Time-resolved spectroscopic study of high-pressure self-sustaineddischarge-pumped atomic xenon lasers

To explore the lasing kinetics of UV-preionized, self-sustained discharge-pumped atomic xenon (5d→6p) lasers, the time-resolved spectroscopy of the laser output from the multiline laser resonator is reported. The dilutents used were Ar and He. Increasing Xe concentration shortened the 1.73-μm laser pulse duration and decreased the total (multiline) laser output energy, because increased Xe metastable state population contributes to the increase of the 6p state population (lower laser level) by electron-impact excitation and radiation trapping during discharge pumping. High-excitation-rate pumping resulted in the decrease of the laser output power of 1.73- and 2.63-μm lines. Increasing the total gas pressure leads to high-efficiency operation due to modest-excitation-rate pumping at high pressures     

Effect of xenon on the gas temperature in carbon monoxide lasers

By experimentally measuring the gas temperature of a discharge in CO-He-(Xe) laser gas mixtures it is established that the advantageous effect of the addition of xenon in > 10 percent efficient room temperature lasers is not a gas temperature effect.     

Similarity and scaling in diffusion-cooled RF-excited carbondioxide lasers

The theoretical and experimental study of alpha RF discharges presented in this paper has resulted in the formulation of a set of similarity and scaling laws for diffusion-cooled alpha RF discharge-excited CW waveguide CO₂ lasers. For the first time, the parametric dependencies of the voltage-current-power characteristics of a transverse alpha RF discharge have been investigated over a range of excitation frequencies 100-160 MHz, for gas pressures 40-100 torr and for interelectrode distances 1-3 mm in a typical waveguide CO₂ laser gas mixture (He:N₂Co ₂=3:1:1+5 percent Xe). Relative to dc discharges, the additional scaling law fD=constant is established, and the analysis indicates both high- and low-frequency limits to the operation of practical self-similar laser devices     

Predicting CMOS speed with gate oxide and voltage scaling andinterconnect loading effects

Sub-quarter micron MOSFET's and ring oscillators with 2.5-6 nm physical gate oxide thicknesses have been studied at supply voltages of 1.5-3.3 V. I_dsat can be accurately predicted from a universal mobility model and a current model considering velocity saturation and parasitic series resistance. Gate delay and the optimal gate oxide thickness were modeled and predicted. Optimal gate oxide thicknesses for different interconnect loading are highlighted     

Effects of helium addition to Ar-Xe mixtures in high-pressureatomic-transition xenon lasers

The output energy and spectral distribution of the atomic-transition xenon laser have been investigated with ternary mixtures based on Ar-Xe to explore kinetic issues and to enhance particular lines of the xenon laser pumped by an e-beam and e-beam sustained discharge. Addition of helium into the Ar-Xe mixtures increased the 2.03 μm line energy by a factor of 3-5 while suppressing the 1.73-μm line even during single-line oscillation. The maximum output energy obtained at 2.03 μm was 1.2 J/L and the intrinsic efficiency was ~1%. Effects of neon or krypton addition have also been studied with e-beam sustained discharge pumping     

Periodic resonators for average-power scaling of stable-resonatorsolid-state lasers

Thermal lensing of solid-state laser gain media causes the resonator-mode parameters to vary with pump power. For a single-rod laser system, this effect limits the output-power range for stable laser operation. For multirod laser systems, the power range for stable operation can be increased beyond the limit of single-rod resonators by placing the rods in a periodic resonator structure     

Power scaling in passively mode-locked large-mode area fiber lasers

We report on a novel approach toward generating high peak powers in passively mode-locked fiber lasers. By appropriate design the fiber's mode area is increased by a factor of ~30 compared to standard fiber. This increased area effectively decreases the nonlinearity thus, increasing the power necessary to form stable soliton-like pulses     

Power scaling of fibre lasers with all-fibre interferometric cavity

Two interferometric laser cavities are proposed for efficient combining of two fibre lasers. A 3 dB gain in power by coherent coupling of two identical erbium-doped fibre lasers is demonstrated. Scaling in power is envisaged through cascading of a coherent combination of elementary lasers     

Observations of xenon gas-treated barley cells in solution by atomic force microscopy

Barley cells cut from a sprout were exposed to either air or high-pressure xenon gas for 3 days and the surface of those cells was observed by atomic force microscopy (AFM) to examine the effect of the gas treatment. This method enabled the direct observation of the fresh surface of the barley cells in solution at high resolution. The cuticle layer was preserved on the primary cell wall of 0.48 MPa xenon gas-treated barley cells, while air-treated barley cells lost the cuticle layer from the primary cell wall. These findings indicate that the high-pressure xenon gas treatment is effective to preserve the cuticle layer attached to the primary cell wall. AFM is a powerful tool for the observation of the surface structure of living plant cells in solution.     

Area scaling in N2 waveguide lasers

The area scaling in a nitrogen (N₂: 337.1 nm) laser excited by the similar longitudinal discharges in single- and multichannel laser structures has been experimentally studied. The results demonstrate the capability of the area scaling method for increasing the average power and pulse-repetition frequency (PRF) of the laser. The variation of the laser output with the channel area and the effects of similar discharges are analyzed     

Saturation effects in semiconductor lasers

This paper describes a theory for a semiconductor active medium interacting with a laser field. In a semiconductor laser, the charge carrier transitions are inhomogenously broadened, and electron-electron and electron-phonon collisions tend to dephase the laser transitions and maintain thermal equilibrium among the carriers. These properties cause semiconductor lasers to frequency tune as though they are inhomogeneously broadened and to saturate as though they are homogeneously broadened. A theory that contains these two aspects of semiconductor laser behavior is presented. From it, we are able to calculate the loaded gain, efficiency, intensity, and carrier-induced refractive index of a semiconductor active medium.     

Finite-temperature effects in free-electron lasers

The effect of energy spread on the gain of a dense-beam free-electron laser amplifier is analyzed. The formalism includes collective effects and allows for the use of an arbitrary distribution function. The dispersion relation is solved numerically. Besides broadening of the spectrum and decrease in gain, lowering of the central emission frequency with energy spread is observed. An initial-value problem is formulated and numerically solved, with power computed as a function of distance. The relative contributions of the different modes when temperature changes are analyzed. In particular, the competing effects of a decrease in coupling loss with temperature together with Landau damping are investigated.     

掺杂石英玻璃管脉冲氙灯及滤光套管在激光器中的应用

采用合适厚度,掺杂合适浓度的铈、铕等稀土元素的石英玻璃管制作的脉冲氙灯和滤光套管,其3500埃以下的紫外辐射基本消除,因而在固体激光器中能替代滤光溶液和黄色玻璃滤光套管,防止工作物质着色.比较了不同滤光材料的滤光特性及其在重复频率钇铝石榴石激光器中的激光效率.在Nd:YAG及钕玻璃激光器中,使用掺杂石英玻璃后,可使激光器效率提高25～100%.     

Average-power scaling of self-heated Sr+ afterglowrecombination lasers

The performance of a large-bore (25-mm) self-heated Sr⁺ (430.5-nm) recombination laser with longitudinal excitation is discussed in relation to the prospects for scaling average output power to the 5-10-W regime. Average-power scaling is found to be limited in large-bore laser tubes by slow interpulse thermal relaxation in the laser gas mixture with strong radial gradients in species' densities and temperatures at only modest pulse repetition frequencies, leading to premature termination of the population inversion on the tube axis. Proposals for circumventing these limitations in order to permit generation of multiwatt average laser output power at 430.5 nm from Sr ⁺ are discussed     

Impact of electron collision mixing on the delay times of anelectron beam excited atomic xenon laser

The atomic xenon (5d→6p) infrared laser has been experimentally and theoretically investigated using a short-pulse (30-ns), high-power (1-10-MW/cm³) coaxial electron beam excitation source. In most cases, laser oscillation is not observed during the e-beam current pulse. Laser pulses of hundreds of nanoseconds duration are subsequently obtained, however, with oscillation beginning 60-800 ns after the current pulse terminates. Results from a computer model for the xenon laser reproduce the experimental values and show that oscillation begins when the fractional electron density decays below a critical value of ≈0.2-0.8×10 ⁶. These results lend credence to the proposal that electron collision mixing of the laser levels limits the maximum value of specific power deposition that can be used to excite the atomic xenon laser efficiently on a quasi-CW basis     

High-power operation and scaling behavior of CW optically pumped FIR waveguide lasers

High-power far infrared (FIR) laser operation at the 10- 100 mW level is described for wavelengths throughout the 40 μm-1.22 mm spectral region. These data correspond to order of magnitude improvements in converting CO2laser energy into FIR laser output. This improved FIR laser performance is attributed to a waveguide laser geometry with reduced losses for the CO2pump and also to a new method of output coupling. The basic design concept of the efficient laser resonator is discussed as well as the prospect for further increases in laser performance through improved efficiency and sealing.     

Thermal effects in kilowatt fiber lasers

Thermal effects and their influences on kilowatt ytterbium-doped double-clad (YDDC) fiber lasers are studied through numerical modeling. Solutions to suppress the thermal effects in the YDDC fiber lasers under bidirectional end pump and distributed pump are presented and compared for the first time. It is shown that lower operating temperature and more uniform heat dissipation in fibers can be obtained by optimizing the arrangement of pump powers, pump absorption coefficients, and fiber lengths.     

Coupled-cavity effects in FM semiconductor lasers

Numerical simulations of frequency modulated (FM) external cavity semiconductor lasers have been performed and a range of dynamic and spectral phenomena observed. It is shown that FM lasing action can be suppressed due to changes in the FM modulation frequency. Coupled cavity effects are seen to be significant in the development of a broad spectral emission associated with experimentally observed coherence collapse in such a configuration     

Power scaling of diode-pumped Nd:YVO/sub 4/ lasers

The evaluation of pump capability and scaling the output power of Nd:YVO/sub 4/ (vanadate) lasers are presented in this paper. Taking into account thermal fracture limitation and fundamental mode operation, systematic investigations of vanadate crystals have been conducted in an effort to scale the output power of diode-pumped lasers to higher levels. Based on the limitation of pump power, the input versus output power and beam propagation factor of vanadate lasers are optimized with knowledge of the thermal lensing effect and maximum pump power. The theoretical analyzes provide a good prediction for the output power of diode-pumped Nd:YVO/sub 4/ lasers, which is in agreement with the experiment. A practical example of a single-end-pumped vanadate laser is demonstrated with continuous-wave output powers of 9.8 W in the TEM/sub oo/ mode and 12.4 W in multimode.