System and fabrication techniques for a solid-state random-access mass memory

This paper describes a development program aimed at improving processing speeds by providing data processing systems with random-access memories approaching the speed of ferrite-core matrix memories, but at a cost that economically permits of mass-memory capacities. Compatible system and fabrication techniques were devised to reach the low cost objective. The paper details the system and fabrication techniques, and in addition to demonstrating low memory cost, describes small power, weight, and size characteristics that might be important in special applications.     

Spatial filters for high-peak-power multistage laser amplifiers

We describe spatial filters used in a Nd:glass laser with an output pulse energy up to 300 J and a pulse duration of 1 ns. This laser is designed for pumping of a chirped-pulse optical parametric amplifier. We present data required to choose the shape and diameter of a spatial filter lens, taking into account aberrations caused by spherical surfaces. Calculation of the optimal pinhole diameter is presented. Design features of the spatial filters and the procedure of their alignment are discussed in detail.     

All solid-state Cr:LiSAF laser

Many kinds of experiments about all solid-state Cr:LiSAF lasers have been reported. A tunable all solid-state cw laser having tunability over more than 100 nm was developed by using the spectrum selection self-injection locking (SSSIL) method in 1992. The authors realize tunable picosecond radiation from an all solid-state laser with 146-200 ps pulses in an 88 nm range. Also, 70 fs pulse generation was achieved using a Kerr-lens mode-locking pumped with an Ar⁺ laser     

Epoxy matrix for solid-state dye laser applications

The preparation and performance of an epoxy-based matrix impregnated with Pyrromethene 580 for solid-state dye laser applications are discussed. The matrix proved to be stable and efficient as a laser medium when pumped by a frequency-doubled, Q-switched Nd:YAG laser with a 10-ns pulse width. Stability measurements were performed on a 1-mm-thick epoxy sample, doped with Pyrromethene 580 at a concentration of 4 x 10(-3) M. When the sample was pumped at millijoule energy levels, the stability was measured to be ~55,000 pulses from a single spot on the sample before the power dropped by a factor of half.     

High-power 980-nm pump laser modules for erbium-doped fiber amplifiers

High-power fiber-coupled pump modules with an emission wavelength of 980 nm and output powers in excess of 200 mW, as measured at the fiber end, have been fabricated. Laser-to-fiber coupling efficiencies in excess of 77% are observed to be in excellent agreement with a mathematical model. Also, the output power stability of these modules has been monitored during severe temperature cycling, and the relative power variation was less than 4% for all the tested modules.     

Capacity planning of serial and batch machines with capability constraints for wafer fabrication plants

Capacity planning is crucial to the investment and performance of wafer fabs. This research proposes a practical procedure to calculate the required number of machines with serial and batch processing characteristics, respectively. Several formulae are first presented. Five heuristic algorithms are then proposed to determine the lower bound, the upper bound, and the near-optimal of the number of machines of the type with capability constraint. Data from real foundry fabs are used in a case study to determine the required number of 64 types of equipment and to evaluate the performance of the proposed procedure. The algorithm using the best ratio of production efficiency and equipment cost to select the machine type with capability constraint results in the least required number of machines, the highest machine utilisation, and the lowest equipment investment. An AutoSched AP simulation model is used to evaluate if a wafer fab using the calculated number of machines of each type can result in a preset monthly output rate. Simulation results indicate that the proposed procedure can quickly and accurately calculate the required number of machines leading to the required monthly production target. Fab managers can use this tool to conduct what-if analysis for equipment investment alternatives.     

Multiple-prism grating solid-state dye laser oscillator: optimized architecture

A multiple-prism grating solid-state dye laser oscillator was demonstrated with its grating, deployed in a Littrow configuration, under total illumination at reduced intracavity beam expansion. This compact cavity yields laser linewidths in the 350-MHz range and smooth temporal pulses with a near-Gaussian profile.     

Stable doped hybrid sol-gel materials for solid-state dye laser

Laser effects have been obtained with dye-doped hybrid xerogel samples prepared several years ago and stored in different "classical" conditions. Firstly, using the same configuration of the laser cavity as was used 4-5 years ago, we have obtained almost identical laser performances, and slope conversion efficiencies were measured up to 80% and operational lifetimes, with 1-mJ initial output energy and 10-Hz repetition rate of several hundred thousand pulses obtained. Secondly, we have introduced the new pyrromethene 605 dye into a hybrid xerogel matrix and obtained good laser performances similar to the rest of the pyrromethene family.     

大功率半导体激光器全固态风冷散热系统

设计并制作了一种全固态大功率半导体激光阵列恒温散热系统。它利用半导体制冷器对大功率半导体激光阵列吸热,然后经由风冷散热。经测试,单bar激光阵列连续输出功率达到15.28W,双 bar 阵列输出达 27.8W 时,全部达到风冷散热控温精度±0.1 ;当环境温度达到 45 时,仍然能够保证激光阵列的正常使用。     

Dynamic model of multipass ultrashort-pulse laser amplifiers and its application

We developed a dynamic model for evaluating the gain and amplified spontaneous emission of multipass ultrashort-pulse laser amplifiers. This model takes into account the time dependence of the population inversion that is due to the time-varying pump power and the evolution of the amplified spontaneous emission. For gain media of a short upper-state lifetime, a time-dependent analysis is essential for the model to extend beyond order-of-magnitude estimation. We verified the model with a femtosecond dye laser amplifier. The calculated output energy is accurate to within +/-5% of the experimental data. We utilized this model to optimize the conversion efficiency of the dye laser amplifier under low-energy pumping. An efficiency of 2.3% is achieved with an optimal pump energy of only 4 muJ.     

Excimer laser micromachining for rapid fabrication of diffractive optical elements

We demonstrate the fabrication of binary, multilevel, and blazed diffractive structures by a fast and flexible direct-write process by using an excimer-laser-based tabletop micromachining workstation with an integrated optical surface profiler.     

Maskless multiple-beam laser lithography for large-area nanostructure/microstructure fabrication

This paper reports a maskless multiple-beam laser lithography technique for large-area nanostructure/microstructure fabrication. This lithography technique can flexibly generate arbitrary nanostructures/microstructures over a large area at a high speed. The feature size of the nanostructures/microstructures can be controlled by exposure time and moving speed of the nanostage. Functional predesigned patterns, including split-ring resonator metamaterials for terahertz waves, can be obtained. More complicated structures can be made by single- and double-exposure schemes to make hybrid nanostructures/microstructures and tune surface plasmonic resonance properties. Meanwhile, microstructures with large height to lateral dimension ratios (2.5D microstructures) fabricated on silicon substrates can be used as mold tools for soft lithography. This technology shows its unique capacity to create various nanostructures/microstructures for extensive applications.     

Noise of He-Cd laser and its suppression

Linear relations have been observed between the reciprocal of the noise ratio and the reciprocal of the output power of the He-Cd laser as well as between the noise ratio and the net gain within the laser cavity. By a feedback method with an acoustooptic modulator in the laser cavity at the Brewster angle for low optical loss, a stable laser with high power output and low noise has been obtained. The noise ratio and the output power are 0.8% and 33 mW, respectively, at 4416 A     

Carbon dioxide laser fabrication of fused-fiber couplers and tapers

We report the development of a fiber taper and fused-fiber coupler fabrication rig that uses a scanning, focused, CO(2) laser beam as the heat source. As a result of the pointlike heat source and the versatility associated with scanning, tapers of any transition shape and uniform taper waist can be produced. Tapers with both a linear shape and an exponential transition shape were measured. The taper waist uniformity was measured and shown to be better than +/-1.2%. The rig was also used to make fused-fiber couplers. Couplers with excess loss below -0.1 dB were routinely produced.     

Preparation, electrochemical, photoelectrochemical and solid-state characteristics of indium-incorporated TiO2 thin films for solar cell fabrication

Titanium dioxide thin films were prepared by the spray-pyrolysis technique, which permitted the convenient incorporation of foreign materials into the oxide matrix during its formation. Pure and indium-incorporated films of different thickness were prepared. The presence of indium in the TiO₂ film affected the characteristics of that material. The effect of incorporation was reflected in the improvement of the properties of the n-Si/oxide heterojunction. The prepared n-Si/TiO₂-In solar cells exhibited better fill factor and solar conversion efficiency than those with pure TiO₂. The electrochemical properties of the prepared oxide films revealed that the charge transfer step at the oxide/electrolyte interface leads to the deterioration in quality of the photoanode. The improved characteristics of the heterojunction n-SiO₂/oxide in the presence of indium incorporation offset the limitation of the photoelectrochemical cell due to the slow charge transfer step at the TiO₂/electrolyte junction. This revised version was published online in November 2006 with corrections to the Cover Date.     

Study of absorption and reflection in solid-state random laser media

Comparing the absorption spectrum of a single-crystalline material and the reflection spectrum of its powder, we have derived a simple empirical formula for the reflection coefficient of absorbing powder. The proposed equation, which slightly resembles the Lambert-Beer law for transmission, does not correspond to the equation derived in the approximation of a simple one-dimensional diffusion model.     

Equivalent optical model for lenslike gain medium in continuously single-end-pumped solid-state laser

In order to conveniently and precisely estimate the spot size of laser modes in continuously single-end-pumped solid-state lasers, a ray matrix for the thermal-induced lenslike medium with exponential heat distribution along the axial direction is, for the first time to our best knowledge, derived under assumptions of only radial heat flow and uniform pump spot size. An equivalent optical model is also developed and especially modified for a lenslike gain medium in a continuously single-end-pumped solid-state laser. The result is verified by discussing how it fits the practical cases much better than the previous simplified model and by numerical simulation in a practice problem. This work is especially important in cases with a relatively long gain medium, which has been used more and more frequently in recent years.