Vol 38, No 5 (2017)

We investigate entangled states of an atomic trapped ion interacting with two phonons in the Λ configuration forming a twelve-dimensional Hilbert space. We study two elaborated measures, namely, the concurrence C and negativity N, which are important in current theoretical studies. Therefore, we work with the three-dimensional reduced density matrix in calculating the measures elaborated for pure qudit states in the ionic–phononic system. To demonstrate the benefits of the family of the two measures elaborated, we perform the calculations for different values of the Lamb–Dicke (LD) parameter η = 0.01, 0.3, and 0.5. Finally, we show that the pure qudit states under study are maximum entangled states.

We study and examine the Goos–Hänchen shifts of a propagating probe light field in a four-level tripodtype cold and hot atomic medium. The behavior of Goos–Hänchen shifts is studied in reflection and transmission beams in the presence of the coherent Kerr effect and the Doppler broadening effect. We observe that these shifts can be controlled by the relative propagation direction of the control field to that of the probe field.

Pulsed transversely exited atmospheric (TEA) CO₂ lasers, employed extensively in various applications such as light detection and ranging (LIDAR), have a pulse duration of about a microsecond due totheir nitrogen tail. In order to promote the measurement accuracy and the mean power of the laser pulse, the pulse duration should be shortened. In this research, we present the details of making a passive pinhole plasma shutter for a LIDAR (DIAL) system, which shortens the pulse duration of CO₂ lasers from 1.5 μs to 25 ns in air at atmospheric pressure. This instrument increases the range resolution of the LIDAR system from 225 to 3.75 m. Also we show the results of investigation of the clipped pulse duration of the microsecond CO₂ laser pulse using aluminum and copper pinhole metal targets with different pinhole diameters (1.5 and 1.8 mm) and at various laser output energies (338 and 309 mJ). Our experimental results show that the aluminum pinhole is more suitable than the copper pinhole for shortening the nitrogen tail of the CO₂ laser pulse with a larger output average power. Thus, the range of the LIDAR system, which is proportional to the logarithm of the output pulse power, is increased.

We present a novel proposal for an all-optical AND logic gate. It is designed based on line and point defects in two-dimensional photonic crystal (PC) rods in air with square lattice. Material of the rods is silicon with dielectric constant 11.56. Dimension of the proposed device is equal to 12.155×12.155 μm. The device elaborated has a simple structure consisting of two inputs – a main output and two idler outputs. Bit rate of the device is equal to 3·10¹² bit/s. Maximum contrast ratio is 5.84 dB. It is a good candidate for optical integrated circuits.

We demonstrate a narrow linewidth Tm:YLF laser with a volume Bragg grating (VBG) that was pumped by an equidirectional-polarization fiber-coupled laser diode using a dual-end-pumping configuration. For an optimized output coupler with a radius of curvature of 150 mm and transmission of 15% at a wavelength of 1.91 μm, the maximum output power was 15.6 W for an absorbed pump power of 51.7 W at 1,907.93 nm, and the output had a narrow linewidth of 0.22 nm. This corresponds to an optical-to-optical conversion efficiency of 30.2% and the slope efficiency was 36.7%.

We investigate the molecular–topological structure of polyvinylidene fluoride (PVDF) irradiated with γ-rays from ⁶⁰Co and IR radiation from a carbon dioxide laser by the thermomechanical spectroscopy method. The initial PVDF has a topological three-block network structure containing the low- and high-temperature amorphous blocks and crystalline fragments. Both types of irradiation can initiate interblock mass transfer of the macromolecular fragments from the amorphous to the crystalline form. As a result, unlike the predominantly amorphous structure of the native polymer, which is 7% crystalline, the weight fraction of the crystalline modification of the PVDF due to irradiation by an IR laser increases to 72%. Comparative analysis leads to the conclusion that the PVDF has a greater resistance to γ-irradiation than to IR laser irradiation. After IR laser irradiation, the pseudo-network structure of PVDF undergoes noticeable changes. The quantitative content of the crystalline fragments of macromolecules increases by almost an order of magnitude; the mobility of chains is reduced, and the rigidity of the chains is increased. However, the molecular flow of the polymer irradiated by the laser and γ-rays begins in the same temperature range (437 – 441 K) near where the native polymer is flowing (438 K).