title: Optical phase conjugation assisted scattering lens: variable focusing and 3D patterning.
abstract: Variable light focusing is the ability to flexibly select the focal distance of a lens. This feature presents technical challenges, but is significant for optical interrogation of three-dimensional objects. Numerous lens designs have been proposed to provide flexible light focusing, including zoom, fluid, and liquid-crystal lenses. Although these lenses are useful for macroscale applications, they have limited utility in micron-scale applications due to restricted modulation range and exacting requirements for fabrication and control. Here, we present a holographic focusing method that enables variable light focusing without any physical modification to the lens element. In this method, a scattering layer couples low-angle (transverse wave vector) components into a full angular spectrum, and a digital optical phase conjugation (DOPC) system characterizes and plays back the wavefront that focuses through the scattering layer. We demonstrate micron-scale light focusing and patterning over a wide range of focal distances of 22-51 mm. The interferometric nature of the focusing scheme also enables an aberration-free scattering lens. The proposed method provides a unique variable focusing capability for imaging thick specimens or selective photoactivation of neuronal networks.
authors.affiliation: Department of Medical System Engineering, Gwangju Institute of Science and Technology, 123 Cheomdan-gwagiro, Buk-gu, Gwangju 61005, South Korea.
authors.forename: Jihee
authors.initials: J
authors.lastname: Ryu
authors.affiliation: Electrical Engineering, California Institute of Technology, 1200 E California Boulevard, Pasadena, California, 91125, USA.
authors.forename: Mooseok
authors.initials: M
authors.lastname: Jang
authors.affiliation: Advanced Photonics Research Institute, Gwangju Institute of Science and Technology, 123 Cheomdan-gwagiro, Buk-gu, Gwangju 61005, South Korea.
authors.forename: Tae Joong
authors.initials: TJ
authors.lastname: Eom
authors.affiliation: Electrical Engineering, California Institute of Technology, 1200 E California Boulevard, Pasadena, California, 91125, USA.
authors.forename: Changhuei
authors.initials: C
authors.lastname: Yang
authors.affiliation: Department of Medical System Engineering, Gwangju Institute of Science and Technology, 123 Cheomdan-gwagiro, Buk-gu, Gwangju 61005, South Korea.
authors.forename: Euiheon
authors.initials: E
authors.lastname: Chung
mesh_terms: D003198:Computer Simulation; D004867:Equipment Design / Q000379:methods*; D019544:Equipment Failure Analysis; D006696:Holography / Q000295:instrumentation* / Q000379:methods; D007909:Lenses; D008027:Light; D055096:Optical Devices; D012542:Scattering, Radiation