Ryosuke Kariyama

Saturation of 640-nm absorption in Cr⁴⁺:YAG for an InGaN laser diode pumped passively Q-switched Pr³⁺:YLF laser.

We measure the absorption recovery time, the ground- and excited-state absorption cross sections of a Cr4+:YAG crystal at 640 nm for the first time. A pump-probe measurement reveals the existence of two recovery times of 26 ns and 5.6 μs. By a Z-scan experiment, the ground- and excited-state absorption cross sections are estimated to be 1.70 - 1.75 × 10(-17) and 0.95 - 1.00 × 10(-17)cm2, respectively. The adequacy of the proposed model and the accuracy of the estimated parameters of the saturable absorber are verified by reproducing the experimentally obtained performance of a passively Q-switched Pr3+:YLF laser with the Cr4+:YAG saturable absorber from rate equation analysis.

InGaN diode pumped actively Q-switched intracavity frequency doubling Pr:LiYF 4 261 nm laser

We demonstrate actively Q-switched deep ultraviolet laser operation at 261 and 320 nm by intracavity frequency doubling of an InGaN laser diode-pumped Pr:LiYF₄ laser. We obtain a maximum peak power of 61.6 W (8.7 μJ/pulse at 7.7 kHz) and 594 W (19.0 μJ/pulse at 7.7 kHz) with a pulse width of 142 and 35 ns at 261 and 320 nm, respectively. The conversion efficiency from the fundamental laser energy at 639 nm to the second-harmonic generation is 88%. Good agreement is obtained with prediction by a rate equation model.

Pr 3+ :YLF mode-locked laser at 640 nm directly pumped by InGaN-diode lasers.

We attain stable mode-locking of an InGaN laser-diode-pumped Pr3+:YLF laser with a pump power of 2.8 W using a semiconductor saturable absorption mirror. A maximum averaged output power of 65 mW was obtained with a 45-ps pulse width at a pulse repetition rate of 108 MHz. We also attempted Kerr-lens mode-locking by employing an SF57 glass in a cavity as a Kerr medium.

Solid-state lasers directly pumped by InGaN diode lasers: Ti:sapphire and Pr3+:LiYF4 lasers

We report our recent progress of solid-state lasers, the titanium-doped sapphire laser and the praseodymium-doped LiYF4 (Pr3+:LiYF4) laser, directly pumped by InGaN diode lasers of green and blue. While the titanium-doped sapphire laser can be pumped by both blue and green diode lasers because of its broad absorption spectrum, we find 450-nm diode laser pumping inefficient for its power scaling owing to the onset of an additional absorption loss induced by the blue pump laser. The degradation of the performance of a Ti:sapphire laser induced by a 450-nm diode pumping is experimentally revealed. Furthermore, we demonstrate a passively mode-locked Ti:sapphire laser pumped by two green diode lasers of 1-W, and 74 fs pulses at a repetition rate of 120 MHz with an averaged output power of 45 mW are obtained. The Pr3+:LiYF4 laser, one of the most promising candidates as a visible laser, has become possible to be pumped directly by blue diode lasers of 440-nm wavelength. We demonstrate the power scaling at 523 and 640 nm oscillation, a passive Q-switching at 640 nm with a Cr4+:YAG saturable absorber by utilizing polarization-combined blue diode lasers as the pump source.

50-kHz, 50-ns UV pulse generation by diode-pumped frequency doubling Pr 3+ :YLF Q-switch laser with a Cr 4+ :YAG saturable absorber

We demonstrate intracavity second-harmonic generation at 320 nm of a diode-pumped praseodymium-doped YLF laser Q-switched by a Cr4+:YAG crystal. By employing two 3.5-W high-power blue InGaN diode lasers as the pump source, we obtained 50-ns Q-switched pulses with a pulse energy of 1.54 μJ at a repetition rate of 50 kHz. A rate equation analysis shows good agreement with the experimental results.

Demonstration of Femtosecond Ti:Sapphire laser oscillation pumped by InGaN diode lasers

We demonstrate a mode-locked Ti: sapphire laser pumped by green InGaN laser diodes from both sides of the crystal. An output power of 45 mW is achieved in mode-locking with a SESAM (semiconductor saturable absorber mirror).

Power scaling and Q-switched operation of a Pr 3 +doped YLF laser pumped by four high power InGaN-Blue-LDs

We demonstrate a 2.9-W cw Pr3+:YLF laser at 640 nm by pumping with four InGaN blue LDs. This laser is further extended to passive and active Q-switching operation using Cr4+:YAG saturable absorber and acousto-optic modulator, respectively.

Intracavity Second Harmonic Generation of Passively Q-switch Mode Locked Pr 3+ -doped Fluoride Lasers using Cr 4+ :YAG Saturable Absorber

We demonstrate passive Q-switching and Q-switched mode locking of Pr³⁺-doped fluoride lasers in the visible region using a Cr⁴⁺:YAG saturable absorber. Intracavity frequency doubling generates deep ultra-violet from the Pr³⁺:YLF laser.