Laser photoacoustic spectroscopy is a laser measurement method with high sensitivity, good selectivity, nondestructive, and fast response (real‐time). In the present work, to detect carbonyl sulfide and ethene gases and measure resonant frequencies and signals, the photoacoustic spectroscopy system was designed and set up. The detection limit of this system to trace ethene and carbonyl sulfide was measured 3 ppb and 8 ppb, respectively. Also, for these two gases at the presence of different buffer gases, the resonant frequency and photoacoustic signal were recorded. The results showed that among the used buffer gases, xenon has the best acoustic performance and gives the highest photoacoustic signal. The signal also increased with increasing pressure of buffer gas, because increasing the pressure leads to improved collisional processes. The study of resonant frequencies of this system for these two gases in the presence of buffer gases showed that with increasing the pressure of xenon, argon, and nitrogen buffer gases from 65 to 765 Torr, the resonant frequency does not change significantly. But in the case of helium buffer gas, these resonant frequency changes are significant, and as the helium pressure increases by 65 to 765 Torr, the resonant frequencies of carbonyl sulfide and ethene change from 2016 to 2630 Hz and from 2100 to 2740 Hz, respectively. The reason for the different behavior of helium is the higher speed of sound in helium than in other buffer gases.

Here, the authors have utilized laser induced breakdown spectroscopy (LIBS) to distinguish cancerous tissues from normal ones. For this purpose, the plasma emission spectra of the normal and cancerous tissues taken from four different organs of interest, i.e, breast, colon, larynx, and tongue are analyzed via the excitation of a pulsed Neodymium-doped Yttrium Aluminum Garnet (ND: YAG) laser at 1064 nm. Results show that the abundance of the trace elements such as Ca, Mg, and Na trace elements are elevated in the cancerous tissues with respect to normal ones. In addition, inductively coupled plasma-optical emission spectroscopy and quadrupole-mass spectroscopy are employed to support the findings given by LIBS. Furthermore, the plasma characteristics such as temperature and electron density are probed by data processing of the plasma spectra at local thermal equilibrium condition as an alternative technique to discriminate between the normal and malignant tissues. It is shown that more energetic plasma is created on the neoplastic specimens resulting in higher electron density and plasma temperature due to the corresponding intense atomic/ionic characteristic emissions of species. The simplicity and low cost of processes benefits the physicians to encourage the clinical application of LIBS in near future.

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Angular dependence of the intensity and the emissive wavelength of the laser-induced fluorescence emission in hybrid media (fluorophores+nanoparticles) are investigated using various TiO densities as guest nanoscatterers in the ethanolic solutions of the host Rd6G and coumarin 4 (C4) molecules. It is shown that the intensity of the scattered photons varies in terms of the detection angle. When the nanoscatterer density increases at a certain excitation energy, the angular anisotropy enhances. While the emissive wavelength exhibits the spectral shift in terms of the angular variation for Rd6G fluorophores, it remains invariant for C4-based suspension. In the former case, the emissive wavelength undergoes a spectral shift in terms of angular variation. Several factors such as the optical path length in the scattering media, the excitation volume, and the re-absorption events of the fluorescence emissions by the non-excited molecules strongly affect the spectral features. In fact, the density of the scatterers, the dye concentration, and the interplay between Stokes shift rate and the overlapping between absorption/emission spectra of the given fluorophores are taken into account as the major parameters to form the angular distribution.