Holographic display for see-through augmented reality using mirror-lens holographic optical element

Li, Gang,Lee, Dukho,Jeong, Youngmo,Cho, Jaebum,Lee, Byoungho OPTICAL SOCIETY OF AMERICA 2016 Optics letters Vol.41 No.11

<P>A holographic display system for realizing a three-dimensional optical see-through augmented reality (AR) is proposed. A multi-functional holographic optical element (HOE), which simultaneously performs the optical functions of a mirror and a lens, is adopted in the system. In the proposed method, amirror that is used to guide the light source into a reflection type spatial light modulator (SLM) and a lens that functions as Fourier transforming optics are recorded on a single holographic recording material by utilizing an angular multiplexing technique of volume hologram. The HOE is transparent and performs the optical functions just for Bragg matched condition. Therefore, the real-world scenes that are usually distorted by a Fourier lens or an SLM in the conventional holographic display can be observed without visual disturbance by using the proposed mirror-lens HOE (MLHOE). Furthermore, to achieve an optimized optical recording condition of the MLHOE, the optical characteristics of the holographic material are measured. The proposed holographic AR display system is verified experimentally. (C) 2016 Optical Society of America</P>

Radial-firing optical fiber tip containing conical-shaped air-pocket for biomedical applications.

Lee, Seung Ho,Ryu, Yong-Tak,Son, Dong Hoon,Jeong, Seongmook,Kim, Youngwoong,Ju, Seongmin,Kim, Bok Hyeon,Han, Won-Taek Optical Society of America 2015 Optics express Vol.23 No.16

<P>We report a novel radial-firing optical fiber tip containing a conical-shaped air-pocket fabricated by deforming a hollow optical fiber using electric arc-discharge process. The hollow optical fiber was fusion spliced with a conventional optical fiber, simultaneously deforming into the intagliated conical-shaped region along the longitudinal fiber-axis of the fiber due to the gradual collapse of the cavity of the hollow optical fiber. Then the distal-end of the hollow optical fiber was sealed by the additional arc-discharge in order to obstruct the inflow of an external bio-substance or liquid to the inner air surface during the surgical operations, resulting in the formation of encased air-pocket in the silica glass fiber. Due to the total internal reflection of the laser beam at the conical-shaped air surface, the laser beam (lambda = 632.8 nm) was deflected to the circumferential direction up to 87 degree with respect to the fiber-axis. (C) 2015 Optical Society of America</P>

Measurement of optical loss in nanophotonic waveguides using integrated cavities

Jeon, Seungwoo,Kim, Heungjoon,Song, Bong-Shik,Yamaguchi, Yuki,Asano, Takashi,Noda, Susumu OPTICAL SOCIETY OF AMERICA 2016 Optics letters Vol.41 No.23

<P>Measurement of optical loss in nanophotonic waveguides is necessary for monitoring the properties of integrated photonic devices. We propose a simple method of measuring the optical loss using integrated nanocavities. It is shown theoretically that weak coupling between the waveguide and cavities leads to a direct estimation of the optical loss by measuring light radiated from the cavities. In addition, we experimentally demonstrate the optical loss in a fabricated photonic crystal waveguide. Our method gives not only a degree of freedom in real-time monitoring of the optical properties of nanophotonic structures, but it also can be used for various waveguide-based applications. (C) 2016 Optical Society of America</P>

Optical see-through Maxwellian near-to-eye display with an enlarged eyebox

Kim, Seong-Bok,Park, Jae-Hyeung Optical Society of America 2018 Optics letters Vol.43 No.4

<P>We propose a Maxwellian near-to-eye display implemented using a multiplexed holographic optical element. Maxwellian configuration removes the focal cue of the displayed virtual image completely, presenting an always-focused image to the observer regardless of the focal length of the eye. The transparent property of the holographic optical element enables the optical see-through feature, making the proposed near-to-eye display suitable for augmented reality applications. The multiplexing of multiple concave mirrors into a single holographic optical element enlarges the effective eyebox, relaxing the limitation of the conventional Maxwellian displays. Optical experiment confirms that the proposed display can present always-focused images on top of the real environment with 9.2 degrees(H) x 5.2 degrees (V) field of view, and 9 mm (H) x 3mm (V) eyebox. (C) 2018 Optical Society of America</P>

Experimental power spectral density analysis for mid- to high-spatial frequency surface error control

Del Hoyo, Javier,Choi, Heejoo,Burge, James H.,Kim, Geon-Hee,Kim, Dae Wook OSA OPTICAL SOCIETY OF AMERICA 2017 Applied Optics Vol.56 No.18

<P>The control of surface errors as a function of spatial frequency is critical during the fabrication of modern optical systems. A large-scale surface figure error is controlled by a guided removal process, such as computer-controlled optical surfacing. Smaller-scale surface errors are controlled by polishing process parameters. Surface errors of only a few millimeters may degrade the performance of an optical system, causing background noise from scattered light and reducing imaging contrast for large optical systems. Conventionally, the microsurface roughness is often given by the root mean square at a high spatial frequency range, with errors within a 0.5 x 0.5 mm local surface map with 500 x 500 pixels. This surface specification is not adequate to fully describe the characteristics for advanced optical systems. The process for controlling and minimizing mid- to high-spatial frequency surface errors with periods of up to similar to 2-3 mm was investigated for many optical fabrication conditions using the measured surface power spectral density (PSD) of a finished Zerodur optical surface. Then, the surface PSD was systematically related to various fabrication process parameters, such as the grinding methods, polishing interface materials, and polishing compounds. The retraceable experimental polishing conditions and processes used to produce an optimal optical surface PSD are presented. (C) 2017 Optical Society of America</P>

Passive Q-switching of microchip lasers based on Ho:YAG ceramics

Lan, R.,Loiko, P.,Mateos, X.,Wang, Y.,Li, J.,Pan, Y.,Choi, S. Y.,Kim, M. H.,Rotermund, F.,Yasukevich, A.,Yumashev, K.,Griebner, U.,Petrov, V. Optical Society of America 2016 Applied Optics Vol.55 No.18

<P>A Ho:YAG ceramic microchip laser pumped by a Tm fiber laser at 1910 nm is passively Q-switched by single-and multi-layer graphene, single-walled carbon nanotubes (SWCNTs), and Cr2+:ZnSe saturable absorbers (SAs). Employing SWCNTs, this laser generated an average power of 810 mW at 2090 nm with a slope efficiency of 68% and continuous wave to Q-switching conversion efficiency of 70%. The shortest pulse duration was 85 ns at a repetition rate of 165 kHz, and the pulse energy reached 4.9 mu J. The laser performance and pulse stability were superior compared to graphene SAs even for a different number of graphene layers (n = 1 to 4). A model for the description of the Ho:YAG laser Q-switched by carbon nanostructures is presented. This modeling allowed us to estimate the saturation intensity for multi-layered graphene and SWCNT SAs to be 1.2 +/- 0.2 and 7 +/- 1 MW/cm(2), respectively. When using Cr2+:ZnSe, the Ho:YAG microchip laser generated 11 ns/25 mu J pulses at a repetition rate of 14.8 kHz. (C) 2016 Optical Society of America</P>

Optimal modified lateral shearing interferometer for submicro-defects measurement of transparent objects

Seo, Kwang-Beom,Shin, Seung-Ho Optical Society of America 2017 Applied Optics Vol. No.

<P>Transparent optical components, which are required for high-precision and high-performance, are made by a plastic injection molding method. This can cause inner defects to appear because of the difference in cooling rate and pressure. However, submicron inner defects, caused by the refractive index error, are extremely difficult to determine. Thus, digital holographic microscopy based on an optimal modified lateral shearing interferometer is proposed. This is to measure submicron defects in transparent objects, such as a defective microlens. In addition, the optimal lateral shearing distance is proposed to efficiently remove duplicate images. Optical experiments using the suggested lateral shearing interferometer are presented, and the experimental results with a test microlens confirm the feasibility of the proposed method. (C) 2017 Optical Society of America</P>

Complementarity between fluorescence and reflection in photoluminescent cholesteric liquid crystal devices.

Kim, Jang-Kyum,Joo, Suk-Hwan,Song, Jang-Kun Optical Society of America 2013 Optics express Vol.21 No.5

<P>The combination of photoluminescence (PL) and cholesteric liquid crystal (CLC) provides interesting complementary features for an optimized display application. Distortion of the Bragg lattice of CLCs decreases selective reflection but increases fluorescence intensity; recovery of a uniform lattice in turn results in increased reflection and decreased fluorescence. This complementary relationship between the fluorescence and the Bragg reflection gives rise to self-compensations for color shifts due to either dynamic slow response of CLC helix or mismatch of oblique incidence of light with respect to the helical axis. These color shifts have long been intrinsic unsolved limitations of conventional CLC devices. Thus, the complementary coupling between the fluorescence and the CLC Bragg reflections plays an important role in improving the color performance and the quality of moving images. (c) 2013 Optical Society of America</P>

Dependence of the birefringence of polystyrene film on the stretching conditions

Ryu, Hee Jung,Hwang, Jiyong,Kim, Jongyoon,Lee, Ji-Hoon Optical Society of America 2018 Applied Optics Vol. No.

<P>We investigated the dependence of the birefringence of polystyrene (PS) film with a negative optical birefringence on the stretching conditions. We varied the stretching ratio (SR), stretching speed (SS), and stretching temperature (ST), and measured the inplane birefringence and the N-z coefficient of the PS film. The inplane birefringence was increased with greater SR and SS but decreased with greater ST. The Nz coefficient of the stretched PS film was around zero and showed similar dependence on the stretching conditions like inplane birefringence. (c) 2018 Optical Society of America</P>

Analysis of Brillouin frequency shift and acoustic waves in a hollow optical fiber.

Jeong, Yoonseob,Song, Kwang-Yong,Hotate, Kazuo,Oh, K Optical Society of America 2009 Optics letters Vol.34 No.20

<P>We propose and demonstrate a new method to manipulate the Brillouin frequency shift in silica optical fiber by introducing a silica hollow optical fiber (HOF) waveguide structure. Propagation characteristics of acoustic waves guided along the HOF were theoretically analyzed, and the corresponding Brillouin frequency shifts were measured by a Brillouin optical-correlation domain-analysis system. We experimentally observed that Brillouin frequency shift v(B) monotonically increases as a function of the central air-hole radius, which showed good agreement with the simulation results. We confirmed that a precise control of Brillouin frequency shift can be obtained by controlling the waveguide parameters of the HOF.</P>