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- [Editor's Pick] Current Optics and Photonics Vol. 8 no. 1 (2024 February) SLODAR System Development for Vertical Atmospheric Disturbance Profiling at Geochang Observatory Ji Yong Joo1, Hyeon Seung Ha1, Jun Ho Lee1,2 *, Do Hwan Jung1,3, Young Soo Kim1,3, and Timothy Butterley4 Current Optics and Photonics Vol. 8 No. 1 (2024 February) pp. 30-37 DOI: https://doi.org/10.3807/COPP.2024.8.1.30 Fig. 1 Schematic diagram illustrating the crossed-beam method. This specific diagram depicts the construction of 8 layers of vertical profiling with 8 sub-aperture wavefront sensing [13]. Keywords: Adaptive optics, Atmospheric turbulence, Fried parameter, Refractive index structure function (C2n), SLODAR OCIS codes: (010.1330) Atmospheric turbulence; (120.4640) Optical instruments; (220.1080) Active or adaptive optics; (350.1260) Astronomical optics Abstract Implemented at the Geochang Observatory in South Korea, our slope detection and ranging (SLODAR) system features a 508 mm Cassegrain telescope (f /7.8), incorporating two Shack-Hartmann wave-front sensors (WFS) for precise measurements of atmospheric phase distortions, particularly from nearby binary or double stars, utilizing an 8 × 8 grid of sampling points. With an ability to reconstruct eight-layer vertical atmospheric profiles, the system quantifies the refractive index structure function (C2n) through the crossed-beam method. Adaptable in vertical profiling altitude, ranging from a few hundred meters to several kilometers, contingent on the separation angle of binary stars, the system operates in both wide (2.5 to 12.5 arcminute separation angle) and narrow modes (11 to 15 arcsecond separation angle), covering altitudes from 122.3 to 611.5 meters and 6.1 to 8.3 kilometers, respectively. Initial measurements at the Geochang Observatory indicated C values up to 181.7 meters with a Fried parameter (r0) of 8.4 centimeters in wide mode and up to 7.8 kilometers with an r0 of 8.0 centimeters in narrow mode, suggesting similar seeing conditions to the Bohyun Observatory and aligning with a comparable 2014–2015 seeing profiling campaign in South Korea.
- [하이라이트 논문] 한국광학회지 Vol. 35 No.1 (2024 February) 나노구조 기반 초박형 적외선 차단 필터 An Ultra-thin IR Cut-off Filter Based on Nanostructures 양현도ㆍ이종권1† 한국광학회지 Vol. 35 No.1 (2024 February) pp. 24-29 DOI: https://doi.org/10.3807/KJOP.2024.35.1.024 Fig. 1 (a) Ellipsoidal and hyperboloidal dispersion relations and (b) schematic of a layered metal-dielectric metastructure with the permittivities of the two constituents given as em and ed . Keywords: 적외선 차단 필터, 나노 패턴, 쌍곡선 메타구조, 초박형 OCIS codes: (120.2440) Filters; (130.1750) Components; (130.3130) Integrated optics materials; (310.6628) Subwavelength structures, nano structures 초록 본 연구에서는 나노패턴된 금속(Ag)-유전체(PDMS) 다층 기반의 쌍곡선 메타구조를 제안하고 영상 소자용 적외선 차단 필터의 성능에 대해 보고한다. 사각형 모양의 Ag 나노 패턴의 크기와 Ag 나노 패턴을 둘러싼 PDMS의 두께를 최적화함으로써, 제안된 IR 차단 필터가 0.70–1.01μm 파장 대역의 빛을 99% 차단하면서도 가시광 영역에서 94% 이상의 높은 투과율을 나타냄을 보였다. 차단 파장 대역은 쌍곡선 메타구조의 epsilon-near-zero 파장보다 긴 파장 영역에서 시작하여 Ag 나노 패턴에 의한 플라즈모닉 흡수가 강한 지점에서 끝나게 된다. 근적외선 차단 대역보다 긴 파장 영역에서는 수평으로 인접한 Ag 나노패턴들 사이의 플라즈모닉 커플링 효과로 다시 투과도가 증가됨을 알 수 있다. 이러한 메타구조체는 적외선 차단 필터의 성능을 향상시킬 수 있을 뿐만 아니라 공정 단순화를 통해 초박형 제조가 가능하여, 다양한 평면 광학 및 집적광학 부품들에 적용될 수 있다. Abstract We propose a hyperbolic metastructure based on a nanopatterned metal (Ag)-dielectric (PDMS) multilayer and report on its performance in an infrared (IR) cut-off filter for imaging devices. By optimizing the size of the square-shaped Ag nanopattern and the thickness of PDMS surrounding the Ag nanopattern, the proposed IR cut-off filter blocks 99% of light in the 0.70–1.01 μm wavelength band while maintaining a high transmittance of over 94% in the visible region. Here, the cut-off wavelength band starts at a region above the epsilon-near-zero wavelength of the hyperbolic metastructure and ends at the point where plasmonic absorption appears strongly. It is observed that transmittance in the wavelength region longer than the IR cut-off band increases again due to plasmonic coupling among horizontally adjacent Ag nanopatterns. This metastructure can improve the performance of IR-locking filters as well as allow it to be manufactured ultra-thin, which is applicable to various planar optical elements and integrated optical components.