• Title, Summary, Keyword: CMOS photonics

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A High Radiation Efficiency and Narrow Beam Width of Optical Beam Steering Using a Silicon-based Grating Structure Integrated with Distributed Bragg Reflectors (분배 브래그 반사기가 집적된 실리콘 기반 격자 구조를 이용한 광학 빔 방사 효율 및 조향 선폭 성능 향상)

  • Hong, Yoo-Seung;Cho, Jun-Hyung;Sung, Hyuk-Kee
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.23 no.3
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    • pp.311-317
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    • 2019
  • We first numerically analyzed the characteristics of a silicon-based grating structure for beam steering. The analysis includes the basic principle of the grating structure according to the wavelength, peak radiation angle, radiation efficiency, and full-width at the half maximum(FWHM) of the radiation angle. Based on the analysis, we propose a silicon-based grating structure integrated with distributed Bragg reflector(DBR) to obtain a high radiation efficiency and narrow beam width simultaneously. We performed the numerical optimization of the radiation efficiency and FWHM of the radiation angle according to the DBR position. By the design optimization using the proposed grating structure compatible with the complementary metal-oxide semiconductor(CMOS) process, we achieved a maximum radiation efficiency of 87.1% and minimum FWHM of radiation angle of $4.68^{\circ}$.

Evaluation of Chromatic-Dispersion-Dependent Four-Wave-Mixing Efficiency in Hydrogenated Amorphous Silicon Waveguides

  • Kim, Dong Wook;Jeong, Heung Sun;Jeon, Sang Chul;Park, Sang Hyun;Yoo, Dong Eun;Kim, Ki Nam;An, Shin Mo;Lee, El-Hang;Kim, Kyong Hon
    • Journal of the Optical Society of Korea
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    • v.17 no.5
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    • pp.433-440
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    • 2013
  • We present an experimental and numerical study of spectral profiles of effective group indices of hydrogenated amorphous silicon (a-Si:H) waveguides and of their chromatic-dispersion effect on the four-wave-mixing (FWM) signal generation. The a-Si:H waveguides of 220-nm thickness and three different widths of 400, 450 and 500 nm were fabricated by using the conventional CMOS device processes on a $2-{\mu}m$ thick $SiO_2$ bottom layer deposited on 8-inch Si wafers. Mach-Zehnder interferometers (MZIs) were formed with the a-Si:H waveguides, and used for precise measurement of the effective group indices and thus for determination of the spectral profile of the waveguides' chromatic dispersion. The wavelength ranges for the FWM-signal generation were about 45, 75 and 55 nm for the 400-, 450- and 500-nm-wide waveguides, respectively, at the pump wavelength of 1532 nm. A widest wavelength range for the efficient FWM process was observed with the 450-nm-wide waveguide having a zero-dispersion near the pump wavelength.

Design and Experiment of an Optical System using a Prism with a High Enough Refractive Index for Wet Fingerprint Identification (물 묻은 지문을 인식하기 위한 프리즘 광학계의 설계 및 실험적 고찰)

  • Kang, Myung-Hoon;Kim, Jin-Su;Jung, Jin-Woo;Ko, Eun-Mi;Kim, Jae-Gu;Cho, Guan-Sik;Song, Han-Jung;Hwang, Jae-Mun
    • Korean Journal of Optics and Photonics
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    • v.18 no.6
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    • pp.395-400
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    • 2007
  • We propose a design and analysis of an optical system using a prism with a high enough refractive index for wet fingerprint identification. Important parameters including the tilting angle($\beta$) of the $1^{st}$ image plane, an anamorphic distortion, and a tilt of image plane are considered in terms of the apex angle of the prism($\alpha$) and refractive index of the prism material. Our suggestion on refractive index and apex angle of the prism corroborates well with experimental results.

Direct Measurement of Distortion of Optical System of Lithography (노광 광학계의 왜곡수차 측정에 관한 연구)

  • Joo, WonDon;Lee, JiHoon;Chae, SungMin;Kim, HyeJung;Jung, Mee Suk
    • Korean Journal of Optics and Photonics
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    • v.23 no.3
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    • pp.97-102
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    • 2012
  • In general, one of the methods used to measure distortion is to use the full image of the regular pattern. However, because of low accuracy, this method is mainly used for an optical system such as a camera.. In order to measure distortion with high accuracy less than 1um, one can use the method of measuring the exact position of a mask image. In this case, a high accuracy stage with a laser encoder is required. In this paper, we investigate measurement of the distortion of high accuracy with a simple manual stage. The main idea is that we split and measure the mask image with the overlapping area by using CCD or CMOS, and then we get an exact position of the mask image by integrating the adjacent split images. We use the Canny Edge Detection method to get the position information of the mask image and we researched the process to exactly calculate distortion by using coordinate transformations and a least square method.

Transition-based Data Decoding for Optical Camera Communications Using a Rolling Shutter Camera

  • Kim, Byung Wook;Lee, Ji-Hwan;Jung, Sung-Yoon
    • Current Optics and Photonics
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    • v.2 no.5
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    • pp.422-430
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    • 2018
  • Rolling shutter operation of CMOS cameras can be utilized in optical camera communications in order to transmit data from an LED to mobile devices such as smart-phones. From temporally modulated light, a spatial flicker pattern is obtained in the captured image, and this is used for signal recovery. Due to the degradation of rolling shutter images caused by light smear, motion blur, and focus blur, the conventional decoding schemes for rolling shutter cameras based on the pattern width for 'OFF' and 'ON' cannot guarantee robust communications performance for practical uses. Aside from conventional techniques, such as polynomial fitting, histogram equalization can be used for blurry light mitigation, but it requires additional computation abilities resulting in burdens on mobile devices. This paper proposes a transition-based decoding scheme for rolling shutter cameras in order to offer simple and robust data decoding in the presence of image degradation. Based on the designed synchronization pulse and modulated data symbols according to the LED dimming level, the decoding process is conducted by observing the transition patterns of two sequential symbol pulses. For this, the extended symbol pulse caused by consecutive symbol pulses with the same level determines whether the second pulse should be included for the next bit decoding or not. The proposed method simply identifies the transition patterns of sequential symbol pulses other than the pattern width of 'OFF' and 'ON' for data decoding, and thus, it is simpler and more accurate. Experimental results ensured that the transition-based decoding scheme is robust even in the presence of blurry lights in the captured image at various dimming levels