마이크로 칩 Yb:YAG 레이저의 동작 및 열적 특성

문희종,홍성기,임창환,Moon, Hee-Jong,Hong, Sung-Ki,Lim, Chang-Hwan 한국광학회 2011 한국광학회지 Vol.22 No.2

본 논문에서는 930 nm 대역 광섬유 결합 레이저 다이오드 여기광을 0.8 mm 두께의 얇은 디스크형 Yb:YAG 결정에 조사하여 레이저 발진 특성을 연구하였다. 구멍이 있는 구리판 사이에 레이저 결정을 고정시켜 발생된 열을 접촉 냉각시키는 구조를 채택하였고, 구리판 구멍 크기에 따른 조사 지점의 온도 변화를 발진 피크 스펙트럼 이동으로부터 조사하였다. 광섬유 결합 LD 여기 광에 대해 발진 레이저 출력은 기울기 효율 42.2%, 광변환 효율 34.8%로 높게 구현되었다. LD 여기 전류 및 구리판 구멍 크기가 증가함에 따라 여기광이 조사된 지점의 온도가 증가하였다. 구리판 구멍 크기가 결정 두께에 비해 상당히 큰 경우, 높은 여기광의 세기에서는 온도 상승이 선형 변화로부터 벗어남을 확인하였다. Operational and thermal characteristics of a thin disk Yb:YAG crystal with a thickness of 0.8 mm were studied using as a pumping source a fiber-coupled 930 nm laser diode. The heat generated in the crystal was dissipated by placing both surfaces in contact with copper plates with central hole, and the dependence of the temperature change in the illuminated spot on hole size was investigated by measuring the spectral change of the lasing peaks. The slope efficiency and optical-to-optical efficiency with respect to the LD pump power were as high as 42.2% and 34.8%, respectively. The temperature at the illuminated spot increased with diode current and with increasing hole size of the copper plate. When the hole size considerably exceeded the crystal thickness, the temperature rise deviated from the linear increase at high pump power.

미세 물방울에서의 공명 유도라만산란의 특성

문희종,김광훈,임용식,고춘수,이재형,장준성 한국광학회 1995 한국광학회지 Vol.6 No.4

Q 스위칭 Nd:YAG 레이저 빔을 펌프광으로 하여 $35~62{\mu}m$ 크기의 물방울에서의 공명 유도라만산란 신호를 검출하였다. 신호광은 간격이 일정한 peak들의 형태로 나타났고 방울크기가 커질수록 그 간격이 좁아짐을 관측하였다. 또한 두 물방울을 결합하면서 유도라만산란 신호를 검출한 결과 결합된 물방울이 거의 구의 형태가 될 때 신호광이 공명 특성을 띠게 됨을 확인하였다. 실험으로 측정한 같은 모드순서의 공명모드 사이의 간격오차는 약 5%였다. We have detected the resonant stimulated Raman scattering signal when the Q-switched Nd:YAG laser beam are incident on the $35~62{\mu}m$ sized water droplet as pump beam. The signals appeared as uniformly spaced peaks and the intervals between peaks become narrow as the droplet size increases. Also we have confirmed the morphology dependent resonances (MDR's) characteristic of the stimulated Raman scattering signal when the water droplet becomes nearly spherical shape after two water droplets are coupled to a droplet. The error in the measured intervals between MDR's of same mode order is about 5%.out 5%.

Lasing of Coupled Guided Modes in Modified Hollow Hexagonal Semiconductor Cavities

문희종,이진영,현경숙,정대철 한국광학회 2014 Current Optics and Photonics Vol.18 No.4

Coupled guided modes, proposed in various modified hollow hexagonal cavities each attached internally to a hexagon, were demonstrated by investigating the laser oscillations in semiconductor cavities. The mode spacing between two adjacent lasing peaks decreased as the size of the internal hexagon increased, due to the increased round-trip length of the coupled guided modes. The linear dependency of the inverse mode spacing to the calculated round-trip length strongly confirmed the lasing of the coupled guided modes. The proposed modes in common-sized external cavities showed resonance structure that could be adjusted widely by controlling the size of the internal hexagon.

다이오드 측면여기 고출력 Nd:YAG 레이저의 발진특성

문희종,이성만,김현수,고도경,차병헌,이종훈 한국광학회 2000 한국광학회지 Vol.11 No.6

Lambertian 산란 특성을 갖는 난반사체를 적용하고 1kW의 출력을 갖는 고출력 레이저 다이오드를 여기광원으로 이용하여 고출력 Nd:YAG 레이저를 제작하였다. 지름이 5mm인 레이저봉을 사용하고 짧은 공진기를 구성하여 연속발진시켰을 때 약 500W의 고출력을 얻을 수 있었고 이때 기울기 효율은 49% 광변환효율 46.7%로 매우 높은 효율을 얻었다. 지름이 6mm인 레이저봉을 사용하였을때에는 LD여기광의 흡수 분포가 불균일해져서 광변환효율은 감소하였다. 발생한 레이저빔의 빔질인자(Beam Quality Factor) M$^2$는 약 70 정도로 관측되었으며 이는 측정된 열렌즈 초점거리로부터 계산된 빔질인자보다 약간 작은 값으로 여기광의 흡수 분포가 매우 균일함을 보여준다. We fabricated a high power Nd:YAG laser pumped by a 1 kW diode laser with a Lambertian-type diffusive reflector. Maximum cw power of 500 W with a slope efficiency of 49%, which corresponds to an optical efficiency of 46.7%, was obtained from a short linear resonator when a 5 mm rod was used. The efficiencies decreased when a 6 mm rod was used, due to the poor quality of the absorption distribution in the rod. The measured beam quality factor of 70, which is slightly smaller than the value calculated from the measured thermal focal lengths, shows that the absorption distribution in the rod is fairly uniform. iform.

Cooling Geometry Dependent Operation Properties in a Diode End-Pumped Monolithic Yb:YAG Laser

문희종,임창환 한국광학회 2016 Current Optics and Photonics Vol.20 No.5

Operation properties, such as output power, beam radius, and crystal temperature rise were investigatedin a diode-pumped edge-cooled monolithic Yb:YAG laser with ~ 4 W pumping level. The output powershowed saturation behavior because of severe temperature rise and poor spatial overlapping between pumpbeam and lasing mode. Face cooling geometry by using a sapphire plate was also investigated. No apparentsaturation behavior in output power was observed due to the reduced temperature rise, which could beattributed to efficient heat removal through the crystal-sapphire interface.

Effect of Corner Shapes on Whispering Gallery Mode Lasing in Semiconductor Square Microcavities

문희종,Kyung-Sook Hyun,Yong-Hwan Kwon,You-Yong Jin 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.4

We investigated the spectral characteristics of whispering gallery mode (WGM) lasing in semiconductor square microcavities with various corner shapes. For a simple square cavity, the lasing spectrum showed a complex peak pattern with a broad envelope due to lasing of multi-spatial WGMs. In order to reduce the number of lasing modes, we proposed and fabricated hollow square cavities with symmetric concave-shaped corners. The lasing peaks appeared as periodic narrow peaks corresponding to closed WGMs due to the strong mode selection roles of proposed geometry. If the corner geometry was modified to form 45-tilted and convex shapes, ring-type WGMs originating from total reflection of light at the four corners could be selectively lased.

Bow-tie Mode Lasing in a Grooved Rectangular Semiconductor Microcavity

문희종,현경숙 한국광학회 2012 Current Optics and Photonics Vol.16 No.2

Bow-tie modes were proposed in a grooved rectangular resonator and their lasing characteristics were investigated in semiconductor microcavities. The observed spacing between two adjacent lasing peaks from the grooved cavity was reduced compared to that of 4-bounce whispering gallery modes (WGMs) from the same-sized simple rectangular cavity due to increased round-trip path length of the bow-tie modes. The lasing spectra of bow-tie modes obtained from two adjacent corners showed highly correlated patterns while those of 4-bounce WGMs did not.

Spectral behaviors of evanescent-wave-coupled gain lasing from dielectric-coated cylindrical microcavities

문희종 한국물리학회 2022 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.80 No.4

The spectral behavior of evanescent-wave-pumped and gain-coupled lasing was investigated in a dielectric-coated optical fiber surrounded by a dye-doped liquid. As the coating thickness increases, the lasing spectrum exhibits a blue shift due to a decrease in the number of the dye molecules in the evanescent field region of the whispering gallery mode. For comparison, lasing spectra of bare fibers with different dye concentrations were also measured. A simple model for evanescent-wave gain-coupled lasing in a coated cavity is proposed to explain the observed shifting behaviour.

다중모드 간섭기를 이용한 반도체 이중사각형 링 공진기에서의 단일모드 발진 특성

정달화,문희종,현경숙,Jeong, Dal-Hwa,Moon, Hee-Jong,Hyun, Kyung-Sook 한국광학회 2009 한국광학회지 Vol.20 No.1

다중모드 간섭기를 이용한 반도체 이중사각형 링 공진기에서의 단일 파장 모드 발진특성을 관찰하였다. 실험에 사용된 공진기의 에피택시는 발진 중심파장이 $1.55{\mu}m$인 InGaAsP-InP 다중양자우물 구조를 활성층으로 사용하여 제작되었다. 공진기의 구조는 다중모드 간섭기를 결합기로 이용한 이중사각형 링 공진기이며 발진특성을 측정하였다. 여러 가지 구조 변수를 즉 공진기의 구조 및 크기, 다중모드 간섭기의 길이를 변화시키며 실험을 진행하였다. 실험 결과 다양한 크기와 구성에서 단일파장모드선택 특성이 잘 나타남을 확인할 수 있었다. We report the spectral characteristics of Multimode Interferometer (MMI)-coupled semicondoctor square ring resonators. The epitaxial layers of the proposed semiconductor ring resonator consists of $1.55{\mu}m$ GaInAsP-InP multiple quantum wells. The lasing characteristics were observed by varying the structure parameters of the MMI-coupled square ring resonators. It is concluded that the MMI-coupled scheme selects a single spectral lasing mode in the double square ring cavities.

Single Mode Lasing in InGaAsP/InP Semiconductor Coupled Square Ring Cavities

현경숙,문희종,이태규 한국광학회 2012 Current Optics and Photonics Vol.16 No.2

This work reports the stability of the resonant characteristics in multimode interferometer coupled square ring semiconductor cavities. Based on the analysis of single square ring cavities, the single mode operations in the multimode interferometer coupled ring cavities are analyzed and the devices are demonstrated on the semiconductor multiple quantum well epitaxial structure. By varying the lasing conditions such as substrate temperature and input pump power, single resonant mode operations are also observed.