumped Yb:YAG slab laser which operates at 10Hz. The device uses a novel endcap design which allows simplified coupling of the 940nm Q-CW InGaAs diode pumps and improves the excitation uniformity of the Yb:YAG. We have achieved 500mJ of laser output operating in the long pulse mode (2ms pulses) in excellent agreement with kinetic code calculations. Very little difference in laser performance between long pulse and Q-switched operation has been observed. To date, Q-switched measurements have been performed at energies to 6OmJ with pulse lengths of 6Ons.

Injection control of a long-pulse electron-beam pumped XeF (C to A) laser

An XeF (C to A) laser, pumped at a rate of 290 kW/cm/sup 3/ with a 600-ns electron-beam pulse, has been operated as an injection-controlled oscillator. A stable cavity has been injected with radiation from a pulsed dye laser source. A significant reduction in laser turn-on time has been achieved, and the laser pulse duration has been extended to 500 ns (FWHM). As a consequence, the laser intrinsic efficiency and specific output energy have been increased by approximately 50%, to 1.8% and 3 J/L, respectively, which represent the best performance obtained thus far for any directly electrically excited XeF (C to A) laser. Also, by injecting a narrowband signal into the cavity, the XeF (C to A) laser linewidth has been reduced by more than two orders of magnitude, to less than 1.3 AA, the resolution of the spectrometer. The laser wavelength has been tuned from 478.6 to 486.8 nm, with less than a factor of two variation in output energy. >

Flashlamp-pumped thin slab solid state plastic dye zig-zag laser

The first demonstration of a flashlamp pumped zig-zag plastic dye laser is presented. Repetitively pulsed measurements with liquid dye solution of Pyrromethene-567 in ethanol/PPH demonstrated 280 mJ per pulse at 1 Hz. Solid plastic dye samples were flashlamp pumped under similar conditions with output energy to 70 mJ. Rapid decay of the laser output was observed in initial measurements with plastic samples (Epoxy Technology EP310) at 1 Hz pulse rate. This design can be used to test various solid state plastic host dyes in a configuration that has demonstrated exceptional beam quality with laser excitation.

Dye laser studies using zig-zag optical cavity

We report a substantial advance in dye laser performance using a zig-zag optical cavity. This configuration drastically reduces the effects of intrapulse medium disturbances due to acoustics and thermal lensing on pulse duration, beam quality, and extraction efficiency. Laser outputs of up to 2 J were observed from Coumarin-498 dye pumped by a KrF excimer laser. The dye laser output faithfully replicates the hat-top KrF laser pump pulse over the entire 1.7-/spl mu/s pulse duration. An intrinsic laser photon conversion efficiency (Photons/sub inPhotons/sub absorbed/) of 44% was measured. When unstable resonator optics were used, beam qualities of about 2 XDL were measured. >

Energy scaling and beam-quality improvement of a zigzag solid state plastic dye laser

Studies of the energy scaling and beam quality improvement of a long pulse laser pumped solid state dye laser are presented. These measurements establish the state of the art for beam quality and single pulse energy of a solid state plastic dye laser.

Flash-lamp-pumped thin slab solid state plastic dye zig-zag laser studies

The first demonstration of a flashlamp pumped zig-zag liquid dye laser is presented. Repetitively pulsed measurements with liquid Pyrromethene-567 demonstrated 230 mJ per pulse at 1 Hz. This design will be used to test solid state plastic host dyes.