Journal of Russian Laser Research最新文献

In this paper, we establish a three-dimensional heat conduction and thermal stress model of a bulk crystal. Based on planar strain assumption of solid-state lasers, we study the thermal conduction and thermal stress of the bulk Ho : CaF₂ laser-medium end-pumped by the Gaussian beam. We establish a thermal model of the plate crystal with complex boundary conditions and discuss the effect of pump energy and pump beam waist radius on the thermal performance of Ho : CaF₂ crystals in details. Out results show that, as the pump power increases, the thermal effect of Ho :CaF₂ crystal increased with the decrease of the pump-spot radius, and the thermal effect of the crystal increases with increase in the pump power. Furthermore, the absolute value of the shear stress of crystals is far smaller than the absolute value of the corresponding normal stress, and the absolute values of the normal stress and shear stress of small size crystals are greater than those of large size crystals.

We develop a quasi-steady-state thermal model to analyze transient thermal effects in a Nd :YAG laser rod under quasi-continuous laser-diode (LD) end pumping. Included is a quasi-adiabatic model for pump durations and a quasi-steady-state heat dissipation model for pump-free durations. We give an approximate expression of the transient temperature-difference distribution function of the crystal under quasi-continuous pumping. The method for calculating the transient thermal focal length is also presented. On this basis, the temperature distribution variation in the crystal with time and the variation range of the transient thermal focal length are quantitatively analyzed. For 50 W, 200 μs pulse-width, and 50 Hz pumping, the temperature at the center of the Nd:YAG rod has a range of 304.52 – 306.28 K, and the thermal focal length varied over 1612.8 – 310.43 mm. Both have saw-tooth periodic distributions. This study provides a theoretical reference for the design of laser-diode-pumped thermal Q-switched Nd :YAG lasers.

In this paper, we propose a dual-channel broadband photonic-crystal fiber polarization filter with high loss based on surface plasmon resonance. We carefully design gold-coated elliptical air hole structure to improve the confinement loss and the isolation of x-polarized and y-polarized guided modes. Multi-order plasmonic modes are excited to broad the filtering band. Moreover, in view of our simulation results, we demonstrate that plasmonic resonance occurs at the wavelength, where birefringence abnormally changes; also, complete and incomplete mode coupling are able to be distinguished by birefringence. At communication wavelengths of 1550 and 1318 nm, the calculated confinement loss of x-polarized and y-polarized core modes are 744.63 and 1089 dB/cm, with crosstalk up to – 1282.54 and 2233.46 dB, respectively. The proposed dual-channel polarization filter will be a good choice for optical fiber communication.

We derive relativistically invariant expressions for the magnetic and electric helicities of free electromagnetic field through the currents, which created those field. We demonstrate that, for radiative fields (e.g., laser pulses), both helicities are conserved and equal to each other. Moreover, the conservation of the helicity means that, in radiative electromagnetic fields, the electric and magnetic vectors are always orthogonal to each other. Proceeding to the quantum theory, we show that the corresponding quantum helicity field operator is equal to the sum of projections of spins of all photons onto their momenta. Finally, as an example, we obtain and discuss the expressions for the total helicity, number of photons, and the total spin momentum of the field of a dipole electromagnetic pulse.

We propose and demonstrate a new Q-switched thulium-doped fiber laser (TDFL) by utilizing a passive saturable absorber (SA) based on Molybdenum–Aluminium boride (MoAlB). The MoAlB is a metal–ceramic-based material; it is embedded in polyvinyl-alcohol (PVA) material to operate as the SA. The laser successfully generates stable Q-switched pulses operating at 1974.7 nm with a maximum repetition rate of 57.7 kHz and a minimum pulse width of 1.79 μs. A maximum pulse energy of 90.2 nJ is recorded at 436 mW pump power. Our experiment is the first demonstration on the use of MoAlB for the pulse laser generation in the 2 μm wavelength region.

We propose a 2 μm Tm: YAP passively Q-switched solid-state laser based on SnSe₂ saturable absorber. With increase in the pump power, the output power of the laser can reach 430 mW corresponding to a shortest pulse width of 810.7 ns, a maximum repetition frequency of 59.55 kHz, a single pulse energy of 7.22 μJ, and a peak power of 8.9 W. The beam quality factor M²_x is measured successfully to be 1.43 under the maximum output power. This is the first time that a pulse width of 810.7 ns is achieved in a solid-state laser, using a Tm: YAP crystal and SnSe₂ as the saturation absorber.

We design two-qubit quantum gates by coupling two Transmon qubits with a capacitor and study the time-dependent dynamics of the qubit–qubit interaction for different inter-qubit interaction strengths in the presence of quantum noise. Particularly, we focus on three famous quantum gates, iSWAP, bSWAP, and CNOT. In this study, we investigate different types of noises, such as emission, absorption, and dephasing. Two-qubit gates, iSWAP and bSWAP, are modeled by direct variable coupling between two Transmon qubits. In addition, we construct the CNOT gate, using three qubits, where the two qubits are used for inputs and outputs, and the middle qubit acts as a tunable coupler between the two qubits. The middle qubit is needed for energy conservation; we called it a garbage bit, since we do not use it in logical operations. For the two input/output coupled qubits, direct variable capacitor coupling is also used. In view of the coupled Lindblad master equations, we study the time-dependent dynamics of our proposed quantum models. A significant impact of emission/absorption quantum noise can be seen on iSWAP, bSWAP, and CNOT gates, as compared to dephasing noise. Additionally, we also discuss the generation of entanglement for different scenarios with and without noises.

Controlled quantum teleportation schemes require the existence of a third party acting as a teleportation controller, so that without its cooperation, quantum information of the unknown state cannot be transmitted. Here, we propose a new controlled quantum teleportation scheme to perfectly transmit an arbitrary entangled three-qubit state. In this scheme, quantum information of unknown three-qubit arbitrary state is transmitted from Alice, the sender to Bob, the remote receiver via a quantum channel consisting of two GHZ entangled states and a Bell entangled state under the supervision of Charlie, the controller. Bob can then recover the desired three-qubit arbitrary state by performing appropriate unitary Pauli transformations, and we find that our protocol works perfectly. This scheme could be quite easily extended to accurately teleport an unknown N-qubit state from Alice to Bob under Charlie’s control, using (N − 1) GHZ entangled states and a Bell entangled state.

Material processing, using water contact laser technology, can enhance the machining, welding, or cutting quality. In this paper, we explore the alteration of Titanium alloy (Ti₆Al₄V) surface properties by nanosecond-pulsed laser-processing method in water and air, under various conditions. In this work, we adopt several analysis approaches, such as crater width, surface morphology, oxidation, and wettability. The results show that, in the case of laser processing in the air up to 500 mJ with 50 pulses, the laser parameters enhance the hydrophilicity. The processing environment would also impact the crater width, shape, and distribution of the created surface structures. Conversely, the surface oxygen content significantly raises on the laser-irradiated surfaces. According to these results, it is more logical to conclude that all of these cooperative chemical and physical changes increase the surface wettability and cause it to be more hydrophilic.