We have developed a high average power zig-zag slab laser based on conduction-cooling and a novel pumping geometry called edge-pumping. The edge-pumping geometry decouples the cooling and optical pumping interfaces, simplifying the laser head design. The advantages of this design include efficient pump absorption, uniform conductive-cooling, high brightness fiber-coupled laser diode pumping, and power scalability. We have demonstrated this new design in a Nd:YAG zig-zag slab laser which operates at 104 W of multimode power for 340 W of pump power with a 40% slope efficiency. TEM₀₀ mode operation was demonstrated at 39.5 W for 250 W of pump power at a slope efficiency of 21%. Thermal lensing measurements indicate an effective focal length of < 0.5 m in both the zig-zag and the non-zig-zag planes for 340 W of pump power.

High power diode pumped solid state lasers are attractive sources for various applications in material processing. One of the advantages of diode pumping of solid state lasers is the higher brilliance (maximum output power/poorest beam parameter product using equal plan-plane resonators) compared to arc lamp pumped solid state lasers.

We report here on a new compact frequency-doubled Nd:YVO₄ laser emitting up to 165 mW of single frequency, TEM₀₀ mode, 532 nm green laser output. This compact, high efficiency, single frequency laser incorporating a novel coupled cavity technology appears promising for use in holographics and the printing industry. This coupled cavity technology provides for a frequency-doubled laser capable of operating in single longitudinal mode while eliminating many intracavity optical components, such as polarizers, waveplates or etalons. The few intracavity elements include a KTP nonlinear optical crystal employed for intracavity frequency doubling. The reduced component count results in a dramatic reduction in optical losses in the laser cavity and increased efficiency. This laser device produces 165 mW of green laser output power from a 1 W pumping laser diode, illustrating that both power and efficiency are improved using this technology. The reduced components also allow for a more compact laser, with the laser head measuring 3 X 3 X 12 cm, and the power control unit measuring 5 X 13 X 15 cm. This laser also features excellent output stability with power variation less than 1% over 4 hours, and less than 0.5% amplitude noise in the 10 Hz to 560 MHz bandwidth range.

We have recently shown that a simple formula, i.e. the generalized Airy function, can quantitatively describe the spectral density of a gas laser. This formula was obtained using semi-classical arguments. Using this model, the evolution of the total intensity as well as the laser linewidth without any discontinuity when the gain increases the well below to well above threshold, can be tracked. It contains the three fundamental effects present in a laser: the spontaneous and stimulated emissions and the resonance effect of the cavity. The source term in this Airy function is the spontaneous spectral density of the light emitted in the laser mode at the frequency v. We have also begun to compare this theory and experimental results, especially in the case of a CW end-pumped Nd:YAG semi-monolithic microchip laser.

Development of the oxyborate Nd³⁺:YCOB has brought about the realization of single crystal elements under diode pumped operation for compact simple, solid state lasers producing visible laser emission. Efficient laser action and self-frequency doubling (SFD) has been obtained for both Ti:Sapphire and diode pumped operations. Comparable results were obtained for a hemispherical linear cavity with a 2% output coupler for fundamental operation. The fundamental output power of the Nd:YCOB under Ti:Sapphire pumping was in excess of 400 mW with a slope efficiency of 44% with approximately 1 W absorbed. Utilizing high brightness laser diodes, over 350 mW of fundamental output power has been obtained with a slope efficiency of 51% for similar absorbed powers. Efficient SFD operation was demonstrated in both pumping modes with no output coupling at the fundamental wavelength and high transmission of the second harmonic using a 5% doped Nd:YCOB crystal. Output powers of approximately 60 mW at 530 nm were obtained with both Ti:Sapphire and laser diode pumping.

Described is a system that will provide isolated electric power for a circuit that drives the core reset of a pulsed power modulator. This can be accomplished by coupling light from a number of diode laser bars to bundles of 200 micrometers multimode optical fibers. This is then coupled to photo- voltaic power converters that will deliver 16 V 29 mA of electricity from 1 watt of optical power. Spot size at the bundle face is a Gaussian ellipse with a major axis of 0.9 mm radius and a minor axis of 0.118 mm with a maximum full angle divergence of 16 X 2.4 degrees. Data is presented from four 20 W laser bars coupled to four bundles of 12 fibers generating a total of 24 W of electrical power. Various schemes are used to maximize coupling into the optical fiber while limiting the number of optical components, and comparing components such as fresnel and aspheric lenses and lens ducts for effectiveness and cost. This will provide a completely isolated low power source for high voltage, high current environments where traditional isolation techniques yield inadequate isolation or prove too cumbersome.

At the first time, tunable (up to 40 nm) single frequency (FWHM < 30 kHz) Yb and Yb/Er doped fiber lasers based on the MOPFA configuration with the output power from 1 W to 10 W in CW have been demonstrated and realized as final products. In particular, the different kind of master oscillators schematics including DBR fiber lasers, ring resonator fiber laser and fiber coupled external cavity LD's have been used. The ultimate output power limitation due to SBS were investigated.

Nonlinear SRS and SBS restrictions for available peak power in single-mode fiber lasers were investigated. Various technical means to overcome the limitations were developed. As result, a feasibility of 100 kW peak power at 5 nsec pulse duration and 20 W average power with near TEMoo output beam quality was demonstrated for ytterbium fiber laser with a MOPFA configuration. As alternative, Q-switch version of similar laser was developed using high-speed acousto-optic switch in ring geometry of fiber resonator. Temporal and spectral behavior of both versions vs peak power, pulse duration and repetition rate was investigated in details.

The X1 accelerator project at Sandia National Laboratory/New Mexico utilizes SF₆ insulated, multi-stage, UV laser triggered gas switches. A 265 nm UV laser system was designed and built to generate eight simultaneous output pulses of 10 mJ each with a 13 nsec pulsewidth.

The demand of machine users towards the complete processing of a workpiece in one setting requires the use of different processing technologies in one machine. In the past years lasers have found new applications in production engineering as a tool for surface modification, cutting, welding and marking. By combination of conventional metal cutting technologies with laser processes in one machine, the complete processing of a workpiece with different technologies in one setting can be realized. The advantages are the processing in one setting and the reduction of material flow between the production machines. The possibility of integrating lasers for material processing in a cutting machine are examined. Processing technology as well as different constructive solutions depending on the type of machine used and integration method are evaluated. Parallel to this approach, examinations of the economy of these systems are carried out.

Our efforts to chemically analyze aromatic hydrocarbons by resonance enhanced multiphoton ionization (REMPI) spectroscopy has been extended to mixtures. Indene has been detected in the headspace over coal tar and creosote via a characteristic band at 287.9 nm. Both sample and data collection occur for ambient pressure and temperature conditions. The indene spectra have also been examined for the effects of pressure broadening, which are discernible but small. High resolution absorbance spectra establish the feasibility for a similar REMPI strategy to detect benzene and toluene via an on-off resonance strategy, similar to that practiced in differential absorbance LIDAR (DIAL) and differential absorbance optical spectroscopy. Angular/wavelength acceptance criteria for the frequency doubling process, by which the tunable ultraviolet light is generated, are considered. Options for ultraviolet tunable solid state lasers, which are the key to real-time monitors based on REMPI technology, are assessed.

Over the past twenty years there has been much research into the laser operation of solid materials doped with laser dyes. Although some research has developed high performance systems for operation at, for example, unusual wavelengths or with narrow linewidth, the most pertinent performance parameters remain the efficiency and the photostability. By reviewing all the published data concerning these parameters it is concluded that the main factor determining performance is the choice of laser dye. The performance of rhodamine 6G in solid-state dye lasers has not been improved and the only progress that has been made in this field is due to the introduction of the pyrromethene dyes which can now be used for many applications. Although optimization of the host material can improve performance of pyrromethene solid-state dye lasers no clear advantage can be gained by choosing either a glass or a plastic host. Long pulse length flashlamp pumped operation remains challenging, at least in part due to triplet state losses.

Presented here are experimental results of polymer dye lasers with various active elements that had different optical surface quality. We investigated these active elements with diamond-turned and conventionally polished surfaces, uncoated and AR coated. Sol gel AR coatings were spin-applied to polymer surfaces resulting in less than 0.25%/surface reflection losses. Excellent refractive index matching coupled with low stress and high optical damage threshold, makes this AR coating ideal for this applications. Sol gel coatings are highly repeatable and easily tailored to these polymer materials. These elements were pumped by a Q-switched, frequency doubled Nd:YAG laser with pulse energies up to 760 mJ, pulsed width of 5 - 7 ns.

Using flashlamp excitation, photostability data on 1,3,5,7,8-pentamethyl-, 1,2,3,5,6,7,8-hepta-methyl-, and 2,6-dipropyl-1,3,5,7,8-pentamethyl-, and 2,6-dinitro- 1,3,5,7,8-pentamethyl-pyrromethene- (P)-BF₂ complexes in the solvent 1,4-dioxane and the solvent mixtures 1,4- dioxane/heptane, 1,4-dioxane/cyclohexane, 1,4- dioxane/ethanol and 1,4-dioxane/hexanol, all ratio 1:4, were obtained. As reference laser dyes, the photostability of Rhodamine 6G in ethanol and the solvent mixture ethanol/hexanol ratio 1:4 and Rhodamine 560 in ethanol and the solvent mixtures ethanol/hexanol, ethanol/cyclohexane, and ethanol/heptane, all ratio, 1:4 were also obtained. Specifically, the laser output energy, (Delta) E (in joules) was recorded as a function of flashlamp excitation pulses, N. 2,6-dinitro-pentamethyl-P-BF₂ was very stable in the heptane mixture, and other P-BF₂ complexes were more stable in 1,4-dioxane. Rhodamine 6G was very stable photo chemically in hexanol. The role of oxygen in laser dye solutions is briefly reviewed.

The first demonstration of a flashlamp pumped zig-zag plastic dye laser is presented. Repetitively pulsed measurements with liquid dye solution of Pyrromethene-567 in ethanol/PPH demonstrated 280 mJ per pulse at 1 Hz. Solid plastic dye samples were flashlamp pumped under similar conditions with output energy to 70 mJ. Rapid decay of the laser output was observed in initial measurements with plastic samples (Epoxy Technology EP310) at 1 Hz pulse rate. This design can be used to test various solid state plastic host dyes in a configuration that has demonstrated exceptional beam quality with laser excitation.

Continuous wave red, green and blue laser light have been generated under infrared pumping crystals of Nd³⁺:YAl₃(BO₃)₄ by a Ti:Sapphire laser. The red (669 nm) and green (532 nm) radiations were obtained by self-frequency doubling of the fundamental laser lines at 1338 nm (⁴F_3/2 yields ⁴I_13/2 channel) and 1062 nm (⁴F_3/2 yields ⁴I_11/2 channel) respectively. Blue laser radiation (458 nm) was achieved by self-sum- frequency mixing of the main laser line at 1062 nm and the pumping radiation at 807 nm. The main spectroscopic and nonlinear properties of this crystal are included. In addition, a simple model devoted to optimize the blue radiation is given.

We demonstrate a highly efficient source of single frequency 266 nm light. A single frequency 532 nm source is frequency doubled in an external ring cavity. Almost 50% internal conversion efficiency in the nonlinear crystal gives a useable output of 660 mW at 266 nm, from 2 W at 532 nm, and up to 1.5 W at 266 nm from 5 W at 532 nm.

An analytical model is described for predicting the gain and performance of cw, singly resonant, optical parametric oscillators with strong idler absorption, strong pump depletion and thermally induced dephasing. Pump and signal beam focusing effects are included by using the Guha, Wu and Falk h_sm parameters. It is shown that significant parametric gain can be generated with an idler absorption- length product exceeding 10, and in some cases idler absorption is seen to enhance the pump depletion by impeding back conversion. The model accurately predicts current experimental results with weak idler absorption, and greatly over predicts the performance with high idler absorption. This difference is believed to be due to thermally induced focus that strongly disturbs the resonant optical cavity for the signal. Shorter crystal lengths, with resonant pump enhancement, offers a possible solution.

Solid state lasers with high average output power in conjunction with high beam quality are required for high brightness applications in industry and science. In master oscillator power amplifier arrangements (MOPA) with phase conjugation the beam quality is determined by the master oscillator and largely preserved after double pass amplification. This paper deals with multi amplifier arrangements to cover a power range up to 1 kW. A serial arrangement reduces the required oscillator power to operate the amplifiers in saturation regime. Using optical systems between the amplifiers the average output power is tunable by variation of average pumping power. Several serial amplifier chains can be coupled parallel to divide the total average output power to various beam lines with moderate amplifier apertures. Different multi amplifier systems are discussed with regard to their possible average output power and beam quality. A flash lamp pumped MOPA system which supplies average output powers above 500 W is described. The system consists of two parallel coupled serial amplifier chains and two additional booster amplifiers. Beam quality and beam profile measurements have been carried out at different positions in the laser system. Average output powers up to 1 kW seem to be possible.

Mode-locking of a pulsed picosecond Nd³⁺:YAG laser using a slow solid-state saturable absorber with microsecond recovery time (Cr⁴⁺:YAG) and a passive negative feedback element (GaAs) is reported.

The behavior of an electro-optic Q-switch in high-average- power laser is presented. Absorption of laser radiation produces heating of the electrooptic crystal which degrades the laser performance. A large increase in output energy stability is achieved by employing a switching voltage pulse of the special temporal shape to the Pockels cell. The optimum pulse waveform has been calculated to reduce the Q- switching intracavity loss to zero at the instant a laser pulse occurs. We have compared the laser performance with the conventional rectangular pulse shape and the calculated one. The experiments have demonstrated that at the novel shape of pulse the permissible temperature range of the laser performance without adjustment of switching voltage was extended by a factor of 2 - 2.5.

Germanium terahertz (THz) lasers based on a heavy hole-light hole population inversion within the valence bands show strong promise for widespread applications due to their unparalleled frequency tuning range and high output power up to several Watts. Germanium lasers have attractive laser properties: tunability from 1 to 4 THz, high finesse of 10⁶ with line widths below 1 MHz and linear polarization. Laser operation is possible with small mm- sized permanent magnets and closed-cycle refrigeration. Since 1995 we have increased the duty cycle (laser on-time) of such lasers from 10^-5 up to 2.5 X 10^-2 (2.5%). We report on our current research efforts aimed at achieving continuous wave emission. These efforts include a reduction of the active laser crystal volume from typical values of 30 - 60 mm³ to and perhaps below 1 mm³ and materials and electric field homogeneity improvements to enhance the conversion efficiency. A planar contact geometry is suggested to allow improved heat sinking. Our planned applications include but are not limited to airborne and satellite based research for the study of molecules in the upper atmosphere or in star-forming regions of the universe.

We describe a high-power blue laser for use in laser video projectors. The laser is based on an intra-cavity, frequency-doubled, Ti:sapphire resonator, longitudinally- pumped by a repetitively Q-switched 532 nm source. With 48 W of pump, the laser produces more than 7 W of continuously tunable blue output (430 <EQ (lambda) equals 460 nm) with a pulse width of 80 ns and a beam quality factor M² equals 2.2. The applicability of this high-power laser as a source of monochromatic blue light for different large-screen laser displays is also discussed.

A 243 nm source is developed based on a Cr:LiSAF laser operating at 25 Hz. The Cr:LiSAF laser is operated at 972 nm and is frequency quadruped in two successive second harmonic generation stages to 243 nm. An innovative multi-crystal design is implemented in each of the second harmonic generation stages. In this way the total crystal length required to efficiently convert temporally long pulses with low peak powers is maintained while broadening the effective spectral acceptance of the nonlinear interaction. Using six BBO (beta-barium borate) crystals in series an effective spectral gain bandwidth that exceeds by as much as 5 times the spectral bandwidth of a single crystal of equivalent length is achieved. The resulting 243 nm source is shown to have a spectral bandwidth of 140 pm (fwhm) and a temporal pulse length of 167 nsec (fwhm).

A high repetition rate diode pumped Erbium glass laser was demonstrated at 50 Hz with Q-switched outputs up to 15 mj by various Q-switch methods.

A gain switched Ti:sapphire laser with 350 mW average output power of near diffraction limited radiation and a bandwidth of more than 40 nm is presented. The Ti:sapphire laser was longitudinally pumped by a passively Q-switched and frequency-doubled Nd:YAG laser. The spectra of the radiation are investigated experimentally as a function of the pump energy. Time resolved measurements of the spectra and of the transversal mode structure show that the spectra and the transverse mode structure vary during one pump pulse of 1 ms. This variation of the spectrum was used to broaden the spectrum of the laser light. Finally we present measurements with the coherence radar on a dark object and with a large field of view.

Progress in the growth of the rare earth calcium oxyborate crystals has now generated a new class of laser materials that can be used as both a laser host and a nonlinear frequency converter. Laser action and self-frequency doubling (SFD) has been observed with both 10% and 20% Yb³⁺-doped YCOB crystals. Laser operation was obtained in a hemispherical linear cavity, end-pumped with a tunable cw Ti:Sapphire or a 980 nm laser diode pump source. Under Ti:Sapphire pumping at 900 nm, an output power of 230 mW and a slope efficiency of 29% was obtained using the 10% doped sample. Laser action was seen at 1050 nm. Laser operation of the 20% sample had a maximum output power of approximately 300 mW with a slope efficiency of 35.8% at 1088 nm. Laser action was not obtained at the peak of the fluorescence emission (approximately 1030 nm) in this crystal as a consequence of self-absorption on the short- wavelength side of the emission band. Diode-pumped operation at the narrow absorption peak of 977 nm was achieved and early results show an improved slope efficiency of 34% in comparison to the 10% doped crystal under Ti:Sapphire pumping. We have also observed self-frequency doubling in Yb³⁺:YCOB. The 20% Yb³⁺:YCOB crystal used for this test was cut with a phase-matching angle of 36.22 degree(s). The self-frequency doubling efficiency was low due to the absence of any frequency selective elements in the cavity to narrow the linewidth of the fundamental emission. The SFD emission occurred at 543 nm.

One possibility for communicating from an airplane above water surface to submarine in sea involves the use of laser- generated underwater sound. Because the air-submarine communication should be in the sea-environment i.e. very large volume of water, higher photoacoustic coefficient is the first important factor to be considered. Solid state laser Nd:YAG as one kind of high-power laser is possible for this application, since it has such advantages: (1) high power to do optical breakdown in water, (2) compact for airborne; (3) 1.06 (mu) IR beam being absorbed strongly by water but still penetrating into water a bit in depth, it will be good for making a sound source under water-surface. In this paper, we introduce the way to generate strong optical breakdown acoustic signal in a limited large volume of water in lab. The optical breakdown mechanism of strong Nd:YAG laser pulse (6 - 8 ns; max 600 mj/p) with water generates acoustic signals in water having pulse widths about 25 microsecond(s) and a frequency spectrum peak about 58 kHz. And, its sound source level of 196 dB for low frequencies less than 58 kHz is to be detected at a distance deep in water. Also, special new requirements are mentioned for solid state laser's designer.

Because of the development of laser technologies, in particularly of the method of laser isotope separation, the necessity to develop kilowatt-class narrow-band tunable laser systems has increased. Organic dyes solutions are the unique active medium that allows to realize laser systems with such characteristics. However the dye solution is a rather complex medium and a careful optimization of the laser system parameters is required to reach a high efficiency. A large number of publications concerning the powerful dye laser systems is devoted to the research of a single amplifier stage. In the present paper the cascade of the dye laser amplifiers is considered as a unit. On the basis of a simplified model of the amplifier stage, the equations describing the whole laser system were solved analytically. Such approach has allowed, on the basic parameters of the laser system, (input and output power, characteristic of active medium) to determine optical parameters of each amplifier stage in the cascade (number and parameters of stages, pump power distribution between stages). On the basis of the offered model the optimization of the 1 kW dye laser system, pumped by copper vapor laser, was carried out. Analytical estimations were compared with the results of a rigorous numerical simulation of the system.

In high power laser systems, the stability of the seed laser is vitally important. This paper focuses on work undertaken to design and make a high stable LD pumped solid state seed laser which had the advantage of being all solid state, compact, easy to manufacture and low cost. The laser was composed of two parts. One part was a LD pumped 0.5 mm thick Nd:YLF laser system in which the instability was around +/- 6% (3(sigma) ). The other part was a close-looped laser power control system using external cavity power feedback. Using an electro-optic modulator, a 1 X 2 optical fiber splitter and a signal processing circuit, we successfully realized the high stable LD pumped Nd:YLF laser in which the instability of laser output power was lower than +/- 0.2%/hour (3(sigma) ). A digital PID control method was used in which the control frequency was 40 kHz. We obtained 3 mW of high stability laser power through the optical fiber.

The gain saturation of Nd-glass amplifier is determined by the relaxation rate of populations. The influences of the thermalization rates among the components of the multiplets to which the laser levels belong and of the depletion rate of terminal laser level are investigated in detail. A modified Frantz-Nodvik model in consideration of the influence of thermalization and depletion between laser levels is obtained. By solving these differential equations, we calculated a practical amplifier. The results indicate that the output of the amplifier can increase remarkably when the thermalization time decreases to pulse duration.

Different ways of varying the output pulse duration in laser schemes comprising a master oscillator, a multipass amplifier and a SBS-mirror are suggested and realized experimentally. Conditions are determined at which introduction of losses between a SBS mirror and an amplifier allow variation of the output pulse duration without any significant decrease in energy. The use of two different SBS media (SnCl₄ and freon) allows construction of a laser where the output pulse duration is varied within 6 - 40 ns and the energy loss is no more than 30%.

The transmission window of the acousto-optic modulator was discussed theoretically. By injecting pulsed higher acoustic power, the FW}{M of the transmission window of the modulator was reduced, so the mode-locked pulse width was reduced to 55ps. In addition, through discharging the λ/4 voltage of the Pockels Cell, a single pulse was dumped out from the intracavity of the laser: the energy was 2mj, the energy variation was ±4%. Besides, the repetition rate of the laser was improved to 30Hz due to the reduction of the laser threshold. It is evinced that this kind of laser has potential for a wide variety of application.

A CPM, Nd:YAP (and YAG) pulsed laser with an ARR-convex unstable resonator is designed. It combines the advantages of both CPM configuration for narrow pulsewidth and unstable resonator for high output energy. This ideal fundamental wave source delivers a single pulse train with energy several tens of mJ, pulsewidth 10 Psec, and energy fluctuation < 2%. Using intracavity frequency doubling and choosing KTP, BBO and LBO as SH generator, a powerful and efficient SHG at green is generated with SH energy > 48 mJ, power density > 5 GW/cm² and conversion efficiency as high as 50 - 70%. The theoretical analysis tallies with the experimental results.

A new way of generating negative group-velocity dispersion in a Ti:sapphire laser is demonstrated. The mathematical formulae of the optical path length and the negative group-velocity dispersion in a singleprism system are given. Both of the theoretical analyses and the experimental results show that the group-velocity dispersion is directly proportional to the distance between the prism and the Ti:sapphire crystal, and the amount of the negative group-velocity dispersion generated by a single-prism system may approach that generated by a pair of prisms.

Using a modified ABCD-matrix approach accounting for nonlinear refraction in active medium, we determined the ranges of cavity parameters that provide a mode-locking of Yb:KYW-laser in usual z-fold cavity configuration. Taking the cavity parameters that provide a most efficient mode locking and based on fluctuation model, we performed a numerical simulation of laser operation. We used for our calculations the side-band pump power of 6 W at 982 nm with 1 cm X 50 micrometers beam cross section in active medium and the length of 1 cm for KYW crystal. Calculations showed that self-starting operation is possible with these parameters and dispersion compensation allows for bandwidth-limited ultrashort pulse generation. The shortest pulse duration was determined to be approximately 200 fs with self-starting build-up time of 130 microsecond(s) . Such a built-up time is comparable and even shorter than that one for the lasers with semiconductor saturable absorbers. The region of negative dispersion provided by prism pair where a stable ultrashort pulse generation takes place was determined to be (-17000 - -42000) fs².

For the first time Nd³⁺:KGd(WO₄)₂ and Nd³⁺:NaLa(MoO₄)₂ crystals was investigated as active media of powerful lasers. The efficiency and the promising of its use in this quality are shown. Dynamics of generation of such lasers was studied in offered us the optical scheme of a resonator and pumping cavity. A good degree of a homogeneity of cross distribution energies in a beam and angular divergence closed to diffraction limit of a radiation with energy up to 60 J were obtained.

The first cw high-power UV laser at 266 nm--DELTATRAIN--is accomplished by frequency doubling the 532 nm output of a diode-pumped Nd:YAG laser with an actively stabilized unidirectional ring cavity based on the novel DELTACONCEPT, where a minimum number of optical components--two mirrors and one prism are used. The symmetrical Brewster-angled beam path through the prism guarantees minimum losses and hence maximum power enhancement and efficiency. The cavity length control is done by moving the prism along its symmetry axis using a piezoelectric element. The beam path in the cavity remains not only completely unaffected during this movement but also unaffected in the first order by small tilts of the prism due to possible imperfection of the piezoelectric element. Furthermore, the stabilization loop has excellent dynamic behavior owing to the small mass of the prism. The name of this concept results from the (Delta) -geometrical configuration of this novel ring resonator. The unique feature of the DELTACONCEPT shown above adopted in the DELTATRAIN results in long term UV power stability, high beam pointing stability, excellent beam profile and reduced effort in alignment. By using Brewster-cut BBO crystals the high-power cw UV laser can deliver 266 nm radiation with an output power of 1.4 Watt at a green pumping power of 5 W.

The application of liquid crystal spatial light modulation devices to reducing deleterious phase distortions on beam quality in flashlamp pumped dye lasers was investigated. Due to the birefringence and nematic properties of the liquid crystal devices (LCDs), the LCDs behaved as tunable etalons when used intra-cavity. Using a grating with a multi-prism Littrow configuration and the LCD intra-cavity, linewidths on the order of 100 MHz were observed.