M. Bode

Ultraviolet single-frequency pulses with high average power using frequency-converted passively Q-switched quasimonolithic Nd:yttrium–aluminum–garnet ring lasers

We demonstrate a compact ultraviolet light source based on frequency-converted diode-pumped passively Q-switched miniature Nd:yttrium–aluminum–garnet (YAG) ring lasers. A unique pulse-to-pulse stability in single-frequency operation is obtained by diffusion-bonding the Nd:YAG crystal with the Cr4+:YAG saturable absorber crystal to form an all-solid-state quasimonolithic ring laser cavity. Amplified in a longitudinally pumped Nd:vanadate (YVO4) crystal and single-pass frequency quadrupled in periodically poled potassium titanyl phosphate and barium borate crystals, an average output power of 485 mW at 266 nm with 25 μJ pulse energy is achieved with an overall efficiency of 3.3% with respect to the diode pump power.

High-power cw Nd:YAG lasers pumped with fiber-coupled diode lasers

We report on diode laser side-pumped, cw Nd:YAG rod lasers operating at output powers of several hundred Watts. Applying fiber-coupled diode lasers as pump sources, linear pump power densities of more than 200 W/cm are attainable. A nearly free adjustment of the pump light distribution inside the laseractive medium allows a significant decrease of thermally- induced effects and minimizes aberration-related losses. In multimode operation at 1064 nm, output powers of more than 320 W cw are observed. Applying an improved resonator design, output powers of more than 80 W in TEM00 mode operation are realized with an optical- to-optical efficiency of more than 20%. Frequency conversion into the visible spectral range with optical-to-optical efficiencies (green power to pump power) of 5% is realized by intracavity second harmonic generation in KTP crystals. Thermal properties and laser performance of laser systems excited by fiber-coupled diode lasers will be discussed.

Ultraviolet single-frequency pulses with 110 mW average power using frequency-converted passively Q-switched miniature Nd:YAG ring lasers

We demonstrate a compact source of ultraviolet single-frequency pulses with high average output power realized by subsequent single-pass frequency doubling and quadrupling of a diode-pumped passively Q-switched miniature Nd:YAG ring laser. Pulse widths of 2 ns (full width at half maximum), 20 μJ single pulse energy, and 10 kW peak power are achieved at a wavelength of 266 nm with kilohertz repetition rates. A single-pass energy conversion efficiency of 22% with respect to the fundamental light at 1064 nm and an overall efficiency of 2.8% with respect to the diode pump power are obtained.

Laser development for LISA

The two most promising configurations for the LISA laser are a stand-alone diode-pumped nonplanar ring oscillator (NPRO) or a fibre amplifier seeded by a low-power NPRO. The stand-alone laser was stabilized in frequency to a ULE cavity and in power to an electronic reference. For the first time the LISA requirement of relative power noise below 2 × 10 −4 /Hz 1/2 was fulfilled in the whole frequency range from 0.1 mHz to 1 Hz. The LISA goal of frequency noise below 30 Hz/Hz 1/2 was achieved for frequencies above 3 mHz. As a first step in the characterization of an oscillator-amplifier system, the excess frequency noise of an ytterbium-doped fibre amplifier was measured. For frequencies between 0.1 mHz and 1 Hz the excess noise was measured to be below 0.1 Hz/Hz 1/2 , which is significantly below the free-running frequency

Ultrastable single-frequency sources with 200 mW @ 526.5 nm based on a Nd:YLF nonplanar ring laser and SHG

In this contribution, we report on the first demonstration of an nonplanar ring lasers (NPROs) at 1.053 /spl mu/m based on Nd:YLF as the active medium. Single-pass and resonant SHG results in ultrastable emission at 526.5 nm.