Pulsed optoacoustic spectroscopy of condensed matter

Patel, C. K. N.; Tam, A. C.

doi:10.1103/revmodphys.53.517

Cited by 610 publications

(242 citation statements)

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“…After excitation of the tissues by short laser pulses, consequent acoustic transients generated as a result of thermal expansion are detected. [22][23][24] A number of scientific groups successfully use the photoacoustic technique for vascular applications. [25][26][27][28][29][30] Previously, we investigated the feasibility of IVPA imaging using commercially available IVUS imaging catheters.…”

Section: Introductionmentioning

confidence: 99%

Development of a catheter for combined intravascular ultrasound and photoacoustic imaging

Karpiouk¹,

Wang²,

Emelianov³

2010

Review of Scientific Instruments

114

120

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Atherosclerosis is characterized by formation and development of the plaques in the inner layer of the vessel wall. To detect and characterize atherosclerotic plaques, we previously introduced the combined intravascular ultrasound ͑IVUS͒ and intravascular photoacoustic ͑IVPA͒ imaging capable of assessing plaque morphology and composition. The utility of IVUS/IVPA imaging has been demonstrated by imaging tissue-mimicking phantoms and ex vivo arterial samples using laboratory prototype of the imaging system. However, the clinical realization of a IVUS/IVPA imaging requires an integrated intravascular imaging catheter. In this paper, two designs of IVUS/IVPA imaging catheters-side fire fiber-based and mirror-based catheters-are reported. A commercially available IVUS imaging catheter was utilized for both pulse-echo ultrasound imaging and detection of photoacoustic transients. Laser pulses were delivered by custom-designed fiber-based optical systems. The optical fiber and IVUS imaging catheter were combined into a single device. Both designs were tested and compared using point targets and tissue-mimicking phantoms. The results indicate applicability of the proposed catheters for clinical use.

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Section: Introductionmentioning

confidence: 99%

Development of a catheter for combined intravascular ultrasound and photoacoustic imaging

Karpiouk¹,

Wang²,

Emelianov³

2010

Review of Scientific Instruments

114

120

View full text Add to dashboard Cite

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“…The ability to measure the Raman effect using a non-optical channel is important because the weak Raman signal can be detected in zero optical background, providing similar sensitivity advantages to that offered by photoacoustic spectroscopy. 2 Furthermore, since we do not need a spectrometer for the measurement, the resolution of the technique can be improved by several orders of magnitude as compared with conventional techniques, since it is only limited by the spectral bandwidth of the lasers used and not by the spectrometer resolution; for diode lasers, this bandwidth can be as narrow as 100 kHz. We present images from our Raman Probe Force Microscope of molecular clusters where single molecules can be discerned within them due to their orientation differences.…”

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confidence: 99%

Raman spectroscopy and microscopy based on mechanical force detection

Rajapaksa

Wickramasinghe

2011

Applied Physics Letters

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The Raman effect is typically observed by irradiating a sample with an intense light source and detecting the minute amount of frequency shifted scattered light. We demonstrate that Raman molecular vibrational resonances can be detected directly through an entirely different mechanism-namely, a force measurement. We create a force interaction through optical parametric down conversion between stimulated, Raman excited, molecules on a surface and a cantilevered nanometer scale probe tip brought very close to it. Spectroscopy and microscopy on clusters of molecules have been performed. Single molecules within such clusters are clearly resolved in the Raman micrographs. The technique can be readily extended to perform pump probe experiments for measuring inter-and intramolecular couplings and conformational changes at the single molecule level. The Raman effect 1 is one of the most widely used phenomenon in chemical spectroscopy. Over the past 80 years, this effect has been measured by irradiating the sample with intense monochromatic light and detecting the minute amount (one part in 10 9 ) of frequency shifted scattered light. A typical Raman setup utilizes a high rejection, low insertion loss, long pass filter to reject the incident pump light. This is followed by a sensitive detector coupled to a high resolution spectrometer to record the molecular vibrational spectrum. We present initial results on an entirely different mechanism for detecting the Raman effect. It is based on the force interaction between a Raman excited molecule and a scanning probe microscope probe tip. The ability to measure the Raman effect using a non-optical channel is important because the weak Raman signal can be detected in zero optical background, providing similar sensitivity advantages to that offered by photoacoustic spectroscopy. 2 Furthermore, since we do not need a spectrometer for the measurement, the resolution of the technique can be improved by several orders of magnitude as compared with conventional techniques, since it is only limited by the spectral bandwidth of the lasers used and not by the spectrometer resolution; for diode lasers, this bandwidth can be as narrow as 100 kHz. We present images from our Raman Probe Force Microscope of molecular clusters where single molecules can be discerned within them due to their orientation differences.The concept of our scheme can be understood by referring to Figure 1. Two collinear optical beams-a pump beam at frequency m 1 and a stimulating beam at frequency m 2 -are focused to a diffraction limited spot on the sample surface to efficiently stimulate molecular vibrations at frequency (m 1 À m 2 ). The stimulating beam at frequency m 2 is tunable, allowing (m 1 À m 2 ) to be tuned through the various Raman vibrational resonances. We probe the force interaction between the excited oscillating molecules and a cantilevered, gold coated, scanning probe microscope tip approached within nm range of the sample surface as the force interaction is modulated at frequency f m . The force ...

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“…They have also greatly expanded the usefulness of a variety of modulation and detection techniques for measuring weak absorptions.C~3, 14) Lasers are of unquestioned value for surface Raman spectroscopy (15) and surface nonlinear spectroscopies,(16) which may prove very useful in the future. The role of laser sources in linear infrared spectroscopy of.…”

Section: Status Of Relevant Technologymentioning

confidence: 99%