When thermal and stress confinement conditions are satisfied, the propagation of laser-induced ultrasound (LIU) is governed by an inhomogeneous wave equation for pressure, and the laser temporal profile can be modeled by a Dirac delta distribution. If these conditions are not fulfilled, the coupled differential equations for temperature and pressure must be solved, considering a laser pulse with finite time-width. Here, an exact solution of the boundary value problem for the 1D-wave equation is obtained in both the frequency domain and the time domain. Since highly absorbent optical materials are out of the validity range of the confinement conditions, these are used as a numerical and experimental model. It is shown that the impulse-response model correctly predicts the time of flight of photoacoustic waves. However, when considering a laser pulse with finite time-width, the resultant theoretical amplitude of the LIU signal decays rapidly to zero, which is not observed in the experiment. To overcome this, we propose a thermal correction on the LIU source, defined typically as the optical penetration length, which imposes a redefinition of stress and thermal confinement in just one statement. Additionally, with the aim of comparing the corrected-theoretical results with the acquired electrical signals, the sensor and the oscilloscope were modeled as an RC circuit in parallel. It was found that the amplitude of the electrical signal was proportional to the difference of the LIU amplitudes at the faces of the sensor. It is demonstrated that even though the sensor impulse response is modeled as a Dirac delta distribution, this difference strongly affects the shape of the LIU electrical signals, hiding relevant information of the acoustic waves.

The self-rotation on the polarization azimuth and the formation of a supramolecular chiral structure when an elliptically polarized light beam propagates through an amorphous azopolymer film are used to implement a two-wavelength chiroptical switch. The macrostructures generated by each excitation beam have different pitches, which produce different rotation angles of the polarization ellipse when an arbitrary probe beam is used. In the proposed device, one of the excitation beams is taken as a probe. The value and the sign of the rotation angle of the polarization ellipse of the probe beam when the second beam is illuminating the sample mainly depend on the relationship between their input states of polarization.

Three types of polarization gratings have been recorded in azopolymer films by the symmetrical superposition of different orthogonal pairs of polarized beams. The inscribed holographic elements have been analyzed microscopically in a Mueller polarimeter in order to image the optical anisotropies photoinduced in the film. In the most of cases, the spatial modulation of diattenuation, birefringence, and optical rotation reproduced quite well previous results reported in the literature. Nevertheless, in the particular case of coherent superposition of p- and s-polarized beams, the spatial frequency for optical rotation (related to the Stokes parameter V) was different from the one observed in linear anisotropy (related to the Stokes parameter U). It is shown by theory and experiment that, in the polarized field used to record this polarization grating, the fourth-Stokes parameter changes sign, which implies a change in circular polarization handedness, practically once between two adjacent maxima.

Polarimeters are useful instruments that measure concentrations of optically active substances in a given solution. The conventional polarimetric principle consists of measuring the rotation angle of linearly polarized light. Here, we present a novel polarimeter based on the study of interference patterns. A Mach–Zehnder interferometer with linearly polarized light at the input is used. One beam passes through the liquid sample and the other is a reference beam. As the linearly polarized sample beam propagates through the optically active solution the vibration plane of the electric field will rotate. As a result, the visibility of the interference pattern at the interferometer output will decrease. Fringe contrast will be maximum when both beams present a polarization perpendicular to the plane of incidence. However, minimum visibility is obtained when, after propagation through the sample the polarization of the sample beam is oriented parallel to the plane of incidence. By using different solute concentrations, a calibration plot is obtained showing the behavior of visibility.

The imaging and digital processing of anisotropic optical properties of in vivo skin may be helpful in the assessment of its heterogeneous anatomy and physiological functioning. The interaction between polarized light and this organ provides information about the structural order beneath the epidermal layer. However, penetration depth is limited by optical absorption and scattering that are related to local skin characteristics such as pigment density, connective tissue organization, and cutaneous layer thickness. In this work, in vivo healthy skin of a murine model was analyzed using Mueller imaging polarimetry. A gray-level co-occurrence matrix analysis of diattenuation, birefringence, and depolarization measures in four different skin locations showed texture properties that can be used to distinguish local physiology.