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We demonstrate the performance of an efficient insertable pulse cleaning module (IPCM) that uses a saturable absorber (SA) pair with a compensating multi-pass amplifier. IPCM consists of a first SA, a grating compressor, a second SA, a stretcher and a compensating Ti:sapphire amplifier. It is implemented with a conventional chirped pulse amplification (CPA) Ti:sapphire laser system, resulting in a double CPA system architecture, and suppresses the amplified spontaneous emission (ASE) level of the pulse pedestal by about three orders of magnitude while preserving the output pulse energy and repetition-rate of the overall laser system. The duration of recompressed cleaned pulses is comparable to that obtained without the cleaning module. The effectiveness of the cleaning module is confirmed in laser-driven proton acceleration experiments. At the 10(9) W/cm2 pedestal level, the surface structure and electrical resistivity of an insulator target (100 nm silicon nitride) are preserved prior to the arrival of the intense ultrashort pulse.

We demonstrate the temporal contrast enhancement in a petawatt-class Ti:sapphire chirped-pulse amplification (CPA) laser system. An extra saturable absorber, introduced downstream after a low-gain optical parametric chirped-pulse amplification (OPCPA) preamplifier, has improved the temporal contrast in the system to 1.4×10(12) on the subnanosecond time scale at 70 TW power level. We have achieved 28 J of uncompressed broadband output energy with this system, indicating the potential for reaching peak powers near 600 TW.

Using a high-contrast (10(10):1) and high-intensity (10(21) W/cm(2)) laser pulse with the duration of 40 fs from an optical parametric chirped-pulse amplification/Ti:sapphire laser, a 40 MeV proton bunch is obtained, which is a record for laser pulse with energy less than 10 J. The efficiency for generation of protons with kinetic energy above 15 MeV is 0.1%.

Kα line emissions from Mo and Ag plates were experimentally studied using clean, ultrahigh-intensity femtosecond laser pulses. The absolute yields of Kα x-rays at 17 keV from Mo and 22 keV from Ag were measured as a function of the laser pulse contrast ratio and irradiation intensity. Significantly enhanced Kα yields were obtained for both Mo and Ag by employing high contrast ratios and irradiances. Conversion efficiencies of 4.28×10⁻⁵/sr for Mo and 4.84×10⁻⁵/sr for Ag, the highest values obtained to date, were demonstrated with contrast ratios in the range 10⁻¹⁰ to 10⁻¹¹.

We have developed a femtosecond high-intensity laser system that combines both Ti:sapphire chirped-pulse amplification (CPA) and optical parametric CPA (OPCPA) techniques and produces more than 30 J broadband output energy, indicating the potential for achieving peak powers in excess of 500 TW. With a cleaned high-energy seeded OPCPA preamplifier as a front end in the system, for the compressed pulse without pumping the final amplifier, we found that the temporal contrast in this system exceeds 10(10) on the subnanosecond time scales, and is near 10(12) on the nanosecond time scale prior to the peak of the main femtosecond pulse. Using diffractive optical elements for beam homogenization of a 100 J level high-energy Nd:glass green pump laser in a Ti:sapphire final amplifier, we have successfully generated broadband high-energy output with a near-perfect top-hat-like intensity distribution.

We report a high-contrast, high-intensity Ti:sapphire chirped-pulse amplification system that incorporates a nonlinear preamplifier based on optical parametric chirped-pulse amplification (OPCPA). By cooling the Ti:sapphire crystal in the final amplifier down to 77 K, the chirped-pulses are amplified to 2.9 J at a 10 Hz repetition rate without a thermal lensing effect. Pulse compression down to 19 fs duration obtained after amplification indicates a peak power of 80 TW. With the OPCPA, the temporal contrast is significantly improved to better than 7x10(-9) in a few picoseconds interval prior to the main laser pulse.

We describe a compact, reliable, high-power, and high-contrast noncollinear optical parametric chirped-pulse amplifier system. With a broadband Ti:sapphire oscillator and grating-based stretching and compression, the chirped pulses are amplified from 0.1 nJ to 122 mJ in type I beta-barium borate optical parametric chirped-pulse amplifiers with a total gain of over 10(9) at 10 Hz repetition rate. Pulse compression down to 19-fs duration achieved after amplification indicates a peak power of 3.2 TW at an average power of 0.62 W. The prepulse contrast is measured to be less than 10(-8) on picosecond time scales.

An algorithm incorporating a stochastic approach is proposed for reducing the computation time of the direct-binary-search algorithm for hologram synthesis. Two variants of this new algorithm are considered for a number of hologram-generation problems. Both variants can reduce the computation time significantly with a very small increase in the reconstruction error on average. The effectiveness of the proposed algorithm is found to improve with the increasing computational complexity of the design problem. Also, the algorithm is able to generate the hologram in a time that is relatively independent of the initial conditions.

Two-dimensional Fourier transform kinoforms can be calculated by use of a discrete Fourier transform. It is well known that the off-axis reconstruction has lower reconstruction error than the on-axis one. Here we make what to our knowledge is a new analysis on the effect of phase quantization in the Fourier domain. We find that the kinoform reconstruction error changes periodically according to the position of the desired image when a large dummy area is added. The error dependence of quantized kinoform reconstruction is simulated on the position of the desired image by use of the iterative dummy area method and the iterative interlacing technique.

There are two kinds of method that utilize the redundancy in kinoform domains for reducing the reconstruction errors of quantized kinoforms. One is the iterative-dummy area (IDA) method, which increases the kinoform size indirectly by the addition of a dummy area to the desired image. The other is the interlacing technique (IT), which increases the kinoform size directly by the interlacing of a number of subkinoforms whose sizes are the same as the desired image. We compare the error reduction of quantized kinoforms between these two methods. Simulation results show that reconstruction errors from the IT method can be reduced further and faster than those from the IDA method when the kinoform size is increased to larger than 4 x 4 times the size of the desired image.

The variation in properties of a fluorocarbon polymer (FCP) film during a drying-curing process is investigated for fabricating FCP-coated silver (FCP/Ag) hollow glass waveguides. A dynamic liquid-phase coating procedure is used. Through the analyses of the loss spectra of hollow waveguides made in various conditions, a relationship between the thickness of the FCP film and the coating velocity is obtained. The optimum fabrication condition is also established for producing FCP/Ag hollow glass waveguides for the mid-IR.

An interlacing technique algorithm is proposed for the synthesis of kinoforms. The conventional iterative methods are quite powerful for optimizing kinoforms, but there is still a large reconstruction error for a quantized kinoform. We suggest the use of a number of subkinoforms interlaced together to synthesize a multikinoform for reconstructing the desired image. The idea of our interlacing technique is to increase the size of a kinoform to reduce the reconstruction error. The first subkinoform is generated from the desired image. Other subkinoforms are generated from the error images between the desired image and the image reconstructed from the previous subkinoforms. A theoretical analysis shows that the reconstruction error will be reduced as the number of subkinoforms is increased. Simulation results show that our interlacing method can reduce the reconstruction error more than do the conventional iterative methods and that the reconstructed image can be improved.

Temperature sensing to as low as 80 K was demonstrated with 1.55-μm fiber Bragg gratings. The gratings were bonded on substrates to increase sensitivity, and a shift of the reflection wavelength was measured. The temperature sensitivity was 0.02 nm/K at 100 K when an aluminum substrate was used and 0.04 nm/K at 100 K when a poly(methyl methacrylate) substrate was used. These values are smaller than those at room temperature because of the nonlinearity of both the thermal expansion and the thermo-optic effect. Extension to the liquid helium temperature is also discussed.

Color shift induced by background color in a nematic liquid crystal display is investigated experimentally. A liquid crystal cell shows a positive dielectric anisotropy and is operated in a tunable birefringence mode. Munsell color chips 5R-, 5G-, 5B-5/6, and N-5 are used as background color. Colorimetric data are shown in the 1976 CIE (L*, a*, b*) color scale. A predict equation based on induction theory is found to apply with fair success to the observations of each of the five observers.

Color contrast in a liquid crystal display using dye dichroism is investigated experimentally. Nematic liquid crystal with a positive dielectric anisotropy is used as the host. Three kinds of merocyanine dye are used as the guest. Optimum solubility of the dye is decided, and its criteria, taking account of the color difference, is established. The color difference is given in the 1976 CIE (L*, a*, b*) color scale. The contrast ratio values show good correlation with observed estimated values, and the validity of the criteria is confirmed.

The theoretical color gamut of a nematic liquid crystal display under ambient illumination is described. The color gamut in the transmission-type of both the tunable-birefringence and guest-host modes is shown by the CIE chromaticity diagram and color solid. Calculation of the color matching between the given chromaticity coordinates and those calculated at the variable lightness of the ambient illumination was executed by the matrix representation method. Calculated data for ambient illumination having the same chromaticity as the reference illumination are in good agreement with the colorimetric data within a tolerable color difference in the 1964 CIE (U*,V*,W*) color scale.

Results of theoretical and experimental studies on the generation of an arbitrary color are presented and compared. The theoretical results were obtained using the matrix representation method. The cell is operated in a tunable birefringence mode with a homogeneous aligned cell. The liquid crystal has a positive dielectric anisotropy. Colorimetric data are in good agreement with the given data within 0.50 CIE Unit color difference in the 1964 CIE (U*,V*,W*) color scale.

The effect of driving waveform, reflective vs backlit transmissive mode, and contrast polarity, on the legibility of a multiplexed twisted nematic (TN) LCD were investigated. The backlit transmissive mode with a white display pattern on dark background (W/B contrast) resulted in superior display legibility, while the reflective mode TN LCD with a dark display pattern on white background (B/W contrast) resulted in the second best legibility. The maximum legibility was obtained at a lower operating voltage for the LCD with W/B contrast compared with the B/W contrast; we believe this can be attributed to the nonlinear response of the human eye.