Sergey A Babin

Sergey A Babin
Russian Academy of Sciences | RAS · Institute of Automation and Electrometry

About

469
Publications
43,121
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6,994
Citations
Citations since 2016
220 Research Items
4551 Citations
20162017201820192020202120220200400600
20162017201820192020202120220200400600
20162017201820192020202120220200400600
20162017201820192020202120220200400600

Publications

Publications (469)
Article
Full-text available
The development of antireflection coatings is crucially important to improve the performance of various photonic devices, for example, to increase the efficiency of harmonic generators based on high-refractive index crystals with significant Fresnel losses. A promising technique for the reducing of radiation reflection is to change the refractive i...
Chapter
In this chapter, we give an overview of high-energy dissipative solitons generation via Raman gain. Such pulses have been proven to be a new kind of solitons—Raman dissipative soliton (RDS). Two basic configurations of the laser cavity with intra- and extra-cavity formation of the RDS are presented and the properties specific to each of them are di...
Article
Full-text available
We present our theoretical model and experimental results on the extreme linewidth narrowing of an erbium-doped fiber distributed feedback (DFB) laser due to an additional random DFB via Rayleigh backscattering in a long single-mode fiber connected to the laser. The relative narrowing of instantaneous (<1 μs) linewidth in such a hybrid cavity confi...
Article
Full-text available
We present our recent experimental results on the pulsed regimes of Raman conversion of highly multimode laser diode (LD) pump radiation into the 1st and higher order Stokes radiation in multimode graded-index fibers. Three different linear cavities of Raman fiber laser with the modulation of losses (by acousto-optic modulator, AOM) or gain (by LD...
Article
We report on the thermalization of light carrying orbital angular momentum in multimode optical fibers, induced by nonlinear intermodal interactions. A generalized Rayleigh-Jeans distribution of asymptotic mode composition is obtained, based on the conservation of the angular momentum. We confirm our predictions by numerical simulations and experim...
Article
Full-text available
In this article, we review recent advances in the technology of writing fiber Bragg gratings (FBGs) in selected cores of multicore fibers (MCFs) by using femtosecond laser pulses. The writing technology of such a key element as the FBG opens up wide opportunities for the creation of next generation fiber lasers and sensors based on MCFs. The advant...
Article
Atoms ionization by the simultaneous absorption of multiple photons has found applications in fiber optics, where it leads to unique nonlinear phenomena. To date, studies of the ionization regime have been limited to gas-filled hollow-core fibers. Here, we investigate multiphoton ionization of standard optical fibers, where intense laser pulses ion...
Article
Full-text available
Raman lasing in multimode GRIN fibers is accompanied by sufficient improvement of the output beam quality in comparison with that for pump radiation, which offers opportunities to wavelength-agile fiber lasers of new type. Here we compare power scaling and brightness enhancement capabilities of Raman laser based on multimode GRIN-fiber of 62.5/125...
Article
Full-text available
Using a point-by-point fs inscription technology, a Rayleigh reflector with unique characteristics has been designed and fabricated. The reflection coefficient of the structure with a length of 5 cm amounts to 0,03%, which corresponds to the reflection of 6-km SMF-28e+ fiber spool. The designed artificial Rayleigh scattering fiber in combination wi...
Article
Full-text available
The main application area for GaSe crystals is nonlinear optics, but there are problems with machining and antireflection coatings due to the layered structure of GaSe. Large GaSe crystals with dominant ε-modification were grown. Using various harmonics of a femtosecond laser, antireflection microstructures (ARM) were fabricated by laser ablation o...
Article
Full-text available
An all-fiber 4-core Yb-doped laser with a cavity formed by fiber Bragg gratings directly inscribed in each core with femtosecond laser pulses and 4% Fresnel reflection from the output fiber end face is demonstrated. It has been shown that the diameter of the active fiber winding significantly affects the power distribution between the cores, since...
Article
Since its first demonstration in graded-index multimode fibers, spatial beam self-cleaning has attracted a growing research interest. It allows for the propagation of beams with a bell-shaped spatial profile, thus enabling the use of multimode fibers for several applications, from biomedical imaging to high-power beam delivery. So far, beam self-cl...
Article
We develop a comprehensive theory for describing the experimental beam profiles from multimode fiber Raman lasers. We take into account the presence of random linear mode coupling, Kerr beam self-cleaning and intra-cavity spatial filtering. All of these factors play a decisive role in shaping the Stokes beam, which has a predominant fundamental mod...
Preprint
Full-text available
Atoms ionization by the simultaneous absorption of multiple photons has found applications in fiber optics, where it leads to unique nonlinear phenomena. To date, studies of the ionization regime have been limited to gas-filled hollow-core fibers. Here, we investigate multiphoton ionization of standard optical fibers, where intense laser pulses ion...
Article
All-fiber Raman lasers have demonstrated their potential for efficient conversion of highly multimode pump beams into high-quality Stokes beams. However, the modal content of these beams has not yet been investigated. In this work, based on a mode decomposition technique, we are able to reveal the details of intermodal interactions in the different...
Conference Paper
We experimentally and theoretically study the thermalization of orbital angular momentum beams in nonlinear multimode graded-index optical fibers. Our results shed new light on the physical mechanism of the beam self-cleaning effect.
Conference Paper
Our theory and experiments show that Kerr nonlinearity leads to the thermalization of multimode optical beams carrying orbital angular momentum. We describe the connection with spatial beam self-cleaning in graded-index fibers.
Preprint
We present a general theory of thermalization of light in multimode optical fibers, including optical beams with nonzero orbital angular momentum or vortex beams. A generalized Rayleigh-Jeans distribution of asymptotic mode composition is obtained, based on the conservation of the angular momentum. We confirm our predictions by numerical simulation...
Article
We report a study of the spatial characteristics of the beam output from a multimode-pumped SRS cascade laser. The intensity profiles of transmitted pump radiation beams, as well as of the first and second orders Stokes SRS generation, is measured in two different laser configurations: in a classical laser with two pairs of reflectors and in a sche...
Article
Inscription of structures by a femtosecond laser beam allows one to produce disordered structures capable of increasing the Rayleigh backscatter intensity in the fibre at relatively low induced losses, which makes them potential candidates for use as reflectors in fibre lasers. Here we report a narrow-band erbium fibre laser with random distributed...
Article
We experimentally and numerically study the ignition of helical-shaped plasma filaments in standard optical fibers. Femtosecond pulses with megawatt peak power with proper off-axis and tilted coupling in the fiber core produce plasma skew rays. These last for distances as long as 1,000 wavelengths thanks to a combination of linear waveguiding and s...
Article
Full-text available
Formation of highly ordered nanostructures on a crystalline silicon surface is highly demanded for novel optoelectronic and nanophotonic designs pushing toward development of inexpensive and high-performing nanostructuring technologies. Here, we demonstrate that laser-induced periodic surface structuring of c-Si protected by a thin Hf over-layer al...
Preprint
Since its first demonstration in graded-index multimode fibers, spatial beam self-cleaning has attracted a growing research interest. It allows for the propagation of beams with a bell-shaped spatial profile, thus enabling the use of multimode fibers for several applications, from biomedical imaging to high-power beam delivery. So far, beam self-cl...
Article
Full-text available
Multimode fibres provide a promising platform for boosting the capacity of fibre links and the output power of fibre lasers. The complex spatiotemporal dynamics of multimode beams may be controlled in spatial and temporal domains via the interplay of nonlinear, dispersive and dissipative effects. Raman nonlinearity induces beam cleanup in long grad...
Article
Full-text available
We review our recent experimental results on the cascaded Raman conversion of highly multimode laser diode (LD) pump radiation into the first- and higher-order Stokes radiation in multimode graded-index fibers. A linear cavity composed of fiber Bragg gratings (FBGs) inscribed in the fiber core is formed to provide feedback for the first Stokes orde...
Conference Paper
All-fiber Raman lasers have demonstrated their potential for the efficient conversion of highly multimode pump beams into a high-quality Stokes beams. However, the modal content of these beams has not been investigated yet. Here we apply, for the first time, a mode decomposition technique for revealing intermodal interactions in different operation...
Article
A distributed temperature monitoring inside a cavity of ytterbium DFB and holmium fiber lasers has been demonstrated with a spatial resolution of 1 and 5 mm, respectively, for the first time to the best of our knowledge. For this, we use an optical backscatter reflectometer, which measures intracore temperature, and compare it with the data of an I...
Conference Paper
Periodic structures were formed on zirconium films with thicknesses of 50 and 170 nm using near-IR femtosecond laser pulses. The dependency of the period and structure uniformity on pulse energy and scanning rate was observed.
Article
Full-text available
The power scaling on all-fiberized Raman fiber oscillator with brightness enhancement (BE) based on multimode graded-index (GRIN) fiber is demonstrated. Thanks to beam cleanup of GRIN fiber itself and single-mode selection properties of the fiber Bragg gratings inscribed in the center of GRIN fiber, the efficient BE is realized. For the laser cavit...
Article
Full-text available
A multimode all-fiber Raman laser enabling cascaded generation of high-quality 1019-nm output beam at direct pumping by highly-multimode (M2>30) 940-nm laser diodes has been demonstrated. The laser is made of a 100/140 graded-index fiber with special in-fiber Bragg gratings which secure sequential generation of the 1st (976 nm) and 2nd (1019 nm) St...
Article
Full-text available
We demonstrate an efficient conversion of highly-multimode (M ² ∼34) pump beam from fiber-combined 938-nm laser diodes into a 976-nm Stokes beam of high quality (M ² =1.7-2 at output powers 10-52 W) that results in record brightness enhancement (BE=73) for Raman lasers based on graded-index fiber (GIF) and other fibers. The measured shapes of the o...
Article
A brightness-enhanced random Raman fiber laser (RRFL) with maximum power of 306 W at 1120 nm is demonstrated. A half-open cavity is built based on a graded-index (GRIN) passive fiber and single high-reflective fiber Bragg grating written in it directly. Due to the beam cleanup effect in the GRIN fiber enhanced in the half-open RRFL cavity, the outp...
Article
Full-text available
A compact random fiber laser based on a short artificial Rayleigh reflector and heavily-doped Er fibers (custom-made and commercial as a reference) has been proposed, characterized and optimized in terms of efficiency, linewidth and noise level. A 10-cm artificial Rayleigh reflector with mean scattering level of +41.3 dB/mm relative to the natural...
Conference Paper
We review our recent results on fiber lasers with distributed feedback based on π-shifted or random fiber Bragg gratings, and random index structures inscribed by femtosecond pulses in singlemode or multicore/multimode fibers.
Conference Paper
Fiber-optic shape sensors based on 7-core optical fibers with twisted and straight cores were integrated into a flexible medical papillotome and the accuracy of shape reconstruction was analyzed for different fiber Bragg gratings spacing.
Conference Paper
We present a narrow-linewidth random Er-doped fiber laser based on fs-pulse-inscribed artificial Rayleigh reflector. A single-frequency regime with 500 Hz linewidth was observed at 1.5 mW output power, and few-mode regime at 12 mW.
Conference Paper
A theory describing experimental beam profiles of multimode fiber Raman lasers is developed: random mode coupling, Kerr self-cleaning and spatial filtering play a decisive role in shaping Stokes beams, whereas depleted pump beams remain insensitive.
Article
Multimode optical fibers (MMF) recently attracted a renewed attention, because of their potential for spatial division multiplexing, medical imaging and high-power fiber lasers, thanks to the discovery of new nonlinear optical effects, such as Kerr beam self-cleaning, spatiotemporal mode-locking, and geometric parametric instability, to name a few....
Article
This paper reports results of a study aimed at producing a Raman fibre laser based on a multicore fibre with high-reflectivity fibre Bragg gratings inscribed in its peripheral cores using femtosecond laser pulses. We present spectral and power characteristics of a Raman laser whose output power at a wavelength of 1090 nm is 2.5 W. The laser emissio...
Article
We examine multimode diode laser pump depletion in a graded index multimode (MM) fibre Raman laser generating a high-quality Stokes beam. Spatial ‘hole burning’ in the transmitted pump beam is demonstrated. A balance model is constructed for interaction of the pump and Stokes waves in the MM Raman laser. Analytical formulas are derived and used in...
Article
A model of coupled modes is proposed, which makes it possible to describe the propagation of a pump wave and a Stokes component in a multimode graded-index fibre. A decrease in the depression in the centre of the profile of the pump wave intensity distribution as a result of the influence of Kerr effects and random linear coupling of modes is demon...
Article
In this paper we investigate the fiber Bragg grating (FBG) arrays selectively inscribed in a multicore fiber for a different sensor and laser applications. Particularly, wavelength-switchable and tunable fiber laser was realized based on uniform and non-uniform FBGs precisely positioned in the selected cores. A quasi-distributed 3D shape sensor bas...
Article
Full-text available
Specially designed composite heavily Er3+-doped fiber in combination with unique point-by-point inscription technology by femtosecond pulses at 1,026 nm enables formation of distributed-feedback (DFB) laser with ultra-short cavity length of 5.3 mm whose parameters are comparable and even better than those for conventional Er3+-doped fiber DFB laser...
Article
Full-text available
Multicore optical fibers are widely used for developing compact shape sensors for various applications. The accuracy of such sensors strongly depends on the resolution of the measured data. In this paper, we analyze the influence of the number of sensing points on the error and mean time of reconstruction of the multicore fiber shape. A criterion o...
Article
Full-text available
Raman dissipative solitons (RDS) have been investigated numerically. It was found that the area of stable generation is bounded in terms of pump spectral bandwidth and pulse energy. Existing optimum is strongly affected by the net cavity dispersion. The spectral bandwidth of the generated RDS linearly depends on its energy and reaches more than 50...
Article
Here, we applied direct laser-induced periodic surface structuring to drive phase transition of amorphous silicon (a-Si) into nanocrystalline (nc) Si imprinted as regular arrangement of Si nanopillars passivated with SiO2 layer. By varying the laser beam scanning speed at a fixed pulse energy, we successfully tailored the resulting unique surface m...
Article
Full-text available
We experimentally demonstrate spatial beam self-cleaning in an Yb-doped graded-index multimode fiber taper, both in passive and active configurations. The input laser beam at 1064 nm was injected for propagation from the small to the large core side of the taper, with laser diode pumping in a counterdirectional configuration. The Kerr effect permit...
Article
Full-text available
Raman conversion in multimode GRIN fibers is accompanied by sufficient improvement of the output beam quality in comparison with that for pump radiation, which offers opportunities to create amplifiers and lasers of new type based on directly 9xx-nm diode pumped passive GRIN fibers, which may operate at almost any wavelength in transmission window...
Conference Paper
We use 7-core optical fiber containing Fabry-Perot interferometers for a spatial division multiplexing of acoustic sensors. The interferometers are inscribed in different cores of the fiber using the femtosecond point-by-point inscription technique.
Conference Paper
Femtosecond point-by-point inscription of pi-shifted fiber Bragg grating in Er ³⁺ -heavily-doped phosphosilicate fiber with ultrashort length of 5.3 mm enables stable linearly-polarized single-frequency generation of 0.5 mW power and 3.5-kHz linewidth.
Conference Paper
We demonstrate beam self-cleaning in a tapered Ytterbium-doped graded-index multimode fiber in both active and passive configurations, without accompanying self-phase modulation induced spectral broadening or frequency conversion.
Conference Paper
Multimode 940-nm diode radiation is shown to be converted in graded-index fibers into high-quality (M2≤2) 976-nm Raman beam due to parabolic pump beam, its homogeneous depletion above threshold, mode-selective feedback by FBG and nonlinear effects.
Preprint
We experimentally demonstrate spatial beam self-cleaning in an Yb-doped graded-index multimode fiber taper, both in passive and active configurations. The input laser beam at 1064 nm was injected for propagation from the small to the large core side of the taper, with laser diode pumping in a counterdirectional configuration. The Kerr effect permit...