89 research outputs found
Active Faraday optical frequency standards
We propose the mechanism of active Faraday optical clock, and experimentally
demonstrate active Faraday optical frequency standards based on 852 nm narrow
bandwidth Faraday atomic filter by the method of velocity-selective optical
pumping of cesium vapor. The center frequency of the active Faraday optical
frequency standards is determined by the cesium 6 = 4 to 6
= 4 and 5 crossover transition line. The optical heterodyne
beat between two similar independent setups shows that the frequency linewidth
reaches 996(26) Hz, which is 5.3 10 times smaller than the
natural linewidth of the cesium 852 nm transition line. The maximum emitted
light power reaches 75 \upmuW. The active Faraday optical frequency standards
reported here have advantages of narrow linewidth and reduced cavity pulling,
which can readily be extended to other atomic transition lines of alkali and
alkaline-earth metal atoms trapped in optical lattices at magic wavelengths,
making it useful for new generation of optical atomic clocks.Comment: 4 pages, 4 figure
An optical phase-locking with large and tunable frequency difference based on vertical-cavity surface-emitting laser
We present a novel technique to phase-lock two lasers with controllable
frequency difference. In our setup, one sideband of a current modulated
Vertical-Cavity Surface-Emitting Laser (VCSEL) is phase locked to the master
laser by injection seeding, while another sideband of the VCSEL is used to
phase lock the slave laser. The slave laser is therefore locked in phase with
the master laser, with a frequency difference tunable up to about 35 GHz. The
sideband suppression rate of the slave laser is more than 30dB at 30 uW seed
power. The heterodyne spectrum between master and slave has a linewidth of less
than 1 Hz. A coherent population trapping resonance of rubidium is achieved
using such beams.Comment: 4 pages, 4 Encapsulated PostScript figure
Hanle detection for optical clocks
Considering the strong inhomogeneous spatial polarization and intensity
distribution of spontaneous decay fluorescence due to the Hanle effect, we
propose and demonstrate a universe Hanle detection configuration of
electron-shelving method for optical clocks. Experimental results from Ca
atomic beam optical frequency standard with 423 nm electron-shelving method
show that a designed Hanle detection geometry with optimized magnetic field
direction, detection laser beam propagation and polarization direction, and
detector position can improve the fluorescence collection rate by more than one
order of magnitude comparing with that of inefficient geometry. With the fixed
423 nm fluorescence, the improved 657 nm optical frequency standard signal
intensity is presented. And the potential application of the Hanle detection
geometry designed for facilitating the fluorescence collection for optical
lattice clock with a limited solid angle of the fluorescence collection has
been discussed. This Hanle detection configuration is also effective for ion
detection in ion optical clock and quantum information experiments. Besides, a
cylinder fluorescence collection structure is designed to increase the solid
angle of the fluorescence collection in Ca atomic beam optical frequency
standard.Comment: 5 pages, 6 figure
Temperature dependent dynamics of photoexcited carriers of Si2Te3 nanowires
We report an optical study of the dynamics of photoexcited carriers in Si2Te3
nanowires at various temperatures and excitation powers. Si2Te3 nanowires were
synthesized, by using gold as a catalyst, on a silicon substrate by the
chemical vapor deposition method. The photoluminescence spectrum of Si2Te3
nanowires was primary dominated by defect and surface states related emission
at both low and room temperatures. We observed that the decay time of
photoexcited carries was very long (> 10 ns) at low temperatures and became
shorter (< 2 ns) at room temperature. Further, the carrier decay time became
faster at high excitation rates. The acceleration of the photoexcited carrier
decay rates indicate the thermal quenching along with the non-radiative
recombination at high temperature and excitation power. Our results have
quantitatively elucidated decay mechanisms that are important towards
understanding and controlling of the electronic states in Si2Te3 nanostructures
for optoelectronic applications.Comment: 12 pages, 4 figures, submitte
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