YAG Ring Laser Research Articles

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.

Narrow-linewidth, pump-enhanced singly-resonant parametric oscillator pumped at 532 nm

is demonstrated. The pump wave is provided by a frequency-doubled miniature Nd:YAG ring laser and is resonantly enhanced in the SRO cavity, resulting in an external threshold of 200 mW. Stable single-frequency emission in the 1000–1135 nm range has been obtained with 2 GHz continuous tunability and signal/idler linewidths <160 kHz.

Intensity-noise dependence of Nd:YAG lasers on their diode-laser pump source

Typically, the intensity noise of solid-state lasers is dominated by a resonant relaxation oscillation, RRO, at intermediate frequencies (kilohertz to megahertz) and by pump-source noise at frequencies below the RRO. The RRO is driven by vacuum fluctuations as well as by pump-source fluctuations and is therefore present irrespective of the pump-source noise level. However, the intensity noise at frequencies below the RRO can be substantially lowered by use of a low-noise pump source. This behavior is experimentally studied for diode-pumped Nd:YAG ring lasers. An experimental comparison is made between pumping with a single-element diode laser (SEDL) or with a diode-laser array (DLA). We find good agreement with theory for the SEDL but not for the DLA because the DLA's output intensity noise is spatially variant. We also show that pump-source frequency noise has only a minor effect on the intensity noise of the Nd:YAG laser. The requirements for low-noise operation of solid-state lasers are discussed.

Toward an optical synthesizer: a single-frequency parametric oscillator using periodically poled LiNbO_3

We demonstrate single-frequency operation of a cw quasi-phase-matched singly resonant optical parametric oscillator (SRO). We obtained widely tunable output from 1.66 to 1.99 mum (signal) and from 2.29 to 2.96 mum (idler) by employing a periodically poled lithium niobate multigrating chip. Using a single-frequency miniature Nd:YAG ring laser as a pump source results in SRO output with high spectral purity and frequency stability(<10 MHz/min), which can be continuously tuned over 2 GHz without mode hops. We obtain a minimum SRO threshold of 260mW by resonating the pump wave in the SRO cavity.

Frequency-tunable 500-mW continuous-wave all-solid-state single-frequency source in the blue spectral region

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.

Stability of the frequency of self-modulation oscillations in a monolithic Nd : YAG solid-state ring laser

An investigation was made of the cause of the instability of the self-modulation frequency ωm of a monolithic Nd : YAG ring laser. One of the main reasons for this instability was a strong temperature dependence of the effective coupling coefficients of counterpropagating waves characterising extracavity components. A method for weakening such coupling was proposed and implemented experimentally. This method made it possible to reduce the instability of the self-modulation frequency by over two orders of magnitude.

Stable, high-power, single-frequency generation at 532 nm from a diode-bar-pumped Nd:YAG ring laser with an intracavity LBO frequency doubler

We obtained 2.5 W of single-frequency TEM(00) output at 532 nm using a Brewster-angled LBO crystal for intracavity second-harmonic generation in a diode-bar-pumped Nd:YAG laser. By inserting a thin uncoated étalon, the 1061.4-nm laser transition can be selected, generating 1.6 W of output at 530.7 nm.

The GEO600 project

GEO600, an interferometric gravitational-wave detector with an arm length of 600 m, is currently being built in northern Germany close to Hannover. GEO600 incorporates an externally modulated fourfold delay-line Michelson interferometer giving a round-trip optical length of 2400 m. A master - slave combination of a monolithic diode-pumped Nd:YAG ring laser and an injection-locked amplifier will give a light power of about 10 W at a wavelength of 1064 nm. Power recycling increases the light power inside the interferometer to a level of about 10 kW. The use of both power and signal recycling will yield a sensitivity of the same order of magnitude as the first stages of the other large-scale gravitational-wave detectors LIGO and VIRGO currently under construction. High signal recycling factors allow the sensitivity to be increased at a chosen frequency while reducing the bandwidth of the detector. This gives an advantage over broad-band detectors in detecting narrow-band periodic sources such as pulsars. The 25 cm diameter mirrors will be suspended as double pendulums from a platform supported by vibration-reduction systems. The passive filtering properties of this system sufficiently reduce the seismic noise in the frequency range of interest, i.e. 50 - 1000 Hz. The detector will start taking data in the year 2000.

Laser frequency stabilization for spaceborne gravitational wave detectors

We report on the development of the frequency stabilization of diode-pumped Nd:YAG ring lasers for use on spaceborne gravitational wave detectors and give results on preliminary investigations of the frequency noise in the low-frequency domain.

Passively Q-switched Nd:YAG ring lasers with high average output power in single-frequency operation

Applying Cr(4+):YAG saturable absorbers, we demonstrate efficient passively Q -switched operation of diode-pumped Nd:YAG lasers with a maximum average output power of more than 800 mW. Pulse durations below 3 ns, energies of 70 microJ, and peak powers of 30 kW are observed with kilohertz repetition rates. Single-frequency operation is accomplished for all output powers by a nonplanar ring geometry.

Intensity stabilised Nd:YAG ring laser with 1.5W single-frequency output power at 1.357 µm

The authors report 1.5 W single-frequency output power at 1.357 /spl mu/m from a diode-pumped Nd:YAG ring laser. Suppression of the close neighbouring transitions at 1.319 and 1.338 /spl mu/m is accomplished by a sophisticated optical coating deposited by the ion-beam-sputtering technique. High intensity stability is achieved by the application of an electronic feedback loop.

High-power single-frequency operation, at 1064 nm and 1061.4 nm of a Nd:YAG ring laser end-pumped by a beam-shaped diode bar

A Nd:YAG laser having a ring configuration, with a Faraday rotator to provide unidirectional operation has been end-pumped by a single 20 W diode bar equipped with a beam-shaper. A single-frequency TEM 00 output of 5.4 W is achieved at 1064 nm. Using a thin intracavity etalon for wavelength selection, a single-frequency output of 4.2 W is obtained on the 1061.4 nm transition.

11-W single-frequency 532-nm radiation by second-harmonic generation of a miniature Nd:YAG ring laser

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.

3 W of single-frequency output at 532 nm by intracavity frequency doubling of a diode-bar-pumped Nd:YAG ring laser

A beam-shaped 20-W diode bar has longitudinally pumped a Nd:YAG laser in a ring configuration. Unidirectional single-frequency operation is enforced by a Faraday rotator. Intracavity frequency doubling with a KTP crystal has produced 3 W of stable single-frequency TEM00 output at 532 nm.

Frequency tuning and stability of Nd:YVO 4 in a dual coupled cavity

Frequency tuning and stability properties of single- and multi-cavity designs have been investigated theoretically and experimentally. Special attention is paid to a dual coupled cavity single-frequency diode-pumped solid-state Nd:YVO 4 laser crystal. 350 mW single frequency output power has previously been demonstrated using dual coupled linear cavity. Frequency tuning versus temperature and cavity length of a coupled cavity Nd:YVO 4 have been investigated and compared to those of a non-planar monolithic, unidirectional Nd:YAG ring laser. A way to extend the tuning range by design of the air to crystal length ratio is proposed. Finally the long term frequency stability of both lasers has been measured. The stability of the lasers are presented through the Allan variance of the frequency fluctuations.

Detection of CO in air by diode-pumped 46-μm difference-frequency generation in quasi-phase-matched LiNbO_3

Detection of CO, N(2)O, and CO(2) in ambient air was performed with a room-temperature cw IR source based on difference-frequency generation in periodically poled LiNbO(3). The source was pumped by a seeded highpower GaAlAs amplif ier at 860 nm and a diode-pumped monolithic Nd:YAG ring laser at 1064 nm. The IR output was tunable between 2160 and 2320 cm(-1) without crystal rotation. The CO detection sensitivity is extrapolated to 5 ppb m/ radicalHz if limited by IR intensity noise.

Quasi-three-level room-temperature Nd:YAG ring laser with high single-frequency output power at 946 nm

Efficient room-temperature operation of a diode-pumped Nd:YAG laser is demonstrated for the quasi-three-level transition at 946 nm. Continuous-wave output powers of more than 800 mW cw in single-frequency operation are generated by application of a composite-cavity nonplanar ring laser. High amplitude and frequency stability of the emitted radiation is observed.

Minimal equations for antiphase dynamics in multimode lasers

We consider two models of multimode lasers: the Tang-Statz-deMars equations modeling a solid-state Fabry-P\'erot laser [C.L. Tang, H. Statz, and G. deMars, J. Appl. Phys. 34, 2289 (1963)] and the rate equations modeling intracavity second-harmonic generation in a Nd:YAG ring laser (where YAG denotes yttrium aluminum garnet). In both models, the dynamics is dominated by a global coupling of the modes of the electromagnetic field in the cavity. Although the equations for these two problems are fairly different, we prove that a dominant asymptotic approximation can be determined in each case that leads to the same conservative problem. It depends on one parameter, which measures the strength of the global coupling, and admits a class of antiphase periodic solutions.

Spectral properties of diode-pumped non-planar monolithic Nd:YAG ring lasers

The coherence length of a single-frequency monolithic Nd:YAG ring laser is determined by using a highly unbalanced all-fiber Mach-Zehnder interferometer. A coherence length larger than ⋍ 1500km and a 3 dB linewidth less than ⋍ 60 Hz is estimated.

Broadly tunable mid-infrared intracavity difference-frequency laser

We generated diffraction-limited laser radiation that is continuously tunable from 3.1 to 4.4 microm by mixing the output from a Ti:sapphire laser with the intracavity field of a single-frequency, 1.064-microm Nd:YAG ring laser. A peak output power of 300 microW was observed near 3.2 microm at a Ti:sapphire input power of 300 mW.