Double-Wall Carbon Nanotube Hybrid Mode-Locker in Tm-doped Fibre Laser: A Novel Mechanism for Robust Bound-State Solitons Generation

The complex nonlinear dynamics of mode-locked fibre lasers, including a broad variety of dissipative structures and self-organization effects, have drawn significant research interest. Around the 2 μm band, conventional saturable absorbers (SAs) possess small modulation depth and slow relaxation time and, therefore, are incapable of ensuring complex inter-pulse dynamics and bound-state soliton generation. We present observation of multi-soliton complex generation in mode-locked thulium (Tm)-doped fibre laser, using double-wall carbon nanotubes (DWNT-SA) and nonlinear polarisation evolution (NPE). The rigid structure of DWNTs ensures high modulation depth (64%), fast relaxation (1.25 ps) and high thermal damage threshold. This enables formation of 560-fs soliton pulses; two-soliton bound-state with 560 fs pulse duration and 1.37 ps separation; and singlet+doublet soliton structures with 1.8 ps duration and 6 ps separation. Numerical simulations based on the vectorial nonlinear Schr¨odinger equation demonstrate a transition from single-pulse to two-soliton bound-states generation. The results imply that DWNTs are an excellent SA for the formation of steady single- and multi-soliton structures around 2 μm region, which could not be supported by single-wall carbon nanotubes (SWNTs). The combination of the potential bandwidth resource around 2 μm with the soliton molecule concept for encoding two bits of data per clock period opens exciting opportunities for data-carrying capacity enhancement.M.C. acknowledges the support of EU Horizon2020 Marie S.-Curie IF MINDFLY project. A.E.B. acknowledges the support of Russian Science Foundation (grant 14-21-00110). M.A.A. acknowledges the support of Ministry of Higher Education Sultanate of Oman. T.H. acknowledges the support of Royal Academy of Engineering Fellowship (Graphlex). The support by the Marie-Curie Inter-national Research Staff Exchange Scheme “TelaSens” project, Research Executive Agency Grant No. 269271, Programme: FP7-PEOPLE-2010-IRSES and European Research Council through the FP7-IDEAS-ERC grant ULTRALASER are gratefully acknowledged

Givetian and Frasnian calcareous microbiotas of the Holy Cross Mountains

Each developmental phase of the Givetian to Frasnian carbonate complex of the southern Holy Cross Mts is marked by distinctive calcareous microbiota. The Stringocephalus bank deposits contain a very rich, well-preserved microproblematica (of chiefly ?algal origin) dominated by calcispheroids, and many calcified cyanobacteria and green algae with filamentous Bevocastria, tubiform Devonoscale, and charophyte Trochiliscus. In the late Givetian biostromal complex more sparse microfossil associations occur, with the exception of locally abundant semitextulariid foraminifera (mainly Nanicella) and tubiform dasyclad(?) Jansaella. Also in the Frasnian back-reef facies, only limited and poorly preserved calcispheroids are identified. Contrarily, reef- and fore-reef microbiotas were present in great profusion. Microbial mats (including calcified cyanobacteria Renalcis and Sphaerocodium), associated with locally frequent solenoporids and multichambered foraminifera (Nanicella, also many nodosariids in the later Frasnian) played a significant depositional role and evidence progressive shoaling conditions within the Dyminy reef-complex.Poszczególne fazy rozwojowe żywecko-frańskiego kompleksu węglanowego południowej części Gór Świętokrzyskich charakteryzują się specyficznym zespołem mikroskamieniałości wapiennych. Osady ławicy stringocefalowej zawierają szczególnie bogato reprezentowane i dobrze zachowane mikroproblematyki (?głównie pochodzenia glonowego) silnie zdominowane przez kalcysferoidy (kalcysfery i pokrewne „jednokomorowe otwornice”), szereg kalcyfikujących cjanobakterii i glonów zielenic, np. nitkowate Bevocastria, rurkowate Devonoscale oraz ramienice Trochiliscus. W poźnożyweckim kompleksie biostromalnym występuje bardziej uboga asocjacja mikroskamieniałości, poza miejscami licznymi semitekstularidami (głównie Nanicella), a zwłaszcza zielenicami (?Dasycladacae) Jansaella. Również z frańskich facji zarafowych znane są tylko mało zróżnicowane kalcysferoidy. Natomiast mikrobiocenozy rafowe i przedrafowe franu są bardzo bogate - przede wszystkim w cjanobakterie (np. kalcyfikujące formy Renalcis i Sphaerocodium), a miejscami też w solenoporidy i różnorodne wielokomorowe otwornice (Nanicella, w młodszym franie - nodozaridy). Odgrywały one znaczącą rolę biosedymentacyjną i dokumentują progresywne spłycanie biotopów kompleksu rafowego

Sub-picosecond Graphene-based Harmonically Mode-Locked Fiber Laser With Repetition Rates up to 2.22 GHz

Passive harmonic-mode locking (PHML) of erbium-doped fiber laser with multilayer graphene is presented. The laser could operate at several harmonics (from 2nd to 21st) of the fundamental repetition frequency of the ring resonator (106 MHz). The highest achieved repetition rate was 2.22 GHz (which corresponds to the 21st harmonic) with 900 fs pulse duration and 50 dB of the supermode noise suppression. The saturable absorber was formed by multilayer graphene, mechanically exfoliated from pure graphite block through Scotch-tape and deposited on the fiber ferrule

Fiber-MOPA sources of coherent radiation

This paper presents the concept and design of medium to high power fiber radiation sources in MOPA (Master Oscillator Power Amplifier) configuration. Research results are presented on a two-stage power amplifier for MOPA applications for the third telecommunications window at 1550 nm based on active erbium-doped and erbium/ytterbium-doped fibers. The amplifier is fabricated entirely in fiber technology and delivers several watts of output power

Sub-picosecond Graphene-based Harmonically Mode-Locked Fiber Laser With Repetition Rates up to 2.22 GHz

Passive harmonic-mode locking (PHML) of erbium-doped fiber laser with multilayer graphene is presented. The laser could operate at several harmonics (from 2nd to 21st) of the fundamental repetition frequency of the ring resonator (106 MHz). The highest achieved repetition rate was 2.22 GHz (which corresponds to the 21st harmonic) with 900 fs pulse duration and 50 dB of the supermode noise suppression. The saturable absorber was formed by multilayer graphene, mechanically exfoliated from pure graphite block through Scotch-tape and deposited on the fiber ferrule

Optical-Optical Double-Resonance Spectroscopy of Methane Using a Cavity-Enhanced Comb Probe

International audienceWe implement a cavity to enhance the absorption of a frequency comb probe in a double-resonance measurement of sub-Doppler 3?3 ? ?3 methane transitions. This yields two orders of magnitude better sensitivity in 15 times shorter acquisition time compared to previous work using a single-pass cell. © 2021 OSA