We find and study the generation regime of microwave waves in a model resonator cavity based on an array of ordered semiconductor carbon nanotubes. Within the framework of the phenomenological approach, the Gunn effect was discovered for aligned carbon nanotubes with a length of 25–150 μm, the influence of the main parameters (changes in the electric field, the distance between the electrodes, the voltage at the contacts, etc.) was studied and it was shown that the electronic efficiency during lasing can reach 13

Photodynamic therapy is an effective modality for treating advanced melanoma. However, melanoma's inherent resistance to laser radiation hinders its widespread clinical application. The near-infrared laser radiation range of 12641270 nm offers unique properties: firstly, its ability to penetrate melanin-producing cells, and secondly, its capability to generate singlet oxygen without xenobiotics. We assess the impact of continuous wave 1265 nm laser radiation on an antioxidant defense system in melanoma B16-F10 and normal CHO-K1 cells. We observe a time-dependent increase in superoxide dismutase and glutathione-S-transferase activities, fluctuations in reduced glutathione levels, as well as a simultaneous increase in melanoma cell proliferation and cell death. We hypothesize that the differential activation of cellular antioxidant defense mechanisms contributes to melanoma cells' resilience to laser radiation.

We demonstrate experimental and numerical studies of supercontinuum generation for silica fibers with longitudinally varying diameter and dispersion. The significant difference in the spectral and temporal transformations of the pump pulse depending on the direction of propagation in the researched fiber samples is shown. Numerical simulations demonstrate the possibility of the supercontinuum spectra management by controlling the longitudinal profile of the fiber. Ways to optimize the output in terms of spectral flatness and efficient energy transfer to the desired wavelength region are presented.

A physical model of compact generator of infrared surface plasmon polaritons based on a planar waveguide structure to produce short pulses with a controllable repetition rate is proposed. The pulse generation is produced by modulation instability of continuous surface plasmon polariton waves in a film structure with graphene sheets (two graphene sheets spatially separated by a dielectric layer).

In this paper, we present a scheme for generating terahertz (THz) radiation using an array of parallel double-walled carbon nanotubes (DWCNTs) subjected to a direct current (DC). The longitudinal surface plasmon polaritons (SPPs) in the DWCNTs are coherently excited by two near-infrared laser beams with slightly different frequencies. Through numerical methods, we investigate the spectral characteristics of the SPPs in the presence of a DC current in the nanotubes. We identify high-quality plasmonic modes with a slowdown factor exceeding 300 in the terahertz frequency region. The amplification of these slow SPP modes is facilitated by the DC current in the DWCNTs, fulfilling a synchronism condition. This condition ensures that the phase velocity of the SPPs is closely matched to the drift velocity of the charge carriers, allowing for an efficient energy exchange between the current and the surface electromagnetic wave. The high-frequency currents on the nanotube walls in the DWCNT array enable the emission of THz radiation into the far field, owing to an antenna effect.

Brillouin amplification, the most prominent effect implemented with Brillouin dynamical gratings (BDG), enables exponential narrowband gain that is Stokes-shifted by some value in the GHz range. In this process, the interaction of the counterpropagating pump and Stokes waves through a BDG they produce causes an increase of the Stokes-shifted wave amplitude and decrease of the pump wave amplitude during their propagation through the fiber. Here, we report on a similar effect that could be implemented in rare-earth-doped fibers with the population inversion dynamical gratings. The effect is the most pronounced in a bidirectional rare-earth-doped optical fiber amplifier. Two monochromatic optical signal waves are introduced into the fiber from opposite ends and experience amplification (if the fiber is pumped) or attenuation (if the fiber is unpumped) as they propagate through the fiber. The signal waves are coherent on a sub-kHz level and slightly detuned. In terms commonly accepted in stimulated Brillouin scattering these counterpropagating signal waves correspond to what is referred to as "pump" and "Stokes" waves. However, in contrast to the Brillouin process, their interference inside the rare-earth-doped fiber creates not acoustic, but the population inversion dynamical gain grating. Then interaction between the signal waves and created population inversion dynamical gratings cause a strong power transfer from one signal wave to another.

Conditions for amplification and modulation of electromagnetic emission in the process of its interaction with the space charge wave formed in a semiconductor cylindrical structure are considered. The possibility of implementing the resulting gain G > 10 5 m –1 and strong phase modulation (chirp) for wave packets propagating on the surface of a semiconductor cylindrical waveguide is shown. A ring laser scheme capable to provide generation of frequency-modulated subnanosecond pulses with a peak power above 1 kW and carrier frequency tunable in a wide spectral range is proposed.

Melanoma is the most dangerous type of cancer, with a high rate of metastasis. The conventional method of treating skin melanoma is photodynamic therapy, yet this type of phototherapy has several side effects. In addition, the photosensitizers used are relatively expensive and toxic. Thus, developing methods of treating melanoma cancer using laser only is a promising area of research. Here we present in vitro effects in melanoma cell culture after 1265 nm laser irradiation exposure.

We propose the principle of a planar surface plasmon polariton amplifier composed of a complex waveguide structure based on a semiconductor thin film separated from a dielectric substrate by a graphene monolayer. The amplification of surface plasmon polaritons in that waveguide in the terahertz regime is driven by a direct current in the graphene layer under a synchronism condition that allows an efficient energy exchange from the collective flux of charge carriers in graphene and the surface electromagnetic wave in the semiconductor film. Positive feedback required for resonant amplification is achieved through surface plasmon polariton reflections at the edges of the active waveguide, one of which is formed by a local thickness defect (a groove) at the upper surface of the semiconductor film that also provides an exit channel for the energy of the amplified surface wave to be transferred to an adjacent passive thin film semiconductor waveguide. We determine the conditions required for the resonant amplification of surface plasmon polaritons in that complex structure, which are essentially governed by the geometry of the groove as well as by the characteristic parameters of the active and passive waveguides.

Moving differential and dynamic window moving averaging are simple and well-known signal processing algorithms. However, the most common methods of obtaining sufficient signal-to-noise ratios in distributed acoustic sensing use expensive and precise equipment such as laser sources, photoreceivers, etc., and neural network postprocessing, which results in an unacceptable price of an acoustic monitoring system for potential customers. This paper presents the distributed fiber-optic acoustic sensors data processing and noise suppression techniques applied both to raw data (spatial and temporal amplitude distributions) and to spectra obtained after the Fourier transform. The performance of algorithms’ individual parts in processing distributed acoustic sensor’s data obtained in laboratory conditions for an optical fiber subjected to various dynamic impact events is studied. A comparative analysis of these parts’ efficiency was carried out, and for each type of impact event, the most beneficial combinations were identified. The feasibility of existing noise reduction techniques performance improvement is proposed and tested. Presented algorithms are undemanding for computation resources and provide the signal-to-noise ratio enhancement of up to 13.1 dB. Thus, they can be useful in areas requiring the distributed acoustic monitoring systems’ cost reduction as maintaining acceptable performance while allowing the use of cheaper hardware.

We report on a model of a fiber frequency comb generator that develops an approach to harmonically mode-locked fiber laser design based on dissipative four-wave mixing. In our version of this approach, we assume an amplifying one-dimensional photonic crystal as a key cavity element combining the properties of an intra-cavity filter and a power amplifier. Using standard equations describing the signal transformation in the ring cavity and the output fiber cascade, we have demonstrated the possibility of the application of the proposed model as a generator of broadband frequency comb with controllable line spacing.

Novel techniques of photonics based on stimulated Brillouin scattering (SBS) in optical fibers are considered. The main attention is paid to the original schemes of narrow-band low-noise lasers and their possible applications in distributed fiber sensors.

We present a theoretical formalism to describe the amplification of two monochromatic waves counter-propagating in a rare-earth-doped optical fiber amplifier. Interaction of the waves through a dynamical population inversion grating inscribed in the active fiber by the waves during their amplification results in a strong power transfer from one wave to another providing a preferable amplification of one wave at the expense of another. In this sense, the effect is similar to stimulated Brillouin scattering and is expected to be observed with both pumped and unpumped rare-earth-doped fibers possessing a finite polarizability difference between the excited and ground states.

A simple Brillouin fiber laser pumped from a self-injection locked distributed feedback (DFB) laser diode delivers radiation with the Lorentzian linewidth of ~75 Hz and phase noise power density less than –100dBc/Hz (>30 kHz).

A carbon nanotube (CNT) can be considered as a plasmonic waveguide enabling propagation of ultraslow (with the effective refractive index >100) surface electromagnetic waves in the THz range. In this work, we theoretically study excitation of SPPs in array of double-walled CNTs by electron beam. The most interesting specific features of the double-walled CNT modes are associated with the presence of interlayer modes enabling a strong confinement of the electromagnetic field between the nanowalls of CNT and thus providing a high deceleration coefficient at a relatively low absorption coefficient at the frequencies up to 40–50 THz. Due to the strong SPP confinement between nanowalls the neighboring CNTs have almost no effect on each other. Array of double-walled CNTs ensuring an effective conversion of the external pump energy into the SPP energy can be employed for design of slow-wave plasmonic nanostructures.

We report on a low-cost Brillouin fiber ring laser pumped from an actively stabilized self-injection locked distributed feedback (DFB) laser diode. Locking of the commercial DFB laser to a ~11-m-length high-Q-factor fiber-optic ring cavity leads to ~10,000-fold narrowing of the laser Lorentzian linewidth down to 400 Hz. Such pump laser operation inside the ring cavity forces the cavity to host Brillouin lasing enabling the laser threshold power as low as ~1.5 mW. The laser operation is perfectly stabilized by active optoelectronic feedback driven by a simple microcontroller. The laser delivers radiation at Stokes frequency with the Lorentzian linewidth reduced down to ~75 Hz and a phase noise less than –100 dBc/Hz (<30 kHz). The reported laser configuration is of great interest for many laser applications where a narrow sub-kHz linewidth, simple design and low cost are important.

In this paper it was investigated the dynamics of frequency-modulated pulses in fiber cascades, consisting of a fibers with sequentially formed refractive index gratings with different periods. It is shown that the proposed scheme can be used to generate picosecond and subpicosecond pulses with peak powers of the order of ~1 MW. In the considered cascade structures, it is shown that it is possible to form stable sequences of pico- and subpicosecond pulses with a subterahertz repetition rate directly from continuous wave signals as a result of a modulation instability regime.