Journal of Quantitative Spectroscopy & Radiative Transfer 206 (2018) 101–104 Contents lists available at ScienceDirect Journal of Quantitative Spectroscopy & Radiative Transfer journal homepage: www.elsevier.com/locate/jqsrt Fully reflective photon sieve Wenbo Sun a,∗ , Yongxiang Hu b , David G. MacDonnell b , Hyun Jung Kim c , Carl Weimer d , Rosemary R. Baize b a Science Systems and Applications, Inc., Hampton, VA 23666, USA b NASA Langley Research Center, Hampton, VA 23681, USA c National Institute of Aerospace, Hampton, VA 23666, USA d Ball Aerospace and Technologies Corp., Boulder, CO 80301, USA a r t i c l e i n f o Article history: Received 28 September 2017 Revised 16 October 2017 Accepted 2 November 2017 Available online 8 November 2017 Keywords: Remote sensing and sensors Optical devices Diffractive lenses a b s t r a c t Photon sieves (PS) have many applications and various designs in focusing light. However, a traditional PS only has a light transmissivity up to ∼25% and a focusing efficiency up to ∼7%, which hinder the application of them in many fields, especially for satellite remote sensing. To overcome these inherent drawbacks of traditional PSs, a concept of reflective photon sieve is developed in this work. This reflec- tive photon sieve is based on a transparent membrane backed by a mirror. The transparent membrane is optimally a fully transparent material sheet with given refractive index and designed geometric thickness which has an optical thickness of a quarter incident wavelength (i.e. an anti-reflective coating). The PS- patterned pinholes are made on the transparent membrane. The design makes the light reflected from pinholes and that from zones of membrane material have 180° phase difference. Thus, light incident on this optical device is reflected and focused on its focal point. This device can have a reflectivity of ∼100% and a focusing efficiency of ∼50% based on numerical simulation. This device functions similar to a con- cave focusing mirror but can preserve the phase feature of light (such as that for the light with orbital angular momentum). It also has excellent wavelength-dependent property, which can exclude most of the undesired light from the focal point. A thin sheet of this component can perform the joint function of lenses and gratings/etalons in the optical path of a remote sensing system, thus is suitable for con- troling/filtering light in compact instruments such as satellite sensors. This concept is validated by the finite-difference time domain (FDTD) modeling and a lab prototype in this study. © 2017 Elsevier Ltd. All rights reserved. 1. Introduction Photon sieves (PS) [1] have many applications [1–5] and vari- ous designs [6–8] in focusing light. However, a traditional PS only has a light transmissivity up to ∼25% and a focusing efficiency up to ∼7%, which hinder the application of them in many fields, es- pecially for satellite remote sensing. To overcome the low trans- mission problem of regular photon sieves, we have developed a concept of a fully transparent photon sieve [9]. Based on the work in [9], a reflective PS concept is developed in this study, to im- prove the transmissivity and focusing efficiency, and for flexibility in application of the PS technique in compact optical devices such as satellite sensors, when a focusing of light by reflection is con- venient in controling of light. Kalläne et al. [10] reported a type of reflective photon sieve constructed by an array of nanomirrors with an off-axis, off-normal incidence reflection geometry. Com- ∗ Corresponding author. E-mail address: wenbo.sun-1@nasa.gov (W. Sun). pared to transmission optical elements, their device’s signal-to- background ratio is significantly increased by separating the first from other diffraction orders without drastically reducing the size of the smallest diffractive element. Their reflection photon sieve produces sharp foci at maximum contrast and offers the advan- tages of effective heat dissipation and a large working space above the focal plane. However, this device is not easily manufactured for specifically positioned discrete nanomirrors, and only less than 50% of the incident light is effectively reflected. In this study, we pro- pose a new type of reflective photon sieve that is fully reflective and relatively easy to manufacture. 2. Method In this study, the reflective photon sieve is based on a transpar- ent membrane backed by a mirror as shown in Fig. 1. The transpar- ent membrane is basically a fully transparent material sheet with given refractive index and designed geometric thickness which op- timally has an optical thickness of a quarter incident wavelength (i.e. an anti-reflective coating). The PS-patterned pinholes are made https://doi.org/10.1016/j.jqsrt.2017.11.002 0022-4073/© 2017 Elsevier Ltd. All rights reserved.