Generation and compression of an intense infrared white light continuum in YAG irradiated by picosecond pulses.

An intense white light (WL) continuum from 1600 to 2400 nm is generated in a 20-mm-long YAG irradiated by 1-ps, 1030-nm pulses. Long filamentation formed in the YAG is proven to be responsible for the enhancement of the longer-wavelength spectral part of the WL. The WL is compressed down to 24.

Gyro-Sensor-Based Vibration Control for Dynamic Humanoid-Robot Walking on Inclined Surfaces.

An efficient motor-control system for stable walking of the lightweight humanoid robot KONDO KHR-3HV on inclined surfaces is investigated. The motor-control system is based on the angular velocity of the pitch motion of the robot, which is detected by a gyro sensor attached to the robot torso and referred to as the angular-pitch velocity. The robot gait is analyzed for different downslopes with and without the motor-feedback control.

Optical parametric oscillator pumped by a 100-kHz burst-mode Yb-doped fiber laser.

We demonstrate an optical parametric oscillator pumped at a repetition rate of 100 kHz by a burst-mode Yb-doped fiber laser. Pulse energies of 1.5 µJ were generated with five 4.

Sub-picosecond regenerative amplifier of Yb-doped Y(2)O(3) ceramic thin disk.

We have developed a 1 kHz regenerative amplifier using an Yb:Y(2)O(3) ceramic thin disk as the gain medium. Furthermore, the thermal conductivity and heat generation property of Yb:Y(2)O(3) ceramic were investigated. In the developed regenerative amplifier, a laser beam is bounced off the thin disk six times in each round trip.

Contact grating device with Fabry-Perot resonator for effective terahertz light generation.

A novel design for a contact grating device with an incorporated Fabry-Perot resonator is proposed for high-power terahertz (THz) light generation. We deposited a multilayer consisting of Ta(2)O(5) and Al(2)O(3) on a magnesium-doped stoichiometric LiNbO(3) substrate and fabricated grating grooves on the outermost layer. The multilayer was designed such that conditions for a Fabry-Perot resonator were satisfied for light diffracted by the grating.

Yb:YAG thin-disk chirped pulse amplification laser system for intense terahertz pulse generation.

We have developed a 1 kHz repetition picosecond laser system dedicated for intense terahertz (THz) pulse generation. The system comprises a chirped pulse amplification laser equipped with a Yb:YAG thin-disk amplifier. At room temperature, the Yb:YAG thin-disk regenerative amplifier provides pulses having energy of over 10 mJ and spectral bandwidth of 1.

Experimental verification of femtosecond laser ablation schemes by time-resolved soft x-ray reflective imaging.

Pump and probe reflective imaging using a soft x-ray laser probe was applied to the observation of the early stage of femtosecond laser ablation process on platinum. In strongly excited area, drastic and fast reflectivity drop was observed. In moderately excited area, the decay of the reflectivity is slower than that in the strongly excited area, and the reflectivity reaches its minimum at t = 160 ps.

Laser ceramic materials for subpicosecond solid-state lasers using Nd3+-doped mixed scandium garnets.

We have successfully developed and demonstrated broadband emission Nd-doped mixed scandium garnets based on laser ceramic technology. The inhomogeneous broadening of Nd(3+) fluorescence lines results in a bandwidth above 5 nm that is significantly broader than that for Nd:YAG and enables subpicosecond mode-locked pulse durations. We have also found the emission cross section of 7.

Single-shot picosecond interferometry with one-nanometer resolution for dynamical surface morphology using a soft X-ray laser.

Using highly coherent radiation at a wavelength of 13.9 nm from a Ag-plasma soft X-ray laser, we constructed a pump-and-probe interferometer based on a double Lloyd's mirror system. The spatial resolutions are evaluated with a test pattern, showing 1.

High-spatiotemporal-quality petawatt-class laser system.

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.

A quantitative measure for discriminating between self and non-self antigens in immune response.

We present a new theory of how lymphocyte-antigen interaction is governed. We present 'chronicity', a quantitative record of previous lymphocyte-antigen interactions, which is used to regulate lymphocyte behavior. When the chronicity of a lymphocyte increases with the interaction and gets beyond the lower threshold, the lymphocyte can proliferate.

Demonstration of a highly coherent 13.9 nm x-ray laser from a silver tape target.

A highly coherent 13.9 nm x-ray laser (XRL) is generated under an oscillator-amplifier configuration using a new tape target system and a driver laser system with a 0.1 Hz repetition rate.

Observation of a plasma waveguide in a preformed plasma pumped by double-pulse laser irradiation for the efficient soft x-ray amplification.

A molybdenum slab target was irradiated by double pulses of a line-focused chirped-pulse-amplification Nd:glass laser. A probe beam was injected in the plasma in the longitudinal direction, and we found that the probe beam was guided in the plasma with the plasma length of up to 4.3 mm at the time of 0.

Development of a chirped pulse amplification laser with zigzag slab Nd:glass amplifiers dedicated to x-ray laser research.

A chirped pulse amplification laser with zigzag slab Nd:glass amplifiers dedicated to x-ray laser research is described. The laser provides a 1.6 ps duration pulse with approximately 7 J energy at a repetition rate of 0.

Population kinetics on K alpha lines of partially ionized Cl atoms.

A population kinetics code was developed to analyze K alpha emission from partially ionized chlorine atoms in hydrocarbon plasmas. Atomic processes are solved under collisional-radiative equilibrium for two-temperature plasmas. It is shown that the fast electrons dominantly contribute to ionize the K-shell bound electrons (i.