• Asian Journal of Atmospheric Environment
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• 제9권1호
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• pp.86-90
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• 2015

Temperature was considered to estimate the minimum detectable absorption coefficient of aerosol particles from photothermal spectroscopy. Light energy absorbed by subsequent emission from the aerosol results in the heating of the aerosol sample and consequently causes a temperature change as well as changes in thermodynamic parameters of the sample. This thermal effect is the basis of photothermal spectroscopy. Photothermal spectroscopy has several types of techniques depending on how the photothermal effects are detected. Photothermal interferometry traces the photothermal effect, refractive index, using an interferometer. Photoacoustic spectroscopy detects the photothermal effect, sound wave, using a microphone. In this study, it is suggested that the detection limit for photothermal spectroscopy can be influenced by the introduction of a slip correction factor when the light absorption is determined in a high temperature environment. The minimum detectable absorption coefficient depends on the density, the specific heat and the temperature, which are thermodynamic properties. Without considering the slip correction, when the temperature of the environment is 400 K, the minimum detectable absorption coefficient for photothermal interferometry increases approximately 0.3% compared to the case of 300 K. The minimum detectable absorption coefficient for photoacoustic spectroscopy decreases only 0.2% compared to the case of 300 K. Photothermal interferometry differs only 0.5% point from photoacoustic spectroscopy. Thus, it is believed that photothermal interferometry is reliably comparable to photoacoustic spectroscopy under 400 K.

• Bulletin of the Korean Chemical Society
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• 제17권8호
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• pp.682-685
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• 1996

Photothermal properties depend on the characteristics of energy transfer processes in solution. In this study, a time-resolved single beam thermal lens experiment in various solvents is employed to investigate the energy coupling effects which govern the energy transfer processes. Interestingly, it is observed that the behaviour of the photothermal propagation in solution depends on the property of solution and the concentration of solute in a single beam thermal lens configuration. These characteristics lead us to consider the solute-solvent coupling effects as well as the solvent-solvent interactions.

• Current Optics and Photonics
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• 제5권5호
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• pp.554-561
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• 2021

Indocyanine green (ICG) is a cyanine dye that has been used in medical diagnostics based on fluorescence imaging, and in medical therapy based on the photothermal effect. It is important to systematically understand the photothermal effect and fluorescence characteristics of ICG simultaneously. By varying a number of conditions such as laser power density, laser irradiation wavelength, concentration of ICG solution, and exposure time of laser irradiation, the intensity properties of fluorescence and the temperature change induced by the photothermal effect are measured simultaneously using a charge-coupled-device camera and a thermal-imaging camera. The optimal conditions for maximizing the photothermal effect are determined, while maintaining a relatively long lifetime and high efficiency of the fluorescence for fluorescence imaging. When the concentration of ICG is approximately 50 ㎍/ml and the laser power density exceeds 1.5 W/cm², the fluorescence lifetime is the longest and the temperature induced by the photothermal effect rapidly increases, exceeding the critical temperature sufficient to damage human cells and tissues. The findings provide useful insight into the realization of effective photothermal therapy, while also specifying the site to be treated and enabling real-time treatment monitoring.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.616-619
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• 2003

Photochemical and photothermal effects have correlation with each other and depend on laser wavelength. Multi-scanning laser ablation process of polymer with DPSS(Diode Pumped Solid State) 3rd harmonic Nd:YVO$_4$ laser with wavelength of 355nm is applied to fabricate three-dimensional micro shape. The DPSSL photomachining system can rapidly and cheaply fabricate 2D pattern or 3D shape with high efficiency because we only use CAD/CAM software and precision stages instead of complex projection mask. Photomachinability of polymer is highly influenced by laser wavelength and its own chemical structure. So the optical characteristics of polymers for 355nm laser source is investigated by experimentally and theoretically.

• 대한기계학회논문집B
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• 제29권1호
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• pp.27-34
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• 2005

We analyze in detail axially symmetric theoretical study for the photothermal pulsed radiometry of a cylindrical model. The theoretical solutions describe the transient infrared radiation from the sample heated by short-duration pulsed heating. In the conventional transmission radiometry technique, the excitation source and the detector are on opposite sides of the sample, otherwise in the new single ended radiometry technique, the excitation source and the detector are on same sides of the sample. The analytical solution described for photothermal radiometry in this study would not need to cut or polish samples to measure the thermal diffusivity. Therefore the radial area and axial thickness of samples are not limited. The effects of excitation pulse duration and the area of heat source are discussed.

• Medical Lasers
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• 제8권2호
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• pp.97-100
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• 2019

Facial pores are a visible topographic feature of skin surfaces and are generally the enlarged openings of pilosebaceous follicles. Enlarged facial pores can be a significant cosmetic problem, particularly for women. Recently, gold nanoshell-mediated photothermal therapy (PTT) has been reported to be effective in treating recurrent acne. The treatment of enlarged facial pores with gold nanoshell-mediated PTT produced excellent results with no side effects. The two cases reported here demonstrate the possibility of gold nanoshell-mediated PTT as a safe and effective treatment for enlarged facial pores.

• Current Optics and Photonics
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• 제5권3호
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• pp.311-321
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• 2021

Indocyanine green (ICG) is a dye approved for use in clinical diagnostics. ICG remains in the intravascular space following intravenous administration, due to its ability to rapidly bind to the plasma proteins, and its therapeutic potential has been studied in well-vascularized cutaneous tumors. Here we have evaluated the clinical response of a subconjunctival tumor to photothermal therapy (PTT) using an ICG-enhanced near-infrared diode laser and its adverse effects, in a rabbit. 22 male New Zealand white rabbits with subconjunctival tumors were enrolled (control group 6, laser-only group 8, laser-with-ICG group 8). Rabbits in the laser-with-ICG group received ICG (twice, 2 mg/kg each time, intravenously) directly followed by irradiation with a diode laser (λ = 810 nm). Rabbits in the laser-only group were irradiated with the diode laser. ICG angiography, ultrasonography, and pathologic examination were performed to evaluate PTT response at specific time points (0, 2, and 4 weeks after PTT). Two weeks after initial treatment, the eight rabbits treated by laser with ICG showed a 100% response rate. There was no clinical response in both laser-only and control groups. ICG-PTT is a potential and effective palliative therapeutic modality for subconjunctival tumors.

• 한국레이저가공학회지
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• 제18권1호
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• pp.12-17
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• 2015

This work performed numerical analysis of electromagnetic field and thermal phenomena occurring in femtosecond laser irradiation of silver nanowires. The local electric field enhancement was computed to calculate the optical energy dissipation as a Joule heating source and the thermal transport was analysed based on the two-temperature model (TTM). Electron temperature increased up to 1000K after 50fs and its spatial distribution became homogeneous after 80fs at the fluence of 100mJ/cm2. The result of this work is expected to contribute to revealing the photothermal effects on silver nanowires induced by femtosecond laser irradiation. Although the highest increase of lattice temperature was substantially below the melting point of silver, the experimental results showed resolidification and fragmentation of the silver nanowire into nanoparticles, which cannot be explained by the photothermal mechanism. Further studies are thus needed to clarify the physical mechanisms.

• 대한소아치과학회지
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• 제48권1호
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• pp.21-30
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• 2021

이 연구의 목적은 indocyanine green (ICG)과 근적외선 diode 레이저의 사용이 다종 우식원성 바이오필름에 미치는 항균 효과를 조사하는 것이다. Streptococcus mutans, Lactobacillus casei, Candida albicans를 포함하는 다종 바이오필름이 ICG와 808 nm 근적외선 diode 레이저를 사용하여 서로 다른 조사 시간에 따라 처리되었다. Colony-forming unit (CFU)을 측정하였고, 바이오필름의 정성적 평가를 위해 공초점 레이저 주사 현미경(Confocal laser scanning microscopy, CLSM) 관찰을 시행하였다. 또한 광열 치료의 효과를 평가하기 위해 온도 측정이 시행되었다. ICG와 근적외선 diode 레이저를 사용한 군에서 CFU의 감소량이 통계적으로 유의하였으나, L. casei와 C. albicans에서는 시간에 따른 항균 효과의 유의한 차이는 관찰되지 않았다. CLSM 관찰에서도 유사한 세균 감소를 확인할 수 있었다. ICG와 근적외선 diode 레이저를 사용한 군은 ICG 없이 광조사를 시행한 군보다 더 높은 온도 상승을 보였으며, 측정된 온도는 열 치료의 온도 범위와 유사하였다. 결론적으로, ICG와 근적외선 diode 레이저는 다종 우식원성 바이오필름에 항균 효과를 보였다. 우식 예방을 위한 보조 수단으로 사용될 가능성을 가지나, 임상적인 적용을 위해서는 적용 프로토콜에 관한 연구가 필요하다.

• Structural Engineering and Mechanics
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• 제82권4호
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• pp.469-476
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• 2022

A mathematical model of Lord-Shulman photo-thermal theorem induced by pulse heat flux is presented to study the propagations waves for plasma, thermal and elastic in two-dimensional semiconductor materials. The medium is assumed initially quiescent. By using Laplace-Fourier transforms with the eigenvalue method, the variables are obtained analytically. A semiconductor medium such as silicon is investigated. The displacements, stresses, the carrier density and temperature distributions are calculated numerically and clarified graphically. The outcomes show that thermal relaxation time has varying degrees of effects on the studying fields.