Journal of Russian Laser Research最新文献

In this paper, we report a multi-wavelength passively Q-switched fiber laser based on reconfigurable Lyot ring filter (RLRF) and Erbium-doped fiber (EDF) saturable absorber (SA). The gain saturable absorption characteristics of the EDF are analyzed in the experiments. When EDF is used as SA, EDF exhibits different nonlinear characteristics at different pump powers. Through the observation of the experimental data, we discuss the relationship between the multi-wavelength and passively Qswitching, in view of the position of the wavelength excitations and the presence or absence of the corresponding pulse sequence. The RLRF in the structure uses a 2 m long polarization maintaining fiber (PMF), and the wavelength interval between 1.5 and 3.0 nm can be effectively switched by adjusting the polarization controller (PC). The laser elaborated can flexibly switch from a single to seven wavelengths, with a corresponding pulse repetition rates of 24.11 – 59.38 kHz, a minimum Qswitched pulse width of 1.16 μs, a maximum average output power of 46.98 μW, and a maximum single pulse energy of 9.64 nJ.

There is a growing interest in the development of transportable optical ground station (TOGS) as an important component of laser communication network. The object of this paper is a TOGS designed for optical LEO satellite downlink as well as for long-distance aircraft downlink. A composite gravity compensation mount is proposed to simplify and efficiently suppress the low-order aberrations of an 800 mm aperture primary mirror with variable orientation of the optical antenna of a TOGS as it changes pointing. In this study, first we describe the composition of the TOGS and the utility of each part. Second, taking the minimization of the primary mirror deformation as the optimization objective, we employ the particle swarm optimization algorithm to find the optima of several key structural parameters by Isight software. Next, the annular Zernike polynomials are adopted to fit the wavefront error over the entire surface of the primary mirror for describing low-order aberrations, proving that the composite mount effectively suppresses the wavefront error to smaller than ⋋ /27, as the elevation angle changes from the horizontal to the vertical one. Finally, the ZYGO interferometer wavefront detections show that, after eliminating fabrication imperfections, the RMS of the wavefront error over the entire surface of the mirrors for horizontal and vertical axes, due to deformation, are 0.04⋋ and 0.035⋋, respectively. Compared to the results of the fitted wavefront error, the relative errors are 9.5% and 8.1%. The results show the validity and feasibility of the optimized composite mount and the wavefront fitting method, which can prove its reference significance for the budget and allocation of the systematic wavefront error in meter-scale optical antenna of the TOGS for satellite downlink.

It is crucial to enhance the efficiency of terahertz radiation in a single crystal for the application of intense field terahertz waves. We devise a trapezoidal lithium niobate prism that, upon side incidence of the terahertz wave, retroreflects the femtosecond laser onto the crystal’s symmetric plane. The conversion efficiency of pump power to THz pulse power for circular cavity increases by 36% compared to that of the conventional cavity. The findings demonstrate that the utilization of sample multiplexing pump can significantly enhance the efficiency of terahertz generation.

We experimentally demonstrate for the first time a tunable orthogonal polarized Pr³⁺: LiGdF₄ dual-wavelength laser. We calculate the conditions for balancing the gain and loss of the orthogonal polarization dual-wavelength with the rotation angles, the Lyot filter, and the incident angle on the uncoated glass. By adjusting the rotation angles, the Lyot filter, and the incident angle on the uncoated glass, the continuous-wave (CW) orthogonal polarized dual-wavelength lasers operating at 519.6 and 522.8 nm, 604.5 and 607.2 nm, and 719.2 and 721.5 nm are obtained.

Single-pixel imaging allows to obtain images without the use of photosensors with spatial resolution. In this method, an image is calculated by measuring the image conformity to a given set of light patterns by a single-pixel detector. However, when implementing single-pixel imaging in practice, one has to deal with various imperfections, which lead to the difference between the experiment and the idealized theoretical model. In this work, we analyze the effect of detector noise on the ability to compute an image using a compressed sampling algorithm. By conducting computer simulations of single-pixel imaging, we investigate methods for suppressing the effects of detector noise and find optimum parameters of the measurement process. As a result, we demonstrate the ability to obtain images with a realistic model of the detector noise.

We consider the 3D coefficient inverse problem for parabolic wave equation. It involves determining the spatial distribution of refractive and absorption indices by processing phase diffraction patterns obtained by irradiating an object with a set of Gaussian beams. Unlike tomography and ptychography, rotation or scanning of the sample is not required. The problem is solved by expanding the wave field and the complex dielectric constant (varepsilon left(overrightarrow{r}right)) over the full set of Gaussian beam functions. To determine (varepsilon left(overrightarrow{r}right),) we obtain a nonlinear matrix equation. The condition of its solvability allows the selection of sampling frequencies by coordinates in accordance with the practical task.

Evaluating quantum Fisher information is an essential task in the parameter estimation and quantum metrology. It quantifies the sensitivity of a quantum state to probe and capture variations in an unknown parameter, which is aimed to be estimated. In this context, the amount of quantum Fisher information measures the operational nonclassicality of a given state, regarded as a quantifiable resource for quantum metrology. We construct su(1, 1) coherent states, using the Perelomov formalism, and present their various optical realizations forming a general class of su(1, 1) algebraic squeezed states. We analyze the nonclassicality of these states and evaluate the corresponding Fisher information. Also, we find that su(1, 1) algebraic squeezed states surpass the standard quantum limit, thereby exhibiting a quantum metrological advantage.

In this study, we present a high peak power Ho :YLF amplifier seeded by an electro-optically diodepumped Ho :GdVO₄ laser operating at 2.05 μm. The diode-pumped Ho :GdVO₄ laser, operating under a continuous-wave (CW) regime, achieved an output power of 7.1 W at an absorbed pump power of 28 W, resulting in a slope efficiency of 41.4%. At a repetition rate of 1 kHz, the laser delivered an average output power of 3.6 W with a pulse width of 4.3 ns. By utilizing a Ho :YLF crystal as the amplification medium, with a seed power of 3 W and an incident pump power of 22.5 W, the amplifier generates an average output power of 15.5 W with a pulse width of 4.5 ns. We calculate the maximum pulse energy and peak power to be 15.5 mJ and 3.4 MW, respectively.

We investigate the quantification of entanglement between the photonic and excitonic modes in a semiconductor microcavity injected with squeezed light. By deriving and subsequently establishing the solutions to the quantum Langevin equations, we quantify the transient entanglement and the steady-state entanglement between the photonic and excitonic modes in the low-excitation regime. It turns out that the cavity mode and the exciton mode are entangled in both the weak and strong coupling regimes, and there is the entanglement between the cavity mode and the exciton mode even in the absence of direct coupling between them. Furthermore, though the transit entanglement increases with the squeeze parameter, it decreases with the initial average intensity of the cavity mode. Also, we demonstrate that, in the strong coupling regime, the steady-state entanglement grows with coupling strength while, in the weak coupling regime, it decreases.