RMS error analysis of spatial uniformity and energy stability of the laser beam in second harmonic generation.

The coupling of the energy stability and spatial uniformity of the laser beam before and after second harmonic generation (SHG) was analyzed. SHG experiments were performed using a Nd:YAG nanosecond laser and LBO crystals, and images, pulse shapes, and energies were measured. The relationship between energy stability and spatial uniformity uses a formula derived from the previous study to analyze changes in energy stability and spatial uniformity of the input beam and converted beam.

Simultaneous Measurement of Group Refractive Index Dispersion and Thickness of Fused Silica Using a Scanning White Light Interferometer.

In this study, we simultaneously measured the group refractive index dispersion and thickness of fused silica using a scanning white light interferometer on a spectral range from 800 to 1050 nm. A delay error correction was performed using a He-Ne laser. The accuracy of the measured group refractive index dispersion of fused silica, when compared to the temperature-dependent Sellmeier equation, is within 4 × 10.

Spatio-temporal coupling of RMS errors in laser amplification.

We developed a theoretical model for the relationship between the input and amplified laser beams of energy stability and spatial uniformity in the amplification process. 10 Hz, 8 ns, 1064 nm Nd:YAG Q-switched resonator with Nd:YAG main amplifier was employed for the experiment. The theoretical model simulation and Frantz-Nodvik simulation were performed by utilizing the obtained beam image, acquired energy from the experiment, and stored fluence from the gain medium.

Performance of zoom homogenizer to control the size of illumination field.

We performed an illumination simulation, wave-optical simulation, and experiment on a zoom homogenizer and conventional beam homogenizer. The wave-optical simulation was performed for each lenslet using the shifted angular spectrum method for effective memory use. In the experiment, the parameters of the zoom homogenizer and beam homogenizer at all zoom positions were set using a system matrix.

Jones calculus modeling and analysis of the thermal distortion in a Ti:sapphire laser amplifier: erratum.

Equations 41-44 in our paper [ Opt. Express26, 14362 (2016)] contain errors. We correct the equations in this erratum.

Design of square-shaped beam homogenizer for petawatt-class Ti:sapphire amplifier.

We have designed a square-shaped beam homogenizer using a lens array for pumping a petawatt-class Ti:sapphire amplifier. The designed beam homogenizer generated a flat-top uniform square pump beam with 5.1% of edge steepness and 2.

Numerical extension of Frantz-Nodvik equation for double-pass amplifiers with pulse overlap.

We developed a new numerical simulation method to calculate the amplification of arbitrary laser pulses in double-pass amplifiers in which two polarization-orthogonal pulses inside the gain medium overlap. The proposed method agrees very well with the experimental results given in this work for the pulse energy and temporal shape.

Jones calculus modeling and analysis of the thermal distortion in a Ti:sapphire laser amplifier.

The mathematical modeling of an anisotropic Ti:sapphire crystal with a significant thermal load is performed. The model is expressed by the differential Jones matrix. A thermally induced distortion in the chirped-pulse amplification process is shown by the solution of the differential Jones matrix.

Transition of proton energy scaling using an ultrathin target irradiated by linearly polarized femtosecond laser pulses.

Particle acceleration using ultraintense, ultrashort laser pulses is one of the most attractive topics in relativistic laser-plasma research. We report proton and/or ion acceleration in the intensity range of 5×10(19) to 3.3×10(20) W/cm2 by irradiating linearly polarized, 30-fs laser pulses on 10-to 100-nm-thick polymer targets.

Enhancement of electron energy to the multi-GeV regime by a dual-stage laser-wakefield accelerator pumped by petawatt laser pulses.

Laser-wakefield acceleration offers the promise of a compact electron accelerator for generating a multi-GeV electron beam using the huge field gradient induced by an intense laser pulse, compared to conventional rf accelerators. However, the energy and quality of the electron beam from the laser-wakefield accelerator have been limited by the power of the driving laser pulses and interaction properties in the target medium. Recent progress in laser technology has resulted in the realization of a petawatt (PW) femtosecond laser, which offers new capabilities for research on laser-wakefield acceleration.

Relativistic frequency upshift to the extreme ultraviolet regime using self-induced oscillatory flying mirrors.

Coherent short-wavelength radiation from laser-plasma interactions is of increasing interest in disciplines including ultrafast biomolecular imaging and attosecond physics. Using solid targets instead of atomic gases could enable the generation of coherent extreme ultraviolet radiation with higher energy and more energetic photons. Here we present the generation of extreme ultraviolet radiation through coherent high-harmonic generation from self-induced oscillatory flying mirrors--a new-generation mechanism established in a long underdense plasma on a solid target.

Single-pulse coherent diffraction imaging using soft x-ray laser.

We report a coherent diffraction imaging (CDI) using a single 8 ps soft x-ray laser pulse at a wavelength of 13.9 nm. The soft x-ray pulse was generated by a laboratory-scale intense pumping laser providing coherent x-ray pulses up to the level of 10(11) photons/pulse.

Generation of high-contrast, 30 fs, 1.5 PW laser pulses from chirped-pulse amplification Ti:sapphire laser.

High-contrast, 30 fs, 1.5 PW laser pulses are generated from a chirped-pulse amplification (CPA) Ti:sapphire laser system at 0.1 Hz repetition rate.

0.1 Hz 1.0 PW Ti:sapphire laser.

We report on the generation of 1.0 PW, 30 fs laser pulses at a 0.1 Hz repetition rate from a chirped-pulse amplification Ti:sapphire laser system.

Long-term carrier-envelope-phase stabilization of a femtosecond laser by the direct locking method.

We have developed a practical solution to implement the direct locking method for the carrier-envelope phase (CEP) stabilization of femtosecond laser pulses and achieved 24-hour CEP stabilization without realignment of any optical components. The direct locking method realizes the CEP stabilization in the time domain by directly quenching the beat signal from an f-to-2f interferometer and, thereby, locking every pulse to a same CEP. We have accomplished the long-term CEP stabilization using commercially available standard feedback electronics, and maintained the CEP stabilization with low jitter without using any frequency-analyzing components, greatly facilitating the accessibility of the CEP stabilization.

Precise and long-term stabilization of the carrier-envelope phase of femtosecond laser pulses using an enhanced direct locking technique.

We demonstrate a long-term operation with reduced phase noise in the carrier-envelope-phase (CEP) stabilization process by employing a double feedback loop and an improved signal detection in the direct locking technique [Opt. Express 13, 2969 (2005)]. A homodyne balanced detection method is employed for efficiently suppressing the dc noise in the f-2f beat signal, which is converted into the CEP noise in the direct locking loop working at around zero carrier-envelope offset frequency (f(ceo)).

Stabilization and control of the carrier-envelope phase of high-power femtosecond laser pulses using the direct locking technique.

We have stabilized and electronically controlled the carrier-envelope phase (CEP) of high-power femtosecond laser pulses, generated in a grating-based chirped-pulse amplification kHz Ti:sapphire laser, using the direct locking technique [Opt. Express 13, 2969 (2005)] combined with a slow feedback loop. An f-2f spectral interferometer has shown the CEP stabilities of 1.

Tunable Q-switched erbium-doped fiber laser based on digital micro-mirror array.

We propose and demonstrate a tunable Q-switched erbium doped fiber laser with a digitally controlled micro-mirror array device. The tunable and pulsed output of the laser was achieved by the pixelated spatial modulation of the micro-mirror array. The wavelength tuning from 1530 nm to 1555 nm was shown with wavelength selectivity of ~0.

100-kHz high-power femtosecond Ti:sapphire laser based on downchirped regenerative amplification.

We have generated femtosecond pulses with a peak power as high as 0.7 GW at the repetition rate of 100 kHz from a downchirped-pulse amplification (DPA) Ti:sapphire laser. For the high-energy amplification with high repetition rate, we employ a regenerative amplifier, acousto-optically switched and pumped by a Q-switched green laser.