Excitation temporal pulse shape and probe beam size effect on pulsed photothermal lens of single particle

Andika, Marta; Chen, George Chung Kit; Vasudevan, Srivathsan

doi:10.1364/josab.27.000796

Cited by 14 publications

(10 citation statements)

References 23 publications

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“…According to the graph shown in Fig. 3b, the MC increases with a longer MIR exposure and saturates above 0.5 ms, due to the existence of the heat diffusion time τ ∝ 1 ∕ α (α: thermal diffusivity of the heat absorber) 20,21 . When the MIR exposure is longer than τ, the supplied heat accumulates to balance with the heat diffusion, building a strong saturated MC.…”

Section: Resultsmentioning

confidence: 97%

Molecular contrast on phase-contrast microscope

Toda

Tamamitsu

Nagashima

et al. 2019

Sci Rep

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An optical microscope enables image-based findings and diagnosis on microscopic targets, which is indispensable in many scientific, industrial and medical settings. A standard benchtop microscope platform, equipped with e.g., bright-field and phase-contrast modes, is of importance and convenience for various users because the wide-field and label-free properties allow for morphological imaging without the need for specific sample preparation. However, these microscopes never have capability of acquiring molecular contrast in a label-free manner. Here, we develop a simple add-on optical unit, comprising of an amplitude-modulated mid-infrared semiconductor laser, that is attached to a standard microscope platform to deliver the additional molecular contrast of the specimen on top of its conventional microscopic image, based on the principle of photothermal effect. We attach this unit, termed molecular-contrast unit, to a standard phase-contrast microscope, and demonstrate high-speed label-free molecular-contrast phase-contrast imaging of silica-polystyrene microbeads mixture and molecular-vibrational spectroscopic imaging of HeLa cells. Our simple molecular-contrast unit can empower existing standard microscopes and deliver a convenient accessibility to the molecular world.

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Section: Resultsmentioning

confidence: 97%

Molecular contrast on phase-contrast microscope

Toda

Tamamitsu

Nagashima

et al. 2019

Sci Rep

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“…Also, because of the cell compression, its thickness is slightly higher and gives rise to an increase in phase at the two peaks. The above inference can be corroborated by the following: The thermal diffusivity of the RBC is 0.0015 cm 2 ∕s [5]. The thermal diffusion length is given by 2 ffiffiffiffiffiffiffiffi αt p , where α is the thermal diffusivity and t is the time taken.…”

Section: Discussionmentioning

confidence: 71%

“…One is the change in refractive index, and the other is the tissue expansion effect. At the center of the RBC, where the pump beam is focused, the temperature is high, and the effect of negative d n∕d T is stronger than the effect of thermal expansion giving rise to an overall phase reduction within the diameter of the 1 μm region (the decrease in phase value is attributed to refractive index change (Δn), which is given by dn∕dT ΔT , where dn∕dT is the refractive index gradient with respect to temperature [5]). At a time delay of 350 ns, the effective thermal penetration has reached 2 μm; however, the outer region of the cell is still at room temperature, thus creating a thermal gradient.…”

Section: Research Articlementioning

confidence: 99%

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Quantitative photothermal phase imaging of red blood cells using digital holographic photothermal microscope

Vasudevan

Chen²,

Lin

et al. 2015

Appl. Opt.

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Photothermal microscopy (PTM), a noninvasive pump-probe high-resolution microscopy, has been applied as a bioimaging tool in many biomedical studies. PTM utilizes a conventional phase contrast microscope to obtain highly resolved photothermal images. However, phase information cannot be extracted from these photothermal images, as they are not quantitative. Moreover, the problem of halos inherent in conventional phase contrast microscopy needs to be tackled. Hence, a digital holographic photothermal microscopy technique is proposed as a solution to obtain quantitative phase images. The proposed technique is demonstrated by extracting phase values of red blood cells from their photothermal images. These phase values can potentially be used to determine the temperature distribution of the photothermal images, which is an important study in live cell monitoring applications.

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“…It has been successfully applied to many diverse areas, such as materials science [13], optical film coating defect inspection [14,15], thermophysical parameters measurement [16][17][18], subnanoliter measurement [19], spectroscopy [20,21], and microscopy [22]. Two types of TL techniques have been reported: mode-matched [23] and mode-mismatched [24] configurations.…”

Section: Introductionmentioning

confidence: 99%

Femtosecond laser-induced thermal lens effect in chromium film

2010

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The thermal lens (TL) effect induced by femtosecond laser pulses in chromium film is reported. A Fresnel diffraction theory is used to explain the TL effect. The intensity profile of the TL calculated by the theoretical model is in agreement with the experimental results. The contrast ratio of the TL is defined to describe the TL effect, and we find that the maximum contrast ratio of the TL effect is obtained when the probe beam is recorded at a characteristic distance. The dependence of the contrast ratio of the TL on different pump laser power levels and delay times is also investigated. Numerical simulations are also consistent with the experimental results.

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Excitation temporal pulse shape and probe beam size effect on pulsed photothermal lens of single particle

Cited by 14 publications

References 23 publications

Molecular contrast on phase-contrast microscope

Molecular contrast on phase-contrast microscope

Quantitative photothermal phase imaging of red blood cells using digital holographic photothermal microscope

Femtosecond laser-induced thermal lens effect in chromium film

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