Ablation efficiency of gold at fs/ps laser treatment in water and air

A comparison of single-pulse laser ablation of gold target by pulses with a 0.3–10 ps duration and a wavelength of 515 nm in air and in water was performed. The radiation was focused on the sample surface through the objectives with numerical apertures NA = 0.65 and 0.25. The influence of the medium, pulse duration, and spot size on the crater morphology was studied. A significant difference in crater morphology was found for different lenses. The ablation efficiency was studied by measuring the profiles of single-shot pulse craters using scanning force microscopy. The contribution of filamentation to the ablation process is shown quantitatively.

Experimental resources needed to implement photon number splitting attack in quantum cryptography

The analysis of the security of quantum key distribution systems with respect to an attack with nondemolishing measurement of the number of photons (photon number splitting—PNS attack) is carried out under the assumption that in the communication channel in each parcel there is a pure Fock state with a different number of photons, and the distribution of states by number of photons has Poisson statistics. In reality, in the communication channel in each parcel there are not individual Fock states, but a pure coherent state with a random phase—a superposition of Fock states with different numbers of photons. The paper analyzes the necessary experimental resources necessary to prepare individual Fock states with a certain number of photons from the superposition of Fock states for a PNS attack. Optical schemes for implementing such an attack are given, and estimates of experimental parameters at which a PNS attack is possible are made.

A look at photodynamic inactivation as a tool for pests and vector-borne diseases control

The control of pests and vector-borne diseases (VDBs) are considered public health issues Worldwide. Among the control techniques and pesticides used so far, photodynamic inactivation (PDI) has been shown as an eco-friendly, low cost, and efficient approach to eliminate pests and VDBs. PDI is characterized using a photosensitizing molecule, light and molecular oxygen (O2) resulting in production of reactive oxidative species which can promote the oxidation of biomolecules on pests and vectors. Herein, we review the past 51 years (1970–2021) regarding the use of photo pesticides, reporting the most important parameters for the protocol applied, the results obtained, and limitations. Moreover, we described the mechanism of action of the PDI, main classes of photopesticides used so far as well as the cell death mechanism resulting from the photodynamic action.

High-fidelity quantum gates for OAM single qudits on quantum memory

The application of high-dimensional quantum systems (qudits) in quantum computing and communications seems to be a promising avenue due to the possibility of increasing the amount of information encoded in one physical carrier. In this work, we propose a method for implementing single-qudit gates for qudits based on light modes with orbital angular momentum (OAM). Method for logical qudits encoding, which ensures the quasi-cyclicity of operations, is introduced. Based on the protocol for converting the OAM of light in the Raman quantum memory scheme (Vashukevich et al 2020 Phys. Rev. A 101 033830), we show that the considered gates provide an extremely high level of fidelity of single-qudit transformations. We also compare quantum gates’ properties for systems of different dimensions and find the optimal conditions for carrying out transformations in the protocol under consideration.

Dynamic characteristics and noise modelling of directly modulated quantum well-dots microdisk lasers on silicon

The small-signal amplitude modulation, threshold, and spectral characteristics of microdisk lasers with InGaAs/GaAs quantum well-dots active region were studied jointly with the spectral and threshold parameters of edge-emitting lasers made from the same epitaxial heterostructure. Using the obtained material parameters, the relative intensity noise of the microdisk lasers was calculated as a function of the bias current and side-mode suppression ratio. It is shown that the integral noise is low enough for error-free optical data transmission with the maximum possible bitrate limited by the microdisk modulation bandwidth, if the bias current is above 1.7× threshold current (for side mode suppression ratio > 20 dB).

Peculiarities of interaction of a quantum dot with non-classical light in the self-phase modulation regime

Influence of the self-phase modulation of quantum light on the induced resonant excitation of a semiconductor quantum dot is studied analytically in the case of the Kerr-nonlinearity of the medium. The phase nonlinearity is found to result actually in a resonance detuning specific for each field photon number state. This effect is shown to provide significant decrease of the excitation efficiency accompanied at the same time by more regular excitation dynamics obtained even for initial squeezed vacuum field state. The enhancement of entanglement between semiconductor and field subsystems with growing non-linearity is demonstrated. As a result, the formation of different types of non-Gaussian field states is found with features being analyzed in details.

Investigation of 6S 1/2–8S 1/2 two-photon transition of cesium atoms by a single 822 nm laser

We experimentally investigate the 6S 1/2–8S 1/2 two-photon transition in cesium vapor by a single laser. A blue (455.5 and 459.3 nm) fluorescence signal is observed as a result of 822.5 nm laser beams illuminating the Cs vapor with a counter-propagating configuration. The dependences of the fluorescence intensity on the polarization combinations of the laser beams, laser power and vapor temperature are studied to obtain optimal experimental parameters. The frequency difference between the two hyperfine components of 4158 (7) MHz is measured with a Fabry–Perot interferometer as a frequency reference. Such a large spectral isolation and the insensitivity to the Earth’s magnetic field enable the 6S 1/2–8S 1/2 transition to be a stable frequency standard candidate for a frequency-doubled 1644 nm laser in the U-band window for quantum telecommunication.

An electron wave packet in the relativistic strophotron FEL

The theory of free electron lasers (FELs) is well developed both in quantum mechanical and classical approaches. In strophotron FEL, in classical approach, resonance frequency and the gain are strongly dependent on initial parameters of electron beam. In the quantum mechanical approach considered by Zaretsky and Nersesov (1983 JETP 57 518), there is no such dependence. The correspondence between the quantum mechanical and classical approaches in a relativistic strophotron FEL is discussed. We study the initial distribution of electrons over vibrational levels determined by the expansion coefficients in relativistic strophotron FEL. It is shown, (presenting electron wave function in the form of Gaussian wave packet), that the number of the vibrational level most efficiently populated at the initial moment of time can be expressed in terms of the initial parameters of the electron beam.

Ultrafast spectroscopy of C-H vibrations in pathogenic bacteria in 3-μm spectral range

Dynamic optical density spectra were obtained under multipulse excitation of bacterial cultures of S. aureus and P. aeruginosa by 3 μm mid-infrared ultrashort laser pulses, corresponding to the vibrational excitation of the C–H bonds of the bacterial cell. These spectra demonstrated pronounced laser intensity-dependent blue spectral shift, presumably associated with the breaking of hydrogen bonds, which are responsible for the formation of secondary and tertiary protein structures.

The influence of axial offset of fusion splicing on a large mode area fiber based oscillator

Fiber oscillators have the potential for achieving high power, high beam quality lasers with simple and compact structure, of which the fusion splicing point is an important aspect to the laser output characteristics. A model taking into account the axial offset of the splicing point and spatial mode competition has been proposed to analyze the mode interaction of a large mode area fiber based oscillator. The calculated results show that the axial offset of the output side fusion point has the main influence on the laser output beam quality, but the axial offset would not obviously reduce the optical efficiency, especially when the value is smaller than 2 μm. The influence of cavity parameters on the laser output characteristics under the existence of splicing point with axial offset has also been discussed. This model can provide a method for analyzing the mode dynamic that may be helpful for understanding the mode interactions in fiber oscillators.