Journal/Magazine
Editors Pick
- [하이라이트 논문] 한국광학회지 Vol. 35 No.5 (2024 Ocotber) Soliton Mode-locking and Numerical Analysis of Yb3+-doped Potassium Double Tungstate Lasers in Compact Laser Cavity Geometries Yb3+ 도핑된 칼륨 이중 텅스테이트 결정을 이용한 소형 공진기에서의 솔리톤 모드 잠금 레이저 구현 및 수치 해석 김덕우 ㆍ고광훈ㆍ이상민† 한국광학회지 Vol. 35 No.5 (2024 October) pp. 241-249 DOI: https://doi.org/10.3807/KJOP.2024.35.5.241 Fig. 1 Schematic of experimental setup. LD, polarization maintaining fiber-coupled laser diode; COL, fiber collimator (NA = 0.50); HWP, half-wave plate; Lens, pump focusing lens with a focal length of 50 mm; M 1,2 , concave mirrors with a radius of curvature of 50 mm; OC, output coupler; CM, GTI chirped mirror; C, laser crystal. Keywords: 펨토초 레이저, 모드 잠금, 이터븀 OCIS codes: (140.3580) Lasers, solid-state; (140.3615) Lasers, ytterbium; (140.4050) Mode-locked lasers; (140.7090) Ultrafast lasers; (190.5530) Pulse propagation and temporal solitons 초록 본 연구에서는 Yb3+ 이온이 도핑된 세 종류의 이중 텅스텐 결정, Yb:KGdW, Yb:KYW 및 Yb:KLuW을 사용하여 1039 nm의 중심파장 영역에서 반복율이 405 MHz인 연속파 모드 잠금된 소형 고체 레이저를 구현하였다. 모드 잠금을 위한 광스위칭 소자로 반도체 포화 흡수체 거울을 사용하였고, 모드 잠금 상태들은 세 결정 모두에서 수 시간 이상 Q-스위칭 불안정성 없이 안정적으로 동작하였다. 특히 Yb:KGdW 결정을 이용한 레이저는 최고 출력 125 mW에서 108 fs의 펄스폭을 갖는 펄스를 방출하였다. 또한 표준 분할 단계 푸리에 방법을 이용하여 공진기의 군지연 분산 및 자체 위상 변조를 고려한 Haus Master 방정식을 수치 해석으로 풀고, 그 결과를 실험결과와 비교 및 분석하였다. Abstract In this study, we demonstrate compact mode-locked laser operations using three different kinds of Yb3+-doped potassium double tungstate laser crystals, Yb:KGdW, Yb:KYW and Yb:KLuW, operating near 1040 nm at a repetition rate of 405 MHz. We utilized a semiconductor saturable absorber mirror (SESAM) as a mode locker, successfully maintaining mode-locked states for several hours without any Q-switching instabilities for all types of laser crystals. Notably, the Yb:KGdW mode-locked laser produces the shortest pulse with a duration of 108 fs, delivering 125 mW of output power. Additionally, we conducted a numerical analysis by solving the Haus Master equation, which incorporates the effect of group delay dispersion and self-phase modulation, using the standard split-step Fourier method.
- [Editor's Pick] Current Optics and Photonics Vol. 8 no. 5 (2024 October) Cell Death Inhibition Effect of Antioxidant Activity by 630 and 850 nm LEDs in RAW264.7 Cells Hee Eun Kim, Eun Young Kim>, Jin Chul Ahn*, and Sang Joon Mo** Current Optics and Photonics Vol. 8 No. 5 (2024 October), pp. 441-455 DOI: https://doi.org/10.3807/COPP.2024.8.5.441 Fig. 1 Photographs showing the lighting conditions during exposure of RAW264.7 cells to red (left) and near-infrared (right) LED lights. LED devices for a cell culture plate with an output irradiance of 10 mW/cm2 light at a distance of 5 cm. To cool the LED board, a cooling fan is installed to control temperature rise. Keywords: Antioxidant activity, Cell death, Light-emitting diode, RAW264.7 cell OCIS codes: (000.1430) Biology and medicine; (170.0170) Medical optics and biotechnology; (170.1420) Biology; (170.1610) Clinical applications Abstract This study objective was to evaluate the effects and mechanisms of low-level laser therapy in H2O2-induced cell death in mouse macrophage RAW264.7 cell. After irradiation with 630 and 850 nm wavelength diode lasers with an intensity of 10 mW/cm2 in RAW264.7 cells treated with 0.7 Mm H2O2, the effects and mechanisms of the two wavelengths on cell death inhibition were evaluated using MTT assay, ROS staining, TUNEL assay, flow cytometry analysis, and Western blot analysis. As a result, 630 or 850 nm light-emitting diodes (LED) were irradiated for 10 or 40 minutes to increase cell viability with H2O2 by about 1.7- or 1.6-fold, respectively. In addition, irradiation with two LEDs showed significant ROS scavenging effects, and TUNEL-positive cells were significantly reduced by 45.7% (630 nm) and 37.8% (850 nm) compared to cells treated with H2O2 alone. The Bax/Bcl-2 ratio of cells irradiated with both LEDs was significantly lower than that of cells treated with H2O2 only, and the expression of procaspase-3 and cleaved PARP was also significantly expressed in the direction of suppressing cell death. In conclusion, ROS scavenging activity by both LEDs irradiation leads to the expression of cell death pathway proteins in the direction of inhibiting cell death.