S. Matsuoka

Cesium vapor laser pumped by a volume-Bragg-grating coupled quasi-continuous-wave laser-diode array

The experimental demonstration of a broad-area Quasi-continuous-wave (QCW) laser-diode array pumped cesium vapor laser is reported in this letter according to our experimental results. We used a volume-Bragg grating to narrow the spectral linewidth for acquirement of enough resonance transitions. A glass cylindrical cell filled with cesium/buffer gas was set in an end-pumped flat-concave cavity and the gas pressure was set lower than 1atm. Using the QCW drive mode with the repetitive rate and pulse width of 1kHz and 50μs, respectively, 13.45μJ pulse energy has been achieved with the slope efficiency of about ∼1.8%.

84 dB amplification, 0.46 J in a 10 Hz output diode-pumped Nd:YLF ring amplifier with phase-conjugated wavefront corrector

A diode-pumped joule class in a 10 Hz output Nd:YLF ring amplifier has been developed. A phase conjugate plate was developed as a wavefront corrector for the residual wavefront distortion of an Nd:YLF rod. We have demonstrated a 0.46 J output of 10 ns pulse duration at 10 Hz repetition rate with 1.5 nJ of input energy. The effective gain of the ring amplifier system was 84.8 dB. To our knowledge, this is the highest magnification with joule-level output energy in a single-stage amplifier system that has ever been built. As a preamplifier system, this system contributed a demonstration of 21.3 J in a 10 Hz output diode-pumped Nd:glass zigzag slab laser system with a stimulated Brillouin scattering- phase conjugation mirror. We describe a robust and effective method of wavefront correction for high-energy laser systems.

Diode-Pumped Zig-Zag Slab Laser for Inertial Fusion Energy and Applications

A quasi-cw 290-kW diode-pumped zig-zag slab laser is being developed in order to demonstrate a concept of the IFE driver. Thermally managed amplifier has yielded a gain of 10, promising 10-J output at 10 Hz.

High power and high repetition Nd:YAG laser pumped by cw LDs

We have been developing a high repetition (5 kHz) and high power (5 kW) Nd:YAG laser system for EUV lithography. Key subjects are (1) reliable front-end, (2) uniform and high density pumping of main amplifier rods, and (3) compensation of thermal effects. Fairly good uniformity was achieved by adjusting pumping geometry. Detail system analysis suggests that 8 amplifier modules pumped at 24.0 kW power are required to get output of 5 kW under relatively small thermal effects.

Demonstration of 4-mm short length fiber laser oscillation in Nd-doped silica fiber fabricated by zeolite method

We demonstrated a laser oscillation in the shortest Nd-doped silica fiber, an only 4-mm multimode Nd-doped silica fiber. This fiber-core glass was fabricated by the zeolite method, and the glass contained 1.25 wt% of Nd2O3.

High order wavefront correction for a 1 joule class Nd:YLF rod amplifier by phase conjugate plate

Wavefront correction until Zernike polynomial of degree three by a phase conjugate plate has been demonstrated in a high-energy Nd:YLF amplifier system. 108, amplification of 380 mJ has been achieved with a near-diffraction-limited beam quality.

High order wavefront correction for high-energy Nd:YLF rod amplifier by phase conjugate plate

Wavefront correction until Zernike polynomial of degree three by a phase conjugate plate has been demonstrated in a high-energy Nd:YLF amplifier system. 108 amplification of 380 mj has been achieved with a near-diffraction-limited beam quality.

Hundred mJ level, high contrast OPCPA/Yb:YAG hybrid laser system

Yb:YAG CPA have a potential to develop a compact, high peak power at high repetition rates. For high energy pulses of short duration Yb:YAG regenerative amplifiers have mainly been studied for which significant prepulse and amplified spontaneous emission (ASE). In laser proton acceleration studies it is very important to suppress the prepulse and ASE levels, because a preplasma is generated before the peak of the laser pulse, therefore the maximum proton energy is limited. To overcome this problem, the OPCPA can efficiently provide high gain for the main pulse while suppressing prepulse amplification. Here we have first demonstrated a hundred mJ level, femtosecond of an OPCPA/Yb:YAG hybrid laser system with a contrast level of 10−9 at −150 ps.

Laser oscillation in 4-cm single-transverse-mode Nd-doped silica fiber fabricated by zeolite method

Short length fiber less than a few centimeters has many attractive applications in information and communication fields, for example, developments of over GHz clocking signals, optical integrated circuit elements.

Multimillijoule optical parametric chirped-pulse amplifier as an alternative to Yb:YAG regenerative amplifiers at 1030 nm

The broad absorption bandwidth of ytterbium (Yb) is well-suited to laser diode pumping at 940 nm. Because Yb is known for its low quantum defect, thermal loading is significantly reduced. Consequently, Yb doped crystals, especially Yb:YAG, show promise for developing compact, high peak power laser systems at high repetition rates. For high energy pulses of short duration Yb:YAG regenerative amplifiers have mainly been studied where the generation of significant prepulse and amplified spontaneous emission (ASE) is known. At higher intensities (for example ∼ 1018Wcm−2 and beyond) laser-matter interactions can require suppression of prepulse and ASE intensity in order to maintain or control the target state that a short or ultrashort main pulse would irradiate. In many cases it is therefore critical to avoid significant preplasma formation. To solve these problem, the optical parametric chirped pulse amplification (OPCPA) can efficiently provide high gain of the main pulse while suppressing prepulse amplification and reducing gain narrowing of the spectrum. We present in this conference the first Yb femtosecond oscillator based OPCPA demonstration at 1030 nm and with spectral bandwidth adequate for amplifying femtosecond pulses. Direct laser diode (LD) amplification of 1030 nm light makes this OPCPA a feasible preamplifier for a compact, high contrast, energetic, short pulse laser systems that can be considered for development of laser-driven proton accelerators.