Intra-system optical interconnection module directly integrated on a polymeric optical waveguide

Rho, B. S.,Hwang, S. H.,Lim, J. W.,Kim, G. W.,Cho, C. H.,Lee, W.-J. The Optical Society 2009 Optics express Vol.17 No.3

<P>A new intra-system optical interconnection module directly integrated on a polymeric optical waveguide is suggested. A polymeric optical waveguide plays a role in the propagation path of optical signals from the transmitter to the receiver and in a platform integrated with various optical/electrical devices such as a vertical cavity surface emitting laser, photodiode, very large scale integrated circuit chips, and electrical connectors. Because the polymeric optical waveguide is simultaneously used as an integrated platform, the fabrication process of the optical interconnection module is very simple, and the proposed process is compatible with the conventional printed circuit board process. The suggested optical interconnection was also successfully demonstrated with a 5-Gb/s data transmission through the module directly integrated on a polymeric optical waveguide.</P>

Design of 3D isotropic metamaterial device using smart transformation optics.

Shin, Dongheok,Kim, Junhyun,Yoo, Do-Sik,Kim, Kyoungsik Optical Society of America 2015 Optics express Vol.23 No.17

<P>We report here a design method for a 3 dimensional (3D) isotropic transformation optical device using smart transformation optics. Inspired by solid mechanics, smart transformation optics regards a transformation optical medium as an elastic solid and deformations as coordinate transformations. Further developing from our previous work on 2D smart transformation optics, we introduce a method of 3D smart transformation optics to design 3D transformation optical devices by maintaining isotropic materials properties for all types of polarizations imposing free or nearly free boundary conditions. Due to the material isotropy, it is possible to fabricate such devices with structural metamaterials made purely of common dielectric materials. In conclusion, the practical importance of the method reported here lies in the fact that it enables us to fabricate, without difficulty, arbitrarily shaped 3D devices with existing 3D printing technology.</P>

Image Quality Evaluation and Tolerance Analysis for Camera Lenses with Diffractive Element

Lee, Sang-Hyuck,Jeong, Ho-Seop,Jin, Young-Su,Song, Seok-Ho,Park, Woo-Je Optical Society of Korea 2006 Current Optics and Photonics Vol.10 No.3

A novel image quality evaluation method, which is based on combination of the rigorous grating diffraction theory and the ray-optic method, is proposed. It is applied for design optimization and, tolerance analysis of optical imaging systems implementing diffractive optical elements (DOE). The evaluation method can predict the quality and resolution of the image on the image sensor plane through the optical imaging system. Especially, we can simulate the effect of diffraction efficiencies of DOE in the camera lenses module, which is very effective for predicting different color sense and MTF performance. Using this method, we can effectively determine the fabrication tolerances of diffractive and refractive optical elements such as the variations' in profile thickness, and the shoulder of the DOE, as well as conventional parameters such as decenter and tilt in optical-surface alignments. A DOE-based 2M-resolution camera lens module designed by the optimization process based on the proposed image quality evaluation method shows ${\sim}15%$ MTF improvement compared with a design without such an optimization.

Optimization of sideband modulation in optical-heterodyne-downmixed electro-optic sensing

Lee, Dong-Joon,Whitaker, John F. The Optical Society 2009 Applied Optics Vol.48 No.8

<P>Enhancements of the modulation depth in an electro-optic sensing application, through optimization of the modulation sidebands in both an electro-optic modulator and a microcavity electro-optic probe, have been investigated. The principles and methods of optimizing the operational bias points for the devices are described from the point of view of both an electro-optic modulator and probe, and their different optimum characteristics for signal-modulation depth, due to their huge scale gap, are presented. We use an optical-heterodyne receiver employing a fast modulator along with the electro-optic sensing technique to achieve high-frequency microwave electric field mapping. The practical limitations to sensitivity enhancement, solutions for compensating distortion, and combined optimization conditions for both electro-optic modulation and sensing are presented by exploring the evolution of field-mapping distributions.</P>

High-speed spectral domain polarization- sensitive optical coherence tomography using a single camera and an optical switch at 1.3 mum.

Lee, Sang-Won,Jeong, Hyun-Woo,Kim, Beop-Min SPIE--the International Society for Optical Engine 2010 JOURNAL OF BIOMEDICAL OPTICS Vol.15 No.1

<P>We propose high-speed spectral domain polarization-sensitive optical coherence tomography (SD-PS-OCT) using a single camera and a 1 x 2 optical switch at the 1.3-mu m region. The PS-low coherence interferometer used in the system is constructed using free-space optics. The reflected horizontal and vertical polarization light rays are delivered via an optical switch to a single spectrometer by turns. Therefore, our system costs less to build than those that use dual spectrometers, and the processes of timing and triggering are simpler from the viewpoints of both hardware and software. Our SD-PS-OCT has a sensitivity of 101.5 dB, an axial resolution of 8.2 mu m, and an acquisition speed of 23,496 A-scans per second. We obtain the intensity, phase retardation, and fast axis orientation images of a rat tail tendon ex vivo. (C) 2010 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3277668]</P>

Auto-focus Control by Chromatic Filtering in Laser Welding

Kim, Cheol-Jung,Baik, Sung-Hoon,Kim, Min-Suk,Chung, Chin-Man,Kim, Kwang-Jung Optical Society of Korea 2000 Current Optics and Photonics Vol.4 No.2

Optical monitoring using the chromatic aberration of focusing optics is applied to auto-focus control in laser welding. The spectral transmittance of thermal radiation from a weld pool through an aperture depends on the wavelength of the spectral band and on the distance of the weld pool from the focusing optics. Its dependence has been used to monitor the focus shift in laser welding by measuring the spectral band signals filtered by the aperture. The difference between pulsed and continuous laser welding is analyzed. Furthermore, the dependence of the focus shift monitoring on the weld pool size variation is optimized to monitor the focus shift independently from the laser power change at the weld pool. The performance of the auto-focus control with chromatic filtering is presented for pulsed laser welding.

Elimination of flux loss by optimizing the groove angle in modified Fresnel lens to increase illuminance uniformity, color uniformity and flux efficiency in LED illumination

Kim, Byungwook,Choi, Minseok,Kim, Hokwan,Lim, Jiseok,Kang, Shinill The Optical Society 2009 Optics express Vol.17 No.20

<P>A Fresnel lens is an optical component that can be used to create systems more compact, cost-effective, and lightweight than those using conventional continuous surface optics. However, Fresnel lenses can usually cause a loss of flux efficiency and non-uniform distribution of illuminance due to secondary refraction by surface discontinuities, especially along the groove facet. We therefore proposed to modify a groove angle in the Fresnel lens and analyzed interrelation between the groove angle and multiple optical performances, such as flux efficiency and the uniformity of illuminance and color. The groove angle was optimized to maximize the uniformity and efficiency in the target viewing angle considering various weights of merit functions. Specifically, in our study, when the uniformity of illuminance had a little more weight than the flux efficiency (ratio of 0.6:0.4), final optimum groove angles of 24.7 degrees , 29.4 degrees , and 31.3 degrees were obtained at target viewing angles of 20 degrees , 30 degrees , and 40 degrees , respectively. We also fabricated a modified Fresnel lens with a groove angle of 29.4 degrees using UV-imprinting. The real optical performance of the fabricated Fresnel lens was then compared to that of a spherical lens.</P>

Spectra of Optical-field Ionized Gases by a Femtosecond Ti:Sapphire Laser

Mock, Tomas,Shin, Hyun-Joon,Cha, Yong-Ho,Lee, Dong-Gun,Hong, Kyung-Han,Nam, Chang-Hee Optical Society of Korea 1998 Current Optics and Photonics Vol.2 No.2

We report on the spectroscopic investigation of optical-field ionized plasmas in the soft X-ray spectral region. The experiment was carried out by focusing pulses of the high-power Ti:Sapphire laser with an energy of ~ 40 mJ and time duration of ~30 fs into a gas jet of krypton, xenon, and argon from a pulsed nozzle. Strong soft X-ray emission on lines from ionic stages of $Kr^{7+} , Kr^{8+} , Xe^{7+} , Ar^{7+} , and Ar^{8+}$ is reported. The experimental result was found to be in good agreement with theoretical prediction.

Feasibility study of the application of radially polarized illumination to solid immersion lens-based near-field optics.

Yoon, Yong-Joong,Kim, Wan-Chin,Park, No-Cheol,Park, Kyoung-Su,Park, Young-Pil Optical Society of America 2009 Optics letters Vol.34 No.13

<P>We analyzed the behavior of the electric field in a focal plane consisting of a solid immersion lens (SIL), an air gap, and a measurement sample for radially polarized illumination in SIL-based near-field optics with an annular aperture. The analysis was based on the Debye diffraction integral and multiple beam interference. For SIL-based near-field optics whose NA is higher than unity, radially polarized light generates a smaller beam spot on the bottom surface of a SIL than circularly polarized light; however, the beam spot on the measurement sample is broadened with a more dominant transverse electric field. By introducing an annular aperture technique, it is possible to decrease the effects of the transverse electric field, and therefore the size of the beam spot on the measurement sample can be small. This analysis could have various applications in near-field optical storage, near-field microscopy, lithography at ultrahigh resolution, and other applications that use SILs for high resolution.</P>

Bandwidth enhancement of electro-optic sensing using high-even-order harmonic sidebands.

Lee, Dong-Joon,Whitaker, John F Optical Society of America 2009 Optics express Vol.17 No.17

<P>We demonstrate that the bandwidth of an electro-optic sensing system can be significantly enhanced by the use of even-order harmonic sidebands (order > 2) produced on an optical-carrier probe beam with two cascaded electro-optic modulators. The sensing frequency range may be routinely expanded by at least four times, with respect to the use of fundamental-harmonic sidebands, by enhancing the nonlinearity of high-order-harmonic electro-optic modulation. The creation of harmonic modulation sidebands up to the sixth order of the drive frequency on a laser-diode output is described analytically, as is photonic heterodyne down-conversion of microwave signals using these high-order even harmonics within an electro-optic sensor crystal. The nonlinear harmonics serve as beneficial local-oscillator modulations for broadband electro-optic detection of microwave fields without nonlinear distortion. Transverse near-field distributions from an 18.5 GHz patch antenna are extracted using the fourth- (sixth-) order-harmonic sidebands at the output of the cascaded electro-optic modulators driven with a 4.6- (3.1-) GHz continuous-wave input.</P>