Masahito Okida

Metal microneedle fabrication using twisted light with spin

Microneedle fabrication on a metal surface based on laser ablation using twisted light with spin was demonstrated, for the first time. The resulting needle showed a height of at least 10 microm above the target surface and a tip diameter of less than 0.3 microm. We also demonstrated the fabrication of a two-dimensional 5 x 6 microneedle array. The needles were uniformly well shaped with an average length and tip diameter of about 10 and 0.5 microm, respectively.

Direct generation of high power Laguerre-Gaussian output from a diode-pumped Nd:YVO 4 1.3-μm bounce laser

We demonstrate direct production of a high power Laguerre-Gaussian mode from a diode-pumped Nd:YVO(4) 1.3-mum bounce amplifier with an asymmetric cavity configuration. A maximum LG output of 7.7 W is obtained.

High repetition rate Q-switching performance in transversely diode-pumped Nd doped mixed gadolinium yttrium vanadate bounce laser.

Up to 700 kHz high repetition active Q-switching was achieved with a pulse-width of < 40 ns by using a diode-side-pumped Nd:Gd_xY_1-xVO₄ bounce amplifier. The average output power of 17.5 W was obtained at a pump power of 41 W.

MW ps pulse generation at sub-MHz repetition rates from a phase conjugate Nd:YVO4 bounce amplifier

We demonstrated high-repetition-rate (sub-MHz) MW pulse generation by combining a picosecond phase conjugate laser system based on a diode-side-pumped Nd:YVO(4) bounce amplifier with a pulse selector based on a RbTiOPO(4) electro-optical modulator. Peak output powers in the range of 2.8-6.8 MW at a pulse repetition frequency range of 0.33-1.0 MHz were achieved at an extraction efficiency of 34-35%.

Optical vortex pumped mid-infrared optical parametric oscillator

The first demonstration of a mid-infrared optical parametric oscillator pumped by 1-μm optical vortex pulses is presented. A 0.5-mJ 2-μm fractional vortex pulse having half-integer topological charge is generated. Using this system, 0.24-mJ vortex pulses with a topological charge of 1 can be created. The topological charges of the mid-infrared vortex pulses are observed by an interferometric technique in combination with second-harmonic frequency conversion.

Power scaling of a picosecond vortex laser based on a stressed Yb-doped fiber amplifier.

Power scaling of a picosecond vortex laser based on a stressed Yb-doped fiber amplifier is analyzed. An output power of 25 W was obtained for 53 W of pumping, with a peak power of 37 kW. Frequency doubling of the vortex output was demonstrated using a nonlinear PPSLT crystal. A second-harmonic output power of up to 1.5 W was measured at a fundamental power of 11.2 W.

Power scaling of a pico-second Nd:YVO 4 master-oscillator power amplifier with a phase-conjugate mirror

We investigated design issues for the power scaling of a pico-second Nd:YVO(4) master-oscillator power amplifier system with a photorefractive phase-conjugate mirror by using standard beam propagation analysis. We also demonstrated a 25 W diffraction-limited pico-second output. A corresponding extraction efficiency of 31 % was achieved.

Sub-100 W picosecond output from a phase-conjugate Nd:YVO 4 bounce amplifier

We demonstrated >80 W picosecond output at a pulse repetition frequency of 100 MHz from a dual Nd:YVO(4) amplifier laser system consisting of a phase-conjugate Nd:YVO(4) bounce amplifier combined with a second diode-side-pumped Nd:YVO(4) bounce amplifier. The output exhibited high quality spatial form with M(2) < 1.8 and a pulse duration (FWHM) of 9.2 ps. A peak power of >7.4 MW with an average power of 78.5 W was also achieved at a pulse repetition frequency of 1.0 MHz.

High power picosecond vortex laser based on a large-mode-area fiber amplifier

The production of pico-second vortex pulses from a stressed large mode-area fiber amplifier is presented, for the first time. 6.8W pico-second output with peak power of ~10kW was obtained at pump power of 29W.

Heat generation in Nd doped vanadate crystals with 1.34 μm laser action

Thermal load in Nd3+ doped vanadate crystals with and without laser action at 1.34 mum is investigated. Excited state absorption contributes significantly to a fractional thermal loading as well as quantum defect.