Jiro Saikawa

Diode-pumped tunable Yb:YAG miniature lasers at room temperature: modeling and experiment

We present a simple design rule for diode-laser pumped quasi-three-level lasers by using the M/sup 2/ factor. The validity of this model was demonstrated by diode-pumped Yb:YAG laser experiments. The maximum output power of 1.33 W and optical slope efficiency of 63% were obtained in a 400-/spl mu/m Yb:YAG chip miniature laser. Using a 200-/spl mu/m Yb:YAG chip, a 70% optical slope efficiency was reached. In a coupled-cavity configuration, with a quartz birefringent tuning filter, 8.2 THz (29 nm) of tuning was obtained at room temperature. By changing to a calcite birefringent filter, single-axial-mode oscillation with an output power of 500 mW was observed.

High Average Power Diode End-Pumped Composite Nd:YAG Laser Passively Q-switched by Cr4+:YAG Saturable Absorber

We report a diode end-pumped composite Nd:YAG laser, passively Q-switched by a Cr4+:YAG crystal as saturable absorber. The maximum peak power exceeded 16 kW for an average power of 2.6 W, laser pulses of 16.8-ns duration and 272-µJ energy. The maximum average power was 4.2 W with the laser operating at 24.0 kHz repetition frequency and 47.8-ns pulses duration (3.7 kW peak power) at a beam quality of M2=1.34. A rate-equation model that considers both the active medium and the saturable absorber dynamics was developed. A good agreement between the experiments and modeling resulted.

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.

Absorption, emission spectrum properties, and efficient laser performances of Yb:Y3ScAl4O12 ceramics

We report on the continuous-wave laser performances of Yb3+-doped disordered Y3Al5O12∕Y3Sc2Al4O12(YAG∕YSAG) ceramics fabricated by sintering method. These materials exhibit relatively low minimum pump intensity (Imin) and broad emission bandwidth even in the yttrium aluminum garnet systems. The value of Imin in the Yb:Y3ScAl4O12 ceramics was found to be 2∕3 compared with the Yb:YAG single crystal under 970nm zero-line pumping. Efficient laser oscillation of 72% slope efficiency was obtained for input pump power. These materials attract great interest for high power femtosecond microchip lasers and amplifier applications.

Tunable frequency-doubled Yb:YAG microchip lasers

Abstract A tunable single-axial-mode oscillation was demonstrated in a diode-pumped 400 μm thick Yb:YAG microchip green laser with 250 mW CW output power, which emits maximum green power of 520 mW. Tuning from 515.3 to 537.7 nm ( Δλ=22.4 nm , Δν=24.4 THz ) with single-axial-mode was obtained using a double quartz-birefringent filter set in a coupled cavity and an angle tuned LBO at room temperature. The tuning range meets Ar+ laser and frequency-doubled Nd:YAG laser wavelengths. This laser can be applied to high-resolution spectroscopy, holography and frequency locking with a molecular iodine filter. We succeeded in applying this laser to a wavelength-multiplexed holographic memory.

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, 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.

Radial-Pumped Microchip High-Power Composite Yb:YAG Laser: Design and Power Characteristics

We present a novel architecture for a quasi-four-level diode-pumped high-power microchip laser. The design uses a Yb:YAG core surrounded by an undoped YAG region of slab or disk shape, and that can be pumped from one side (unsymmetrical pumping) or from both slab sides (symmetrical pumping). Theoretical descriptions of the pumping optimization, pump-beam distribution, and output-to-input power characteristics are presented. The simulations show that from a composite Yb:YAG chip, which consists of a Yb:YAG core of 2.0-mm diameter and 13.0-at.% Yb concentration surrounded by an undoped YAG slab of 5.0-mm width and 0.8-mm thickness, a TEM00 output beam of 100 W continuous-wave power could be obtained. The expected optical-to-optical efficiency is 39%.

Passive mode locking of a mixed garnet Yb:Y3ScAl4O12 ceramic laser

We have demonstrated a passively mode-locked Yb3+-doped Y3ScAl4O12 ceramic laser, which is a solid solution of Y3Al5O12 and Y3Sc2Al3O12, by using a semiconductor saturable-absorber mirror. The maximum average output power was as high as 150 mW with a pulse duration of 500 fs. With a 0.5% output coupler, pulses as short as 280 fs having an average output power of 62 mW at 1035.8 nm were obtained.

Diode end-pumped passively Q-switched Nd:YAG laser intra-cavity frequency doubled by LBO crystal

Abstract A diode end-pumped Nd:YAG laser, passively Q-switched by a Cr 4+ :YAG medium as saturable absorber and intra-cavity frequency doubled employing a LBO crystal is described. The device produces 532-nm wavelength pulses of 226-μJ energy, 86-ns width and 4.2-kHz repetition rate, with a laser beam of M 2 =1.8.