60 research outputs found
Laser Cooled High-Power Fiber Amplifier
A theoretical model for laser cooled continuous-wave fiber amplifier is
presented. The amplification process takes place in the Tm3+-doped core of the
fluoride ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF) glass fiber. The cooling process takes
place in the Yb3+:ZBLAN fiber cladding. It is shown that for each value of the
pump power and the amplified signal there is a distribution of the
concentration of the Tm3+ along the length of the fiber amplifier, which
provides its athermal operation. The influence of a small deviation in the
value of the amplified signal on the temperature of the fiber with the fixed
distribution of the Tm3+ions in the fiber cladding is investigated.Comment: 10 pages and 5 figure
Heat Evacuation from Active Raman Media Heat Evacuation from Active Raman Media Using Quasi-PT Symmetry Coupling
We propose to use frequency-selective quasi parity-time symmetry to reduce
the heat generated by coherent anti-Stokes Raman scattering (CARS) reversed
cycles in active Raman media with phase mismatch. This is accomplished using a
coupled-waveguide structure, which includes the active Raman waveguide (RW),
where the Stokes signal undergoes amplification via stimulated Stokes Raman
scattering (SSRS), and a dissipative waveguide (DW), which is tuned to the
anti-Stokes wavelength so as to evacuate the corresponding anti-Stokes photons
from the RW by coupling. The DW introduces optical loss that partially offsets
the growth of the anti-Stokes signal in the RW and hence suppress the reversed
CARS cycles that would otherwise result into heat generation in the RW. It is
shown that the frequency-selective quasi parity-time symmetry provided by the
DW can reduce the heat in active Raman media by a very factor of up to five
when the CARS phase mismatch is compensated for by the optimum level of
coupling between the RW and the DW.Comment: 8 pages, 9 figure
Raman fiber amplifier with integrated cooler
We present a new scheme for a laser cooled Raman optical fiber amplifier. The
heat generated in the process of stimulated Raman scattering is compensated for
with laser cooling provided by anti-Stokes fluorescence of ytterbium ions doped
in the core of the fiber. The device is pumped with two pump sources. One of
the pump sources provides Raman amplification of the signal and does not
interact with the ytterbium ions in the core of the fiber. The second pump
provides laser cooling of the fiber with anti-Stokes fluorescence of the Yb3+
ions. The proper arrangement of Yb3+distribution can provide athermal
performance of the device.Comment: 13 pages, 6 figure
Heat evacuation from active Raman media using frequency-selective dissipative coupling
ABSTRACT: We propose to use frequency-selective dissipative coupling to reduce the heat generated by coherent antiStokes Raman scattering (CARS) reversed cycles in active Raman media with phase mismatch. This is accomplished using a coupled-waveguide structure, which includes the active Raman waveguide (RW), where the Stokes signal undergoes amplification via stimulated Stokes Raman scattering (SSRS), and a dissipative waveguide (DW), which is tuned to the anti-Stokes wavelength so as to evacuate the corresponding anti-Stokes photons from the RW by coupling. The DW introduces optical loss that partially offsets the growth of the anti-Stokes signal in the RW and hence suppress the reversed CARS cycles that would otherwise result into heat generation in the RW. It is shown that the frequency-selective dissipative coupling provided by the DW can reduce the heat in active Raman media by a very factor of up to 5 when the CARS phase mismatch is compensated for by the optimum level of coupling between the RW and the DW
Silica bottle resonator sensor for refractive index and temperature measurements
We propose and theoretically demonstrate a bottle resonator sensor with a nanoscale altitude and with alength several of hundreds of microns made on the top of the fiber with a radius of tens microns for refractive index and temperature sensor applications. The whispering gallery modes (WGMs) in the resonators can be excited with a taper fiber placed on the top of the resonator. These sensors can be considered as an alternative to fiber Bragg grating (FBG) sensors.The sensitivity of TM-polarized modes is higher than the sensitivity of the TE-polarized modes, but these values are comparable and both polarizations are suitable for sensor applications. The sensitivity similar to 150 (nm/RIU) can be reached with abottle resonator on the fiber with the radius 10 m. It can be improved with theuse of a fiber with a smaller radius. The temperature sensitivity is found to be similar to 10 pm/K. The temperature sensitivity can decrease similar to 10% for a fiber with a radius r(co) = 10 m instead of a fiber with a radius r(co) = 100 m. These sensors have sensitivities comparable to FBG sensors. A bottle resonator sensor with a nanoscale altitude made on the top of the fiber can be easily integrated in any fiber scheme
Surface plasmon resonance-based fiber and planar waveguide sensors
Bulk surface Plasmons resonance devices have been researched for several decades. These devices have found a special niche as
high-sensitivity refractive index sensor in biomedical applications. Recent advances in guided wave devices are rapidly changing
the capabilities of such sensors, not only increasing convenience of use but also opening opportunities due to their versatility. This
paper reviews many of these devices and presents some of their salient features
A new technique for laser cooling with superradiance
We present a new theoretical scheme for laser cooling of rare earth doped
solids with optical super-radiance (SR), which is the coherent, sharply
directed spontaneous emission of photons by a system of laser excited rare
earth ions in the solid state host (glass or crystal). We consider an Yb3+
doped ZBLAN sample pumped at the wavelength 1015 nm with a rectangular pulsed
source with a power of ~433W and duration of 10ns. The intensity of the SR is
proportional to the square of the number of excited ions. This unique feature
of SR permits a dramatic increase in the rate of the cooling process in
comparison with the traditional laser cooling of the rare earth doped solids
with anti-Stokes spontaneous incoherent radiation (fluorescence). This scheme
overcomes the limitation of using only low phonon energy hosts for laser
cooling.Comment: 10 pages,6 figure
Development of ytterbium-doped oxyfluoride glasses for laser cooling applications
Oxyfluoride glasses doped with 2, 5, 8, 12, 16 and 20 mol% of ytterbium (Yb3+) ions have been prepared by the conventional melt-quenching technique. Their optical, thermal and thermo-mechanical properties were characterized. Luminescence intensity at 1020 nm under laser excitation at 920 nm decreases with increasing Yb3+ concentration, suggesting a decrease in the photoluminescence quantum yield (PLQY). The PLQY of the samples was measured with an integrating sphere using an absolute method. The highest PLQY was found to be 0.99(11) for the 2 mol% Yb3+: glass and decreases with increasing Yb3+ concentration. The mean fluorescence wavelength and background absorption of the samples were also evaluated. Upconversion luminescence under 975 nm laser excitation was observed and attributed to the presence of Tm3+ and Er3+ ions which exist as impurity traces with YbF3 starting powder. Decay curves for the Yb3+: F-2(5/2)-> F-2(7/2) transition exhibit single exponential behavior for all the samples, although lifetime decrease was observed for the excited level of Yb3+ with increasing Yb3+ concentration. Also observed are an increase in the PLQY and a slight decrease in lifetime with increasing the pump power. Finally, the potential of these oxyfluoride glasses with high PLQY and low background absorption for laser cooling applications is discussed
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