8,309 research outputs found
The Future of Stellar Populations Studies in the Milky Way and the Local Group
The last decade has seen enormous progress in understanding the structure of
the Milky Way and neighboring galaxies via the production of large-scale
digital surveys of the sky like 2MASS and SDSS, as well as specialized,
counterpart imaging surveys of other Local Group systems. Apart from providing
snaphots of galaxy structure, these "cartographic" surveys lend insights into
the formation and evolution of galaxies when supplemented with additional data
(e.g., spectroscopy, astrometry) and when referenced to theoretical models and
simulations of galaxy evolution. These increasingly sophisticated simulations
are making ever more specific predictions about the detailed chemistry and
dynamics of stellar populations in galaxies. To fully exploit, test and
constrain these theoretical ventures demands similar commitments of
observational effort as has been plied into the previous imaging surveys to
fill out other dimensions of parameter space with statistically significant
intensity. Fortunately the future of large-scale stellar population studies is
bright with a number of grand projects on the horizon that collectively will
contribute a breathtaking volume of information on individual stars in Local
Group galaxies.Comment: 12 pages, 0 figures, IAU Symposium No. 262, Stellar Populations -
Planning for the Next Decad
Mode-locked dysprosium fiber laser: picosecond pulse generation from 2.97 to 3.30 {\mu}m
Mode-locked fiber laser technology to date has been limited to sub-3 {\mu}m
wavelengths, despite significant application-driven demand for compact
picosecond and femtosecond pulse sources at longer wavelengths. Erbium- and
holmium-doped fluoride fiber lasers incorporating a saturable absorber are
emerging as promising pulse sources for 2.7--2.9 {\mu}m, yet it remains a major
challenge to extend this coverage. Here, we propose a new approach using
dysprosium-doped fiber with frequency shifted feedback (FSF). Using a simple
linear cavity with an acousto-optic tunable filter, we generate 33 ps pulses
with up to 2.7 nJ energy and 330 nm tunability from 2.97 to 3.30 {\mu}m
(3000--3400 cm^-1)---the first mode-locked fiber laser to cover this spectral
region and the most broadly tunable pulsed fiber laser to date. Numerical
simulations show excellent agreement with experiments and also offer new
insights into the underlying dynamics of FSF pulse generation. This highlights
the remarkable potential of both dysprosium as a gain material and FSF for
versatile pulse generation, opening new opportunities for mid-IR laser
development and practical applications outside the laboratory.Comment: Accepted for APL Photonics, 22nd August 201
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