Kenji Furuki

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.

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.

Adjustable dispersion-slope compensator using entirely thin-film coupled-cavity allpass filters in a multi-reflection parallel configuration

A novel multi-reflection device composed of two coupled-cavity filters in a parallel configuration is reported. The device provides adjustable dispersion slope between -0.9 and -16.5 ps/sup 3/ over a bandwidth of 3 nm.

Tunable mid-infrared (6.3–12 μm)optical vortex pulse generation

We demonstrated widely tunable mid-infrared (6.3-12 μm) optical vortex pulse generation from a ZGP difference frequency generator pumped by a 2 μm optical vortex laser with a cascaded KTP geometry. The mid-infrared vortex output carried the same topological charge as that of the 1 μm pump output without any destruction. A pulse energy of >135 μJ was obtained in the wavelength region of 6.3-7.0 μm.

Picosecond master-oscillator, power-amplifier system based on a mixed vanadate phase conjugate bounce amplifier

We demonstrate a high average power approximately 4 ps output from a phase conjugate laser system based on a diode-side-pumped Nd:Gd(0.6)Y(0.4)VO(4) bounce amplifier. An average output power of 16.2 W with a peak power of 210 kW was achieved. A corresponding extraction efficiency of 23% was measured.

Ultracompact Gain Block with Bi2O3-Based Erbium-Doped Fiber

An ultracompact gain block with Bi2O3-based erbium-doped fiber (Bi-EDF) is presented. The ultracompact gain block includes two pump LDs, two isolators, a photodiode, dichromatic mirrors and a Bi-EDF 23 cm long in the amplifier package with a size of only 45×43×10 mm. We can obtain a net gain of 25 dB and output power of 10 dBm at 1560 nm in the C-band region.

Low nonlinearity bismuth oxide-based erbium-doped fiber amplifiers for short pulse amplification

We compare the nonlinearity tolerance of a conventional silica-based fiber amplifier and a bismuth-based fiber amplifier. The bismuth-based amplifier has shown superior performance over the conventional amplifier for short pulse amplification.

Tunable mid-infrared (6.3-7.8 μm) optical vortex laser

We demonstrate a tunable mid-infrared (6.3-7.8-μm) vortex laser formed of a 1-μm vortex pumped optical parametric oscillator and a difference frequency generator. Maximum output energy of 160-μJ was obtained at a wavelength of 6.5-μm.

Pico-second vortex output from a large-mode area fiber amplifier

High intense optical vortex pulses, exhibiting an orbital angular momentum, have potentially to be applied in various fields, such as optical tweezers, laser micro-fabrication, and laser acceleration. Several researchers have successfully demonstrated ways to produce vortex outputs through mode-conversion in an optical fiber, including a stressed optical fiber as well as a hollow fiber. However, they used mostly a passive fiber as well as a continuous-wave laser. In this paper, we present the production of intense pico-second vortex pulses by selectively coupling a pico-second master laser into LP11 modes in a stressed large mode-area fiber amplifier with an off-axis fiber injection method, for the first time.