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Nd:YVO4 has a high gain transition at 1.34 μm. It can be q-switched by the saturable absorber Vanadium:YAG, which has quick recovery, enabling repetition rates above 1 MHz. I demonstrated a 1.34 μm laser for LIDAR with 1.08 nsec pulse duration, 24 kHz repetition rate and 1.75 kW peak power, and in another configuration, 4.8 nsec pulse duration, 1.82 MHz repetition rate and 68 W peak power. Several intermediate cases are described as well. These lasers have part-for-part correspondence with green pointer lasers sold for under $5 which are the size of a penlight. The eye-safe class 1 power at 1.34 μm is 1.9 times that allowable in the 1.4-1.6 μm range.

The brightness of a laser-generated guide star is determined not only by the power of the laser, but also by the spectral and temporal properties of the laser. We show that a guide star laser pulsed at the Larmor frequency of the sodium atoms enhances guide star brightness by up to 2X, compared to an optimized cw laser at the same average power. We describe a frequency-addition source of optical radiation that can provide such pulsed light, while providing any desired spectral shape.

In order to meet the ever increasing demands of many high power laser diode customers, Nuvonyx has worked to improve a number of key metrics of the diode laser package. The most often challenged specifications are power per bar, efficiency, and reliability in both hard pulse and constant current mode. In response to these requests, Nuvonyx has worked to offer commercial component devices in excess of 100 and 150 watts per bar package in multiple wavelengths. The packages are routinely combined to form single stacks that generate greater than 3.5 kilowatts each and two-dimensional arrays which produce light in excess of 10 kilowatts. These parts all demonstrate predicted lifetimes in excess of 10,000 hours. The micro-channel cooled heat sink has also been improved by closer matching the coefficient of thermal expansion of the cooler to the laser diode bar, which allows for harder solders such as gold-tin to be employed. All of this work has helped to meet the specifications of the most demanding laser diode customers.

We describe a passively mode-locked, diode-pumped Nd:YAG laser that is used for frequency-conversion applications. The laser is based on a Direct-coupled Pump gain element and saturable Bragg reflector. The laser produces a 20-ps pulse with a 100-MHz repetition rate in a compact commercial package. It has typically 1 W at 355 nm. In addition, we have generated super-continuum output in the visible and infrared from micro-structured nonlinear fiber with pumping both at 1064 nm and 532 nm. Current applications for this laser, primarily in the ultraviolet, include flow cytometry, stereolithography, and semiconductor inspection.

The laser guide star adaptive optics (AO) module for the Subaru Telescope will be installed at the f/13.9 IR Nasmyth focus, and provides the compensated image for the science instrument without change of the focal ratio. The optical components are mounted on an optical bench, and the flexure depending on the telescope pointing is eliminated. The transferred field of view for the science instrument is 2 arcmin diameter, but a 2.7 arcmin diameter field is available for tip-tilt sensing. The science path of the AO module contains five mirrors, including a pair of off-axis parabolic mirrors and a deformable mirror. It has also three additional mirrors for an image rotator. The AO module has a visible 188-element curvature based wavefront sensor (WFS) with photon-counting avalanche photodiode (APD) modules. It measures high-order terms of wavefront using either of a single laser (LGS) or natural guide star (NGS) within a 2 arcmin diameter field. The AO module has also a visible 2 x 2 sub-aperture Shack-Hartmann WFS with 16 APD modules. It measures tip-tilt and slow defocus terms of wavefront by using a single NGS within a 2.7 arcmin diameter field when a LGS is used for high-order wavefront sensing. The module has also an infrared 2 x 2 sub-aperture Shack-Hartmann WFS with a HgCdTe array as an option. Both high- and low-order visible WFSs have their own guide star acquisition units with two steering fold mirrors. The AO module has also a source simulator. It simulates LGS and NGS beams, simultaneously, with and without atmospheric turbulence by two turbulent layer at about 0 and 6 km altitudes, and reproduces the isoplanatism and the cone effect for the LGS beam.

We present the development status of the laser system for Subaru Laser Guide Star Adaptive Optics System. We are manufacturing the quasi-continuous-wave sum frequency laser as a prototype. The optical efficiency of sum frequency generation normalized by the mode-locked fundamental YAG (1064 nm) laser output power is achieved to be 14 % using the non-linear crystal, periodically poled potassium titanyl phosphate (PPKTP). Output power at sodium D2 line was about 260 mW. The optical relay fiber and the laser launching telescope are also described in this paper. For the optical relay fiber, we are testing an index guided photonic crystal fiber (PCF), whose core material is filled by fused silica, and whose clad has close-packed air holes in two dimension. The coupling efficiency was evaluated as about 80 % using 1mW He-Ne laser. We introduce the design of laser launching telescope (LLT), which is a copy of VLT laser launching telescope, and the interface to the Subaru Telescope.

The laser guide star adaptive optics (AO) system for Subaru Telescope is presented. The system will be installed at the IR Nasmyth platform, whereas the current AO system with 36 elements is operating at the Cassegrain focus. The new AO system has a 188 element wavefront curvature sensor with photon counting APD modules which is the largest control element curvature sensor system ever. The system will have 4-10 W solid state sum-frequency laser to generate a laser guide star. The laser launching telescope with 50 cm aperture will be installed at behind the secondary mirror. The laser unit will be installed on the third floor of the dome and the laser beam will be transferred to the laser launching telescope using single mode photonic crystal fiber cable. The field of view of the optics is 2.7 arcmin to maximize the probability to find tilt guide stars for laser guide star operation. The expected Strehl ratio as raw AO performance is 0.46 at H-band under 0.60" seeing with 12 th mag guide star, and 0.71 for 8 th mag stars. New wavefront modulation technique, dual stroke membrane mirror control, is developed to reduce the tilt error which is more dominant for curvature sensor AO system. The superb contrast imaging capability will be expected as natural guide star system. The first light as the natural guide star system is planned in March 2006, the laser first light will be expected in March 2007.

The Subaru Telescope LGSAO system is a 188 elements curvature AO system currently under construction, and scheduled to have first light in March 2006 for the Natural Guide Star mode and March 2007 for the Laser Guide Star mode. A particularity of this system will be to perform curvature wavefront sensing with several extra-pupil distances, which significantly improves the closed-loop performance. An overview of the predicted performance of the system is given for Natural Guide Star and Laser Guide Star modes.

The trend in micro-machining lasers is toward greater average power and higher repetition rate, in order to increase throughput, with pulse energy and peak power held roughly constant, as determined by the small scale of the feature. At repetition rates beyond 500 kHz, conventional high-power Q-switched Nd lasers will reach fundamental limits. We demonstrated a fiber-based oscillator-amplifier architecture which produces pulse repetition rates in the 0.5 - 5 MHz range and pulse durations in the 0.5 - 1.5 nsec range. The oscillator is a compact (35 cm3 package) passively Q-switched Nd:YVO4 laser oscillating at a single frequency. By amplifying this laser in fiber, we demonstrated 10-W average power at the two wavelengths of 914 nm and 1064 nm. At 1064-nm, Yb-doped large mode area fiber will allow scaling of average power to over 100 Watts, with peak power of tens of kW, in a diffraction-limited beam. Excellent conversion will be possible to visible and UV using the robust nonlinear material LBO. By opening up a new range of repetition rates and pulse lengths, at IR, visible and UV wavelengths, in a high power design that has the packaging and efficiency advantages of fiber, new micro-machining applications may be enabled.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

S-band amplification with >30 dB peak gain at 1500 nm, >20 dB gain for wavelengths between 1475 nm and 1520 nm, and 5 dB noise figure is demonstrated in Erbium-doped Alumino-germanosilicate fiber. Using standard MCVD processing and solution doping, we combined a depressed-cladding fiber design with erbium doping to create a new type of gain fiber. A fundamental mode cutoff near 1530 nm provides distributed suppression of C-band amplified spontaneous emission, thereby enabling the high population inversion required for S-band gain. This type of S-band amplifier is compatible with standard fusion splicing techniques and is pumped by standard 980 nm pump lasers. In this talk, we will describe gain and noise characteristics for several amplifier architectures, gain saturation characteristics, and gain flattening.

This paper describes present day wind-measuring and air-data systems, the limitations of these systems, and the formation of a consortium to develop solutions using the laser Doppler velocimeter (LDV). The LDV concept is discussed as well as the issues related to developing such systems. Significant progress towards making practical, reliable, and affordable eye-safe LDV systems is being gained through the many systems built to date and flight tests. The technical goal of this program is to demonstrate that small, low-power, diode pumped, 2 micrometers wavelength, eye-safe coherent LDV systems can be built and flown on both high-performance military fighter aircraft and advanced military attack helicopters. An industry-government consortium will develop LDV systems with the name Laser Wind and Hazard Profiler.

Lightwave Electronics manufactures diode-pumped single-frequency Nd:YAG lasers at 1064 nm and 1319 nm. Short term (msec) frequency fluctuations of these lasers are in the kHz range, while longer term (hour) fluctuations are many MHz. The rms intensity fluctuations of these lasers have been lowered to 0.0038% using a noise-reducing feedback circuit. A laser has been tested operationally from -54 degree(s)C to +54 degree(s)C. Lasers can be tuned from 1319.03 nm to 1319.44 nm or from 1064.43 nm to 1064.73 nm.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A diode-pumped 2 micrometers LIDAR was installed aboard the NASA Ames DC-8 Flying Laboratory. The LIDAR was used to measure true airspeed through a variety of flight operating conditions. Data was successfully obtained during all four six-hour flights.

We have built a diode-pumped Nd:YAG optical amplifier with 52 dB small-signal gain and 1.125 Watts cw extractable power as gain approaches 0 dB. The amplifier is compact (15 cm X 10 cm X 5 cm). Two 2-Watt laser diodes provide the pump power for the amplifier. Gain is at the wavelength of 1.064 micrometers . We have modulated the output of an Nd:YAG diode-pumped cw oscillator with a waveguide modulator and amplified the modulated output. With an M equals 4 PPM modulation, the transmitted pulse power was 1.8 Watts increasing to 6.5 Watts at M equals 64. A greater increase would be possible if the modulator had a better contrast ratio. For pulse rates greater than 200 kHz inter-symbol interference was not a problem.

A high-power three-stage laser suitable for use in a space communication system has been built. This laser uses three diode-pumped Nd:YAG oscillators coherently combined using the technique of injection chaining. All three oscillators are in one compact and permanently aligned package, and are actively frequency locked to provide CW single frequency output. The three stages provide the redundancy desirable for space communications.

Laser-diode pumping of monolithic ND:YAG rings can lead to output powers of hundreds of milliwatts from a single laser. We have built several lasers with diffraction-limited single-mode output of 380 mW. These lasers can be injection—locked in a chain configuration to sum their power, while maintaining diffraction-limited, single-frequency operation. We demonstrated this chaining technique with two lasers, with a total output of 340 mW, and expect that it is practical for up to about ten lasers. Thus with lasers of 380 mW, output of 3 Watts is possible. The chaining technique, if properly engineered, results in redundancy. Monolithic, diode-pumped Nd:YAG ring lasers can provide narrow-linewidth, tunable output which is adequate for use as a local oscillator in a coherent conununication system. We build a conunercial laser which has a linewidth of about 2 kHz, a power of 5 inilliwatts, and which is tunable over a range of 30 MHz in a few microseconds. We phase—locked one of these lasers to a second, similar laser. This demonstrates that the powerful technique of heterodyne detection is possible with a diode-pumped laser used as a local oscillator. A key to the usefulness of these lasers in space communication is modulation. We have experimented with a technique for converting the cw, infrared output of these lasers into randomly pulsed, green output useful for Pulse—Position Modulation. Energy storage in an external resonant cavity permits peak green output to be much more powerful than cw infrared input. We have also begun experimentation with techniques for phase and amplitude modulating the output of these lasers. We are taking advantage of the coherence of the output in order to reduce the voltage required for conventional electro—optic modulation.

The sensitivity of a monolithic unidirectional nonplanar ring laser to optical feedback depends on the polarization eigenmodes of the resonator, which are complicated functions of the resonator geometry. Resonator geometries that increase the loss difference between the two directions of propagation around the ring improve the resistance of the lasers to optical feedback. Here, measurements on Nd:YAG nonplanar ring lasers having two different ring geometries are discussed. Currently, 1 percent optical feedback produces a 10 percent reduction in useful output power for the more feedback-resistant oscillator, a tenfold improvement over previous designs.

A slab geometry, with a zig-zag totally internally reflected optical path, significantly reduces thermal focusing, stress induced biaxial focusing and birefringence in a solid state laser host. We present results of a theoretical and experimental study of slab geometry Nd:Glass and Nd:YAG laser systems.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.