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Control over volatile products of metabolic processes in human body in exhaled air is a promising method for noninvasive medical diagnostics. The mid-IR range (2 – 12 mm) is of great interest for diagnostic applications of the exhaled air spectral analysis. Laser optoacoustic spectroscopy is quite attractive for detecting a large set of gaseous substances; however, high-power sources of tunable radiation are required to increase the method sensitivity. We consider the possibility of using a parametric light generator based on a BaGa4Se7 crystal as a broadband tunable mid-IR laser source for laser optoacoustic spectroscopy.

In this paper a spectroscopic characterisation method based on the optoacoustic technique has been used to investigate the optical properties of two separate spherical gold nanoparticle (SGNP) solutions where an absorption peak located at 520 nm has been observed. This analysis has been carried out over the visible wavelength range from 410 to 650 nm using a Q-switched Nd:YAG pumped optical parametric oscillator (OPO). To verify the reliability of optoacoustic spectroscopy (OAS), the results obtained have been compared to those from more standard and limited spectrophotometer and reference collimated optical transmission schemes, where good agreement is shown. The experimental procedure presented here demonstrates the potential of this technique for integration along with optoacoustic imaging methods to identify physiological information for non-destructive in-vivo applications.

Background: Anemia is an underdiagnosed, significant public health concern afflicting >2 billion people worldwide. The detrimental effects of tissue oxygen deficiency on the cardiovascular system and concurrent appearance of anemia with numerous high-risk disorders highlight the importance of clinical screening. Currently there is no universally accepted, clinically applicable, noninvasive hemoglobin/hematocrit screening tool. The need for such a device has prompted an investigation into a breadth of techniques. Methods: A synopsis of the literature and current directions of research in noninvasive total hemoglobin measurement was collected. Contributions highlighted in this review are limited to those studies conducted with a clinical aspect, and most include in vivo patient studies. Results: The review of potential techniques presented here includes optoacoustic spectroscopy, spectrophotometric imaging, diffuse reflectance spectroscopy, transcutaneous illumination, electrical admittance plethysmography, and photoplethysmography. The technological performance, relative benefits of each approach, potential instrumentation design considerations, and future directions are discussed in each subcategory. Conclusions: Many techniques reviewed here have shown excellent accuracy, sensitivity, and specificity in measuring hemoglobin/hematocrit, thus in the near future a new clinically viable tool for noninvasive hemoglobin/hematocrit monitoring will likely be widely used for patient care. Limiting factors in clinical adoption will likely involve technology integration into the current standard of care in each field routinely dealing with anemia.

Time-resolved laser-induced optoacoustic spectroscopy (LIOAS) is a sensitive photobaric method for nondestructive probing of materials that monitors the pressure changes induced in a liquid or a solid sample after photoexcitation with a pulsed laser. LIOAS is an interesting tool for investigating photo-induced chemical processes as well as ‘optically silent’ intermediates, i.e., those displaying no changes in absorption or emission. A phenomenological approach to the equations related to this technique is employed and a description is given of the equipment and data handling as well as a few examples of applications of LIOAS to small molecules either in solution or in a solid powder matrix.

Pulsed laser optoacoustic detection system is being developed to monitor SO2, NOx, NH3, CO, CO2, H2O, O3 gases. The gases will be analysed using UV-VIS and IR sources. Results obtained with the UV-VIS system will be described herein.

This paper contains a review of results of the experimental investigation of linear and nonlinear absorption of atmospheric gases using the methods of multichannel optoacoustic spectroscopy with pulsed visible and IR lasers.

We report the observation of saturation Lamb-dips in the optoacoustic spectrum of CH 3 OH and CO 2 excited by CO 2 laser. An intermodulation technique is used to get Doppler-free resolution of the lines. Because of the small sample size and the high sensitivity intermodulated optoacoustic spectroscopy compares favorably with other Doppler-free methods.

Optoacoustic spectroscopy (OAS) is based on measuring the OA signal as a function of wavelength of the monochromatic radiation impinging on the sample. In this chapter we consider mainly the general experimental techniques and potentialities of laser OAS of gaseous media.

Optoacoustic spectroscopy investigate solid, semi conductor and liquid samples which are strongly or weakly absorbing, or which preclude the use of reflectance or transmission spectroscopy due to scattering of the incident radiation. The material presented in this chapter demonstrates the great potentiality of OAS of condensed media.

Optoacoustic spectroscopy can also be used to solve nonspectroscopic problems, in particular, to measure and control the parameters of laser radiation, to study the thermal properties of various media, to investigate electron-phonon interaction, etc. In this chapter we consider some interesting areas of such nonspectroscopic applications.

Optoacoustic (OA) detection apparatus can be used for analysis of various optical absorbers in very dilute concentrations. Parameters of pulse OA spectroscopy as applied to highly transparent samples are derived allowing to compare the potentialities to these of conventional absorption methods. We consider a frequently used OA device based upon linear thermoelastic OA conversion. Practice of both amplitude and dynamic versions of OA method are discussed. The role of pure solvent contribution is revealed. Useful estimates are provided.

An analysis is made of the suppression of fluctuations of an acoustic signal and of reduction of the intrinsic relaxation times in stochastic excitation of a Raman-active transition.

Molecular spectroscopists have studied the absorption of optical radiation for over 100 years, but only in the last five years have experiments come forth on the subsequent relaxation of the molecular excitation to produce heat. By detecting this heat as an acoustic pulse using sensitive microphones and bolometers, the eventual fate of absorbed photons can be followed, both energetically and kinetically. Several examples of the unique information derived from this acoustic method of molecular spectroscopy will be presented.

A method and apparatus that significantly increases the sensitivity and flexibility of laser optoacoustic spectroscopy, with reduced size. With the method, it no longer is necessary to limit the use of laser optoacoustic spectroscopy to species whose absorption must match available laser radiation. Instead, "doping" with a relatively small amount of an optically absorbing gas yields optoacoustic signatures of nonabsorbing materials (gases, liquids, solids, and aerosols), thus significantly increasing the sensitivity and flexibility of optoacoustic spectroscopy. Several applications of this method are demonstated and/or suggested.

(1986). Laser Optoacoustic Spectroscopy. Optica Acta: International Journal of Optics: Vol. 33, No. 11, pp. 1338-1338.