RESUMO
The components of electric field of the third harmonic beam, generated in isotropic medium with cubic nonlinearity by a monochromatic light beam carrying polarization singularity of an arbitrary type, are found analytically. The relation between C-points characteristics in the fundamental and signal beams are determined, as well as the impact of the phase mismatch on the shape of the C-lines.
RESUMO
The second harmonic generation in the bulk of an isotropic chiral liquid with spatial or temporal nonlocality of its quadratic response is studied analytically. The fundamental pulsed beam has Gaussian time envelope and carries a polarization singularity at its axis. The influence of the topological charge and the handedness of the polarization singularity on the polarization state of the signal beam is revealed.
RESUMO
We describe a universal system for research in combined real-time optoacoustic (OA) and laser-ultrasonic (LU) imaging. The results of its testing on the task of needle insertion into the blood vessel model diagnostics are presented. In OA mode, where laser light is absorbed directly in the sample, the contents of blood vessel model is clearly visible. In LU mode, where the short ultrasonic probe pulse scattered on the sample is detected, the needle is clearly visible. The developed solution combining OA and LU imaging modalities due to the common detection system allowed real-time diagnostics of the position of medical needles (0.63 mm and 0.7 mm in diameter) inside blood vessel models (1.6 mm and 2.4 mm in diameter). Frame rate was 10 Hz. High longitudinal spatial resolution of the system - 0.1 mm - allows distinguishing the two walls of the vessel model and the position of the needle inside.
