Ryota Sawada

Wavelength-multiplexed pumping with 478- and 520-nm indium gallium nitride laser diodes for Ti:sapphire laser

We experimentally reveal the pump-induced loss in a Ti:sapphire laser crystal with 451-nm indium gallium nitride (InGaN) laser diode pumping and show that 478-nm pumping can reduce such loss. The influence of the pump-induced loss at 451-nm pumping is significant even for a crystal that exhibits higher effective figure-of-merit and excellent laser performance at 520-nm pumping. We demonstrate the power scaling of a Ti:sapphire laser by combining 478- and 520-nm InGaN laser diodes and obtain CW output power of 593 mW.

Influence of crystal's nominal figure of merit on Ti:sapphire laser directly pumped by InGaN laser diodes

We experimentally confirm a pump-induced loss in a Ti:sapphire laser pumped by 451-or 478-nm laser diode. Such loss is significant even for a crystal producing better output performance at 520-nm pumping. We demonstrate a power scaling of a CW Ti:sapphire laser using two 520-nm green diodes and two 478-nm blue diodes, and obtained an output power of 593 mW at an absorbed pump power of 2.5 W.

Solid-state lasers directly pumped by InGaN-based green and blue laser diodes

Development of solid-state lasers, titanium-doped sapphire and praseodymium doped LİYF4 lasers, directly pumped by indium gallium nitride-based green or blue semiconductor lasers is presented. We experimentally revealed the existence of an additional absorption induced at 450-nm pumping, and compared the laser performance with respect to the pump wavelength (450, 478 and 520 nm). A mode-locking operation is demonstrated with a pulse width of 126 fs and an average power of 315 mW. For Pr:LiYF4 lasers, power scaling up to 4.8 W is achieved utilizing four 3.5-W 445-nm diodes at 640 nm with a slope efficiency of 50%. Intracavity second harmonic generation of passively Q-switched laser at 320 nm and a SESAM mode-locking at 640 nm are also obtained.

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.

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).

Generation of photon-number squeezed states with a fiber-optic symmetric interferometer

We numerically and experimentally demonstrate photon-number squeezed state generation with a symmetric fiber interferometer in an 800-nm wavelength and compared with an asymmetric fiber interferometer, although photon-number squeezed pulses have been generated only with asymmetric interferometers. Even though we obtain -1.0dB squeezing with an asymmetric fiber interferometer, since perfect spectral phase and intensity matching between displacement and signal pulses are achieved with a symmetric fiber interferometer, we obtain better squeezing of -3.1dB. We also numerically calculate and clarify this schemes usefulness at a 1.55-μm wavelength.