• Korean Journal of Optics and Photonics
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• v.7 no.3
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• pp.238-243
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• 1996

We have developed XeCl laser pumped double-resonator Dye laser and two-stage amplifier system, and generated simultaneously of alternatively two wavelengths suitable in DIAL system. The developed double-resonator is composed of 1st and 2nd diffraction orders on light incidence angle in grazing-incidence grating method with 1200 g/mm. We have obtained spectral linewidth below 10 pm and the total efficiency dependent on pump energy over 6%. The tuning ranges dependent on 1st and 2nd diffraction orders are 434~470 nm and 436~468 nm, respectively. The amplification gain and rine-450 dye laser by using the double-resonator laser system and measured the distribution of $NO_2$ concentration over Suwon as the result of transmission of laser output of 6 mJ in this DIAL system. Consequently, we have confirmed that the developed dye laser system is very useful as the tunable source for DIAL.

• Korean Journal of Optics and Photonics
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• v.12 no.2
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• pp.143-149
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• 2001

We performed the intracavity frequency-doubling of a tunable continuous-wave Ti:sapphire laser using a lithium triborate $(LiB_3O_5, LBO)$ crystal. For an efficient intracavity frequency-doubling, we measured the spectral and the angular bandwidth about the $\theta$-direction of LBO crystal. The measured values at a fundamental wavelength of 800 nm were 1.54 nm.cm and 3.8 mrad.cm, respectively. As a result of an intracavity frequency-doubling, we obtained the second-harmonic generation output power of 5.3 mW at 400 nm with the full width at half maximum(FWHM) of 0.089 nm from the fundamental output power of 185 mW at 800 nm. The frequency-doubled output was tuned from 397 nm to 403 nm.403 nm.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.3
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• pp.199-205
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• 2014

We propose a new variant of lateral shearing interferometer with a tunable laser source that enables 3D surface profile measurements of freeform optics with high speed, high vertical resolution, large departure, and large field-of-view. We have verified the proposed technique by comparing our measurement result with that of an existing technique and measuring a representative sample of freeform optics. Moreover, we propose a new algorithm that is able to compensate the rotational inaccuracy.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.04a
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• pp.197-200
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• 2000

All-optical NOR logic device was realized by use of two pump signals with a single wavelength and a semiconductor optical amplifier(SOA). Specially, Mach-Zehnder(MZ) modulator was used for an external modulation of the pump signals. To obtain the sufficient gain saturation of the SOA, pump signals are amplified by an Er-doped fiber amplifier(EDFA) at the input of the SOA. Pump and probe signals are obtained from a DFB laser diode(${\lambda}_p$=1554 nm) and a tunable laser diode(${\lambda}_s$=1535 nm), respectively. The operation characteristics of the NOR logic device are successfully measured and demonstrated at the modulation frequency of 4.83 MHz.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.05a
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• pp.787-790
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• 2003

A 4-wavelength optical transceiver system is designed and implemented by using 4 OADMs (optical add-drop multiplexers), WDMs, and optical transceivers. In this new system, the wavelengths of 1510 nm and 1530 nm are used for upload and download signals, respectively, as well as the wavelengths of 1550 nm and 1310 nm which have been utilized in a 2-wavelength optical transceiver systems. The 4-wavelength optical module shows very encouraging pass characteristics of about - 5 dB and isolation characteristics of less than -40 dB, which is configured with two OADMs, 4 couplers, and WDM couplers by fusion splicing. Noise figure (NF) of the one-stage balanced amplifier designed and fabricated for receiver module is 0.38 dB and the amplifying gain is 14.2 dB. S$_{11}$, S$_{22}$ and input, output VSWR are -28.81 dB, -32.08 dB, 1.05 : 1, 1.08 : 1, respectively.y.

• Korean Journal of Optics and Photonics
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• v.30 no.4
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• pp.154-158
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• 2019

We have used a mid-IR (mid-infrared) continuous-wave (cw) optical parametric oscillator (OPO), developed previously and described in Ref. 12, to build a performance-evaluation setup for a mid-IR spectrometer. The used CW OPO had a wavelength tuning range of $ 2.5-3.6{\mu}m$ using a pump laser with a wavelength of 1064 nm and a fan-out MgO-doped periodically poled lithium niobate (MgO:PPLN) nonlinear crystal in a concentric cavity design. The OPO was combined with a near-IR integrating sphere and a Fourier-transform IR optical spectrum analyzer to build a performance-evaluation setup for mid-IR spectrometers. We applied this performance-evaluation setup to evaluating a mid-IR spectrometer developed domestically, and demonstrated the capability of evaluating the performance, such as spectral resolution, signal-to-noise ratio, spectral stray light, and so on, based on this setup.

• Journal of the Optical Society of Korea
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• v.15 no.3
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• pp.293-299
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• 2011

In this study, we demonstrated Fourier-domain/swept-source optical coherence tomography (FD/SS-OCT) at a center wavelength of 800 nm for in vivo human retinal imaging. A wavelength-swept source was constructed with a semiconductor optical amplifier, a fiber Fabry-Perot tunable filter, isolators, and a fiber coupler in a ring cavity. Our swept source produced a laser output with a tuning range of 42 nm (779 to 821 nm) and an average power of 3.9 mW. The wavelength-swept speed in this configuration with bidirectionality is 2,000 axial scans per second. In addition, we suggested a modified zero-crossing method to achieve equal sample spacing in the wavenumber (k) domain and to increase the image depth range. FD/SS-OCT has a sensitivity of ~89.7 dB and an axial resolution of 10.4 ${\mu}m$ in air. When a retinal image with 2,000 A-lines/frame is obtained, an acquisition speed of 2.0 fps is achieved.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.1182-1182
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• 2001

In this study, the newly constructed optical measurement system, which was mainly composed of a parametric tunable laser and a near infrared photoelectric multiplier, was introduced to clarify the optical characteristics of wood as discontinuous body with anisotropic cellular structure from the viewpoint of the time-of-flight near infrared spectroscopy (TOF-NIRS). The combined effects of the cellular structure of wood sample, the wavelength of the laser beam λ, and the detection position of transmitted light on the time resolved profiles were investigated in detail. The variation of the attenuance of peak maxima At, the time delay of peak maxima Δt and the variation of full width at half maximum Δw were strongly dependent on the feature of cellular structure of a sample and the wavelength of the laser beam. The substantial optical path length became about 30 to 35 times as long as sample thickness except the absorption band of water. Δt ${\times}$ Δw representing the light scattering condition increased exponentially with the sample thickness or the distance between the irradiation point and the end of sample. Around the λ=900-950 nm, there may be considerable light scattering in the lumen of tracheid, which is multiple specular reflection and easy to propagate along the length of wood fiber. Such tendency was remarkable for soft wood with the aggregate of thin layers of cell walls. When we apply TOF-NIRS to the cellular structural materials like wood, it is very important to give attention to the difference in the light scattering within cell wall and the multiple specular-like reflections between cell walls. We tried to express the characteristics of the time resolved profile on the basis of the optical parameters for light propagation determined by the previous studies, which were absorption coefficient K and scattering coefficient S from Kubelka-Munk theory and n from nth power cosine model of radiant intensity. The wavelength dependency of the product of K/S and n, which expressed the light-absorbing and -scattering condition and the degree of anisotropy, respectively, was similar to that of the time delay of peak maxima Δt. The variation of the time resolved profile is governed by the combination of these parameters. So, we can easily find the set of parameters for light propagation synthetically from Δt.

• Clean Technology
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• v.26 no.4
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• pp.293-303
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• 2020

According to the World Health Organization (WHO), air pollution is a typical health hazard, resulting in about 7 million premature deaths each year. Sulfur dioxide (SO2) is one of the major air pollutants, and the combustion process with sulfur-containing fuels generates it. Measuring SO2 generation in large combustion environments in real time and optimizing reduction facilities based on measured values are necessary to reduce the compound's presence. This paper describes the concentration measurement for SO2, a particulate matter precursor, using a wavelength modulation spectroscopy (WMS) of tunable diode laser absorption spectroscopy (TDLAS). This study employed a quantum cascade laser operating at 7.6 ㎛ as a light source. It demonstrated concentration measurement possibility using 64 multi-absorption lines between 7623.7 and 7626.0 nm. The experiments were conducted in a multi-pass cell with a total path length of 28 and 76 m at 1 atm, 296 K. The SO2 concentration was tested in two types: high concentration (1000 to 5000 ppm) and low concentration (10 ppm or less). Additionally, the effect of H2O interference in the atmosphere on the measurement of SO2 was confirmed by N2 purging the laser's path. The detection limit for SO2 was 3 ppm, and results were compared with the electronic chemical sensor and nondispersive infrared (NDIR) sensor.

• Korean Journal of Optics and Photonics
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• v.13 no.4
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• pp.347-355
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• 2002

We have constructed a high efficiency and broad tunable cw Ti:sapphire laser with a four-mirror symmetric Z-type laser cavity to increase the laser usability. From theoretical analyses and experimental data for a symmetric Z-type laser cavity containing a Kerr medium, the cavity mode size and the Kerr-lens mode-locking (KLM) strength for KLM lasers can be confirmed as function of the position in the cavity, the intracavity laser power, and the stability parameter. As a result, the slope efficiency and the maximum average output power of cw Ti:sapphire laser at 5 W pumping power of Ar-ion laser were 31.3% and 1420 ㎽ respectively. The tunablility was ranged from 730 ㎚ to 908 ㎚ with average output power above 700 ㎽. We obtained the KLM operation easily by self-aperturing effect in the Kerr medium and the slope efficiency and the maximum average output power of KLM Ti:sapphire laser was 16% and 550 ㎽ respectively. The spectral bandwidth was 33 ㎚ at the center wavelength of 807 ㎚ and the pulse width was 27 fs with a repetition rate of 82 ㎒.