Absorption coefficient of nearly transparent liquids measured using thermal lens spectrometry

Cabrera, Humberto; Marcano, Arı́stides; Castellanos, Y.

doi:10.5488/cmp.9.2.385

Cited by 59 publications

(28 citation statements)

References 11 publications

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“…Moreover, the EB is focused onto the sample, whereas the PB is expanded and highly collimated [17,18]. The proposed configuration enables the use of achromatic or chromatic objective lenses, thus making the system more versatile in comparison with conventional TLM setups [12][13][14][15].…”

Section: Introductionmentioning

confidence: 98%

Determination of Fe(II) by Optimized Thermal Lens Microscope

2015

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A simple and accurate method for the determination of Fe(II) species in liquid solutions was developed. The measurement principle was realized by the photothermal effect and performed by the use of a thermal lens microscope (TLM) in its optimized, mode-mismatched configuration with a counter-propagating probe beam (PB) and an excitation beam (EB). Additionally, due to the combination of the collimated PB and tightly focused EB measurement, the detection limit was significantly decreased. Our preliminary results demonstrated that a TLM enables the detection of iron ions at the levels of µg·L −1 , which makes this technique an alternative to traditional spectroscopic methods as a promising detector for the ultrasensitive determination of different compounds in liquid solutions.

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Section: Introductionmentioning

confidence: 98%

Determination of Fe(II) by Optimized Thermal Lens Microscope

2015

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“…where Previous experimental methods have been developed to approximate this phase shift and then used to measure very low absorption coefficients of materials, demonstrating good agreement with expected values through a far-field diffraction technique [1,2] . These methods require additional mathematical approximation and fitting to determine the change in the wavefront of the incident beam and, therefore, the phase shift resulting from the thermal lens.…”

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confidence: 66%

High-precision method for measuring the photothermal properties of transparent media with digital holography (Invited Paper)

Clark¹,

Kim²

2011

中国光学快报

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Quantitative phase microscopy by digital holography provides direct access to the phase profile of a transparent subject with high precision. This is useful for observing phenomena that modulate phase, but are otherwise difficult or impossible to detect. In this letter, a carefully constructed digital holographic apparatus is used to measure optically induced thermal lensing with an optical path difference precision of less than 1 nm. Furthermore, by taking advantage of the radial symmetry of a thermal lens, such data are processed to determine the absorption coefficient of transparent media with precisions as low as 1×10 When a beam of incident light passes through a medium, that medium may absorb some energy of the beam. This absorbed energy causes a change in temperature of the absorbing region of the media, which diffuses to other parts of the medium in a way described by its thermal properties. Since the index of refraction is a temperature dependant property, the temperature gradient results in a refractive index gradient and, therefore, an optical path difference. This effect is referred to as thermal lensing and has been the focus of many other studies as an indicator of the optical and thermal properties of materials [1−3] . Due to the change in optical path length, a resulting phase shift can be detected at a plane on the far side of the medium. The description of this result can be simplified if the dimensions of the sample are such that the edge effects and container medium can be ignored relative to the effects in the sample medium itself. Such a model has previously been developed, and is known as the two-dimensional (2D) infinite model [4] . This model mathematically relates the resulting phase shift to the photothermal properties of the medium in a focused continuous wave (CW) excitation laser beam and an unfocused or collimated imaging beam, such as that used in this letter.The validity of the 2D infinite model is based on several assumptions, and the experimental design should take these into account. The sample cell path length should be comparable to the confocal parameter (twice the Rayleigh range) of the excitation beam to ensure that the spot size remains relatively constant through the sample. In addition, the sample cell dimensions should be large compared with the excitation beam radius so that both radial and axial edge effects can be ignored. The sample should absorb very little power to avoid convection effects. Finally, the temperature coefficient of the refractive index, dn dT , should be constant in the range of temperatures observed. With these assumptions in mind, the laser-induced change in temperature within the sample can be described. Using expressions for the heat generated in a sample by a Gaussian excitation beam and the corresponding solution to the heat transfer equation, a previous study [4] has derived the following relation:where r is the radial distance from the beam axis; t is the time of exposure to the excitation beam; P is the total excitation beam power at the...

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“…The average value of D obtained for the core-shell nanocrystals solutions in function of CdSe/ZnS PMMA concentrations are showed in Table 1. For chloroform, THF and toluene solvents the average value obtained for D= 0.81, 0.92 and 0.92 x 10"^ cm^/s, respectively [5,6,[9][10][11]. Considering that the volume fraction of the nanoparticles/PMMA in our solutions is very low, it is possible to conclude that thermal parameter of the solvents is dominant in the colloidal solution samples analyzed in this work.…”

Section: Resultsmentioning

confidence: 93%

“…We supposed a negligible fluorescence for the solvent used for determine cp, where all absorbed energy is converted into heat by the sample, i.e., cpsoL = 1 (TISOL = 0). Using mean values obtained in the References [5,6,10,11] for K and dn/dT for chloroform, toluene and tetrahydrofuran , we calculated the value of the ©SOLV (value for the solvents) using the Eq. 2 [9].…”

Section: Resultsmentioning

confidence: 99%

Photothermal Spectroscopic Characterization in Core-Shell Quantum Dots Nanoparticles

Pilla¹,

Cruz²,

Catunda³

et al. 2008

AIP Conference Proceedings

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Thermal Lens (TL) for fluorescence quantum efficiency measurements were performed in CdSe/ZnS core-shell nanoparticles embedded into the poly(methyl methacrylate) (PMMA) and suspended in tetrahydrofuran (THF), chloroform and toluene. TL transient measurements were performed using the mode-mismatched dual-beam (excitation and probe) configuration. A He-Ne laser at Ap= 632.8 nm was used as the probe beam and either an Ar laser (at Ag=476, 488, 501 or 514.5 nm) or a HeNe laser (at Ag= 594 nm) was used as the excitation beam for solution of nanocrystal suspended in THF. The value obtained for the fluorescence quantum efficiency rj was 0.68. Thermo-optical parameters as thermal diffusivity D and the refractive index temperature coefficient dn/dT were determined by TL technique in function of the Xg. The values for dn/dT obtained by TL technique corroborate with the results performed with refractometer measurements.

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Absorption coefficient of nearly transparent liquids measured using thermal lens spectrometry

Cited by 59 publications

References 11 publications

Determination of Fe(II) by Optimized Thermal Lens Microscope

Determination of Fe(II) by Optimized Thermal Lens Microscope

High-precision method for measuring the photothermal properties of transparent media with digital holography (Invited Paper)

Photothermal Spectroscopic Characterization in Core-Shell Quantum Dots Nanoparticles

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