Journal of Russian Laser Research最新文献

We propose a method for calculating parameters of the eye safe parametric converter, considering the largest number of factors existing under real conditions and a limit of the conversion efficiency. We present the results of a theoretical study of single-cavity parametric generation in depleted pump approximation, where it is possible to simultaneously consider the influence of the intensity of the idler wave, the phase mismatch between interacting waves, losses on mirrors during reflection, as well as absorption in a nonlinear medium. When analyzing in the constant intensity approximation (CIA), in contrast to the constant field approximation (CFA), an additional term (Gamma_{i}^{2}sim I_{i0}) appears, which leads to increase in the threshold pump intensity. We present a numerical estimate of the threshold intensity for KTP along with a comparison with the experiment. The results hint at a research method that holds promise for the development of efficient parametric frequency converters for visual observation of biological objects and in medical research.

We consider the impact of a photon crystal (PC) element on mode locking in a laser. We show that placing of an additional PC in an actively/passively mode-locked laser results in the enhancement of the mode-locking effect. The effect is demonstrated on a passively mode-locked ring cavity laser using a numerical model. We show that the laser generates a few times shorter and almost an order of magnitude more powerful pulses due to the PC element.

In this paper, an auxiliary liquid modulated photonic crystal fiber (PCF) refractive index (RI) sensor based on local surface plasmon resonance (LSPR) is proposed, featuring an adjustable wide detection range and high RI sensitivity. The modulation of the electric field intensity distribution within the PCF is achieved by filling specific air holes with auxiliary liquid, leading to improved properties of the PCF-LSPR sensor. Moreover, the detection range of the sensor can be tailored by adjusting the RI of the auxiliary liquid. Using the full-vector finite element method (FEM), simulations of sensor performance are conducted. Results demonstrate that with an auxiliary liquid RI of 1.41, the sensor achieves a maximum RI sensitivity of 52438.02 nm/RIU and a detection range of 1.27–1.41. Similarly, with an auxiliary liquid RI of 1.43, the sensor achieves a maximum RI sensitivity of 46611.18 nm/RIU and maintains a detection range of 1.23–1.41. This approach allows for customization without altering the sensor geometry, facilitating the adjustment of the auxiliary liquid RI based on specific sensing requirements. Consequently, it offers tailored solutions for various sensing needs, thereby expanding the potential applications of PCF-LSPR sensors.

We successfully develop a pulsed fiber laser, operating at 1088 nm, by utilizing a neodymium-doped fiber (NDF) as the gain medium and black phosphorus (BP) material as a saturable absorber (SA). We construct the SA by transferring multilayer BP material onto a fiber ferrule tip via mechanical exfoliation, subsequently integrated into an NDFL ring cavity to modulate the cavity loss and generate Q-switched pulses. Notably, as the 808 nm pumping power increases from 44.7 to 90.6 mW, the laser’s output pulse duration decreased from 15.1 to 10.6 µs, while the repetition rate increases from 21.93 to 42.92 kHz. Demonstrating stable pulse train output, the laser exhibits a fundamental frequency with a signal to background noise ratio of 35 dB. This pioneering work represents the first report to employ BP as SA within an NDFL cavity.

Using spin-1/2 state (qubit state) description by the conditional probability distributions of dichotomic random variables, we construct the irreducible Lie su(2) algebra representations by means of the probability distribution functions. We obtain explicit 2×2-matrices of the Lie algebra elements and express them in terms of Pauli matrices. Then we discuss the possibility to obtain the probability representation of arbitrary Lie algebra, using the symmetry Lie group of quantum system states. Finally, we write Pauli matrices in the probability representation of dichotomic random variables.

Optical lattices, created by interfering laser beams, are efficient tools to manipulate cold atoms by adjusting the lattice geometry and parameters. A number of dynamical effects has been studied with cold atoms in one-dimensional optical lattices in classical, quantum, and semiclassical regimes. Recently, it has been shown that multi-dimensional optical lattices may lead to deeply different dynamics of non-interacting atoms allowing us to investigate the quantum–classical correspondence. We discuss the recent progress in studying classical, semiclassical, and quantum chaotic dynamics of cold atoms in two-dimensional and three-dimensional optical lattices with non-trivial geometry. The special attention is paid to classical versus quantum dynamics of atoms with the coupling between the internal and translational degrees of freedom. The dynamical mechanisms of transition to chaos and inhibition of the onset of chaos for atoms trapped inside wells of the optical potential and moving between different wells are discussed. We propose the experimental schemes that could distinguish between the regular and chaotic dynamics. The perspectives for observation of quantum chaos with cold atoms, that is the quantum regime of a system, whose classical dynamics is chaotic, are considered.

Besides the correlation vortices, the correlation edge dislocation of partially coherent beams is shown to be in existence. The analytical expression of the cross-spectral density (CSD) for the Gaussian Schell-model (GSM) beams with two correlation edge dislocations propagating through oceanic turbulence is derived, which is used to study the interaction of them in free space and oceanic turbulence. It is shown that the correlation edge dislocations are generally unstable and easy to vanish, while correlation vortices or correlation edge dislocation may appear with propagation. The interaction is influenced by the propagation distance and parameters, such as the spatial correlation length, the off-axis distances, and the slope of the edge dislocations. Besides, the oceanic turbulence parameters affect the appearance, position and number of correlation singularities in the fields. The stronger oceanic turbulence, the faster the decrease of the distance for the first reappearance of the correlation vortices.

In this paper, we present a Mach–Zehnder interferometer (MZI) sensor utilizing an optical fiber offset. The sensor core comprises multimode fiber (MMF), single-mode fiber (SMF), and offset no-core fiber (NCF), enabling it to detect the refractive index (RI) of liquids. The sensing mechanism of the sensor is theoretically analyzed, and various structural parameters are simulated, using the Beam Propagation Module (BPM). Simulation results indicate that the sensor efficiently operates across the entire wavelength range of 1.5–1.61 µm, providing continuous calibration curves for RI measurement. The sensor sensitivity to RI ranges of 1.3330–1.3340, 1.3334–1.3335, 1.3530–1.3540, and 1.3630–1.3640 are –14342, –14700, –17628, and –19600 nm/RIU, respectively. Additionally, the sensor exhibits a favorable linear response, laying a crucial foundation for developing the high-sensitivity liquid RI sensor design. The sensor boasts a simple, compact design, high sensitivity, and significant application potential in liquid RI measurements.

In this paper, we consider an implementation of the difference logical operation on sets represented as images in the accumulated photon echo mode. We show that this operation can be performed in the presence of a phase difference between pairs of exciting laser pulses.

We design a fourth harmonic beam splitter for ND : YAG laser fabricated by electron beam evaporation with HfO₂/SiO₂. At 45° incident angle, the transmittance of the as-deposited film is 99.49% at 1064 nm and 98.96% at 532 nm, while the reflectivity is 99.80% at 266 nm. The films are annealed in air at temperatures from 200 °C to 400 °C. We study the optical properties, microstructure, and surface morphology of as-deposited and annealed films. The transmission spectra of the films show blue shift with increasing annealing temperature. X-ray diffraction (XRD) results show that all the films exhibit polycrystalline with a monoclinic structure of HfO₂ and an amorphous structure of SiO₂. The crystallite size and crystallinity of the film increase at annealing temperature of 400 °C, and there is no obvious change at annealing temperatures of 200 °C and 300 °C. According to the results of atomic force microscopy (AFM), the surface root-mean-square (RMS) roughness of the film significantly decreases at annealing temperatures of 400 °C.