Keshri Sanjay, Murphy Kevin, Toal Vincent, Naydenova Izabela, Martin Suzanne
Appl Opt. 2018 Aug 1;57(22):E163-E172. doi: 10.1364/AO.57.00E163.
A holographic optical element (HOE) was developed to collimate a monochromatic light-emitting diode (LED). The fabrication was achieved by the interference of collimated and diverging beams from a 532 nm laser to produce the required photonic structure in a self-developing photopolymer material. The experimental values of diffraction efficiency and spatial period across the HOE were compared with their expected theoretical values. Good agreement was found for the spatial period; however, the diffraction efficiency varied significantly across the lens. In this paper, two approaches have been taken to address this variation: (1) modification of recording geometry and (2) optimization of recording intensity and exposure time at constant energy. The performance of an optimized HOE (cylindrical holographic lens) was then demonstrated using a 532 nm laser beam. The optimized conditions for the cylindrical holographic lens were used to fabricate a spherical holographic lens of the same numerical aperture for LED applications. This type of lens has the potential to be used in combination with LED sources.
开发了一种全息光学元件（HOE）来准直单色发光二极管（LED）。通过532纳米激光器发出的准直光束和发散光束的干涉，在自显影光聚合物材料中产生所需的光子结构，从而实现制造。将HOE上衍射效率和空间周期的实验值与其预期理论值进行了比较。发现空间周期吻合良好；然而，整个透镜的衍射效率变化显著。本文采取了两种方法来解决这种变化：（1）记录几何结构的修改；（2）在能量恒定的情况下优化记录强度和曝光时间。然后使用532纳米激光束展示了优化后的HOE（柱面全息透镜）的性能。利用柱面全息透镜的优化条件，制造了用于LED应用的具有相同数值孔径的球面全息透镜。这种类型的透镜有潜力与LED光源结合使用。
