Hideki Ishizuki

High-energy quasi-phase-matched optical parametric oscillation in a periodically poled MgO:LiNbO 3 device with a 5?mm×5?mm aperture

Fabrication of a 5 mm thick periodically poled MgO-doped LiNbO3 device with a 32.1 microm period for mid-infrared generation was demonstrated. The periodic structure was evaluated by measurement of second-harmonic generation with the d31 coefficient. Optical parametric oscillation using this device with an uncoated 5 mm x 5 mm aperture and a 36 mm effective length realized a high-energy output of 77 mJ for both signal (wavelength 1.83 microm) and idler (2.54 microm) waves with a 72% slope efficiency at 110 mJ pumping of a Q-switched Nd:YAG laser with a 12 ns pulse duration.

Periodical poling characteristics of congruent MgO:LiNbO3 crystals at elevated temperature

A structure for quasi-phase matching of large cross section using 5 mol % MgO-doped LiNbO3 (MgO:LN) crystal for high-power wavelength conversion was realized. We have found that the coercive field to invert polarization of the crystal reduces drastically with elevated temperature. The coercive field reduces to 1.2 kV/mm at 250 °C, which is about 1/4 compared with that for MgO:LN at room temperature (RT) and about 1/17 of that for LN at RT. 3 mm thick periodically poled MgO:LN has been fabricated with 30 μm period.

Generation of carrier-envelope-phase-stable 2-cycle 740-μJ pulses at 2.1-μm carrier wavelength

We produce carrier-envelope-phase-stable 15.7-fs (2-cycle) 740-μJ pulses at the 2.1-μm carrier wavelength, from a three-stage optical parametric chirped-pulse amplifier system, pumped by an optically synchronized 49-ps 11-mJ Nd:YLF laser. A novel seed pulse spectral shaping method is used to ascertain the true amplified seed energy and the parametric superfluorescence levels.

Carrier-envelope-phase-stable, 1.2 mJ, 1.5 cycle laser pulses at 2.1 μm

We produce 1.5 cycle (10.5 fs), 1.2 mJ, 3 kHz carrier-envelope-phase-stable pulses at 2.1 μm carrier wavelength, from a three-stage optical parametric chirped-pulse amplifier system, pumped by an optically synchronized 1.6 ps Yb:YAG thin disk laser. A chirped periodically poled lithium niobate crystal is used to generate the ultrabroad spectrum needed for a 1.5 cycle pulse through difference frequency mixing of spectrally broadened pulse from a Ti:sapphire amplifier. It will be an ideal tool for producing isolated attosecond pulses with high photon energies.

High-energy, narrow-bandwidth periodically poled Mg-doped LiNbO3 optical parametric oscillator with a volume Bragg grating

We have demonstrated a simple, high-energy, narrow spectral bandwidth optical parametric oscillator (OPO) by use of a large aperture periodically poled Mg-doped LiNbO3 device with a volume Bragg grating (VBG). A free-running degenerate OPO pumped by a Q-switched 1.064 μm Nd:YAG laser exhibits maximum output pulse energy of 110 mJ with high slope efficiency of 75% around room temperature. Broad spectral bandwidth (Δλ~100 nm) around the degeneracy wavelength was suppressed by using a VBG as an output coupler. Up to 61 mJ of the output pulse energy with narrowed spectral bandwidth of less than 1.4 nm was obtained at the degeneracy wavelength of 2.128 μm.

Half-joule output optical-parametric oscillation by using 10-mm-thick periodically poled Mg-doped congruent LiNbO 3

We present a next generation of large-aperture periodically poled Mg-doped LiNbO3 (PPMgLN) device with 10-mm thickness. Efficient optical parametric oscillation with 540 mJ output energy at 709 mJ pumping by 1.064 µm laser in 10 nanoseconds operation could be demonstrated using the 10-mm-thick PPMgLN with an inversion period of 32.2 µm at total conversion efficiency > 76%. We also confirmed that degradation effect of conversion-efficiency distribution by wedged-inversion structures, which is inevitable in current poling condition of the large-aperture PPMgLN, can be ignored in high-intensity operation.

52 mJ narrow-bandwidth degenerated optical parametric system with a large-aperture periodically poled MgO:LiNbO3 device

We have demonstrated efficient, high-energy, narrow-spectral-bandwidth 2.128 microm pulse generation by use of periodically poled MgO:LiNbO3 devices with a 36 mm length and a 5 mm x 5 mm large aperture. A free-running degenerated optical parametric oscillator (OPO) pumped with a Q-switched 1.064 microm Nd:YAG laser exhibits a high slope efficiency of 75% and an optical-to-optical conversion efficiency of 70% with a broad spectral bandwidth (>100 nm). In a configuration with a spectrally narrowed master oscillator followed by a power amplifier, we have achieved an output pulse energy of 52 mJ with a spectral bandwidth of less than 2 nm at the degeneracy point. The total optical-to-optical conversion efficiency of the system reached 50%.

High energy quasi-phase matched optical parametric oscillation using Mg-doped congruent LiTaO 3 crystal

We report on high energy optical parametric oscillation of 118 mJ output with ~70% slope efficiency in 10 ns duration of 30 Hz operation by using Mg-doped congruent composition LiTaO(3) (MgLT). The periodically poled MgLT device with ~30 microm period for quasi-phase matching (QPM) in 5-mm-thick crystal are prepared. MgLT crystal could become a candidate for high-energy and higher durability material of QPM device, compared to conventional Mg-doped congruent composition LiNbO(3).

High-energy quasi-phase-matched optical parametric oscillation in a 3-mm-thick periodically poled MgO:LiNbO 3 device

We have demonstrated high-energy quasi-phase-matched optical parametric oscillation in a 3-mm-thick periodically poled 5-mol. % MgO-doped LiNbO3 device with a 32.1-microm grating period and a 30-mm length. With a large-spot-size pump laser of 2.2-mm diameter, we obtained a total output pulse energy of 22 mJ for both the signal (wavelength 1.82 microm) and the idler (2.56 microm) waves at an input pump energy of 46 mJ.

High-energy, broadly tunable, narrow-bandwidth mid-infrared optical parametric system pumped by quasi-phase-matched devices.

We have developed a tunable, narrow-bandwidth (<2 cm(-1)) mid-infrared (MIR) optical parametric system with a large-aperture periodically poled Mg-doped LiNbO(3) (LA-PPMgLN)-based high-energy pump source. The system has a continuously tunable tuning range from 4.6 to 11.2 mum and produces a maximum output energy of 2.0 mJ at 5.1 mum. Practical use of the MIR source is demonstrated by MIR-UV double-resonance spectroscopy of jet-cooled acetanilide.