Guang-Hoon Kim

A three-stage laser amplification system based on thin Yb : YAG rods with diode laser pumping is developed and fabricated. In this system, the average power of a continuous train of femtosecond pulses from a Yb : KGW master oscillator with a pulse repetition rate of 80 MHz and initial pulse duration of 128 fs was raised by a factor of 100 to above 100 W. Preliminarily chirped laser pulses provided compensation of dispersion in optical elements of the system and obtaining 580-fs output pulses. The longer duration of output pulses relates to spectrum narrowing in the amplifiers.

A diode-pumped Yb:Y₂O₃ ceramic thin-rod amplifier which operates in the femtosecond regime is studied here. In a single-stage and direct four-pass amplification scheme, the amplifier delivers maximum output power of 8.1 W at a center wavelength of 1030.5 nm and spectral bandwidth of 4.8 nm. Assume a sech²-shaped pulse, a pulse duration of 239 fs is measured, exhibiting a time-bandwidth product value of 0.324. To the best of our knowledge, our Yb:Y₂O₃ ceramic thin-rod femtosecond amplifier exhibits the shortest pulse duration with Watt-level output power among all Yb:Y₂O₃-based femtosecond amplifiers.

A Micro holes in a diamond are presented by using a homemade femtosecond (fs) Yb:KGW laser. An fs laser source was used emitting pulse duration of 230 fs at 1030 nm wavelength, whereas the spot size amounted to 8.9 μm. Parameters like pulse energy, and pulse number were varied over a wide range in order to evaluate their influence both on the micro hole geometry like hole diameter, circularity, taper angle, and on the drilling quality. Hourglass-shaped micro holes whose diameters decrease and increase again after a certain depth have important applications. The results demonstrate the feasibility of extending the drilling of an hourglass-shaped hole in a diamond sample, which has similar diameters at the hole entrance (92 μm) and exit (95 μm), but a much smaller diameter (28 μm) at a certain waist section inside the hole.

We have studied experimentally a high power booster of Yb:YAG single-crystal fiber with regenerative amplifier based on dual-slab Yb:KGW crystals. The booster provided the output power of 45 W with the gain of 3. It allowed the laser system to maintain the spectral bandwidth.

This paper proposes a solid-state pulsed power modulator (PPM) with fast rising/falling time and high repetition rates to drive pockels cells. Since the proposed circuit is based on the modular structure using silicon carbide (SiC) metal oxide silicon field effect transistors (MOSFETs) for bypass devices as well as for main switches, it can achieve fast switching speed and high reliability. In addition, by a control scheme employing the voltage difference, the proposed circuit can accomplish a high repetition rate and short pulse width. Design and implementation of 1.8kV PPMs with repetition rate of 1MHz and rising/falling time below 6ns are presented. Also, important issues for the practical use of the SiC-based PPM are discussed. Experiments results from the developed PPMs are shown to verify the proposed works.

High-Power Diode-Pumped Short Pulse Lasers Based on Yb:KGW Crystals for Industrial Applications | InTechOpen, Published on: 2016-09-07. Authors: Guang-Hoon Kim, Juhee Yang, Byunghak Lee, et

A diode-pumped, ultrafast Yb:KYW laser system utilizing chirped-pulse amplification in a dual-slab regenerative amplifier with spectral shaping of seeding pulse from a master oscillator has been developed. A train of compressed pulses with pulse length of 181 fs, repetition rate up to 200 kHz, and average power exceeding 8 W after compression and pulse picker was achieved.