Yong-Ho Cha

External-cavity frequency doubling of a 5-W 756-nm injection-locked Ti:sapphire laser

We have developed a 5-W 756-nm injection-locked Ti:sapphire laser and frequency-doubled it in an external enhancement cavity for the generation of watt-level 378-nm single-frequency radiation, which is essential for isotope-selective optical pumping of thallium atoms. With a lithium triborate (LBO) crystal in the enhancement cavity, 1.1 W at 378 nm was coupled out from the cavity. Such results are to our knowledge the highest powers of continuous-wave single-frequency radiation generated from a Ti:sapphire laser and its frequency doubling.

Generation of continuous-wave single-frequency 1.5 W 378 nm radiation by frequency doubling of a Ti:sapphire laser

We have generated continuous-wave single-frequency 1.5 W 378 nm radiation by frequency doubling a high-power Ti:sapphire laser in an external enhancement cavity. An LBO crystal that is Brewster-cut and antireflection coated on both ends is used for a long-term stable frequency doubling. By optimizing the input couplers reflectivity, we could generate 1.5 W 378 nm radiation from a 5 W 756 nm Ti:sapphire laser. According to our knowledge, this is the highest CW frequency-doubled power of a Ti:sapphire laser.

Silver-mirror-based multipass preamplifier for a broadband terawatt Ti:sapphire laser.

We have developed a silver-mirror-based multipass preamplifier for a broadband amplification in a terawatt Ti:sapphire laser. With the extremely broad bandwidth of the silver mirrors, a very broad amplified spectrum can be generated at an amplified energy of 4 mJ; the amplified spectral width is 65 nm at half maximum and 160 nm at -25 dB without any spectral shaping technique. Such a broad amplification can be explained well by the simulation that includes gain narrowing and gain saturation. Even after a further amplification to an energy of 600 mJ, the amplified spectrum is broad enough to support an approximately 20 fs transform-limited pulse duration.

Development of advanced radiation sources at KAERI

The KAERI Center for Quantum Beam-Based Radiation Research, was founded in 2011. The center pursues the development of advanced radiation sources and their applications in biology, material science, and nuclear physics. There are two main research topics in the development of advanced radiation sources: a system with high-power T-ray pump and an ultrashort X-ray probe system and a compact electron storage ring based on a laser-accelerated electron beam.

270-W 15-kHz MOPA System Based on Side-pumped Rod-type Nd:YAG Gain Modules

We have developed a 270-W 15-kHz MOPA system based on side-pumped rod-type Nd:YAG gain modules. The master oscillator is a 3-W 15-kHz

300-W spectral beam combination of narrow-linewidth pulsed rod-type fiber lasers

TEM_{00}

A pulsed diode-oscillator fiber-amplifier with wavelength tunable Fourier-transform limited linewidth

Nd:YVO_4

Isotope Selective Optical Pumping in a Dense Thallium Atomic Beam

laser with a pulse duration of 30 ns. To preserve the high beam quality during the amplification, we use image relay and polarization rotation which can simultaneously compensate for thermal lensing and thermal birefringence generated in the rod-type gain modules. After the amplification to 270 W with six rod-type gain modules, the beam quality factor (

270-W 15-kHz MOPA system based on side-pumped rod-type Nd:YAG gain modules

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