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High-order harmonic generation (HHG) is currently utilized for developing compact table-top radiation sources to provide highly coherent extreme ultraviolet (XUV) and soft X-ray pulses; however, the low repetition rate of fundamental lasers, which is typically in the multi-kHz range, restricts the area of application for such HHG-based radiation sources. Here, we demonstrate a novel method for realizing a MHz-repetition-rate coherent XUV light source by utilizing intracavity HHG in a mode-locked oscillator with an Yb:YAG thin disk laser medium and a 100-m-long ring cavity. We have successfully implemented HHG by introducing two different rare gases into two separate foci and picking up each HH beam. Owing to the two different HH beams generated from one cavity, this XUV light source will open a new route to performing a time-resolved measurement with an XUV-pump and XUV-probe scheme at a MHz-repetition rate with a femtosecond resolution., Extreme ultraviolet: generating coherent pulses inside a laser A compact table-top laser system developed by researchers in Japan can generate extreme ultraviolet radiation (XUV) for ultrafast spectroscopy. Coherent XUV pulses are used to accurately measure data on electronic transitions in atoms and molecules, however they can usually only be generated via synchrotron radiation from large particle accelerators. A possible route to generating XUV on a smaller lab scale is to direct high-order harmonic pulses from a femtosecond laser onto a gas. Katsumi Midorikawa at the RIKEN Center for Advanced Photonics in Wako and co-workers have developed a novel method where the gas targets are actually placed inside the laser cavity. By using two different gases, they can simultaneously generate an XUV pump and a probe, opening a route to very accurate timing of atomic measurements, perhaps resolving events as short as a few femtoseconds.

We demonstrated intra-cavity high harmonic generation (HHG) in a Yb:YAG thin disk mode-locked oscillator with a repetition rate of 3MHz. Two HHG ports are simultaneously operated in a single mode-locked oscillator.

We have developed a pulsed Yb:YAG thin disk green laser for pumping a 100 kHz and 10 W femtosecond laser. We optimized numerically and experimentally the open duration of the acousto-optic (AO) Q-switcher and the internal SHG method, generating stable output energy at a 100 kHz repetition rate. We demonstrated a 515 nm output power of over 80 W with a pulse-to-pulse stability of less than 1% RMS with an LD power to green power conversion efficiency of 24%. With the developed green laser, we obtained 16 W of a Ti:sapphire laser in a cavity dumped mode.

We have developed a 6–12 μm mid-infrared (MIR) femtosecond laser source for glyco-protein structure analysis. The MIR femtosecond laser pulses are generated by a differential frequency generation (DFG) configuration with a combination of Ti:sapphire based regeneratively amplified femtosecond laser pulses (780 nm, 160 fs, 1 mJ) and a β-BaB2O4 (BBO) based optical parametric amplifier (OPA). The MIR pulse energy exceeds 4.5 μJ, where a glyco-protein molecule has resonant absorption lines due to the vibrational–rotational transitions. The pulse width is estimated to be less than 1 ps according to the cross correlation measurement between the two OPA output pulses. Using the MIR femtosecond laser pulses, we demonstrated photo-dissociation of the sialyl Lewis X (sLeX) proton added ion, which is the first time to the best of our knowledge.

We report a Kerr lens mode-locked Yb:Lu 2 O 3 ceramic oscillator with a pulse energy of 23.5 nJ, which is the highest value in bulk Yb:Lu 2 O 3 ceramic oscillators, to the best of our knowledge.

We have developed an automatic pulsewidth-adjustable femtosecond Ti:Sapphire laser system that can generate an output of 50 fs-1 ps in duration, and sub-mJ/pulse at a repetition rate of 1 kpps. The automatic pulse compressor enables one to control the pulsewidth in the range of 50 fs-1 ps by use of a personal computer (PC). The compressor can change the distance in-between and the tilt angle of the grating pairs by use of two stepping motors and two piezo-electric transducer(PZT) driven actuators, respectively. Both are controlled by a PC. Therefore, not only control of the pulsewidth, but also of the optical chirp becomes easy. By use of this femtosecond laser system, we fabricated a waveguide in fused quartz. The numerical aperture is chosen to 0.007 to loosely focus the femtosecond laser. The fabricated waveguides are well controllable by the incident laser pulsewidth. We also demonstrated the ablation processing of hydroxyapatite (Ca10(PO4)6(OH)2), which is a key component of human tooth and human bone for orthopedics and dentistry. With pulsewidth tunable output from 50 fs through 2 ps at 1 kpps, the chemical content of calcium and phosphorus is kept unchanged before and after 50-fs-2-ps laser ablation. We also demonstrated the precise ablation processing of human tooth enamel with 2 ps Ti:Sapphire laser.

We have generated 1-mJ pulses with a pulse duration of 520 fs at a repetition rate of 2.85 MHz in a mode-locked oscillator cavity. These pulses can be used for generating high-harmonics in the cavity.

We have demonstrated the second harmonic generation with output pulses of a 50 kHz Ti:sapphire regenerative amplifier. 280 fs pulses with an average power of 3.1 W were generated at 389 nm.

As a pump laser of a Ti:sapphire femtosecond laser, the authors developed high power, high repetition rate and highly stable Yb:YAG thin disk green laser. We achieved 200 kHz, 73 W operation.

We solved the stability, life-time and cost problems of femtosecond lasers and opened the door to their huge commercial market in near future. Femtosecond lasers will be used in the semiconductor and LCD manufacturing factory.

We report Kerr lens mode-locking of a Yb:Lu2O3 bulk ceramic oscillator with an output power of 1.83 W, a pulse duration of 135 fs at a repetition rate of 78 MHz, corresponding to a pulse energy of 23.5 nJ. Single-mode oscillation and Kerr lens mode-locking have been achieved with a special geometry using a multimode laser diode with a low brightness as a pump source. To the best of our knowledge, the obtained pulse energy is the highest in any mode-locked Yb:Lu2O3 bulk ceramic oscillator.

We have developed a mid-infrared femtosecond laser source with high stability and optical system for glycol-protein structure analysis. The DFG (difference frequency generation) light was irradiated to the SLeX proton added ion to a photo-dissociate it

We have developed a high-repetition, 1-W, and 70 fs regenerative amplifier system. The stable operation was obtained due to a seeding fiber laser, a compact folded cavity, and a green pump source built by ourselves.

We demonstrated stable operation of the femtosecond laser continuously over 10,000 hours only with compensation of power loss of LDs.

We report a mid-infrared (MIR) optical pulse source (6-12 mum), which is constructed by a regenerative amplifier and an OPA followed by a DFG unit. The maximum pulse energy at 6.8 mum is near 4 muJ

Achievement of more than 100 mW of pure continuous-wave deep-ultraviolet radiation at 213 nm has been demonstrated in an efficient all-solid-state laser system that uses two Brewster-cut CsLiB6O10 (CLBO) crystals. The first crystal is used for 266-nm generation by external resonant doubling of 532-nm radiation from a frequency-doubled Nd:YVO4 laser. Subsequent sum-frequency mixing is performed in a second CLBO crystal placed in a diode-pumped Nd:YAG laser cavity to mix the single-pass 266-nm output with circulating 1064-nm light.

Summary form only given. Precise mechanical control of grating pulse compressor in chirped pulse amplification system is of paramount importance in a wide range of application of high intensity femtosecond lasers, because the accurate pulse characterization and the reduced alignment tasks for attaining a tailored ultrashort pulse are desired. We have proposed a femtosecond automatic pulse compressor for use in a chirped pulse amplifier using stepping motors and PZT driven actuators controlled by PC. Introducing the new parameters that are measured by SPIDER, a further improvement is obtainable.

We have developed an automatic pulsewidth tunable femtosecond Ti:sapphire laser system that can generate an output of 50fs-1ps and sub-mJ/pulse at a repetition rate of 1 kpps. The automatic pulse compressor enables on to control the pulsewidth in the range of 50fs-1ps by the use of a personal computer (PC). We describe our recent results of tailored ablation processing of advanced functional materials such as GaN, BN, and hydroxyapatite. By use of the femtosecond laser pulse tailored for a specific material, we have demonstrated precise processing without chemical composition change and heat affected zone.