Timothy Johnston

Beam characterization and measurement of propagation attributes

Beam waist size, waist location and the times-diffraction-limit number, M2, are the most basic and fundamental parameters describing the propagation characteristics of laser beams. This information is useful in the engineering development of lasers and beam delivery systems, and provides a meaningful way to monitor, compare and control quality both in the manufacture and in the application of laser devices. An instrument that allows real-time access to this information is described.

High performance laser diode bars with aluminum-free active regions.

We present operating and lifetest data on 795 and 808 nm bars with aluminum-free active regions. Conductively cooled bars operate reliably at CW power outputs of 40 W, and have high efficiency, low beam divergence, and narrow spectra. Record CW powers of 115 W CW are demonstrated at 795 nm for 30% fill-factor bars mounted on microchannel coolers. We also review QCW performance and lifetime for higher fill-factor bars processed on identical epitaxial material.

High power single frequency operation of dyes over the spectrum from 364 nm to 524 nm pumped by an ultraviolet argon ion laser

Abstract An argon ion laser is operated at double the conventional ultraviolet output power level on three groups of lines spanning 300.3 nm to 385.8 nm. These ion laser lines are used to pump several dyes, giving single frequency tunable outputs covering 364 nm to 524 nm, with a peak output power of 1.02 W at 435 nm. Performance is reported for the first time for the dyes Polyphenyl 1 and Polyphenyl 2 operated single frequency in a ring laser, and for the dye Coumarin 102 pumped at high efficiency with the long wavelength UV group, as well as for the dyes Stilbene 1 and Stilbene 3 at double the previous output levels.

Review of cw high-power diode-pumped green lasers

Recent progress in pump sources and basic materials have allowed the production of commercially viable, high-power, diode-pumped, continuous-wave, green lasers. We will review the history and the technological developments that have allowed this progress.

Effect of pump laser mode quality on the mode quality of the cw dye laser

Measurements with a beam propagation analyzer of the mode characteristics of the cw dye laser as a function of pump laser input power and mode quality, indicate that the thermal lens (of cylindrical form, induced by pump absorption in the flowing dye) controls the dye beam mode quality. At high pump power, if the dye laser resonator is adjusted for maximum output power, a degraded quality dye mode results, which is lower for lower quality pump modes. When the dye resonator is adjusted for maximum output power density (a direct output of the analyzer), typically a 12% power drop is sufficient to produce a nearly perfect beam quality (M2 < 1.1) and a +27% increase in beam power density for a multimode pumped dye laser.

Compact, solid state, green, blue, and ultraviolet lasers

Solid-state laser sources in the visible and ultraviolet have several advantages over gas laser sources with regard to size, efficiency, lifetime, and amplitude stability. We will discuss the approaches that we have taken to build compact solid-state lasers operating at 532 nm, 430 nm, and 266 nm. We will review the different techniques we use to generate these wavelengths and consequent implications for performance characteristics such as output power, spatial mode, noise, and the possibility for modulation.

In-situ measurement of output coupler absorption using a beam propagation analyzer

Optical characteristics of the output coupler in a high-power CO2 laser can be measured while the optic is in the laser and functioning normally. This is done by using a beam propagation analyzer to measure the rate at which the beam waist location changes with increasing beam power. The characteristics that can be measured with this technique include the fraction of beam power absorbed by the optic and its radius of curvature.

Ultraviolet High Power Near Fundamental Mode Output From An Argon Ion Laser With Applications As A Ring Dye Laser Pump Source For Blue And Near UV Dyes

A wavelength and power survey of the 275 nm to 400 nm region has been made with commercial large-frame argon ion lasers operating at elevated discharge currents and various gas pressures. The UV output in the 300 nm to 386 nm region is separated into three groups of lines and used to pump several dyes giving single-frequency tunable outputs from a ring dye laser covering 364 nm to 524 nm. Intracavity frequency doubling with B-BaBA in the ring laser with the dye Stilbene 3 has produced milliwatt level single-frequency output tunable from 215 nm to 235 nm.