• Title/Summary/Keyword: Laser absorption spectroscopy

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Semiconductor laser-based absorption spectroscopy for monitoring physical vapor deposition process (증기증착 공정 감시를 위한 반도체 레이저 흡수 분광학)

  • 정의창;송규석;차형기
    • Journal of the Korean Vacuum Society
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    • v.13 no.2
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    • pp.59-64
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    • 2004
  • A study on the semiconductor laser-based atomic absorption spectroscopy was performed for monitoring physical vapor deposition process. Gadolinium metal was vaporized with a high evaporation rate by electron beam heating. Real-time atomic absorption spectra were measured by using tunable semiconductor laser beam at 770-794 nm (center wavelength of 780 nm) and its second harmonic at 388-396 nm. Atomic densities of metal vapor can be calculated from the absorption spectra measured. We plot the atomic densities as a function of the electron beam power and compare with the evaporation rates measured by quartz crystal monitor. We demonstrate that the semiconductor laser-based spectroscopic system developed in this study can be applied to monitor the physical vapor deposition process for other metals such as titanium.

Real-time Analysis of Exhaust Gas Temperature Field in Turbulent Flow Using Laser Absorption Spectroscopy (레이저흡수분광을 이용한 난류유동 배기가스 온도장 실시간 분석 연구)

  • Doo Won Choi
    • Journal of the Korean Society for Heat Treatment
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    • v.37 no.2
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    • pp.73-78
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    • 2024
  • This study presents a real-time method that uses Laser Absorption Spectroscopy (LAS) to measure exhaust gas temperatures in turbulent flow fields. It was possible to measure temperature by passing a laser beam through the exhaust gas in a grid pattern, and obtain a temperature distribution image through time series analysis at 0.1 second intervals. Temperature image resolution has been improved with CT reconstruction algorithms. Estimating maximum temperature values and locations enabled 2D temperature analysis, surpassing single-point methods like thermocouples. The accuracy of LAS measurements was evaluated by comparison with thermocouple measurements. This approach will contribute to automotive technology and environmental protection by providing reliable temperature data for interpreting turbulent temperature distributions.

Detection of Methane and Ethane by Continuous-Wave Cavity Ring-Down Spectroscopy Near 1.67 μm

  • Oh, Myoung-Kyu;Lee, Yong-Hoon;Choi, Sung-Chul;Ko, Do-Kyeong;Lee, Jong-Min
    • Journal of the Optical Society of Korea
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    • v.12 no.1
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    • pp.1-6
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    • 2008
  • We report the simple detection method of the small hydrocarbons, methane and ethane, by continuous-wave cavity ring-down spectroscopy near 1.67 ${\mu}m$ using an external cavity diode laser. The absorption lines of methane between 6002.48 $cm^{-1}$ and 6003.37 $cm^{-1}$ and ethane between 5955.65 $cm^{-1}$ and 5956.4 $cm^{-1}$ have been resolved and employed for the gas detection. The largest absorption cross sections were found to be 6.5$\times10^{-20}cm^2$ and 7.4$\times10^{-21}cm^2$ for methane and ethane, respectively, in each spectral range. The minimum detectable absorption limit of our spectrometer was 4.8${\times}10^{-9}cm^{-1}$/$\sqrt{Hz}$, which corresponds to the detection limits of 3 ppb/$\sqrt{Hz}$ and 27 ppb/$\sqrt{Hz}$ for methane and ethane, respectively. The near-IR continuous-wave cavity ring-down spectroscopic detection method of the small hydrocarbons can be applied for medical diagnosis and environmental monitoring as a fast and convenient method.

Tunable Diode Laser Absorption Spectroscopy for Environmental Monitoring (파장가변 다이오드 레이저 흡수 분광학을 사용한 대기환경분석)

  • Ju Sang-U;Kim Seong-Geun
    • Proceedings of the Korea Air Pollution Research Association Conference
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    • 2003.11a
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    • pp.247-248
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    • 2003
  • Tunable diode laser absorption spectroscopy (TDLAS) has been widely used in environmental monitoring of gaseous species in the past decade. TDLAS is a direct measurement technique for pollutants such as NOx without any interference from other species. Because of its superior spectral purity (~0.001 ­$cm^{-1}$), absorption linewidths with resolvable rotational structure can be studied in the mid infrared region where strong fundamental vibrational transitions of molecules appear. (omitted)

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I2-Saturated Absorption Spectroscopy for Frequency-Stabilization of He-Ne Laser at 543 nm (543 nm 헬륨네온 레이저의 주파수 안정화를 위한 I2 포화흡수분광)

  • Kim, Kyung-Chan;Eum, Nyeon-Sik;Hong, Joo-Hyun;Seo, Ho-Sung
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.11 no.3
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    • pp.859-865
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    • 2010
  • We have designed and assembled a saturated absorption-spectroscopy system of $^{127}I_2$ for the frequency stabilization of the 543 nm He-Ne laser. The frequency of a internal-mirror 543 nm He-Ne laser was swept by utilizing the temperature and PZT change of the laser cavity length. Frequency modulation was applied to the output laser mirror with a PZT modulator for the third harmonic signal. A portion of the hyperfine spectrum originated from the R(12)26-0 and R(106)28-0 transitions of the B-X system of $^{127}I_2$ was observed as the third-derivative signal using a saturated absorption spectroscopy. The signal-to-noise ratio of a typical hyperfine spectrum signal was estimated to be 30:1.

Integrated Cavity Output Spectroscopy Using an External Cavity Diode Laser for the Density Absorption Measurement of Trace Gases (미량 기체의 밀도 측정을 위한 외부 공진기 반도체 레이저 광학공동 적분 투과 분광법)

  • Ryoo Hoon Chul;Yoo Yong Shin;Lee Jae Yong;Hahn Jae Won
    • Journal of the Korean Vacuum Society
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    • v.15 no.1
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    • pp.24-30
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    • 2006
  • Integrated cavity output spectroscopy(ICOS) is a simple, non-intrusive absorption measurement technique that can detect and quantify trace-level gas species. The spectral absorbance of a gas is quantified from the integrated optical output of the modulated high-finesse cavity containing the sample which is irradiated by a wavelength-swept laser source. We constructed an experimental setup by using a tunable single mode external cavity diode laser operating at the wavelength near 765 nm and a Fabry-Perot cavity with length modulation achieved by a piezoelectric transducer where one of the cavity mirrors sat on. In the experiment performed on minute oxygen gas at the wave-length near 764.5nm, we demonstrated the minimum detectable absorption of $8.45\times10^{-8}cm^{-1}$.

Nanosecond Laser Flash Photolysis Study of 5-Styryl-1,3-dimethyluracil

  • Shim Sang Chul;Shin Eun Ju;Chae Kyu Ho
    • Bulletin of the Korean Chemical Society
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    • v.6 no.4
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    • pp.234-238
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    • 1985
  • The photoisomerization of 5-styryl-1,3-dimethyluracil is studied with nanosecond laser flash photolysis technique at room temperature. The laser flash photolysis of E-isomer produces the transient absorption spectrum regarded as the triplet-triplet absorption, but the transient absorption of Z-isomer does not show the typical decay curve, probably due to the facile photocyclization reaction during the laser flash photolysis. Using the energy transfer method on nanosecond laser spectroscopy, the energy of the lowest triplet state for E isomer is estimated to lie between 41.8 and 47 kcal/mol. The triplet lifetime for E-isomer obtained from the decay curve of the transient absorption is ca. 93ns. The $S_1 → T_1$ intersystem crossing of E-isomer on direct excitation is relatively inefficient at room temperature supporting the singlet mechanism for direct photoisomerization.

Air Density Measurement in a Narrow Test Section Using a Laser Absorption Spectroscopy (레이저 흡수 분광법을 사용한 좁은 시험 구간 내 공기 밀도 측정)

  • Shim, Hanseul;Jung, Sion;Kim, Gyeongrok;Park, Gisu
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.49 no.11
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    • pp.893-900
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    • 2021
  • In this study, air density in a narrow test section is measured using a laser absorption spectroscopy system that detects oxygen absorption lines. An absorption line pair at 13156.28 and 13156.62 cm-1 are detected. A gas chamber with a height of 40 mm is used as a narrow test section. A triangular spiral-shaped laser path is applied in the gas chamber to amplify absorption strength by extending laser beam path length. A well-known logarithm amplifier and a secondary amplifier are used to electrically amplify absorption signal. An AC-coupling is applied after the logarithm amplifier for signal saturation prevention and noise suppression. Procedure of calculating spectral absorbance from output signal is introduced considering the logarithm amplifier circuit configuration. Air density is determined by fitting the theoretically calculated spectral absorbance to the measured spectral absorbance. Test conditions with room temperature and a pressure range of 10~100 kPa are made in a gas chamber using a Bourdon pressure gauge. It is confirmed that air density in a narrow test section can be measured within a 16 % error through absorption signal amplification using a triangular spiral-shaped beam path and a logarithm amplifier.

Study on Optimal Arrangements of Laser Beams in Tunable Diode Laser Absorption Spectroscopy Based Tomography (TDLAST) (레이저흡수분광 토모그래피법에서의 레이저빔의 최적 배치에 관한 연구)

  • KIM, KYUNGWON;YOON, DONGIK;CHOI, DOOWON;CHO, GYEONGRAE;DOH, DEOGHEE
    • Transactions of the Korean hydrogen and new energy society
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    • v.28 no.6
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    • pp.729-737
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    • 2017
  • The measurement accuracy of Tunable Diode Laser Absorption Spectroscopy based Tomography (TDLAST) for the temperature and concentration fields are dependant upon the arrangement method of the used laser beams. This paper reports on the optimization of laser beam arrangements using phantom data. It has been verified that the measurement error of the TDLAST decreased with increase of laser beam numbers. Further, it has been confirmed that perpendicular arrangements between the horizontal and the vertical laser beams without additional diagonal laser beams shows the minimum measurement errors.

Fiber Ring Laser Intra-cavity Absorption Spectroscopy for Gas Sensing: Analysis and Experiment

  • Li, Mo;Liu, Kun;Jing, Wencai;Peng, Gang-Ding
    • Journal of the Optical Society of Korea
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    • v.14 no.1
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    • pp.14-21
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    • 2010
  • Fiber ring laser based intra-cavity absorption spectroscopic sensor has great potential for high sensitivity gas detection. Using the rate equations and propagation equations, we investigated theoretically factors that affect the sensitivity of such fiber ring laser sensors and determined the optimal design parameters and conditions for significant enhancement of the system sensitivity. Experiments have been conducted to determine the sensitivity enhancement performance. The results showed a factor of 25 ~ 30 in sensitivity enhancement in the experimental system, agreeing well with the theoretical expectations. Experiments on acetylene detection have also been carried out and the results showed that the ring cavity significantly increases the signal absorption and that high sensitivity can be obtained for gas detection.