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Current Optics and Photonics

Optical Society of Korea

  • Bimonthly
  • /
  • 2508-7266(pISSN)
  • /
  • 2508-7274(eISSN)

Domain

  • Electricity/Electronics ＞ Optical Instrument

Aim & Scope

Current Optics and Photonics is the full-open-access, peer-reviewed journal published in English by the Optical Society of Korea (OSK). Current Optics and Photonics is dedicated to publish papers reporting recent advances and state-of-the-art research and development results in all aspects of optical science and technology. Current Optics and Photonics is published bi-monthly with six issues a year (February, April, June, August, October, and December). Current Optics and Photonics considers original research articles, short communications, invited research articles, and invited review articles. Original contributions may be categorized into nine main topics: (1) Optical Science, (2) Optical Technology, (3) Digital Holography and Information Optics, (4) Quantum Electronics, (5) Photonics, (6) Biophotonics, (7) Displays, (8) Quantum Optics and Quantum Information, and (9) Lithography/Optical Materials. Current Optics and Photonics started in February 2017, maintaining the tradition of the Journal of the Optical Society of Korea (JOSK) that had been published as one of the official journals of the OSK since 1997. Current Optics and Photonics is indexed in SCIE, SCOPUS, and KCI, and is also available via OSA Publishing in partnership with the OSA (https://www.osapublishing.org/copp/home.cfm).

KSCI KCI SCOPUS SCI SCIE

Volume 2 Issue 6

  1. Oh, Sung Suk;Park, Hye Jin;Min, Han Sol;Kim, Sang Dong;Bae, Seung Kuk;Kim, Jun Sik;Ryu, Rae-Hyung;Kim, Jong Chul;Kim, Sang Hyun;Lee, Seong-jun;Kang, Bong Keun;Choi, Jong-ryul;Sohn, Jeong-woo 499
    https://doi.org/10.3807/COPP.2018.2.6.499 PDF KSCI HTML
    For the spatiotemporally aligned observation of photothrombosis induction and transient variations of in vivo brain stroke, we developed a novel photothrombosis inducing system compatible to a magnetic resonance imaging (MRI) system using nonmagnetic stereotaxic equipment. From the spatial point of view, the system provides a more reliable level of reproducibility of the photothrombosis in each brain. From the temporal point of view, from T1- and T2-weighted in vivo MR (magnetic resonance) images, the transient variations such as incidence, location, and size of the thrombosis are measured quantitatively. In addition, the final variation is observed in the ex vivo brain by TTC (Triphenyltetrazolium chloride) staining based on histological assay and utilized for the verification of the MR images. From the experimental result of the rat brain, the proposed system shows more reliable characteristics for transient variations of brain strokes.
  2. Choi, Soo Bong;Byeon, Clare Chisu;Park, Doo Jae 508
    https://doi.org/10.3807/COPP.2018.2.6.508 PDF KSCI HTML
    We report the development of a theoretical model describing the strong field tunneling of electrons in an extremely small nanogap (having a width of a few nanometers) that is driven by terahertz-pulse irradiation, by modifying a conventional semiclassical model that is widely applied for near-infrared wavelengths. We demonstrate the effects of carrier-envelope phase difference and strength of the incident THz field on the tunneling current across the nanogap. Additionally, we show that the dc bias also contributes to the generation of tunneling current, but the nature of the contribution is completely different for different carrier-envelope phases.
  3. Kim, Ahram;Son, Byung Hee;Kim, Hwan Sik;Ahn, Yeong Hwan 514
    https://doi.org/10.3807/COPP.2018.2.6.514 PDF KSCI HTML
    Carrier diffusion length in the light-sensitive material is one of the key elements in improving the light-current conversion efficiency of solar-cell devices. In this paper, we measured the carrier diffusion length in lead-halide perovskite ($MAPbI_3$) and mixed lead-halide ($MAPbI_{3-x}Cl_x$) perovskite devices using scanning photocurrent microscopy (SPCM). The SPCM signal decreased as we moved the focused laser spot away from the metal contact. By fitting the data with a simple exponential curve, we extracted the carrier diffusion length of each perovskite film. Importantly, the diffusion length of the mixed-halide perovskite was higher than that of the halide perovskite film by a factor of 3 to 6; this is consistent with the general expectation that the carrier mobility will be higher in the case of the mixed lead-halide perovskites. Finally, the diffusion length was investigated as a function of applied bias for both samples, and analyzed successfully in terms of the drift-diffusion model.
  4. Chen, Han;Li, Changqing;Min, Jing 519
    https://doi.org/10.3807/COPP.2018.2.6.519 PDF KSCI HTML
    We propose a transverse load sensor with reconfigurable measurement accuracy based on a microwave photonic filter in the $K_u$ band, incorporating a polarization-maintaining fiber Bragg grating. A prototype sensor with a reconfigurable measurement accuracy tuning range from 6.09 to 9.56 GHz/(N/mm), and corresponding minimal detectable load range from 0.0167 to 0.0263 N/mm, is experimentally demonstrated. The results illustrate that up to 40% manufacturing error in the grating length can be dynamically calibrated to the same corresponding measurement accuracy for the proposed transverse load sensor, by controlling the semiconductor optical amplifier's injection current in the range of 154 to 419 mA.
  5. Rao, MP Srinivasa;Singh, Vivek 525
    https://doi.org/10.3807/COPP.2018.2.6.525 PDF KSCI HTML
    The effect of eccentricity on dispersion and nonlinear properties of a photonic crystal fiber having elliptical air holes is investigated using a fully vectorial effective index method. It is found that the effective refractive index increases with increase of eccentricity. The dependence of dispersion and nonlinear properties of the PCF on the eccentricity of the air hole is investigated. It is revealed that eccentricity of the air hole affects the zero dispersion wavelength. Further, the nonlinear properties such as mode field area, nonlinear coefficient and self phase modulation of the Photonic crystal fibers are analyzed. The mode field area increases and the nonlinear coefficient decreases with increase in eccentricity. The variation of the self phase modulation with elliptical air hole is also discussed.
  6. Kim, Byung Wook;Jung, Sung-Yoon 532
    https://doi.org/10.3807/COPP.2018.2.6.532 PDF KSCI HTML
    Multiple LED arrays can be utilized in visible-light communication (VLC) to improve communication efficiency, while maintaining smart illumination functionality through dimming control. This paper proposes a modulation scheme called "Spatial Intensity Modulation" (SIM), where the effective number of turned-on LEDs is employed for data modulation and dimming control in VLC systems. Unlike the conventional pulse-amplitude modulation (PAM), symbol intensity levels are not determined by the amplitude levels of a VLC signal from each LED, but by counting the number of turned-on LEDs, illuminating with a single amplitude level. Because the intensity of a SIM symbol and the target dimming level are determined solely in the spatial domain, the problems of conventional PAM-based VLC and related MIMO VLC schemes, such as unstable dimming control, non uniform illumination functionality, and burdens of channel prediction, can be solved. By varying the number and formation of turned-on LEDs around the target dimming level in time, the proposed SIM scheme guarantees homogeneous illumination over a target area. An analysis of the dimming capacity, which is the achievable communication rate under the target dimming level in VLC, is provided by deriving the turn-on probability to maximize the entropy of the SIM-based VLC system. In addition, a practical design of dimmable SIM scheme applying the multilevel inverse source coding (MISC) method is proposed. The simulation results under a range of parameters provide baseline data to verify the performance of the proposed dimmable SIM scheme and applications in real systems.
  7. Sun, Wenqing;Wang, Lei;Wang, Jun;Li, Hua;Wu, Quanying 540
    https://doi.org/10.3807/COPP.2018.2.6.540 PDF KSCI HTML
    We propose an implementation scheme for an optical encryption system with hybrid-pattern random keys. In the encryption process, a pair of random phase keys composed of a white-noise phase key and a structured phase key are positioned in the input plane and Fourier-spectrum plane respectively. The output image is recoverable by digital reconstruction, using the conjugate of the encryption key in the Fourier-spectrum plane. We discuss the system encryption performance when different combinations of phase-key pairs are used. To measure the effectiveness of the proposed method, we calculate the statistical indicators between original and encrypted images. The results are compared to those generated from a classical double random phase encoding. Computer simulations are presented to show the validity of the method.
  8. Jang, Jin;Jeon, Jun Woo;Kim, Jin Sub;Joo, Ki-Nam 547
    https://doi.org/10.3807/COPP.2018.2.6.547 PDF KSCI HTML
    In this paper, a new method for spatial filtering in digital holography is proposed and verified by simulations compared to conventional methods. The new method is based on the simultaneous acquisition of two digital holograms, which can be separated by distinct spatial modulation, in a single image. Two holograms are generated by two reference waves, which have different spatial modulation orientations. Then, the overlapping region between the DC term and the object wave in the first hologram can be replaced with a less-overlapping region of the object wave in the second hologram because the whole image contains two holograms where the same objective wave has been recorded. In the simulation results, it is confirmed that the reconstructed image by the new method has better quality than for the original method.
  9. Ko, Youngjun;Yi, Sooyeong 554
    https://doi.org/10.3807/COPP.2018.2.6.554 PDF KSCI HTML
    This study presents a color 3D scanner based on the laser structured-light imaging method that can simultaneously acquire 3D shape data and color of a target object using a single camera. The 3D data acquisition of the scanner is based on the structured-light imaging method, and the color data is obtained from a natural color image. Because both the laser image and the color image are acquired by the same camera, it is efficient to obtain the 3D data and the color data of a pixel by avoiding the complicated correspondence algorithm. In addition to the 3D data, the color data is helpful for enhancing the realism of an object model. The proposed scanner consists of two line lasers, a color camera, and a rotation table. The line lasers are deployed at either side of the camera to eliminate shadow areas of a target object. This study addresses the calibration methods for the parameters of the camera, the plane equations covered by the line lasers, and the center of the rotation table. Experimental results demonstrate the performance in terms of accurate color and 3D data acquisition in this study.
  10. Kwon, Won-Bae;Lee, Chung Ghiu;Seo, Dongjun;Park, Chang-Soo 563
    https://doi.org/10.3807/COPP.2018.2.6.563 PDF KSCI HTML
    We propose and experimentally demonstrate a simple tunable photonic microwave band-pass filter with high resolution using a reflective semiconductor optical amplifier (RSOA) and an optical time-delay line. The RSOA is used as a gain medium for generating cross-gain modulation (XGM) effect as well as an optical source. The optical source provides narrow spectral width by self-injection locking the RSOA in conjunction with a partial reflection filter with specific center wavelength. Then, when the RSOA is operated in the saturation region and the modulated recursive signal is injected into the RSOA, the recursive signal is inversely copied to the injection locked optical source due to the XGM effect. Also, the tunability of the passband of the proposed microwave filter is shown by controlling an optical time-delay line in a recursive loop.
  11. Kang, Sewon;Ryu, Inkeon;Kim, Daekeun;Kauh, Sang Ken 568
    https://doi.org/10.3807/COPP.2018.2.6.568 PDF KSCI HTML
    Various techniques to measure the three-dimensional (3D) surface profile of a 3D micro- or nanostructure have been proposed. However, it is difficult to apply such techniques directly to industrial uses because most of them are relatively slow, unreliable, and expensive. The HiLo optical imaging technique, which was recently introduced in the field of fluorescence imaging, is a promising wide-field imaging technique capable of high-speed imaging with a simple optical configuration. It has not been used in measuring a 3D surface profile although confocal microscopy originally developed for fluorescence imaging has been adapted to the field of 3D optical measurement for a long time. In this paper, to the best of our knowledge, the HiLo optical imaging technique for measuring a 3D surface profile is proposed for the first time. Its optical configuration and algorithm for a precisely detecting surface position are designed, optimized, and implemented. Optical performance for several 3D microscale structures is evaluated, and it is confirmed that the capability of measuring a 3D surface profile with HiLo optical imaging technique is comparable to that with confocal microscopy.
  12. Zhang, Jiahong;Zhu, Chuyi;Yang, Xiumei;Li, Yingna;Zhao, Zhengang;Li, Chuan 576
    https://doi.org/10.3807/COPP.2018.2.6.576 PDF KSCI HTML
    A new approach for identification of a microwave frequency using an integrated optical waveguide chip, combined with a phase modulator (PM) and two microring resonators (MRRs), is proposed, theoretically deduced, and verified. By wavelength tuning to set the PM under the condition of a double side band (DSB), the measurement range can be started from the dc component, and the measurement range and response slope can be adjusted by designing the radius and transmission coefficient of the MRR. Simulations reveal that the amplitude comparison function (ACF) has a monotonic relationship from dc to 32.5 GHz, with a response slope of 5.15 dB under conditions of DSB modulation, when the radius values, transmission coefficients, and the loss factors are designed respectively as $R_1=400{\mu}m$, $R_2=600{\mu}m$, $t_1=t_2=0.63$, and ${\gamma}_1={\gamma}_2=0.66$. Theoretical calculations and simulation results both indicate that this new approach has the potential to be used for measuring microwave frequencies, with the advantages of compact structure and superior reconfigurability.
  13. Li, Yue;Yu, Yong-Ji;Wang, Yu-Heng;Liu, Hang;Liu, He-Yan;Jin, Guang-Yong 582
    https://doi.org/10.3807/COPP.2018.2.6.582 PDF KSCI HTML
    A $Nd:YVO_4$ laser dual-end-pumped by a wavelength-locked 878.6 nm laser diode is presented. At the repetition rate of 500 KHz, the absorbed pump power of 58 W, an output power of 26.1 W at 1064 nm is obtained, corresponding to an optical-optical efficiency of 45%. The pulse width is 44.2 ns. Meanwhile, the effects of traditional 808 nm pumping and 878.6 nm dual-end-pumping on the output laser beam quality and pulse width are compared and analyzed in an experiment.
  14. Lee, Woojin;Kim, Minwoo;Yang, Hanyi;Kyhm, Kwangseuk;Murayama, Akihiro;Kheng, Kuntheak;Mariette, Henri;Dang, Le Si 589
    https://doi.org/10.3807/COPP.2018.2.6.589 PDF KSCI HTML
    We have investigated the dimensional nature of center-of-mass exciton confinement states in a CdMnTe/CdTe/CdMnTe heterostructure, where the CdTe well is too wide (144 nm) to confine both electrons and holes but able to confine whole excitons in the center-of-mass coordinate. Fine multiple photoluminescence spectra with a few meV separation were observed at 6 K. From the thickness dependence of the transition rate, they were attributed to even numbered center-of-mass exciton confinement states (N = 2, 4, 6, ${\cdots}$, 18). Dimensionality of the center-of-mass exciton confinement states was also investigated in terms of temperature dependence of radiative decay time. At low temperatures (${\leq}12K$), we found that the ground state excitons are likely localized possibly due to the barrier interface fluctuation, resulting in a constant decay time (~350 ps). With increased temperature (${\geq}12K$), localized excitons are thermally released, giving rise to a linear temperature dependence of radiative decay time as an evidence of two-dimensional nature.
  15. Boutilier, Richard M.;Park, Jae Sung;Lee, Ho 595
    https://doi.org/10.3807/COPP.2018.2.6.595 PDF KSCI HTML
    The two-photon process of microscopy provides good spatial resolution and optical sectioning ability when observing quasi-static endogenous fluorescent tissue within an in vivo animal model skin. In order to extend the use of such systems, we developed a two-photon laser scanning microscopy system capable of also capturing $512{\times}512$ pixel images at 90 frames per second. This was made possible by incorporating a 72 facet polygon mirror which was mounted on a 55 kRPM motor to enhance the fast-scan axis speed in the horizontal direction. Using the enhanced temporal resolution of our high-speed two-photon laser scanning microscope, we show that rapid processes, such as fluorescently labeled erythrocytes moving in mouse blood flow at up to 1.2 mm/s, can be achieved.
  16. Kumar, CH. S.S. Pavan;Kim, Jiung;Kim, Byoung Joo;Cha, Myoungsik 606
    https://doi.org/10.3807/COPP.2018.2.6.606 PDF KSCI HTML
    Measurement of the nonlinear optical coefficients is not an easy task since it requires complicated experimental setup and analysis. We suggest an easy way to estimate the relative nonlinear optical tensor components by direct measurement of the output powers of the second harmonic generation and spontaneous parametric down conversion experiments. The experiments were done in quasi-phase-matched type-0 as well as type-1 interactions at similar pump wavelengths in a 5% MgO-doped periodically poled $LiNbO_3$ crystal to obtain the ratio of the nonlinear optical tensor components $d_{33}/d_{31}$ in each experiment. The obtained ratios were then compared with the previously ascertained values [J. Opt. Soc. Am. B, 14, 2268-2294 (1997)].
  17. Cui, Suying;Zhao, Xiaohui;He, Xu;Gu, Haijun 612
    https://doi.org/10.3807/COPP.2018.2.6.612 PDF KSCI HTML
    In wave-front-sensor-less adaptive optics (WFS-less AO) systems, the Jacopo Antonello (JA) method belongs to the model-based class and requires few iterations to achieve acceptable distortion correction. However, this method needs a lot of measurements, especially when it deals with moderate or severe aberration, which is undesired in free-space optical communication (FSOC). On the contrary, the stochastic parallel gradient descent (SPGD) algorithm only requires three time measurements in each iteration, and is widely applied in WFS-less AO systems, even though plenty of iterations are necessary. For better and faster compensation, we propose a WFS-less hybrid approach, borrowing from the JA method to compensate for low-order wave front and from the SPGD algorithm to compensate for residual low-order wave front and high-order wave front. The correction results for this proposed method are provided by simulations to show its superior performance, through comparison of both the Strehl ratio and the convergence speed of the WFS-less hybrid approach to those of the JA method and SPGD algorithm.
  18. Nahm, Kie B. 623
    https://doi.org/10.3807/COPP.2018.2.6.623 PDF KSCI HTML
    Clotting properties of human blood are important clinical information to monitor for patients with platelet and coagulation disorders. Most devices used to diagnose these disorders utilize blood plasma together with tissue factors and $Ca^{{+}{+}}$ additives. In some instruments, magnetic particles were mixed with blood samples and a rotating magnetic field was applied, resulting in the rotation of magnetic particles, which was probed by impinging light. The working principle seems obvious yet had not been investigated in depth. We modeled the collective behavior of light propagating through magnetic needles, aligned in the direction of the rotating external magnetic field, with scattering light analysis software. Simulation results indicated that the scattering pattern undergoes periodic undulations with respect to the slant angle of the magnetic needles. Also provided is a means of extracting meaningful information from the scattering measurement.
  19. Qi, Limei;Shah, Syed Mohsin Ali 629
    https://doi.org/10.3807/COPP.2018.2.6.629 PDF KSCI HTML
    A broad dual-band terahertz metamaterial filter with sharp out-of-band rejections is designed and demonstrated. The center frequencies of the first and the second bands occur at 0.35 THz and 0.96 THz with 3 dB relative bandwidth of 31% and 17%, respectively. Results are measured using a THz time-domain spectroscopy system that shows agreement with simulations. Physical mechanisms of the broad dual-band resonance are clarified based on transmissions of different structures and surface current density distributions. Influence of structure parameters on the transmission characteristics are discussed. Symmetry of the structure ensures the filter polarization independence at normal incidence. These results supported by the design of the filter could find applications in broad multi-band sensors, terahertz communication systems, and other emerging terahertz technologies.