• Korean Journal of Optics and Photonics
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• v.15 no.5
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• pp.449-454
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• 2004

The optical limiter is an optical component which reduces laser beam intensity for the protection of eyes and light sensors. Carbon nanotube is now known as a highly efficient optical limiting material. Optical limiting effect of the multi-walled carbon nanotube suspensions, in several kinds of solvents such as distilled water, chloroform, ethanol and ethylene glycol, were measured in the range from room temperature to near to the boiling points of the solvents. The pulsed Nd:YAG laser whose wavelength is 1064 nm and pulse duration is 6 ns was used as a light source. The experimental result shows that the limiting efficiency was reduced as the temperature increased, and the suspension which has lower boiling point, viscosity and surface tension has highest efficiency.

• Current Optics and Photonics
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• v.7 no.6
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• pp.721-731
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• 2023

This paper studies various roughness parameters, besides waviness, texture, and nonlinear parameters of Bismarck brown Y (BBY)-doped Poly(methyl methacrylate) (PMMA) films based on the computed values of optical limiting (OL) threshold power and nonlinear refractive index. The films' morphology, grain size, and absorption spectra were investigated using atomic force microscopy in conjunction with ultraviolet-visible (UV-Vis) spectrophotometer. The particle size of the films ranged between 4.11-4.51 mm and polymer films showed good homogeneity and medium roughness, ranging from 1.11-4.58 mm. A polymer film's third-order nonlinear optical features were carried out using the Z-scan methodology. The measurements were obtained by a continuous wave produced from a solid-state laser with a 532 nm wavelength. According to the results, BBY has a nonlinear refractive index of 10^-6 cm²/W that is significantly negative and nonlinear. The optical limiting thresholds are roughly 10.29, 13.52, and 18.71 mW, respectively. The shift of nonlinear optical features with the film's concentration was found throughout the experiment Additionally, we found that the polymer samples have outstanding capabilities for restricting the amount of optical power that may be transmitted through them. We propose that these films have the potential to be used in a wide variety of optoelectronic applications, including optical photodetectors and optical switching.

• Proceedings of the Optical Society of Korea Conference
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• 2004.02a
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• pp.38-39
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• 2004

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.3
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• pp.52-59
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• 1997

Design and performance of principal four ICs for the 10-Gb/s optical communication system are presented. AlGaAs/GaAs HBTs are basic devices to implement a laser diode driver, apre-amplifier, and a limiting amplifier, and GaInP/GaAs HBTs are used for an AGC amplifier. We fbricated 11.5-GHz LD driver, a pre-amplifier, and a limiting amplifier, an dGaInP/GaAs HBTs are used for an AGC amplifier. We fabricated LD deriver, 10.5 GHz pre amplifier, 7.2 GHz AGC amplifier, and 10.3 GHz limiting amplifier, optimized circuit design and the stabilized MMIC fabrication process.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.7 s.349
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• pp.13-19
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• 2006

A 5Gb/s cross coupled transimpedance amplifier (TIA) & limiting amp(LA), regulated cascode(RGC) is realized in a 0.18$\mu$m CMOS technology for optical printed circuit board applications. The optical receiver demonstrates $92.8db{\Omega}$ transimpedance and limiting amplifier gain, 5Gb/s bandwidth for 0.5pF photodiode capacitance, and 9.74mW power dissipation from 1.8V, 2.4V supply. Input stage impedance is $50{\Omega}$. The circuit was implemented on an optical PCB, and the 5Gb/s data output signal was measured with a good data eye opening.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.7
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• pp.15-22
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• 1997

A 10Gbit/s limiting amplifier IC for optical transmission system was implemented with AlGaAs HBT (heterojunction bipolar transistor) technology. HBTs with 2x10.mu. $m^{2}$ and 6x20.mu. $m^{2}$ emitter size were used. The HBT structures are based on metal-organic chemical vapor deposition (MOCVD) epitxy and employ a mesa structure with self-aligned emitter/base and sidewall dielectric passivation. IC was designed to support differnetial input and output. Small signal performance of the packaged IC showed 26dB gain and $f_{3dB}$ of 8GHz. A single ouput has 800m $V_{p-p}$ swing with more than 26dB dynamic range. The performance of the limiting amplifier was verified through single mode fiber320km transmission link test.est.

• Journal of the Korea Society of Computer and Information
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• v.23 no.2
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• pp.1-7
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• 2018

The adaptive optics for compensating for optical wavefront distortion due to atmospheric turbulence has recently been used in systems that improve beam quality by eliminating the aberrations of high power laser beam wavefront. However, unseen-mode, which can not be measured in the wavefront sensor, increases the instability of the laser beam wavefront compensator on the adaptive optics system. As a method for improving such instability, a mathematical method for limiting the number of singular values is used when generating the command matrix involved in generation of the drive command of the wavefront compensator. In the past, however, we have relied solely on experimental methods to determine the limiting range of the singular values. In this paper, we propose a criterion for determining the limiting range of the singular values using the driving characteristics and the correlation technique of the wavefront compensator's actuators and have proved its performance experimentally.

• Journal of the Optical Society of Korea
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• v.14 no.1
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• pp.1-13
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• 2010

This paper describes a development of a fiber optic common-path optical coherence tomography (OCT) based imaging and guided system that possess ability to reliably identify optically transparent targets that are on the micron scale; ability to maintain a precise and safe position from the target; ability to provide spectroscopic imaging; ability to imaging biological target in 3-D. The system is based on a high resolution fiber optic Common-Path OCT (CP-OCT) that can be integrated into various mini-probes and tools. The system is capable of obtaining >70K A-scan per second with a resolution better than $3\;{\mu}m$. We have demonstrated that the system is capable of one-dimensional real-time depth tracking, tool motion limiting and motion compensation, oxygen-saturation level imaging, and high resolution 3-D images for various biomedical applications.

• Journal of Electrical Engineering and information Science
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• v.2 no.6
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• pp.197-201
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• 1997

To realize 10-Gbit/s optical transmission systems, we designed and fabricated a limiting amplifier with extremely high operation frequencies over 10-GHz using AlGaAs/GaAs heterojunction bipolar transistors (HBTs), and investigated their performances. Circuit design and simulation were performed using SPICE and LABRA. A discrete AlGaAs/GaAs HBT with the emitter area of 1.5${\times}$10$\mu\textrm{m}$$^2$, used for the circuit fabrication, exhibited the cutoff frequency of 63GHz and maximum oscillation frequency of 50GHz. After fabrication of MMICs, we observed the very wide bandwidth of DC∼15GHz for a limiting amplifier from the on-wafer measurement. Ceramic-packaged limiting amplifier showed the excellent eye opening, the output voltage swing of 750mV\ulcorner, and the rise/fall time of 40ps, measured at the data rates of 10-Gbit/s.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.6
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• pp.119-124
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• 2008

Transimpedance amplifier(TIA) is the most significant element to determine the performance of the optical receiver, and thus the TIA must satisfy tile design requirements of high gain and wide bandwidth. In f)is paper, we propose a novel single chip optical receiver that exploits an analog adaptive equalizer and a limiting amplifier to enhance the gain and bandwidth performance, respectively. The proposed optical receiver is designed by using a $0.13{\mu}m$ CMOS process and its post-layout simulations show $120dB{\Omgea}$ transimpedance gain and 5.88GHz bandwidth. The chip core occupies the area of $0.088mm^2$, due to utilizing the negative impedance converter circuit rather than using on-chip passive inductors.