1,807 research outputs found
Optofluidic circular grating distributed feedback dye laser
We demonstrate an optically pumped surface emitting optofluidic dye laser using a second-order circular grating distributed feedback resonator. We present a composite bilayer soft lithography technique specifically developed for the fabrication of our dye laser and investigate a hybrid polymer material system [poly(dimethylsiloxane)/perfluoropolyether] to construct high-resolution Bragg gratings. Our lasers emit single frequency light at low lasing thresholds of 6 µJ/mm^2. These optofluidic dye lasers can serve as low-cost and compact coherent light sources that are fully integrated within microfluidic analysis chips and provide an efficient approach to construct compact spectroscopy systems
Structural Order for One-Scale and Two-Scale Potentials
We perform molecular dynamics simulations to investigate the relationship
between structural order and water-like dynamic and thermodynamic anomalies in
spherically-symmetric potentials having either one or two characteristic length
scales. %The first potential has only one length scale which is the diameter of
the ramp %without the hard core, and the second potential has two length
scales: one is the %diameter of a ramp(softcore) and another one is the
diameter of a %hard core with a ratio of 1.76. Structural order is
characterized by translational and orientational order parameters. %analogous
to those used in previous cases for water and %silica.Only the two-scale ramp
potential exhibits properties %remarkably similar to those found for water and
silica regarding the %relationship between structural order, dynamic anomalies,
and thermodynamic %anomalies. We find that (i) dynamic and thermodynamic
anomalies exist for both one-scale and two-scale ramp potentials, and (ii)
water-like structural order anomalies exist only for the two-scale ramp
potential. Our findings suggest that the water-like relationship between
structural order and anomalies is related to the presence of two different
length scales in the potential.Comment: 12 pages, 5 figure
Structure of the First and Second Neighbor Shells of Water: Quantitative Relation with Translational and Orientational Order
We perform molecular dynamics simulation of water using the TIP5P model to
quantify structural order in both the first shell (defined by four nearest
neighbors)and second shell (defined by twelve next-nearest neighbors) of a
central water molecule. We find the anomalous decrease of orientational order
upon compression occurs in both shells, but the anomalous decrease of
translational order upon compression occurs {\it mainly in the second shell}.
The decreases of translational and orientational orders upon compression
("structural anomaly") are thus correlated only in the second shell. Our
findings quantitatively confirm the qualitative idea that the thermodynamic,
dynamic and structural anomalies of water are related to changes in the second
shell upon compression.Comment: 12 pages, 5 figure
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