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/Hz1/2 was fulfilled in the whole frequency range from 0.1 mHz to 1 Hz. The LISA goal of frequency noise below 30 Hz/Hz1/2 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/Hz1/2, which is significantly below the free-running frequency noise of NPROs.

We demonstrate, for the first time to our knowledge, a longitudinally diode-pumped, monolithic ytterbium ion-doped YAG non-planar ring laser (NPRO). We achieved a continuous-wave (cw) single-frequency output power of 1 W with 45.0% slope efficiency and a beam quality factor of M(2)<1.1. In view of iodine frequency stabilization we have characterized the frequency tuning properties and have measured the relative intensity noise. Additionally, 6.1 mW second harmonic power at 515 nm was achieved using a periodically poled KTP crystal in a single-pass setup.

The development of a space qualifiable laser system based on a monolithic non-planar Nd:YAG ring laser is reported. Such a system can be used in a satellite-based measurement setup to measure wind velocities. (C) 2001 Optical Society of America.

We report on a compact approach to obtain single-frequency pulses with high average power at 266 nm. An amplified, passively Q-switched monolithic Nd:YAG ring laser was frequency quadrupled with periodically-poled KTP and BBO as nonlinear media. (C) 2000 Optical Society of America.

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.

The authors report reliable single-pass second harmonic generation (SHG) of more than 400 mW of 532 nm average power from a compact, all-solid state non-planar ring Q-switched Nd:YAG laser. A maximum single-pass efficiency of 65% is observed. The second harmonic output is a single-frequency mode and has diffraction limited beam quality.

We report on an all-solid-state source of broadly tunable single-frequency radiation from a continuous-wave (CW), doubly resonant optical parametric oscillator (OPO) based on non-critically phase-matched magnesium oxide-doped lithium niobate (MgO:LiNbO3). The oscillator is pumped by the second harmonic of a single-frequency Nd:YAG miniature ring laser at 532 nm and provides combined signal and idler output power of nearly 400 mW CW. Covering a tuning range between 1007 and 1128 nm, stable operation on a single-axial-mode pair is obtained for several hours without mode hops using an FM sideband-locking technique. The output frequencies of the OPO can be continuously tuned over a range of 8 GHz via precise control of the pump laser frequency.

We report on an all-solid-state source of broadly tunable single-frequency radiation from a continuous-wave (CW), doubly resonant optical parametric oscillator (OPO) based on non-critically phase-matched magnesium oxide-doped lithium niobate (MgO:LiNbO3). The oscillator is pumped at 532 nm by the second harmonic of a single-frequency Nd:YAG miniature ring laser and provides combined signal and idler output power of nearly 400 mW CW. Covering a tuning range between 1007 and 1128 nm, stable operation on a single-axial-mode pair is obtained for several hours without mode hops by use of an FM sideband-locking technique. The output frequencies of the OPO can be continuously tuned over a range of 8 GHz via precise control of the pump laser frequency. We demonstrate that operation of frequency doubler and OPO cavities with watt level pump powers is not necessarily deteriorated by optical degradation due to thermal or photorefractive effects.

Pulsed sources of ultraviolet radiation are attractive for a growing number of applications, ranging from trace gas monitoring with extremely high sensitivity to micromachining of highly integrated electronic devices. The pulse to pulse stability of laser parameters like output energy, peak power and pulse width required by these applications is ideally fulfilled by laser sources emitting on a single optical frequency. This can be achieved by subsequent frequency doubling and quadrupling of diode pumped solid state lasers with high stability.

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.

The active Q-switching of a miniature Nd:YAG ring laser in single-frequency operation has been realised. Pulse parameters are controlled by a Cr/sup 4+/:YAG saturable absorber while the trigger is actively provided by a frustrated total internal reflection switch. With repetition rates up to 3 kHz, pulsewidths range from 3.4 to 9 ns, and pulse energies from 30 to 53 /spl mu/J.

Compact and efficient sources of stable single-frequency radiation in the green and blue spectral region are presented. Based on ultra-stable miniature Nd:YAG ring lasers oscillating at 1064 nm and the quasi-three-level transition at 946 nm, frequency doubling in external resonators is performed. Applying MgO:LiNbO3 as nonlinear crystal, up to 1.1 W are generated at 532 nm, while 250 mW are achieved at 473 nm with KNbO3. High conversion efficiencies and excellent long term stabilities are measured. Due to a semi-monolithic cavity for the frequency conversion, modehop-ffee frequency tuning of the visible radiation over several tens of GHz is possible.

A compact source of stable cw single-frequency radiation at 473 nm has been realized by second-harmonic generation of a diode-pumped miniature Nd:YAG ring laser operating on the (4)F(3/2) - (4)I(9/2) laser transition. By use of potassium niobate (KNbO(3)), single-longitudinal-mode output powers of 500 mW cw with high stability and maximum optical-to-optical conversion efficiencies >81% are achieved. An external semimonolithic cavity permits mode-hop-free frequency tuning of blue radiation over as much as 20 GHz.

For laser-based metrology, efficient sources of stable coherent radiation in the visible and near infrared spectral region are required. While stablity is a common request of most metrology applications, the desired laser wavelength differs with the specific application. Fiber sensors require laser emission at their attenuation minimums at 1.3µm and 1.5µm [1], whereas visible light sources are advantageous when the signal strength increases with the laser frequency, for example in laser-Doppler-velocimetry [2]. A further advantage of visible light is the easy optical alignment. Diode-pumped solid-state lasers are attractive sources for metrology applications because of their high inherent intensity and frequency stability. However, the emission of most solid-state lasers is limited to the near infrared spectral region. We report on stable single-frequency light sources with emission wavelength covering the spectral range from visible to near infrared.

Summary form only given. Diode-pumped solid-state lasers operating at high cw power levels are attractive sources for various applications in materials processing and fundamental research. We present the design of our Nd:YAG rod laser system based on fibre 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.

We report on diode laser side-pumped, cw Nd:YAG rod lasers. Applying fiber-coupled diode lasers as pump sources, linear pump power densities of more than 200 W/cm are attainable and an 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 300 W cw are observed. Applying an improved resonator design, output powers up to 80 W in TEM00 mode operation are realized with an optical-to-optical efficiency of more than 20%. Thermal properties and laser performance of laser systems excited by fiber-coupled diode lasers will be discussed.

Diode laser side-pumped, cw Nd:YAG rod lasers operating at pump powers up to 1.1 kW will be reported on. In multimode operation at 1064 nm, output powers of more than 300 W cw are observed. Higher pump powers up to several 100 W/cm can be achieved by using fiber-coupled diode lasers as pump sources.

A compact and efficient source of cw single-frequency radiation at 532 nm with excellent long-term stability has been realized by external frequency doubling of a diode-pumped miniature Nd:YAG ring laser. With a semimonolithic MgO:LiNbO(3) resonator an optical-to-optical conversion efficiency of 89% from 1064 to 532 nm at an output power of 1.1 W was achieved, with a wall plug efficiency of 9%. This system represents an ideal pump source for narrow-linewidth cw optical parametric oscillators with good frequency stability.