760 research outputs found
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Tunable Q-switched fiber laser based on saturable edge-state absorption in few-layer molybdenum disulfide (MoSâ‚‚).
We fabricate a few-layer molybdenum disulfide (MoSâ‚‚) polymer composite saturable absorber by liquid-phase exfoliation, and use this to passively Q-switch an ytterbium-doped fiber laser, tunable from 1030 to 1070 nm. Self-starting Q-switching generates 2.88 ÎĽs pulses at 74 kHz repetition rate, with over 100 nJ pulse energy. We propose a mechanism, based on edge states within the bandgap, responsible for the wideband nonlinear optical absorption exhibited by our few-layer MoSâ‚‚ sample, despite operating at photon energies lower than the material bandgap.EJRK acknowledges support from the Royal Academy of Engineering (RAEng), through a
RAEng Fellowship, RCTH from EPSRC (EP/G037221/1), GH from a CSC Cambridge International
Scholarship, and TH from the RAEng (Graphlex). The authors also acknowledge
ThorLabs for access to their technical drawings.This is the accepted manuscript. The final version is available at http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-22-25-31113. © 2014 Optical Society of America. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited
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Scalar nanosecond pulse generation in a nanotube mode-locked environmentally stable fiber laser
We report an environmentally stable nanotube mode-locked fibre laser
producing linearly-polarized, nanosecond pulses. A simple
all-polarization-maintaining fibre ring cavity is used, including 300 m of
highly nonlinear fibre to elongate the cavity and increase intracavity
dispersion and nonlinearity. The laser generates scalar pulses with a duration
of 1.23 ns at a centre wavelength of 1042 nm, with 1.3-nm bandwidth and at
641-kHz repetition rate. Despite the long cavity, the output characteristics
show no significant variation when the cavity is perturbed, and the degree of
polarization remains at 97%
Solution processed MoS2-PVA composite for sub-bandgap mode-locking of a wideband tunable ultrafast Er:fiber laser
Abstract
We fabricate a free-standing few-layer molybdenum disulfide (MoS2)-polymer composite by liquid phase exfoliation of chemically pristine MoS2 crystals and use this to demonstrate a wideband tunable, ultrafast mode-locked fiber laser. Stable, picosecond pulses, tunable from 1,535 nm to 1,565 nm, are generated, corresponding to photon energies below the MoS2 material bandgap. These results contribute to the growing body of work studying the nonlinear optical properties of transition metal dichalcogenides that present new opportunities for ultrafast photonic applications.MZ wishes to acknowledge funding from the EPSRC (EP/K03705), RCTH from the EPSRC (EP/G037221/1), GH from a CSC Cambridge International Scholarship, EJRK from the Royal Academy of Engineering (RAEng), through a RAEng Fellowship and TH from the RAEng (Graphlex).This is the final version. It was first published by Springer at http://link.springer.com/article/10.1007%2Fs12274-014-0637-
Tm-doped fiber laser mode-locked by graphene-polymer composite.
We demonstrate mode-locking of a thulium-doped fiber laser operating at 1.94 ÎĽm, using a graphene-polymer based saturable absorber. The laser outputs 3.6 ps pulses, with ~0.4 nJ energy and an amplitude fluctuation ~0.5%, at 6.46 MHz. This is a simple, low-cost, stable and convenient laser oscillator for applications where eye-safe and low-photon-energy light sources are required, such as sensing and biomedical diagnostics
High Resolution Spectroscopy of Two-Dimensional Electron Systems
Spectroscopic methods involving the sudden injection or ejection of electrons
in materials are a powerful probe of electronic structure and interactions.
These techniques, such as photoemission and tunneling, yield measurements of
the "single particle" density of states (SPDOS) spectrum of a system. The SPDOS
is proportional to the probability of successfully injecting or ejecting an
electron in these experiments. It is equal to the number of electronic states
in the system able to accept an injected electron as a function of its energy
and is among the most fundamental and directly calculable quantities in
theories of highly interacting systems. However, the two-dimensional electron
system (2DES), host to remarkable correlated electron states such as the
fractional quantum Hall effect, has proven difficult to probe
spectroscopically. Here we present an improved version of time domain
capacitance spectroscopy (TDCS) that now allows us to measure the SPDOS of a
2DES with unprecedented fidelity and resolution. Using TDCS, we perform
measurements of a cold 2DES, providing the first direct measurements of the
single-particle exchange-enhanced spin gap and single particle lifetimes in the
quantum Hall system, as well as the first observations of exchange splitting of
Landau levels not at the Fermi surface. The measurements reveal the difficult
to reach and beautiful structure present in this highly correlated system far
from the Fermi surface.Comment: There are formatting and minor textual differences between this
version and the published version in Nature (follow the DOI link below
Magnetoelastic nonlinear metamaterials
We introduce the concept of magnetoelastic metamaterials with electromagnetic
properties depending on elastic deformation. We predict a strong nonlinear and
bistable response of such metamaterials caused by their structural reshaping in
response to the applied electromagnetic field. In addition, we demonstrate
experimentally the feasibility of the predicted effect.Comment: 4 pages, 5 figure
Genome wide analysis of gene expression changes in skin from patients with type 2 diabetes
Non-healing chronic ulcers are a serious complication of diabetes and are a major healthcare problem. While a host of treatments have been explored to heal or prevent these ulcers from forming, these treatments have not been found to be consistently effective in clinical trials. An understanding of the changes in gene expression in the skin of diabetic patients may provide insight into the processes and mechanisms that precede the formation of non-healing ulcers. In this study, we investigated genome wide changes in gene expression in skin between patients with type 2 diabetes and non-diabetic patients using next generation sequencing. We compared the gene expression in skin samples taken from 27 patients (13 with type 2 diabetes and 14 non-diabetic). This information may be useful in identifying the causal factors and potential therapeutic targets for the prevention and treatment of diabetic related diseases
Multi-scale polarisation phenomena
Multi-scale methods that separate different time or spatial scales are among the most powerful techniques in physics, especially in applications that study nonlinear systems with noise. When the time scales (noise and perturbation) are of the same order, the scales separation becomes impossible. Thus, the multi-scale approach has to be modified to characterise a variety of noise-induced phenomena. Here, based on stochastic modelling and analytical study, we demonstrate in terms of the fluctuation-induced phenomena and Hurst R/S analysis metrics that the matching scales of random birefringence and pump–signal states of polarisation interaction in a fibre Raman amplifier results in a new random birefringence-mediated phenomenon, which is similar to stochastic anti-resonance. The observed phenomenon, apart from the fundamental interest, provides a base for advancing multi-scale methods with application to different coupled nonlinear systems ranging from lasers (multimode, mode-locked, random, etc.) to nanostructures (light-mediated conformation of molecules and chemical reactions, Brownian motors, etc.)
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