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We experimentally demonstrate bidirectional Raman soliton-like combs in a whispering gallery mode microresonator with a unidirectional pump for the first time, to the best of our knowledge. We develop a relatively simple theoretical model and find an analytical solution for forward- and backward-propagating Raman sech 2 -shaped solitons in an anomalous dispersion region under unidirectional pumping in a normal dispersion region. Raman solitons exist, thanks to the balance between losses and Raman gain from a CW wave (which is equal in both directions) as well as between dispersion and Kerr nonlinearity.

The generation of coherent light based on inelastic stimulated Raman scattering in photonic microresonators has been attracting great interest in recent years. Tellurite glasses are promising materials for such microdevices since they have large Raman gain and large Raman frequency shift. We experimentally obtained Raman lasing at a wavelength of 1.8 µm with a frequency shift of 27.5 THz from a 1.54 µm narrow-line pump in a 60 µm tellurite glass microsphere with a Q-factor of 2.5 × 10 7 . We demonstrated experimentally a robust, simple, and cheap way of thermo-optically controlled on/off switching of Raman lasing in a tellurite glass microsphere by an auxiliary laser diode. With a permanently operating narrow-line pump laser, on/off switching of the auxiliary 405 nm laser diode led to off/on switching of Raman generation. We also performed theoretical studies supporting the experimental results. The temperature distribution and thermal frequency shifts in eigenmodes in the microspheres heated by the thermalized power of an auxiliary diode and the partially thermalized power of a pump laser were numerically simulated. We analyzed the optical characteristics of Raman generation in microspheres of different diameters. The numerical results were in good agreement with the experimental ones.

We experimentally demonstrate optical frequency comb generation in a tellurite microsphere, for the first time to the best of our knowledge, for tellurite glass microresonators. The TeO 2 -WO 3 -La 2 O 3 -Bi 2 O 3 (TWLB) glass microsphere has a maximum Q-factor of 3.7 × 10 7 , which is the highest ever reported for tellurite microresonators. We obtain a frequency comb containing seven spectral lines in the normal dispersion range when pumping the microsphere with a diameter of 61 µm at a wavelength of 1.54 µm.

In recent years, the use of optical methods for temperature measurements has been attracting increased attention. High-performance miniature sensors can be based on glass microspheres with whispering gallery modes (WGMs), as their resonant frequencies shift in response to the ambient parameter variations. In this work, we present a systematic comprehensive numerical analysis of temperature microsensors with a realistic design based on standard silica fibers, as well as commercially available special soft glass fibers (GeO 2 , tellurite, As 2 S 3 , and As 2 Se 3 ). Possible experimental implementation and some practical recommendations are discussed in detail. We developed a realistic numerical model that takes into account the spectral and temperature dependence of basic glass characteristics in a wide parameter range. To the best of our knowledge, spherical temperature microsensors based on the majority of the considered glass fibers have been investigated for the first time. The highest sensitivity dλ / dT was obtained for the chalcogenide As 2 Se 3 and As 2 S 3 microspheres: for measurements at room temperature conditions at a wavelength of λ = 1.55 μm, it was as high as 57 pm/K and 36 pm/K, correspondingly, which is several times larger than for common silica glass (9.4 pm/K). Importantly, dλ / dT was almost independent of microresonator size, WGM polarization and structure; this is a practically crucial feature showing the robustness of the sensing devices of the proposed design.

Bright squeezed light can be generated in optical fibers utilizing the Kerr effect for ultrashort laser pulses. However, pulse propagation in a fiber is subject to nonconservative effects that deteriorate the squeezing. Here, we analyze two-mode polarization squeezing, which is SU(2)-invariant, robust against technical perturbations, and can be generated in a polarization-maintaining fiber. We perform a rigorous numerical optimization of the process and the pulse parameters using our advanced model of quantum pulse evolution in the fiber that includes various nonconservative effects and real fiber data. Numerical results are consistent with experimental results.

The investigation of optical microcavity solitons is in demand both for applications and basic science. Despite the tremendous progress in the study of microresonator solitons, there is still no complete understanding of all features of their nonlinear dynamics in various regimes. Controlling soliton properties is also of great interest. We proposed and investigated experimentally and theoretically a simple and easily reproducible way to generate Raman solitons with controllable spectral width in an anomalous dispersion region in a functionalized silica microsphere with whispering gallery modes (WGMs) driven in a normal dispersion regime. To functionalize the microsphere, coating (TiO 2 + graphite powder) was applied at the pole. The coating is used for effective thermalization of the radiation of an auxiliary laser diode launched through the fiber stem holding the microsphere to control detuning of the pump frequency from exact resonance due to the thermo-optical shift of the WGM frequencies. We demonstrated that the thermo-optical control by changing the power of an auxiliary diode makes it possible to switch on/off the generation of Raman solitons and control their spectral width, as well as to switch Raman generation to multimode or single-mode. We also performed a detailed theoretical analysis based on the Raman-modified Lugiato-Lefever equation and explained peculiarities of intracavity nonlinear dynamics of Raman solitons. All experimental and numerically simulated results are in excellent agreement.

Glass microresonators with whispering gallery modes (WGMs) have a lot of diversified applications, including applications for sensing based on thermo-optical effects. Chalcogenide glass microresonators have a noticeably higher temperature sensitivity compared to silica ones, but only a few works have been devoted to the study of their thermo-optical properties. We present experimental and theoretical studies of thermo-optical effects in microspheres made of an As 2 S 3 chalcogenide glass fiber. We investigated the steady-state and transient temperature distributions caused by heating due to the partial thermalization of the pump power and found the corresponding wavelength shifts of the WGMs. The experimental measurements of the thermal response time, thermo-optical shifts of the WGMs, and heat power sensitivity in microspheres with diameters of 80-380 µm are in a good agreement with the theoretically predicted dependences. The calculated temperature sensitivity of 42 pm/K does not depend on diameter for microspheres made of commercially available chalcogenide fiber, which may play an important role in the development of temperature sensors.

Concentrating light strongly calls for appropriate polarization patterns of the focused light beam and for up to a full 4π solid angle geometry. Focusing on the extreme requires efficient coupling to nanostructures of one kind or another via cylindrical vector beams having such patterns, the details of which depend on the geometry and property of the respective nanostructure. Cylindrical vector beams can not only be used to study a nanostructure, but also vice versa. Closely related is the discussion of topics such as the ultimate diffraction limit, a resonant field enhancement near nanoscopic absorbers, as well as speculations about nonresonant field enhancement, which, if it exists, might be relevant to pair production in vacuum. These cases do require further rigorous simulations and more decisive experiments. While there is a wide diversity of scenarios, there are also conceptually very different models offering helpful intuitive pictures despite this diversity., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Miniature lasers based on rare-earth ion-doped tellurite microsphere resonators with whispering gallery modes (WGMs) are promising devices for basic research and applications. However, the excitation of WGMs using an external pump is not a simple task requiring passive or active control. We propose and demonstrate the implementation of thermo-optical control of the L-band laser generation in an Er-doped in-band pumped tellurite glass microsphere using a cheap low-power blue laser diode and a constant-wavelength telecom laser as a pump. The proposed scheme ensures simplification and cost reduction of microlasers.

Brillouin microlasers based on microresonators with whispering gallery modes (WGMs) are in high demand for different applications including sensing and biosensing. We fabricated a microsphere resonator with WGMs from a synthesized high-quality tellurite glass with record high Q-factors for tellurite microresonators (Q ≥ 2.5 × 10 7 ), a high Brillouin gain coefficient (compared to standard materials, e.g., silica glasses), and a Brillouin frequency shift of 9 ± 0.5 GHz. The high density of excited resonance modes and high loaded Q-factors allowed us to achieve experimentally cascade Stokes-Brillouin lasing up to the 4th order inclusive. The experimental results are supported by the results of the theoretical analysis. We also theoretically obtained the dependences of the output Brillouin powers on the pump power and found the pump-power thresholds for the first five Brillouin orders at different values of pump frequency detuning and Q-factors, and showed a significant effect of these parameters on the processes under consideration.

An efficient optical scheme for coherent combining of radiation from the output of a multicore fiber (MCF) with a square array of cores in the out-of-phase supermode is proposed. The scheme uses only simple optical elements and is suitable for an arbitrary number of MCF cores. In a proof-of-concept experiment broadband pulses transmitted through a 25-core fiber were combined with 81% efficiency and good beam quality. In numerical modeling a close to unity efficiency is obtained for a large number of cores. The proposed scheme can be used in a reverse direction for efficient beam splitting and launching the out-of-phase supermode into the MCF.

The fabrication of microsphere resonators and the generation of optical frequency combs (OFC) have achieved a significant breakthrough in the past decade. Despite these advances, no studies have reported the experimental implementation and demonstration of silica microsphere OFCs for data transmission. In this work, to the best of our knowledge, we experimentally for the first time present a designed silica microsphere whispering-gallery-mode microresonator (WGMR) OFC as a C-band light source where 400 GHz spaced carriers provide data transmission of up to 10 Gbps NRZ-OOK modulated signals over the standard ITU-T G.652 telecom fiber span of 20 km in length. A proof-of-concept experiment is performed with two newly generated carriers (from 7-carrier OFC) having the highest peak power. The experimental realization is also strengthened by the modeling and simulations of the proposed system showing a strong match of the results. The demonstrated setup serves as a platform for the future experimental implementation of silica microsphere WGMR-OFC in more complex WDM transmission system realizations with advanced modulation schemes.

We demonstrate experimentally Raman lasing in an As 2 S 3 chalcogenide glass microsphere pumped by a C-band narrow line laser. Single-mode Raman lasing tunable from 1.610 μm to 1.663 μm is attained when tuning a pump laser wavelength in the 1.522-1.574 μm range. When the pump power significantly exceeds the threshold, multimode cascade Raman lasing is achieved with the maximum Raman order of four at a wavelength of 2.01 μm. We also report an up-converted wave generation at 1.38 μm which is interpreted as the result of four-wave mixing between the pump wave and the wave generated in the second Raman order. The numerical results based on the simulation of the Lugiato-Lefever equation agree with the experimental results.

The coherent propagation and amplification of high-power laser radiation in a multicore fiber consisting of a square array of weakly bound cores are studied. Exact stable analytical solutions are found for the out-of-phase mode, which describes the coherent propagation of wave beams in such fibers. The analytical results are confirmed by direct numerical simulation of the wave equation. The stability conditions of the out-of-phase mode in the active medium are found.

We propose and investigate theoretically the Kerr squeezing of light at a wavelength of 2 µm in chalcogenide fibers with large nonlinearity and-this is the advance-with much reduced attenuation. We present suitably realistic but straightforward designs of low-loss step-index single-mode fibers with the nonlinear Kerr coefficient 3 to 4 orders of magnitude higher than for standard telecommunication fibers, and we give estimations of optimal squeezing for continuous wave laser signal in the considered fibers based on A s 2 S 3 or A s 2 S e 3 glasses.

Propagation and amplification of intense coherent laser pulses in a multicore fiber of 24 weakly coupled cores arranged in the form of seven close-packed hexagons were studied. Exact stable analytical solutions are found for the out-of-phase mode, which describes the coherent propagation of wave beams and temporal soliton solutions in such fibers. Their stability is demonstrated. The analytical results are confirmed by the direct numerical simulation of the wave equation.

A mechanism for self-compression of laser pulses in a multicore fiber on the basis of nonlinear combining of radiation from many cores, surrounding the central core in a ring and its trapping into the central core in a chirp-free and pedestal-free soliton-like pulse, is proposed. It is shown that the compression ratio is weakly dependent on the energy and the number of cores in the fiber and approximately equal to 6 with an almost 100% energy efficiency. The compression ratio can be increased to 40 with an efficiency of more than 50% by using additional compression of longer pulses with approximately the same energy. The possibility of a 38-fold compression of a laser pulse to a duration of 15 fs with a pulse energy of 4 nJ in the fiber with realistic parameters was demonstrated numerically.

Nonlinear spatiotemporal dynamics of femtosecond pulses in a hexagonal seven-core silica fiber pumped by a sub-μJ 370 fs Er:fiber chirped pulse amplification (CPA) system were studied. Nonlinear pulse shaping and compression in the central core and pedestal coupling to the outer cores were directly measured by frequency-resolved optical gating. Further compression of the pulses spectrally broadened in the multicore fiber down to 53 fs was demonstrated. Two orders of magnitude contrast enhancement of the pulses after compression was observed.

Aim: To assess the use of ERAS in laparoscopic Frey procedure., Material and Methods: From August 2012 to November 2017 laparoscopic Frey procedure were performed in 35 patients. Fully laparoscopic were performed 31 (88.5%) procedures. We use fast-track protocol from 13 patients. We included from statistic analyses patients where procedure was changed or was conversion or was simultaneous procedure. The total number of patients analyzed was 27. The patients were divided into two groups: I - before the fast-track protocol (n=11), II - after the protocol implementation (n=16)., Results: The operating time was 460 (365-530) minutes in I group and 420 (295-540) minutes in II group. Blood loss was 150 (5-300) and 150 (40-700) ml. The median postoperative stay period was 10 (5-25) days and 6.5 (3-11) days (p=0.007)., Conclusion: The combination of laparoscopic technologies and fast-track protocol reduces the duration of the postoperative stay period.

Ultrabroadband amplification and two-color CW lasing simultaneously near 1.9 μm and 2.3 μm in a Tm 3+ -doped tellurite fiber were demonstrated experimentally, for the first time to the best of our knowledge. A low-loss Tm 3+ -doped core fiber from TeO 2 -ZnO-La 2 O 3 -Na 2 O glasses stable against crystallization was produced by a special technique, providing a low concentration of hydroxyl groups. Supercontinuum from a highly GeO 2 doped silica fiber pumped by an Er fiber laser system was used as a seed for an amplifier. A maximum gain of 30 dB and 7 dB was measured at 1.9 μm and 2.3 μm, respectively. We report detailed experimental and theoretical studies, which are in a very good agreement, of laser amplification and generation in the manufactured fiber with carefully measured and calculated parameters. A quantitatively verified numerical model was used to predict power scalability at 2.3 μm in schemes with optimized parameters at increased pump power. The presented results show that a high-quality tellurite fiber is a promising candidate for developing lasers in the 2.3 μm atmospheric window which are particularly relevant for applications in gas sensing, eye-safe laser radars, breath analysis, remote sensing and stand-off trace gas detection.

Aim: To analyze the features and efficacy of laparoscopic Frey procedure., Material and Methods: For the period from August 2012 to May 2017 Frey procedure was carried out in 31 patients with chronic calculous pancreatitis Buchler type C. There were 20 men and 11 women aged 48.6±9 years. Mean pancreatic head dimension was 35.5±14 mm, diameter of the main pancreatic duct - 9.6±2.7 mm., Results: Completely laparoscopic procedure was made in 28 (90.3%) cases. One patient required intraoperatively Beger's technique without conversion. The last was need in 2 (6.5%) cases. Time of surgery and blood loss were 447.3±90.4 min and 215±177.7 ml respectively. Mean postoperative hospital-stay was 8.4±4.5 days. Postoperative complications occurred in 7 patients. Mortality was absent. Follow-up was 1-41 months. Recurrent pain syndrome was observed in 1 case. However, it was less severe and does not require analgesia.

A simple design of a fiber laser system for generating high-quality pulses with a duration of order 100 fs with ultrabroad wavelength tunability in the 2-5 μm range is discussed. This design incorporates conventional fs near-IR lasers and specially developed tungstate-tellurite fibers with two zero-dispersion wavelengths (ZDW) and relies on nonlinear wavelength conversion via either soliton self-frequency shift (SSFS) or red-shifted dispersive wave (DW) generation. The fiber parameters needed for such optical conversion have been scanned numerically and showed a possibility of SSFS beyond 4 μm and of DW generation beyond 5 μm. We have also studied and prepared tungstate-tellurite glasses and preforms that are highly stable against crystallization, exhibit extremely low level of hydroxyl groups absorption, and from which the suspended-core two-ZDW fibers can be manufactured.

With the use of spatial light modulators it became possible to implement in experiments the method of controlling the space-time intensity distribution of femtosecond laser pulses stretched to picosecond duration. Cylindrical and quasi-ellipsoidal intensity distributions were obtained and characterized by means of a 2D spectrograph and a cross-correlator.

Duodenal dystrophy (DD) is the pathological change in the wall of the duodenum, which is caused by chronic inflammation in its ectopic pancreatic tissue. The most common complications of DD are acute or chronic pancreatitis and impaired duodenal patency, which along with severe pain are an indication for surgical treatment. Pancreaticoduodenal resection is recognized as the operation of choice. The paper describes a clinical case demonstrating the efficiency and safety of minimally invasive (laparoscopic) surgical technologies in this category of patients. Resectional interventions of this volume are also shown to be accompanied by the development of pancreatic insufficiency that necessitates continuous enzyme replacement therapy.

Rapidly developing nanophotonics needs microresonators for different spectral ranges, formed by chip-compatible technologies. In addition, the tunable ones are much in demand. Here, we present site-controlled III-nitride monocrystal cup-cavities grown by molecular beam epitaxy. The cup-cavities can operate from ultraviolet to near-infrared, supporting quasi whispering gallery modes up to room temperature. Besides, their energies are identical in large 'ripened' crystals. In these cavities, the refractive index variation near an absorption edge causes the remarkable effect of mode switching, which is accompanied by the spatial redistribution of electric field intensity with concentration of light into a subwavelength volume. Our results shed light on the mode behavior in semiconductor cavities and open the way for single-growth-run manufacturing the devices comprising an active region and a cavity with tunable mode frequencies.

A turnkey fiber laser source generating high-quality pulses with a spectral sech shape and Fourier transform-limited duration of order 100 fs widely tunable in the 1.6-2.65 μm range is presented. It is based on Raman soliton self-frequency shifting in the suspended-core microstructured TeO2-WO3-La2O3 glass fiber pumped by a hybrid Er/Tm fiber system. Detailed experimental and theoretical studies, which are in a very good agreement, of nonlinear pulse dynamics in the tellurite fiber with carefully measured and calculated parameters are reported. A quantitatively verified numerical model is used to show Raman soliton shift in the range well beyond 3 μm for increased pump energy.

We investigated a diode-pumped multipass disk Yb:KGW amplifier intended for amplifying a train of 3D ellipsoidal pulses of a laser driver for a photocathode of a linear electron accelerator. The multipass amplification geometry permitted increasing the energy of broadband (about 10 nm) pulses with a repetition rate of 1 MHz from 0.12 µJ to 39 µJ, despite large losses (two orders of magnitude) introduced by a beam shaper of 3D ellipsoidal beam. The distortions of the pulse train envelope were minimal due to optimal delay between the moment of pump switching on and arrival of the first pulse of the train.

Femtosecond pulses with broad tunability in the range of 2-3 μm are generated in a germanate-glass core silica-glass cladding fiber with a driving pulse at 2 μm produced by an all-fiber laser system consisting of an Er:fiber source at 1.6 μm, a Raman fiber shifter, and a Tm:fiber amplifier. We demonstrate optical pulses with a duration of the order of 100 fs that are the shortest ones reported in the 2.5-3 μm range obtained by fiber laser systems.

A method of producing high quality, optically synchronized two-color ultrashort pulses in an active thulium-doped fiber is proposed. We show that sech-shaped femtosecond pulses with essentially different wavelengths can be generated directly from a Tm/Yb-co-doped amplifier: one pulse at about 2 μm and the second pulse with a tunable wavelength up to 2.3 μm, which covers the pump and gain regions of Cr:ZnSe and Cr:ZnS amplifiers. The shortest pulses with durations of 145 fs at 2.25 μm and 125 fs at 2 μm were measured by the FROG (frequency-resolved optical gating) technique.

We report generation of femtosecond optical pulses tunable in the 1.6-2.5 μm range using GeO2-doped core silica-cladding fibers. Optical solitons with a duration of 80-160 fs have been measured by the FROG technique in the 2-2.3 μm range. To the best of our knowledge, these are the longest wavelength temporally characterized solitons generated in silica-based fibers. We have also demonstrated more than octave-spanning femtosecond supercontinuum generation in the 1.0-2.6 μm range.

We report a simple all-fiber design of an Er-doped laser system that is capable of generating widely tunable two-cycle pulses. In particular, 13-fs pulses at a wavelength of 1.7 μm are produced. The mechanism of pulse shortening is identical to the higher-order soliton compression and is supported by modeling based on the slowly evolving wave approximation, which is well suited for down to single-cycle pulse propagation in nonlinear dispersion-shifted fibers.

In the last 5 years the authors had 10 patients with Ogilvie's syndrome under observation. The frequency of the development of the syndrome among all patients who were in the department in this period of time was 0.09%, those who underwent operation accounted for 0.1%. Mortality was 60%. Seven patients were treated by operation. In all patients the syndrome developed in a severe internal disease of an operative intervention. The authors encountered the following clinical diagnostic signs in these patients: moistened tongue, mild tachycardia, absence of hypertrophy of the intestinal wall, and no fecal masses found in the lumen of the large intestine on operation.

The authors intensified and improved considerably the qualitative indices of surgical activity in a department of general surgery by means of simple and practicable organizational measures and by changing the tactics of surgical management of some diseases. This allowed the conclusion that the number of beds in the department must be reduced by 15 without reduction of the staff, which will not affect the activity of the department unfavourably. The organization of a resuscitation department without additional expenses is planned at the cost of the measures mentioned above.