Photothermal Refraction Research Articles

Feedback and compensation scheme to suppress the thermal effects from a dipole trap beam for the optical fiber microcavity.

Cavity quantum electrodynamics (cavity QED) with neutral atoms is a promising platform for quantum information processing and optical fiber Fabry-Pérot microcavity with small mode volume is an important integrant for the large light-matter coupling strength. To transport cold atoms to the microcavity, a high-power optical dipole trap (ODT) beam perpendicular to the cavity axis is commonly used. However, the overlap between the ODT beam and the cavity mirrors causes thermal effects inducing a large cavity shift at the locking wavelength and a differential cavity shift at the probe wavelength which disturbs the cavity resonance. Here, we develop a feedback and compensation scheme to maintain the optical fiber microcavity resonant with the lasers at the locking and probe wavelengths simultaneously. The large cavity shift of 210 times the cavity linewidth, which makes the conventional PID scheme ineffective can be suppressed actively by a PIID feedback scheme with an additional I parameter. Differential cavity shift at the probe wavelength can be understood from the photothermal refraction and thermal expansion effects on the mirror coatings and be passively compensated by changing the frequency of the locking laser. A further normal-mode splitting measurement demonstrates the strong coupling between 85Rb atoms and cavity mode after the thermal effects are suppressed, which also confirms successful delivery and trapping of atoms into the optical cavity. This scheme can solve the thermal effects of the high-power ODT beam and will be helpful to cavity QED experimental research.

Dynamics of light-induced thermomechanical mirror deformations in high-finesse Fabry–Perot microresonators

Light recirculating inside an optical resonator can spontaneously trigger persistent cyclical thermomechanical mirror deformations. We have observed and characterized the dynamics of such deformations in high-finesse Fabry–Perot microcavities built following three distinct designs. The designs differed in form factor and confinement geometry, incorporating either (A) two nominally planar bulk mirrors, (B) one planar and one microconcave bulk mirror, or (C) one microconcave bulk mirror and one microconcave mirror at the tip of an optical fiber. For all cases, the cavity transmission exhibited bistability and high-frequency (∼MHz), high-amplitude pulsations for input powers greater than ≈10 mW at a cavity finesse of ≈30000. A theoretical analysis reveals that these pulsations are the result of the competition between photothermal expansion and photothermal refraction in the mirror coatings that induces “slow-fast” dynamics. We model these dynamics for the three different cavities and show that their varying duty cycles and periods are consistent with light-induced heating and heat dissipation conforming to the cavity mode spot size and the mechanical mirror support structure.

Self-sustained photothermal oscillations in high-finesse Fabry-Perot microcavities

We report the experimental investigation of a regime of microscopic Fabry-Perot resonators in which competing light-induced forces---photothermal expansion and photothermal refraction---acting oppositely and on different timescales lead to self-sustained persistent oscillations. Previously concealed as ordinary thermo-optic bistability---a common feature in low-loss resonator physics---these dynamics are visible as fast pulsations in cavity transmission or reflection measurements at sufficiently high time resolution. Their underlying mathematical description is shared by many slow-fast phenomena in chemistry, biology, and neuroscience. Our observations are relevant in particular to microcavity applications in atom optics and cavity quantum electrodynamics, even in nominally rigid structures that have not undergone lithography.

Thermal loss mechanism in the generation of multifrequency laser emission via stimulated Raman scattering and four-wave Raman mixing studied by photothermal refraction spectroscopy

The heat produced in conjunction with the processes of stimulated Raman scattering and four-wave Raman mixing in hydrogen was measured by photothermal refraction spectroscopy. Many vibrational, rotational, and vibrationally shifted rotational Raman lines are exclusively/simultaneously generated by changing the polarization of the laser beam and the hydrogen pressure. Thermal loss occurs predominantly from vibrational Raman scattering, which can be ascribed to a large Raman shift frequency of 4155 cm-1 for the vibrational transition. In contrast to stimulated Raman scattering, little or no thermal loss is observable during the process of four-wave Raman mixing.

Progress toward a better understanding of signal generation in laser-excited photothermal spectrometry of homogeneous samples

This article examines some recent experiments and theories that have advanced our understanding of the physical effects following thermal relaxation of the excited state. Experiments which show that the temperature-dependent refractive index is composed of density and pure-thermal terms are discussed. The importance of the purely thermal term is that it allows ultra-fast pulsed excitation sources to be used in photothermal refraction spectroscopy. This opens up new areas of applications in ultra-fast measurement. The effect of and progress towards the elucidation of specific volume changes are reviewed. Finally, recent progress in understanding nonlinear optical absorption and its effect on the photothermal signal are summarized.

Analytical characterization of laser photothermal transient deformation spectrometry

The radiationless relaxation process of excited molecules has developed as the basis for many laser photothermal spectroscopies. For example, laser photoacoustic spectrometry, laser thermal lens spectrometry, laser photothermal deflection spectrometry, laser photothermal refraction spectrometry and laser photothermal interference spectrometry have been applied to analytical chemistry and evolved into a kind of high sensitivity and high space resolution absorption spectrometries.

Studies of Multichannel Photothermal Refraction for the Measurement of Absolute Absorptivity

Multichannel crossed-beam photothermal refraction experiments have been performed. Iron(II)-phenanthroline in methanol was the test solute. The response as a function of concentration exhibited a nonlinear relationship, which does not agree with the current theoretical description of the phenomena. Although photophysical and photochemical processes were not totally eliminated as possible causes of the nonlinear concentration response, arguments are presented which indicate, for the experimental conditions employed in this study, that these processes are negligible. It is proposed that the heat transfer model must be modified to include refractive index gradients in both the radial and axial coordinates of the pump laser beam.

Dual-Wavelength Photothermal Refraction Spectrometry for Small-Volume Samples

A novel dual-wavelength photothermal refraction spectrometer that is capable of simultaneously measuring photothermal refraction at two different wavelengths has been developed. In this instrument, the two excitation wavelengths were provided by an argon-ion (488 nm) and a He-Ne (632.8 nm) laser. These two pump beams were sequentially modulated at the same frequency by means of two mechanical choppers. The photothermal refraction signals produced by the sample absorption of these two pump beams were monitored by a probe beam which was derived from the same He-Ne laser by a beamsplitter. Compared to the single-wavelength techniques, this dual-wavelength apparatus has advantages that include its ability to provide fingerprints and identification of the analyte (as the ratio of the two signals at the two different excitation wavelengths) and to simultaneously determine two-component samples. With this apparatus, the detection limit for two-component samples containing oxohydroxy bis-(8-hydroxy quinoline)-vanadium and 1,2-diamino-anthraquinone in methanol with the use of 25-mW excitation beams modulated at 3.4 Hz is estimated to be 10−7 M. This corresponds to the absorbance of 10−6 for a probe volume of 10−11 L.

Pulsed-laser photothermal refraction detection in capillary liquid chromatography

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPulsed-laser photothermal refraction detection in capillary liquid chromatographyC. N. Kettler and M. J. SepaniakCite this: Anal. Chem. 1987, 59, 13, 1733–1736Publication Date (Print):July 1, 1987Publication History Published online1 May 2002Published inissue 1 July 1987https://doi.org/10.1021/ac00140a032RIGHTS & PERMISSIONSArticle Views39Altmetric-Citations20LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (591 KB) Get e-Alerts Get e-Alerts

Double-Beam Lens Spectroscopy with Dual-Beam Configuration Based on Photo-Differential Detection

Photothermal lensing spectroscopy, such as thermal lens spectroscopy and photothermal refraction, has been the subject of much interest as a new analytical technique for ultrasensitive absorption measurements. However, the limit of detection of this technique is often dominated by the background signal caused by the absorption of solvent itself or by impurities in the solvent. A simple method for diminishing the background signal is to use a solvent with low absorptivity, like carbon dioxide in supercritical fluid chromatography. Another method is to use a differential technique. In thermal lens spectroscopy (TLS), both single-beam and dual-beam configurations have been used. A dual-beam configuration with a single laser has also been reported. In a single-beam configuration, a differential response of the system was obtained by the use of the antisymmetric dependence of the thermal lens effect on the position of the lens relative to the waist in a Gaussian beam. This technique was applied to the detection of liquid chromatographic effluents to compensate for solvent absorbance. On the other hand, no study has been made on a double-beam system with a dual-beam optical configuration. In this paper, a new double-beam system based on a dual-beam configuration is proposed to compensate for the background signal due to solvent absorption.

Pulsed photothermal refraction spectrometry using an elliptic gaussian excitation beam.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPulsed photothermal refraction spectrometry using an elliptic Gaussian excitation beamNorio. Teramae, Edward. Voigtman, Jose. Lanauze, and James D. WinefordnerCite this: Anal. Chem. 1986, 58, 4, 761–765Publication Date (Print):April 1, 1986Publication History Published online1 May 2002Published inissue 1 April 1986https://doi.org/10.1021/ac00295a025RIGHTS & PERMISSIONSArticle Views69Altmetric-Citations11LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (596 KB) Get e-Alerts Get e-Alerts

Optimization of Photothermal Refraction for Flowing Liquid Samples

A model has been developed for photothermal refraction using flowing liquid samples. In photothermal refraction, a cylindrical thermal lens is formed within the sample because of the temperature rise produced by the absorbance of a pump laser beam. This cylindrical thermal lens is intersected at right angles with a second probe laser. For static samples, the maximum signal results when the pump and probe beams are coplanar. Defocusing of the probe beam by the cylindrical thermal lens is detected as a change in the far-field probe beam center intensity. Flow acts to distort the temperature distribution by transporting heat down stream. For flowing samples, the optimum signal is found when the probe beam is located about one pump beam spot size down stream from the pump beam axis.

Photothermal refraction as a microbore liquid chromatography detector in femtomole amino acid determination

Photothermal refraction as a microbore liquid chromatography detector in femtomole amino acid determination

Photothermal Refraction For Scanning Laser Microscopy

Photothermal refraction is a novel thermo-optical technique that measures absorbance from localized regions within larger samples. In this technique, a modulated pump laser beam and a coplanar continuous-wave probe laser beam cross at right angles within the sample. Absorbance of the pump laser beam generates a time-varying localized temperature rise within the sample. This heated region acts as a thermal cylindrical lens that periodically defocuses the probe beam and results in a change in the probe beam center intensity. Since the pump and probe beams interact only in their intersection volume, a localized measure of sample absorbance is produced. A high spatial resolution image of sample absorbance may be made by recording the photothermal refraction signal as the sample is scanned through the intersection of the laser beams.

Laser-induced photothermal refraction for small volume absorbance determination

La theorie de la refraction optothermique est verifiee experimentalement. Une limite de detection de 0,4 fg de Fe est obtenue pour un volume d'echantillon de 25 pl

Theory for laser-induced photothermal refraction

Theory for laser-induced photothermal refraction