• Korean Journal of Optics and Photonics
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• v.26 no.6
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• pp.312-317
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• 2015

We investigate the effect of laser-resonator mode size on the output of a Yb:YAG laser that is mode-locked by a semiconductor saturable absorber mirror (SESAM). We demonstrate that the smaller the product of the mode sizes at a SESAM and at a Yb:YAG crystal, the more stable the mode-locked output is. Also, we found numerically that there is a resonator length at which the mode-locked output occurs, regardless of the thermal lens effect of a Yb:YAG.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.365-368
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• 2001

입사면에서 발생하는 열을 효율적으로 제거하기 위하여 Yb:YAG 결정의 표면에 sapphire 창을 부착하여 레이저를 발진 시켰다. Yb:YAG 결정에서 발생하는 열이 sapphire 창을 통하여 구리판으로 전달되는 경우 와 Yb:YAG 결정의 측면에서 냉각하는 경우의 레이저 출력을 측정하여 각각의 레이저 발진 특성을 비교하여 보았다. 여기면을 sapphire 창으로 냉각하는 micro-chip Yb:YAG 레이저의 레이저 에너지 전환 효율은 38%였으며 레이저 발진 문턱값은 4 kw/mm$^2$, slope efficiency는 56%로 측정되었다. Sapphire 창을 사용하는 경우 표면에서의 열전달도는 10 W/mm$^2$이상으로 관측되었다. Yb:YAG의 도핑율, 출력경의 반사율 등을 레이저 변수를 최적화할 경우 같은 구조에서 50 W급 레이저도 발진 가능할 것으로 예상된다.

• Korean Journal of Optics and Photonics
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• v.26 no.1
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• pp.38-43
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• 2015

We propose a linearly polarized long-cavity Yb:YAG laser with a variable-reflectivity output coupler and investigate its output characteristics. The variable output coupler consists of a polarized beam splitter and a quarter-wave plate. The linearly polarized laser has a long cavity length of about 3.7 m. The slope efficiency of the proposed laser is 19%, and the beam quality ($M^2$) is about 1.2.

• Korean Journal of Optics and Photonics
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• v.25 no.2
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• pp.90-94
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• 2014

We propose a Yb:YAG laser Q-switched by a semiconductor saturable absorber and a laser output coupler composed of a polarizer and a quarter-wave plate, and we investigate the output characteristics of the proposed Q-switched laser. We show that the laser power can be varied by rotation of the quarter-wave plate.

• Current Optics and Photonics
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• v.4 no.2
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• pp.127-133
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• 2020

We successfully constructed a passively Q-switched Yb:YAG laser ignitor pumped by a diode laser with low power and long pulse width. To the best of our knowledge, this is the first study to achieve a quasi-MW output power from an optimized Q-switch Yb:YAG laser ignitor by using a pumping diode laser module emitting at under a power of 23 W. The output pulse energy of our optimized laser is 0.98 mJ enclosed in a 1.06 ns pulse width, corresponding to a peak power of 0.92 MW.

• Journal of Welding and Joining
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• v.33 no.3
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• pp.54-61
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• 2015

In this study, effect of laser power on hardness and microstructure of SKD61 Hot Die steel of which surface was melted and hardened with Yb:YAG disk laser was investigated. Beam speed was fixed at 70 mm/sec and distance between them was 0.8 mm about Laser surface melting. The only thing that was changed laser power. Laser powers were 2.0, 2.4 and 2.8 kW. No defect was found under all conditions. As the laser power increased, the penetration depth were deepened and the bead width was also widened. There was no hardness deviation of fusion zone at same laser power and it was higher than that of heat affected zone. In addition, the more laser power increased, the more hardness in fusion zone decreased. Fusion zone was macroscopically dendrite structure. However, core matric in dendrite was lath martensite of 100 nm size. There were $M_{23}C_6$ of 500 nm and the VC and $Mo_2C$ of a nano meters on boundary of dendrite.

• Proceedings of the Optical Society of Korea Conference
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• 2001.08a
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• pp.108-109
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• 2001

• Proceedings of the Optical Society of Korea Conference
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• 2000.08a
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• pp.246-247
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• 2000

Yb$^{3+}$ 이온은 InGaAs LD 및 Ti:sapphire 레이저로 펌핑할 수 있는 940 nm에서의 흡수대를 가지고 있고, 1.03 $mu extrm{m}$의 형광방출 특성을 가지고 있으며, 지금까지 알려진 1 $\mu\textrm{m}$ 파장대의 레이저 활성이온 중에서 가장 적게 열을 발생하는 특성을 가지고 있음이 알려져 최근에는 Yb$^{3+}$ 이온을 첨가한 여러 가지 레이저 매질이 연구되고 있다.[1] 그 중에서도 Yb$^{3+}$ ion doped yttrium aluminum garnet (Yb:YAG) 단결정은 충분하게 넓은 흡수선폭, 좋은 열광학적 특성, 고출력 작동을 하게 하는 stokes shift, 그리고 LD에 의한 펌핑을 가능하게 하는 940 nm 영역에서의 흡수 및 긴 여기시간을 가진 이상적인 매질로 알려져 있다.[2] 이러한 특성으로 인해 Yb:YAG 단결정은 femtosecond 레이저 등 각종 레이저 시스템의 소형화[3]를 가져왔으며, 레이저 결정의 양산 가능성 및 레이저 기기의 소형화에 따르는 시스템의 가격 감소가 가능하므로 Yb:YAG microchip 레이저는 향후 고출력 레이저 기기 산업의 중추가 될 것으로 기대된다. (중략)

• Proceedings of the Korea Crystallographic Association Conference
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• 2000.05a
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• pp.34-34
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• 2000

• Current Optics and Photonics
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• v.5 no.2
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• pp.180-185
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• 2021

A femtosecond-laser inscribed Yb:YAG surface channel waveguide (WG) laser with single-walled carbon nanotubes deposited on the top surface of the WG was passively Q-switched by evanescent field interaction. Q-switched operation of the 14-mm-long compact Yb:YAG WG laser was achieved near 1031 nm with two different pumping schemes (single- and double-pass pumping) with an output coupling transmission of 91%. The Q-switched pulse characteristics depending on the absorbed pump power were investigated for both pumping geometries and analyzed in detail based on theoretical modeling. The best performances (energy/pulse duration) for each configuration were 204.4 nJ/75 ns at a repetition rate of 1.87 MHz, and 201.1 nJ/81 ns at 1.75 MHz for single- and double-pass pumping, respectively.