Optics and Spectroscopy最新文献

The results of laboratory measurements of the transparency of fresh ice blocks in the optical range in the temperature range from –15 to 0°C are presented. The studies were performed at two wavelengths in the visible range (at a wavelength of 535 nm) and the ultraviolet range (at a wavelength of 370 nm). We studied the ice of a natural fresh water body with a characteristic predominant spatial orientation of the main optical axis of the crystals. It has been established that when approaching a temperature of 0°, the sample becomes bleaching (decrease in attenuation). The effect occurs in the range –0.5–0°C. It is determined by the occurrence of plastic deformation due to thermal stresses caused by the initial stage of the ice-water phase transition. The bleaching in experiments with ice blocks ~10 cm thick was 3–25%. The results obtained are of interest for solving remote sensing problems, since melting ice is a widespread object due to its significant heat of phase transition. Previously, the effect of bleaching of fresh ice was also discovered in the microwave range when the temperature of the sample approached the phase transition point.

The quantum vortices formed as a result of barrier-suppression ionization of a two-dimensional hydrogen atom by an ultrashort laser pulse are theoretically investigated. Using an analytical expression for the wave function of a photoelectron in the momentum representation, the probability flux density is investigated. In this case, both the standard definition of a flux and an alternative “symmetrical” one are used. The latter, due to the sensitivity to the phase of the wave function, makes it possible to identify quantum vortices in the momentum space.

One-dimensional photonic crystals with an arbitrary number and spectral position of photonic band gaps in the optical spectral range are experimentally demonstrated. The absence of mutual influence of the photonic band gaps was shown. No features corresponding to higher harmonics or combination frequencies were found in the spectral response of the multifrequency photonic crystals created.

When excited by a powerful picosecond pulse of the second harmonic of a YAP:Nd laser, inelastic scattering lines with frequency detunings in the range of  ~10–130 GHz relative to the laser line were detected in suspensions of morphologically similar AltMV and PVX viruses. This scattering has a threshold nature, and the sets of its spectral lines are different for different virus samples.

The laser generation characteristics of microdisc lasers with optically coupled waveguide operating in continuous wave mode at elevated temperatures are investigated. Laser generation and waveguide effect at temperatures up to 92.5°C were demonstrated. The measured characteristic temperature of microlasers was 65 K in the range of 25–92.5°C.

The paper presents a technique for broadband two-dimensional infrared spectroscopy with signal detection in visible range by nonlinear chirped-pulse upconversion. This approach helps to avoid direct measurement of the mid-infrared signal that requires cryogenic technology, and instead uses low-cost high-sensitivity multichannel silicon linear arrays. This leads to a reduction by two orders of magnitude of the measurement time of a single two-dimensional spectrum, which makes it possible to observe the fast dynamics of complex molecular compounds. The use of a quasi-phase-cycling achieved by sub-cycle delay modulation suppresses scattering background by almost two orders of magnitude and increases the measurement speed twice compared to optical chopping. Numerical simulation using the density matrix formalism and analysis of its evolution based on the solution of the Bloch–Redfield equation effectively reproduces the features of the two-dimensional infrared spectrum of inorganic octacarbonyl dicobalt compound.

Observation of molecular optomechanical effects is complicated by the need to localize electromagnetic energy in metal gaps about 1 nm in size. We propose to use a nanocavity with an epsilon-near-zero medium so that the conditions required for optomechanical coupling are less stringent. In this work, we simulate the enhancement of Raman scattering depending on the permittivity of the material and the polarization of the near field of the nanoparticle. It is shown that when the real part of dielectric permittivity close to zero, Raman scattering demonstrates an additional enhancement.

The effect of the electron-rotational interaction induced by an external magnetic field on the values of Lande g-factors is systematically investigated within the quantum mechanical model of coupled radial Schredinger equations for locally and regularly perturbed electronic-vibrational-rotational (rovibronic) levels of nonadiabatically coupled X ²Σ⁺, A²Π and B²Σ⁺ states of the CN radical, whose isotopomers are of persistent astronomical interest due to their wide use in optical diagnostics of various regions of the interstellar and near-stellar medium.

In this work we present results of numerical modeling of a ZGDC polarization splitter based on SiN thin films. The magnitude of the interference is –15 dB for the TM-mode and –10.4 dB for TE-mode. The transmission coefficient is 43%.

We introduce a strategy to develop multiple-phase structure of inorganic lead halide perovskite CsPbBr₃. The method is based on local optical heating, which allows the creation of strong temperature gradients. Using Raman spectroscopy, it was determined that such gradients induce a distribution of phase transitions within the perovskite crystal. We show that such gradients lead to perovskite multiple-phase structure.