회전형 기하학적-위상 회절격자 제작

Abstract

Optical devices based on geometric phases are attracting attention in order to overcome the limitations of existing refractive and diffractive optical devices. Among Geometric phase optical elements (GPOE), Polarization volume gradings (PVG) have larger wavelength and angular bandwidth than conventional holographic volume gradings (HVG), making it one of the methods to increase output efficiency compared to input in AR/VR fields such as AR glass. In this paper, Half wave plate (HWP) and Quarter wave plate (QWP) were added to Lloyd's mirror interference system to make it operate by circular polarization interference, and then non-chiral GPOE and chiral GPOE were manufactured by photoalignment. Non-chiral GPOE satisfying QWP was manufactured for each period, and the alignment quality was confirmed by diffraction efficiency measurement and polarization microscopy. Chiral GPOE was designed and manufactured so that the diffraction angle satisfies the total reflection condition. Polarization selectivity was confirmed with the manufactured PVG, and the alignment quality was analyzed through diffraction efficiency and transmittance spectrum measurement.|기존의 굴절 및 회절 광학 소자의 한계를 넘어서기 위해 기하학적 위상(Geometric phase)을 이용한 광학 소자가 주목을 받고 있다. Geometric phase optical elements (GPOE) 중 Polarization volume gratings (PVG)은 기존의 holographic volume gratings (HVG)보다 파장과 각도 대역폭이 커서 AR 글라스와 같은 AR/VR 분야에서 입력 대비 출력의 효율을 높이는 방법 중 하나가 된다. 본 논문에서는 Lloyd’s mirror interference system에 Half wave plate (HWP), Quarter wave plate (QWP)를 추가해 원형 편광 간섭으로 작동되게 만든 뒤 광 배향 방식으로 non-chiral GPOE, chiral GPOE를 제작하였다. QWP를 만족하는 non-chiral GPOE를 주기 별로 제작해 액정이 배향된 정도를 회절 효율 측정 및 편광 현미경으로 확인하였다. chiral GPOE는 회절각이 전반사 조건을 만족하도록 설계 및 제작하였다. 제작된 PVG로 편광 선택성을 확인하였으며 액정이 배향된 정도를 회절 효율 및 투과도 스펙트럼 측정을 통해 분석하였다.