Fluidic lens by using thermal lens effect

Doan, Hong Duc; Akamine, Yoshihiko; Fushinobu, Kazuyoshi

doi:10.1016/j.ijheatmasstransfer.2012.07.024

Cited by 8 publications

(5 citation statements)

References 21 publications

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“…While, the experiment they showed was not especially innovative, the idea alone was. The same authors [187] used their top-hat HL beam to produce a TL almost free of spherical aberrations, with the focal length tuned using the HL power. This result was in accordance with the Reitze et al [164] observation of the supremacy of HL top-hat profile over Gaussian one in terms of spherical aberrations introduced by a TL formed by such an HL.…”

Section: Thermal Lens Applications As Tunable Lensmentioning

confidence: 99%

Thermal lensing: outside of the lasing medium

Dobek

2022

Appl. Phys. B

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The thermal lens formed in a thermo-optical material as a result of its inhomogeneous heating, is a well-known phenomenon that has found widespread interest in the last decades, especially in the field of laser engineering and photo-thermal spectroscopy. In recent years, growing interest in the application of thermal lensing in different fields of optics and material studies has been observed. This review summarizes the latest efforts made by the scientific community to develop ways of using the phenomenon of thermal lensing. Its applications in spectroscopy, in laser beam formation and in imaging are described. The advantages and disadvantages of the thermal lensing in regard to these areas along with the potential future applications of the phenomenon are discussed.

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Section: Thermal Lens Applications As Tunable Lensmentioning

confidence: 99%

Thermal lensing: outside of the lasing medium

Dobek

2022

Appl. Phys. B

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“…The authors of [10] obtained the values from approximately f = −2.5 to −0.5 m for the heating laser power range P HL = 2 to 8 mW in a solution of the sunset yellow dye in ethanol. In [11], the values of f are reported to vary from 1.25 to 10 m for P HL changed from 0.5 to 6 W for a thermal lens formed in a colour glass filter.…”

Section: Macroscopic Aperture Thermal Lensmentioning

confidence: 99%

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mentioning

confidence: 99%

“…As shown by the authors of Refs. [9][10][11], ∇n formation can lead to the formation of a few millimetre (thus macroscopic)-size aperture thermal lenses whose focal length depends on the heating laser intensity. However, the authors of these two works did not take into account that ∇n at a selected heating laser intensity can depend as well on the bulk temperature of the thermal lens element, irrespective of this element being a liquid [9, 10] or solid [11].…”

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confidence: 99%

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Thermal lens in a liquid sample with focal length controllable by bulk temperature

et al. 2016

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In this paper, we propose a new solution, which is an improvement to recent propositions given in [9][10][11]. In contrast to many of the above-cited ideas, which rely on modification of the lens shape, one can induce a refractive index distribution, ∇n, that acts as a lens, without changing the shape of the lensing element. Optical elements with such n distribution, called GRIN (gradient refractive index), are e.g. lenses or fibres, but these elements have ∇n fixed. Therefore, they do not conform to the idea of flexible optical elements (as used e.g. in adaptive optics). Meanwhile, such ∇n can be induced thermally, by irradiation of the thermal lensing element by a heating laser beam, absorbed by this elements material, or by controlled electrical heating of the thermal lensing element [12]. As shown by the authors of Refs. [9][10][11], ∇n formation can lead to the formation of a few millimetre (thus macroscopic)-size aperture thermal lenses whose focal length depends on the heating laser intensity. However, the authors of these two works did not take into account that ∇n at a selected heating laser intensity can depend as well on the bulk temperature of the thermal lens element, irrespective of this element being a liquid [9, 10] or solid [11]. This particular dependence was the subject of our interest, and this work presents the results of our studies.In principle, the laser can also induce the nonlinear Kerr effect or electrostriction force-both of which can lead to nonzero ∇n [13]. In this work, we assume these effects negligible and we focus only on the thermo-optical effect. It follows from nonzero thermo-optical ∂n ∂T parameter of the medium illuminated by heating laser. We present results for a liquid thermal lens material, but thermal lenses can be formed in solids as well, e.g. in glasses. This last case is more attractive from the application point of view. Solids are free from convection and easier to use in different optical set-ups. Additionally, due to the thermal expansion, Abstract An experimental and numerical investigation of the applicability of the temperature-controlled focal length of a thermally induced lens is reported. The thermal lens is formed as a result of absorption of a heating laser beam. Numerical simulations and experimental results show that changing the bulk temperature of the material of the lensing element allows for the selection of its focal length. The range of focal length changes for an example lens is given.

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“…Table 1 summarizes the major parameters of the laser. The spatial profile of the Nd:YAG laser beam, referred to as "beam shape" in the following descriptions, is controlled by using the beam shaper developed by the authors in previous studies [2,26]. The beam shaper consists of the DPSS laser 1 and the cuvette with a dye solution, as shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

Nanosecond time-resolved visualization of short pulse laser ablation processes for various laser beam profiles

Doan

Iwatani

Sasaki

et al. 2014

Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)

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Thermal and fluid behavior are governing factors for the via processing of semiconducting substrates. In order to investigate the fundamentals, nanosecond (ns) time-resolved visualization of ns-pulse Nd:YAG laser ablation of SiC substrate has been performed for various conditions. Timeresolved visualizations have been conducted by using a ultra high speed camera with the frame rate of 200 million frames/second for the first time to reveal the ablation process in a single event with the temporal resolution of 5 ns. Both self-emitting light from the ablation plume and the shadow image due to the refractive index profile are visualized. The results show unique features for each spatial beam profiles (Gaussian, quasi-flat top, annular) with different beam energy. Combined with the previous experimental observations, the results help modeling the thermo-fluid numerical modeling of the ablation process. KEY WORDS: laser ablation, short pulse laser, time-resolved visualization, ultra high speed camera, laser beam profile, thermo-fluid modeling NOMENCLATURE E Pulse energy, J t Time, s 978-1-4799-5267-0/14/$31.00 ©2014 IEEE

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Fluidic lens by using thermal lens effect

Cited by 8 publications

References 21 publications

Thermal lensing: outside of the lasing medium

Thermal lensing: outside of the lasing medium

Thermal lens in a liquid sample with focal length controllable by bulk temperature

Nanosecond time-resolved visualization of short pulse laser ablation processes for various laser beam profiles

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