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A high-power multifrequency ultrasonic actuator is proposed and characterized. The actuator is used in many applications as a multifrequency ultrasound power generator, but also as a mirror with variable bend radius to deflect laser beams in optical applications.

The operation of positive index-guided submicrometer-ridge laser arrays (SLAs) that produced a near-diffraction-limited single-main-lobe far-field profile (FFP) is described. The SLAs have favored the lasing of in-phase array modes and have produced a near-diffraction-limited single-main-lobe FFP.

Practical laser communication is impeded by the inherent strict requirements on agile and accurate steering of the laser beam over a wide angular range that are addressed by the pointing, acquisition, and tracking (PAT) system. While the vehicle carrying the optical instrumentation is in motion, a PAT system is required to compensate for the vibrations applied to the optical platform through the proper application of advanced control laws. This paper presents a feedforward vibration rejection system interacting with an optical tracking system to successfully perform the PAT task. It features a set of inertial navigation sensors to monitor the optical platform orientation, and the optical tracker monitoring the optical alignment errors. The control effort is defined on the basis of both signals and upon amplification drives the actuators of a novel singularity-free fuill-hemisphere-range robotic manipulator supporting the optical platform. The resultant technology enables two ground vehicles navigating through a difficult terrain to maintain optical connectivity sufficient for reliable laser communication. The paper presents the development of an extended Kalman filter 'fusing' the inertial navigation sensor data, the design and implementation of the disturbance rejection/optical tracking control system, and the results of the experimental evaluation of the overall system performance.

The experimental results on laser beam guiding by a self-tightening lattice photo induced in a strontium barium niobate (SBN) photorefractive crystal is reported. The gradual transformation of the optical lattice into array of weakly coupled ones revealed significant role of induced modulation instability in the strong laser beam guiding.

A theoretical model is presented for describing the finite beams incident on reflective volume Bragg gratings. Findings reveal that the reflection of a finite beam is a convolution of the transverse beam profile and a general filter function of the Bragg grating.

The effectiveness of the wavenumber domain analysis of two-dimensional (2D) images captured by phase-sensitive laser probe systems in the characterization of RF SAW devices is studied. The wavenumber domain analysis can be usefully applied to the selective characterization of unwanted responses of RF SAW devices and also offers information like types and characteristics and the place of origin of spurious signals.

A new experimental technique is used to analyze the transient response of partially depleted SOI devices to pulsed laser irradiation. This new technique allows calibration of the deposited charge in the sensitive volume (i.e., the body region of the measured SOI transistors) and then the quantitative analysis of the device transient response. In particular 50-nm gate length SOI transistors have been tested with the pulsed laser, and their response is compared to 0.25-[micro]m partially depleted SOI transistors. The transient current and the collected charge are investigated as a function of the supply voltage for both types of SOI devices. The technology optimization for low leakage or high performance applications is shown to have large effects on the SOI device sensitivity. Index Terms--Bipolar amplification gain, charge calibration, critical charge, partially depleted SOI, pulsed laser irradiation, threshold LET.

A new device concept based on coherent processing of optical signals and allowing generation of ultrafast all-optical functions is presented. The device is modeled by rate equations and its functionality is demonstrated by studying the re-amplification and re-shaping (2R) regeneration of a 30-GHz signals in detail.

Continuous-wave (CW) as well as pulsed-laser-emission from a midinfrared IV-VI vertical-cavity surface-emitting laser (VCSEL) at 1.8K is presented. The results on the linewidth and the emitted power of CW and pulsed laser emission from PbSe VCSEL at 8 (mu)m are discussed.

Two-dimensional distribution of the ground-state NO molecules density was investigated using laser-induced fluorescence (LIF) technique in a dc positive streamer corona reactor (needle-to-plate electrode geometry) during NO removal from a flue gas simulator (NO/air). NO density in the corona discharge reactor was monitored under the steady-state dc corona discharge condition. It was found that NO molecules density decreased due to the corona discharge processing not only in the discharging region but also in the upstream vicinity of the discharge. Index Terms--DC positive streamer corona, ground-state NO molecule, laser-induced fluorescence, NO removal.

A theoretical analysis of a thermal defocusing optimal limiter's performance in a transient environment is presented. The situation occurs when the duration of the laser pulse is comparable to the time of the acoustic transit. The analysis, which used space- and time-dependent refractive index changes to calculate the nonlinear pulse change experienced by the pulse as it travels through the medium, supports the idea that the performance of the optical limiter is dependent on the laser pulse's duration.

A study of the time evolution of the transversal modes contained in a TEA CO2 laser cavity has been conducted via the analysis of the time-varying beam quality factor of the emitted pulse. The study reveals a substantial change in the beam quality factor during the pulse evolution stage. The results, when interpreted based on the appearance of a specific mode and its growth process, suggest an evolution by the laser cavity modes towards an almost stationary behavior.

This paper proposes a beamforming scheme for suppressing coherent interference with an array of arbitrary geometry. The scheme first uses estimates of the source directions to construct a transformation, which removes the desired signal while retaining the coherent interference. Optimum beamforming is then performed on the transformed data containing only interference and noise to produce the maximum output signal-to-interference-plus-noise ratio (SINR). Analysis and numerical results demonstrate that the proposed complementally transformed beamformer significantly outperforms the conventional multiply constrained minimum variance (MCMV) beamformers. Index Terms - Adaptive arrays.

A study was conducted to examine the lasing properties of a circular grating-coupled surface-emitting laser (GCSEL's) with an integrated focusing outcoupler. Results show that GCSEL's are lasing in mutually incoherent and near-orthogonal quasi-linear distributed Bragg reflector elements, rather than the ideal clean circular modes. This behavior is observed to effect the degradation of the focused spot quality.

An x-ray emission computed tomography technique has been demonstrated to diagnose the laser implosion uniformity of spherical targets. Three-dimensional images of compressed core were reconstructed from five pinhole camera images obtained at different viewing directions by using an iterative algorithm. The uniformity of the heated plasma is estimated from the intensity distribution of the x-ray emitted from the surface of the target.

Coherence growth and beam quality are analyzed for the laser radiation of stable and unstable cavities with the Gaussian reflectivity output mirror. The time evolution of laser beam parameters depends on the cavity configuration and the Gaussian mirror reflectivity profile. Far-field beam characterization explains the coherence growth of the laser beam in the Gaussian cavity as influenced by cavity configuration. Analysis of the near-field beam quality provides the filling nature of the active medium by the radiation.

The optical properties of a rectangular bore discharge-excited Sr+ recombination laser are discussed. Under optimum operating conditions, the laser intensity has a uniform spatial distribution. For a flat-flat optical cavity, the laser beam divergence in both the vertical and the horizontal plane is about 1.5 times the diffraction limit. The beam divergence is higher for a stable hemispherical plane in the horizontal plane. The recombination flux of Sr2+ is maximum in the central region of the rectangular bore.

Frequency up-conversion of a laser beam causing gas ionization in a cavity is considered in a fully relativistic fashion. A simple ionization model, based on one-photon and multiphoton processes is used. A Vlasov fully nonlinear and ionization-model independent description is used in calculating the current which drives the wave equation for the electric field. The evolution of the wave frequency and its upshift are contrasted with those obtained in the nonrelativistic limit. It is found that the nonrelativistic treatment overestimates the frequency upshift by a factor more than two. Purely relativistic effects, such as a significant frequency modulation and a respective temporal pulse compression, are observed in the exact case.

An overview is given of the physics issues relevant to the plasma wakefield accelerator, the plasma beat-wave accelerator, the laser wakefield accelerator, including the self-modulated regime, and wakefield accelerators driven by multiple electron or laser pulses. Basic properties of linear and nonlinear plasma waves are discussed, as well as the trapping and acceleration of electrons in the plasma wave. Formulas are presented for the accelerating field and the energy gain in the various accelerator configurations. The propagation of the drive electron or laser beams is discussed, including limitations imposed by key instabilities and methods for optically guiding laser pulses. Recent experimental results are summarized.

Numerical investigations are carried out to analyze thermally-induced optical aberration in an Nd:YAG laser. An 'intensity moment formalism' is used to characterize the overall spatial properties of the laser beam under a wide range of resonance conditions. The behavior of the beam quality parameter is also studied as a function of the refractive power. Results show that optical aberration exhibited by the laser beams can be eliminated by reducing the device's small-signal gain.

Laboratory experiments and numerical investigations are carried out to analyze the limit of optical frequency comb (OFC) generation due to the material dispersion in an electrooptic crystal. A modified monolithic OFC generator is used to make a detailed analysis of the OFC spectrum. Numerical approximations are also performed to support the experimental studies. The results are used to formulate new methods for stabilizing the resonant frequency of a Fabry-Perot cavity used in the OFC generator.

Investigation of the behaviour of a pulsed laser beam as a function of the number of round-trips in a Gaussian cavity showed that, with the number of round-trips the beam spot size and divergence decreases while the beam quality increases. The evolution of the first cavity round-trips depends upon the beam parameters' initial values. The laser system does not reach equilibrium during the pulse time. Discovery of a successful experiment and numerical data are discussed.

Experimental studies confirm the feasibility of transmission to total internal reflection switching of a step-on CO2 laser beam for the infrared spectral region by a dielectric, isotropic liquid crystal film. The isotropic phase enables the switching processes to be polarization-independent and maintains a moderate thermal nonlinearity. Incident angle and energy density exert an influence over the switching speed.

An array of multiple mirrors combined with an fs laser produces high frequency pulse bursts, unique time signals and digital pulse codes at 800 GHz. The nonlinear impulse response of the signals is a function of the reflection coefficients of the mirrors. Energy transfer laws formulated as 2 x 2 scattering product matrices yield the reflection coefficients.

An analysis of thermal beam disturbances in end-pumped Nd:GSGG, Nd:YAG and Nd:YLF rods reveals the influence on face- and edge-cooling on the disturbances. Surface deformation, thermal dispersion and strain-induced birefringence effects help compute space-resolved alterations in the rods. Optical path difference computations are verified using a polarized HeNe probe beam and a Twyman-Green interferometer.

Radio frequency discharge excitations of the transverse-flow CO(2) laser improves beam quality, electrical transformation efficiency and the maximum power input of the laser. Flow velocity, temperature concentrations of O(2), N(2) and CO and pressure operate as the experimental parameters during the excitation. A distinct laser power of 4.6 kW per M reveals the transverse-flow scaling law of the laser.

Incorporation of azimuthally unstable and radially stable resonators into the annular gain regions of diffusion-cooled CO(2) lasers enhances output beam quality. 3D-diffraction codes involving misalignment and gain parameters aid the numerical computations of resonator modes. Gain length and output power of 1.8 m and 2 kW are achieved using the resonators.

The FEL instability with a warm plasma background is performed for all range of values of plasma and beam densities with unspecified wiggler number of period and strength. The excited plasma mode is responsible for a dramatic increasing of the exponential growth rate of the instability, in comparison with a plasma-free FEL, when the plasma has a very small thermal speed, in comparison with the fixed beam resonant velocity and for small group velocity of the plasma mode in comparison with the radiation group velocity.

A study of walk-off attenuation for Type II Second-Harmonic-Generation (SHG) in KTiOPO4 (KTP), on both weak and strong focusing, reveals that the Gaussian model describes well the optimum strong focusing cases and the saturation length. Optimization is done through the ratio L/Z(sub R). This shows that, for avoiding potential optical damages, one must use the longest crystal so that corresponding beam waist size can be raised.

A chirped pulse amplification (CPA) laser configuration capable of driving a plasma beat wave into saturation before modulation instabilities can grow is reported. The proposal is based on generating a single sub-ps, broad bandwidth pulse (~16 nm) and stretching and filtering to select two wavelength components (separation ~7 nm). The two spectral components are temporally stretched (to [is greater than] 100 ps) and separated (by ~1 ns). The pulses are then amplified sequentially in a single Nd : glass chain to greater than 15 J per pulse. Using a single-pass reflective grating compressor, the pulses are compressed (from 2 to 5 ps) and automatically synchronized. The system is capable of introducing a chirp, such that the compressed pulses can compensate for relativistic detuning of the plasma wave. The optimum laser amplification and recombination configuration for generating a saturated laser-driven beatwave is presented, and options for future work are discussed.

The nine-micrometer hot-band lines of CW CO2 lasers, when subjected to oscillation, reveal 40 lines possessing powers that extend up to 8 watts. These lines serve as a laser radiation source for spectroscopic applications. A heterodyne technique that employs a CO2 laser standard determines the line frequencies essential for line identification.