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We present the optical layout and actual design of a compact high-aperture referenceless point diffraction interferometer with a diffraction reference wave. The basic concept of this interferometer is based on a single-mode optical fibre with a subwave output aperture, which is used as a source of spherical reference waves. The interferometer is designed for high-precision measurements of the surface shape and aberrations of optical elements. It makes use of a diffraction reference wave and is developed for mass industrial applications. The proposed design does not require the involvement of special external conditions, and reduces the need for calibrated reference surfaces. We evaluate the performance of our interferometer for highprecision measurements and demonstrate its use by presenting results obtained from measuring the shapes of spherical references from various manufacturers and the aberration of a five lens objective.

We experimentally demonstrate generation of mode-locked pulses in dissipative soliton resonance (DSR) regime. The DSR pulses are obtained from a passively mode-locked figure-8 Er:Yb doped fiber laser operating in large net anomalous dispersion regime. The modelocked laser emission is based on a polarization-imbalanced nonlinear optical loop mirror (NOLM), acting as artificial saturable absorber. Stable square DSR pulses, obtained by carefully adjusting the NOLM properties, increase their duration from 2.47 ns to 46.52 ns as the pump power is increased from 0.68 to 6.31 W. With the maximum pump power launched, average output power of 73.95 mW with pulse energy of 53.39 nJ is achieved.

The article systematizes the results of the work carried out at YSPU named after K. D. Ushinsky under the grant of the Russian Scientific Foundation «Philosophical and Anthropological Analysis of Soviet Life. Prerequisites, dynamics, influence on modernity». The grant implementation period is from 2020 to 2022, the analysis was done based on the results of half of the completed path. Information is provided on publications (more than 30 publications from the lists of the Higher Attestation Commission and the ID), on scientific events held from May 2020 to March 2021.: the seminar-discussion «Soviet existence on the eve of the formation of totalitarian and authoritarian framework», the school of young researchers «Soviet existence as it is: aspects of analysis», a round table with the involvement of researchers and practitioners from Russian regions «Soviet existence: from rooting to overcoming», a socio-cultural survey on the topic «Soviet existence-the rejected past or the origins of the present?». Information is given about 10 members of the research team – Doctors of Philosophical Sciences S. A. Nikolsky (Moscow, Institute of Philosophy of the Russian Academy of Sciences), G. L. Tulchinsky (St. Petersburg, Higher School of Economics), Doctors of Sciences and young participants of the project (Yaroslavl, YSPU). The materials of the seminar-discussion with the participation of colleagues from Moscow, St. Petersburg, Samara, Yekaterinburg, Ulyanovsk, Vologda, and other cities of Russia are analyzed. The analysis of scientific publications and reports made under the grant, scientific reflection allows us to believe that the initial hypothesis of the grant is confirmed. The unflagging interest in the Soviet life on the part of people of different generations was established, manifestations of nostalgia among the young were found, signs of forgetting certain phenomena were revealed, the presence of an emotionally acute sense of the events of the Soviet past. We believe that the awakening and consolidation of a respectful and devoid of ideological rigidity attitude to the complex phenomena of the cultural and historical past is being carried out in society.

We report on the results of development, fabrication, and analysis of broadband Mo/Si multilayer mirrors for spectroheliographs at the KORTES solar observatory, which operate in the spectral bands of 17–21 and 28–33 nm. The advantages of the stack approach are demonstrated. The results of measurements of reflection characteristics of mirrors are considered.

Recent significant progress in the development of multilayer normal-incidence EUV mirrors is primarily related to an increase in the reflection coefficient at the working wavelength, a decrease in the spectral width of the reflection curve, and application of high-efficiency multilayer coatings for short-wavelength (3–9 nm) and long wavelength (greater than 50 nm) spectral ranges. Such mirrors allow astrophysical study of the Sun, since relatively narrow spectral widths of the mirrors and high reflection coefficients make it possible to image corona in monochromatic lines. Telescopes based on the mirrors are promising for dynamic spectral diagnostics of the solar disk with the aid of imaging spectroscopy. The method is based on the detection of monochromatic images of the Sun using the EUV spectral lines with relatively high spatial and temporal resolution. Possible progress in the solar study related to application of specified optical elements is discussed.

The SOLPEX complex consists of two instruments for recording soft X-ray radiation from the Sun and is a part of the KORTES equipment, which will be installed on board the International Space Station. The first instrument is a fast-rotating multi-crystalagg spectrometer designed to record solar spectra in the range of 0.4–23 A with a time resolution of no less than 0.1 s. The second instrument is a pinhole camera with a focal length of 58 cm. The camera has a field of viewof 2° × 2°, angular resolution of 2 arcmin, and time resolution up to 0.2 s. The energy range is determined by the input filter and is 1–10 keV; the energy resolution is 0.5 keV. The combination of these two instruments makes it possible to locate hot solar sources in the corona, determine their speed, and conduct spectral diagnostics.

A method for fabrication of a concave spherical mirror made of crystalline quartz is proposed and X-ray optical properties of the mirror are studied. The radius of curvature is 1630 mm. The shape of the mirror surface is studied using an interferometer with a diffraction reference wave. In the entire processing region, the maximum deviation from the nearest sphere is about 0.2 μm and the rms is 34 nm, so that high quality of imaging is provided with an angular error of about 2″ (angular seconds). Reflection coefficient (about 7%) and lower bound limit of spectral selectivity (λ/δλ ≈ 1775) are determined in the vicinity of a wavelength of λ = 0.834 nm, which is close to the working wavelengths of the MgXII doublet (λ = 0.8418 and 0.8423 nm). Position of the Bragg peak and spectral selectivity remain unchanged upon bending of the crystal mirror within measurement accuracy.

Due to losses in metals, the propagation length of the surface plasmon-polariton (SPP) waves on metal surfaces is small. This severely limits development of numerous applications of the SPP optics: in the near-infrared spectral region propagation length of SPP waves is no longer than 200 μm as for plane SPP waves and for all types of SPP waveguides. In this work, we show that the focusing of SPPs allows for the first time realizing open-type waveguide for SPP waves characterized by long distance of SPP effective propagation length up to 1 mm at a wavelength of 780 nm. We show that focused SPP waves in such a waveguide can be effectively excited by a 16 fs laser as well as be amplitude modulated within a bandwidth about 3.5 THz. The fast dynamics of the focused SPP waves is limited by the SPP group velocity dispersion. The large effective propagation length of the SPPs and its ultra-high bandwidth open up new possibilities for using focused SPPs in different areas of plasmonics and photonics.

We propose and realize a single-mode surface plasmon polariton (SPP) waveguide formed by two parallel grooves on the surface of a high-quality silver film. In the waveguide, the SPP wave undergoes the Goos–Hänchen shift of up to 0.77 ⋅ λ S P P at each successive reflection, with the electric field of the SPP wave outside the metal, which significantly reduces the metal loss of the guided SPP wave. Using the waveguide, we demonstrate a complex on-chip optical circuit that includes (1) SPP plane wave excitation, (2) SPP plane wave focusing with a parabolic mirror, and (3) coupling of the focused SPP wave to the waveguide.

The results of resolution enhancement of the stellar imaging system by using a Rayleigh laser guide star are presented. The estimation of residual phase error value of adaptive correction is carried out at various position of a laser guide star.

The numerical simulation on determination of the necessary number of adaptive mirror’s actuators for a problem of the correction of phase distortions accumulated by a laser beam under its propagation through an airway has been carried out. For this purpose, a set of wavefronts of the laser radiation passed through the airway has been registered by a Shack-Hartmann wavefront sensor. The stacked actuators’ response functions of 107- and 203-element adaptive mirrors have been experimentally determined as well. The dynamic range of adaptive mirrors’ actuators has been considered in calculations. It is established that the 203-element adaptive mirror is not suitable for correction of the registered aberrations due to the limited dynamic range. Meanwhile by means of 107-element adaptive mirror it is possible to obtain a corrected laser beam with the Strehl ratio St=0.65.

A simple method for the estimation of the wavelength of a fiber laser system is proposed. The method is based on the use of a high-birefringence-fiber loop mirror (HBFLM). The HBFLM exhibits a periodic transmission/reflection spectrum whose spectral characteristics are determined by the length and temperature of the high-birefringence fiber (HBF). Then, by the previous characterization of the HBFLM spectral transmission response, the central wavelength of the generated laser line can be estimated. By using a photodetector, the wavelength of the laser line is estimated during an HBF temperature scanning by measuring the temperature at which the maximum transmitted power of the HBFLM is reached. The proposed method is demonstrated in a linear cavity tunable Er/Yb fiber laser. This method is a reliable and low-cost alternative for laser wavelength determination in short wavelength ranges without the use of specialized and expensive equipment.

A TKPF269 rotating mirror digital streak camera with a photosensitive element based on a CMOS array was developed for the purpose of replacing film in high-speed streak cameras (SFR-2M, USF-2, etc.). A brief description of the TKPF269 streak camera design is given. The space-time picture of the emergence of light from the ends of optical fibers upon firing of an explosive in a model assembly was simultaneously recorded by a TKPF269 streak camera and an USF-2 streak camera to compare the metrological characteristics of these devices. The results of experimental data processing are presented.

The WSO-UV (World Space Observatory—Ultraviolet) space mission, optical design of the telescope, and main scientific instruments are briefly overviewed. A description of the photosensitive device of the WSO-UV mission based on a back-illuminated CCD with an antireflection coating is presented. Methods to improve the radiation resistance and reduce contamination on the CCD surface are described.

We demonstrate effective, up to 30%, reflection of the surface plasmon-polariton wave (SPP) from a nanogroove made on Ag film surface. The use of SPP reflection from a nanogroove having a shape of parabola helps to realize a new element in nanoplasmonics—parabolic SPP mirror. It was found that the mirror allows focusing of the SPP into a diffraction-limited spot with a lateral size of about λSPP (λSPP = 800 nm—SPP wavelength). The possibility of spatial scanning the focusing spot of SPP on the surface of Ag film is shown.

A tunable dual-wavelength thulium doped fiber laser is demonstrated experimentally. For the first time for the 2- $\mu \text{m}$ wavelength band we propose the independent tuning of the generated laser lines based on fiber Bragg gratings and the use of a Hi-Bi fiber optic loop mirror for the fine adjustment of the cavity losses to obtain stable dual-wavelength operation. Dual-wavelength laser generation with the laser lines separation in the range from 0.3 to 6.5 nm is obtained. The laser emission exhibits an optical signal-to-noise ratio better than 56 dB. Improved stability with output power fluctuations less than 1 dB is observed in dual-wavelength generation with equal power of lines.

An experimental study on optical pulses generation using single-wall carbon nanotubes as a saturable absorbers in an Er 3 + -doped fiber laser is reported. The saturable absorber was made by the photodeposition technique to place single-wall carbon nanotubes onto an optical fiber end. This technique consists of light laser provided by an Er 3 + -doped fiber amplifier and single-wall carbon nanotubes suspended in an aqueous solution. Using a fiber splice tube, the optical fiber with the single-wall carbon nanotubes is placed in the Er 3 + -doped fiber laser cavity. The nonlinear absorption of the saturable absorber was characterized by P-scan technique using a high gain pulsed Er 3 + -doped fiber amplifier. The results demonstrated that is possible to obtain optical pulses generation by using the single-wall carbon nanotubes as saturable absorber. The pulses duration are from 8.5 to 18 μs with a repetition rate around of 16–19.5 kHz. The nonlinear absorption of the single-wall carbon nanotubes photodeposited onto an optical fiber end is approximately − 5.25 × 10 − 6 m / W .

Comparative measurements of the height of the nanorelief steps of the surface of a silicon wafer by methods of three-dimensional reconstruction using a scanning electron microscope and profilometry were carried out. To realize the method of three-dimensional reconstruction, an islet gold film is formed on the surface of the test sample. The AlphaStep D-600 profiler is calibrated with a KTS-4500 QS step height gauge. The coincidence of the results of measurements with the methods of three-dimensional reconstruction and profilometry is established. The possibilities of reducing the uncertainty of the measurement results by the method of three-dimensional reconstruction were analyzed.

We report the spectral dynamics of actively Q-switched erbium-doped fiber lasers implemented in two common laser configurations: linear Fabry-Perot cavity with a pair of fiber Bragg gratings as reflectors and one-directional ring cavity without spectrally selective elements. In both geometries, the spectral width of sub-pulses, forming a Q-switch pulse, depends on the sub-pulse number, the spectrum of the most powerful sub-pulse is much broader than those of the rest, less powerful, ones. In the case of the ring laser, the optical spectra of sub-pulses shift to the Stokes side with increasing a sub-pulse's number. Possible reasons for such laser spectral dynamics are discussed. We also reveal the details of supercontinuum generation in a 100-m-long telecom fiber when such Q-switch pulses are employed as pump.

Measuring the characteristics of radiation scattered by surface plasmon polariton waves and detecting them in the far field is the only efficient method for studying the directivity of propagation, wave vector magnitude, and propagation length of such waves. In the present work, we demonstrate that it is possible to control the properties of surface plasmon polaritons propagating along the surface of metal nanofilms by scattering from nanoobjects, namely, nanogrooves and nanopits, formed in the nanofilms. It is shown that this technique allows the main parameters of surface plasmon polaritons to be measured.

A new method is proposed for calibrating scanning electron microscopes (SEM) with magnification in the 10–50000× range using an end gauge and an auxiliary structure. Use of a certified end gauge ensures traceability of the calibration results to the primary standard for the meter. The relative expanded uncertainty of measurements on an S-4800 SEM at magnifications of 1000, 10000, and 50000× is less than 0.14%.

We report a passive mode-locked fiber laser (PMLFL) in a novel configuration to generate a single soliton with ultra-low repetition rate. The configuration includes a Faraday mirror after the first half of the cavity length to counteract the nonlinear polarization rotation effects. The total cavity length is 428 m including a 400-m SMF-28 fiber which was twisted to cancel the linear birefringence. The strict polarization control establishes a relation between the regimes of generation and the polarization state of the pulses propagating in the cavity. By properly adjusting the initial polarization state, we observed three different emission regimes, the single soliton regime (SR), conventional noise-like pulses (NLP) and noise-like square-waveform pulse (NLSWP). In the SR, we obtain a 2.9 ps pulse duration centered at 1558.7 nm with a 467.2 kHz repetition rate.

We have employed VEPP-4 synchrotron radiation to measure CCD detector absolute responsivity in vacuum ultraviolet (115-310 nm) spectral range. The detector is designed in the form of a stainless steel enclosure containing a backside-illuminated CCD to protect the CCD from contamination. The entrance window of the enclosure is a round MgF2 spectral filter transparent for ultraviolet radiation with wavelengths longer than 112 nm. The measurements were carried out at Kosmos Metrological Station at the operating temperature of -100°C on the sensitive surface of the CCD. We utilized SPD calibrated silicon photodiode with 1 cm2 sensitive area and a known spectral sensitivity profile as a reference detector. The resultant measurements show a clear CCD responsivity dip near 280 nm, and a great potential to improve the CCD responsivity values using specially designed anti-reflection coatings.

In the present work we demonstrate a novel single-soliton ultra-low pulse repetition frequency passively mode-locked erbium-doped fiber laser. We mitigate the residual linear birefringence of fiber by fiber twist to achieve a strict control of polarization. For mode-locking the nonlinear polarization rotation (NPR) was used. Special technique was applied to reduce the overdriving of NPR that allows the generation of single soliton in ultra-long cavity. The strict control of polarization yields a stable relation between the polarization state of the pulses propagating in the cavity and the regimes of generation. A 192.12-kHz train of soliton pulses was obtained with pulse duration of 4.7 ps at 1560.1 nm, the average power was 29 μW and the estimated peak power was 30.8 W with an energy of 150.9 pJ.

We study numerically complex noise-like pulse dynamics in a passively mode-locked erbium-doped fiber laser. Wavelength-dependent gain dynamics is modeled as a combination of a three-level and a four-level system, which approximate the gain behavior in the 1530-nm and 1560-nm regions, respectively. The typical deformation of the erbium gain spectrum as it saturates is properly reproduced by this approach. Several puzzling noise-like pulse dynamics that were recently observed experimentally are qualitatively reproduced numerically, in particular slow quasi-periodic energy variations and the emergence and walkoff of wavelength-shifted radiation components. These results clearly reveal that gain dynamics is deeply involved in the onset of such complex temporal and spectral instabilities in these sources.

We present a novel X-ray assembly of functionally related instrument blocks intended to measure solar flare and active region (AR) spectra from within the Russian instrument complex KORTES, to be mounted aboard the International Space Station (ISS). SolpeX consists of three blocks: fast-rotating multiple flat crystal Bragg spectrometer, pin-hole X-ray spectral imager and Bragg polarimeter. This combination of measuring blocks will offer an opportunity to detect/measure possible X-ray polarization in soft X-ray emission lines/continuum and record spectra of solar flares, in particular during their impulsive phases. Polarized Bremsstrahlung and line emission may arise from presence of directed particle beams colliding with denser regions of flares. As a result of evaporation, the X-ray spectral-components are expected to be Doppler shifted, which will also be measured. In this paper, we present details of the construction of three SolpeX blocks and discuss their functionality. Delivery of KORTES with SolpeX to ISS is expected in 2020/2021.

We report dual-wavelength mode-locked operation of a passively mode-locked Er-doped fiber laser (EDFL) including two sections of a fiber with equal length, one right hand twisted and another left hand twisted, and a double-pass amplifier with Faraday Mirror (FM). The configuration allows cancellation of the influence of both linear and circular birefringence and strict control of the polarization of pulses in the cavity. Depending on the polarization azimuth we observed synchronous dual-wavelength, 1532 nm and 1560 nm, noise-like pulses (NLP), and desynchronized soliton emission.

Passively mode-locked fiber lasers are capable of generating a variety of optical pulses, depending of the pump power and cavity adjustments, which makes them attractive for research in multidisciplinary fields. In this paper, we analyze the experimental results of a fiber laser operating in passively mode-locked regime. The figure-eight laser cavity configuration uses 4 m of a co-doped Er/Yb double clad fiber, as a gain medium, pumped by a 976 nm diode laser. The cavity is completed by an isolator for ensure unidirectional propagation, two quarter-wave retarders (QWR), and a nonlinear optical loop mirror (NOLM) with 120 m of twisted standard single-mode fiber in the loop acting as saturable absorber. We used a couple of quarter-wave retarders (QWR) QWR1 at the NOLM input and QWR2 into the NOLM loop. By carefully adjusting of the QWRs the laser generates noise-like square pulses at the 1.54 μm range. With the increase of the pump power, the laser generates harmonics of the mode-locking fundamental mode with repetition frequency of 1.38 MHz, from which we can obtain the second, third and fourth harmonic in a controlled mode.

A new method of surface plasmon waves excitation based on the photoluminescence of a nanostructured metal surface is proposed. The method was demonstrated using a plasmonic crystal formed by an array of nanoholes in 200 nm thick Ag film (supporting SPP resonances) covered by a 10 nm thin Au layer (for efficient excitation of photo-induced luminescence). It was shown that using this method it is possible: (i) to excite SPP waves in ultra-large spectral range, (ii) to measure plasmonic crystal optical properties, (iii) to measure optical characteristics of the SPP waves.

A broadband stigmatic (imaging) soft X-ray (λ > 120 A) spectrometer is experimentally realised. The optical configuration of the spectrometer comprises a plane grazing-incidence reflection grating with a spacing varying across its aperture according to a preassigned law [a so-called varied line-space (VLS) grating] and a broadband spherical normal-incidence mirror with an aperiodic Mo/Si multilayer structure. The average plate scale amounts to ~5.5 A mm−1. The radiation is recorded with a matrix CCD detector (2048 × 1024 pixels of size 13 μm). The line spectra of the multiply charged ions LiIII and FV–FVII excited in laser-produced plasma are recorded with a spatial resolution of ~26 μm and a spectral resolving power R ≈ 500 is experimentally demonstrated.

We have realized a plasmonic interferometer formed by a nanoslit and a nanogroove in a single-crystal gold film. The possibility of measuring laser pulses of ultimately short durations, corresponding to two periods of a light wave (6 fs pulse duration), has been demonstrated using this interferometer.

We present research results of three-dimensional surface reconstruction from stereo images of silicon structures with trapezoidal profile of the relief elements. The stereo images were obtained from a scanning electron microscope. We compared results from transmission scanning electron and atomic force microscopy. It was found that the formation of an insular film of gold on the surface of the test object can increase the accuracy of the results of the three-dimensional reconstruction. Reconstruction error for a protrusion height of 597–600 nm was less than 4%.

In this work we study statistically the internal structure of noiselike pulses generated by a passively mode-locked fiber laser. For this purpose, we use a technique that allows estimating the distribution of the amplitudes of the sub-pulses in the bunch. The technique takes advantage of the fast response of the optical Kerr effect in a fiber nonlinear optical loop mirror (NOLM). It requires the measurement of the energy transfer characteristic of the pulses through the NOLM, and the numerical resolution of a system of nonlinear algebraic equations. The results yield a strongly asymmetric distribution, with a high-amplitude tail that is compatible with the existence of extreme-intensity sub-pulses in the bunch. Following the recent discovery of pulse-energy rogue waves and spectral rogue waves in the noiselike pulse regime, we propose a new way to look for extreme events in this particular mode of operation of mode-locked fiber lasers, and confirm that rogue wave generation is a key ingredient in the complex dynamics of these unconventional pulses.

We present analysis results of factors influencing the systematic error in 3-D reconstruction of surface reliefs based on stereo images obtained using the scanning electron microscope S-4800. The typical size for the surface relief elements is less than 1 μm. The main sources of the error are found. It is shown that for typical samples the main factor influencing the systematic error of 3-D reconstruction is the parallax measurement error.

The nonlinear optical interaction of laser radiation with nanostructures formed in gold and aluminium nanofilms has been experimentally studied. It is shown that, despite the high susceptibility χ3 of aluminium in comparison with gold, the third-harmonic generation efficiency at a wavelength of 260 nm is much higher for the nanostructures formed in a gold nanofilm because of the efficient excitation of a localised plasmon resonance at the fundamental frequency.

The feasibility of using the diffraction peaks in x-ray emission spectra detected with energy dispersion for measuring the spacing between lattice planes in crystalline substances is demonstrated.

We report the experimental investigation of a dual-wavelength passively mode-locked fiber laser (PMLFL) with double-twist fiber to cancel both, circular and linear birefringence. To obtain dual-wavelength emission, we vary the losses inside the cavity.

Cleaning and compressing soliton spectrum is an important part of the all-optical processing systems. In the present work, we report the suppression of Kelly sideband as well as compressing the soliton spectrum through a polarization-imbalanced nonlinear loop mirror (NOLM). The polarization-imbalanced NOLM has zero transmission at low power signals, which can make it a valuable mechanism for cleaning of soliton by elimination of noise and Kelly sidebands which are always present at the output of fiber soliton lasers. Polarization imbalance in the NOLM can be produced by inserting the quarter wave retarder (QWR) in the loop. Rotation of the angle of the QWR allows adjustment of the characteristics of the NOLM that can be used to choose the features that are most adequate to clean solitons with different pulse duration. As an input source, we used a mode-locked fiber ring laser with 0.6 ps duration and 1550 nm central wavelength. The results show more than 95% suppression of Kelly sidebands and two times compression of bandwidth. The maximum transmission of NOLM was 20%. Cleanup of soliton spectrum is possible using a NOLM as intensity filter without dependence of wavelength.

The SPIRIT telescope aboard the CORONAS-F satellite (in orbit from 26 July 2001 to 5 December 2005), observed the off-limb solar corona in the 175 Å (Fe IX, X and XI lines) and 304 Å (He II and Si XI lines) bands. In the coronagraphic mode the mirror was tilted to image the corona at the distance of 1.1...5 Rsun from the solar center, the outer occulter blocked the disk radiation and the detector sensitivity was enhanced. This intermediate region between the fields of view of ordinary extreme-ultraviolet (EUV) telescopes and most of the white-light (WL) coronagraphs is responsible for forming the streamer belt, acceleration of ejected matter and emergence of slow and fast solar wind. We present here the results of continuous coronagraphic EUV observations of the solar corona carried out during two weeks in June and December 2002. The images showed a "diffuse" (unresolved) component of the corona seen in both bands, and non-radial, ray-like structures seen only in the 175 Å band, which can be associated with a streamer base. The correlations between latitudinal distributions of the EUV brightness in the corona and at the limb were found to be high in 304 Å at all distances and in 175 Å only below 1.5 Rsun. The temporal correlation of the coronal brightness along the west radial line, with the brightness at the underlying limb region was significant in both bands, independent of the distance. On 2 February 2003 SPIRIT observed an expansion of a transient associated with a prominence eruption seen only in the 304 Å band. The SPIRIT data have been compared with the corresponding data of the SOHO LASCO, EIT and UVCS instruments.

A switchable and tunable multi-wavelength Tm-doped fiber laser is successfully demonstrated using a filter constructed with two tapered fiber elements in the cavity. The proposed system design uses a low-cost simple filter that allows stable dual, triple, quadruple, and quintuple-wavelength emission operation in the region around 1.9 μm. In the dual wavelength regime, the laser is capable of independently tuning each wavelength. For switching and tuning, a curvature is applied to the tapered fibers.

We report a study of an all-fiber Tm-doped fiber laser with tunable single wavelength emission and dual-wavelength generation operating in different laser wavelength ranges depending on the Tm-doped fiber (TDF) length. The wavelength selection and tuning for single wavelength laser operation and the adjustment of cavity losses for dual wavelength laser operation is obtained by temperature variations of the high birefringence fiber loop in a fiber optical loop mirror. Stable dual wavelength operation is achieved at the single wavelength tuning limits when cavity losses are balanced to generate two simultaneous laser lines with equal powers. A linear cavity fiber laser setup with TDF lengths of 2, 4, 8 and 12 m is used to obtain tunable single wavelength operation in a range of ~40 nm for each TDF length. A total tuning range of ~110 nm with the four different TDF lengths is achieved. At dual-wavelength laser operation the wavelength separation was ~48 nm. The maximal power efficiency of ~34.9% with a maximum output power of 274 mW was obtained with the use of TDF length of 4 m.

Due to a strong light absorption by metals, it is believed that plasmonic nanostructures cannot be used for generating intensive radiation harmonics in the UV spectral range. We present results of investigation of the nonlinear optical interaction of laser radiation with a single gold nanostructure in the geometry of the Split-Hole Resonator (SHR) [1, 2] under the-state-of-the-art experimental realized conditions: (1) the laser pulse duration is ultimately short (two cycles of the laser pulse wave) to maximally reduce the thermal effects on the nanostructure; (2) the laser light intensity is ultimately high and close to the air ionization threshold; (3) the geometry of the nanostructure is optimal ensuring a record-high efficiency of the nonlinear optical interaction; and (4) the SHR nanostructure is formed in a single crystal gold nanofilm that is flat on the atomic level. Several multipole plasmon resonances can simultaneously be excited in the SHR nanostructure. A strong nonlinear optical interaction at the frequencies of these resonances that leads to (i) the second-harmonic generation, (ii) the third harmonic generation (THG), and (iii) the light generation at mixed frequencies. The THG near field amplitude reaches 0.6% of the fundamental frequency field amplitude, which enables the creation of UV radiation sources with a record high intensity. The UV light may find many important applications including biomedical ones (such as cancer therapy).

Excitation of channel plasmons in a 1D array of V-shaped grooves in a metal film in the Kretschmann configuration was theoretically investigated. The channel plasmons were shown to be excited by the s -polarized incident wave. The excitation of channel plasmons in every single groove of the array manifested itself in a local minimum in the angular spectrum of reflection from the array of the grooves.

Results of measurements of the thickness of natural oxide on a silicon structure in the form of a set of elements (protrusions) with trapezoidal profile, 2 μm step, width of upper base 10 nm, height of elements 500 nm, and tilt angle of lateral side of element relative to its base 54.7° are presented. The entire structure is covered with a natural oxide that appeared at room temperature. The distance between the {111} planes of silicon is used to assure traceability of the measurements.

A method of estimating the stability of the scale factor of the JEM-2100 transmission electron microscope using a test-object, constructed in the form of a thin section of a crystalline relief nanostructure with a known shape of the profile, is proposed. The results of an experimental estimate, obtained over a two-week period, are presented.

Results are given for an experimental study of pulsed laser action on an oxide-carbide ceramic surface with single-coordinate treatment in distilled water. It is established that the production medium has a marked effect on single track geometric parameters and new surface morphology. The results obtained make it possible to choose laser action parameters with the aim of controlling high-density ceramic surface microstructuring.

We propose and study analytically and numerically a nonlinear amplifying loop mirror scheme for multilevel amplitude regeneration, whose operation relies on the manipulation of light polarization. Polarization control increases the number of degrees of freedom of the setup, making it easier to meet the demanding requirements for regenerating complex modulation formats. By adjusting one of those additional parameters, namely, the ellipticity of input polarization, if all the other ones are properly set and fixed, the transfer characteristic is shaped for optimal two-level amplitude regeneration for two different state power ratios. The cascadability of the proposed scheme is demonstrated for the optical star-8 quadrature amplitude modulation format as an example.

We study experimentally the polarization of the radiation resulting from the pulse break-up process in a SMF-28 twisted fiber. The fiber twist causes circular birefringence and also mitigates the linear birefringence. The twisted fiber may be considered for nonlinear effect as fiber without linear birefringence, which allows the investigation of polarization properties which cannot be studied in common fibers because of the random residual birefringence. We found that the polarization of the formed solitons is more stable when the input pump polarization has elliptical polarization with big angle of ellipticity. At input polarization close to linear we observed that the polarization ellipticity angle tends to be higher than the polarization ellipticity angle of the input pump. The fluctuation of the polarization grows when the input polarization approaches to the linear.