55 research outputs found
Design and performance of a diode laser spectrometer for a stratospheric aircraft
We report the instrument description and the results
of the laboratory calibration and tests of a mid-infrared
tunable diode spectrometer for in situ trace gas
concentration measurements in the stratosphere operating
on a stratospheric aircraft. The spectrometer is dedicated
to the measurement of the HNO3 amount in the
stratospheric aerosols by means of gas-phase absorption
spectroscopy on molecular roto-vibrational lines in the
mid-infrared, using a tunable diode laser and a multipass
absorption cell. The instrument was specifically designed
for operation aboard of the stratospheric aircraft M55
Geophysica, in the frame of the Airborne Platform
for Earth observation (APE) project. The instrument is
part of a measurement package for the measurement of the
chemical content of Polar Stratospheric Clouds (PSCs) and
other atmospheric aerosols. This system can be also used
as a stand-alone detector of molecular trace gases. Design
criteria include an efficient optical layout, with a very
low sensitivity to the vibration and thermal stresses and
a very small footprint, and a detection scheme based on
the sweep integration technique for fast data acquisition
and high signal-to-noise (S/N) ratio.
We report a new set of testing measurements on ammonia as
the calibration gas with one order of magnitude improvement
with respect to what we previously reported
Figure of merit for nonlinear materials in second-order cascaded nonstationary processes
In this paper, we present and discuss an extension
and an improvement of the Figure of Merit (FoM) that we
introduced in a previous paper. The FoM describes the effectiveness
of the frequency doubling materials for ultrashort light
pulse modulators via second-order cascaded effects.
In the present work, as an input pulse we use a temporal
Gaussian pulse so that our perturbative method allows an
analytical expression even for the output pulse field after
the second pass inside the crystal. For the first time
together with the completely analytical expression for
the second pass, we report also the exact numerical coefficients
for the peak phase modulation. With the FoM it is possible
to choose the more appropriate nonlinear material and the
use of the cascaded interaction process. Finally, we present
for the first time the FoM dependence from the wavelength
in the interval 0.5–1 μm, and to a table already
shown we added more nonlinear materials
Modeling the thermal response of the retina during Indocyanine Green-assisted peeling of the internal limiting membrane
Previous works and surgical practices had shown that Indocyanine Green (ICG)-assisted peeling of the internal limiting membrane (ILM) in macular hole surgery may cause retinal damage. Different hypothesis were proposed in order to explain the induced damage. In this study the possibility of heat damage to the retina is investigated.
High efficiency laser action of 1% at. Yb 3+ :Sc 2 O 3 ceramic
We report the spectroscopic characteristics and the laser performances of a low-doped 1% at. Yb:Sc(2)O(3) ceramic sample. Under end- pumping at 933 nm and 968 nm in quasi-CW mode, at 1040.5 nm the laser delivers a maximum output power of 4.3 W and 1.77 W, respectively with a corresponding slope efficiency of 74% and 80%, which are, to the best of our knowledge, the highest value reported in literature for ceramics. We explored the tuning range of the sample, which spans from 1005 nm to 1050.5 nm, and finally we characterized the low losses tunable cavity at 1032 nm
Tunability enhancement of Yb:YLF based laser.
We present a comprehensive characterization of a laser, based on a high-quality heavily doped Yb:YLF crystal. The analysis includes the comparison of the laser efficiency in respect of the absorbed pump for both pi and sigma-polarization. In particular, for the tunable laser, we report an enhancement of the tuning range obtained by adapting the output coupler transmission in respect of the lasing wavelength. The experimental results obtained for various output coupling have also been compared with a numerical model in order to give information for a further enlargement of the tuning range
Effects of the excitation density on the laser output of two differently doped Yb:YAG ceramics
We report the behavior of two Yb(3+) doped ceramics (i.e. 10% at. and 20% at.) under quasi-continuous wave laser pumping. Two different behaviors are found depending on the density of Yb(3+) in the excited level. Experimental results show that at low population inversion density, the maximum output power and the efficiency are almost independent on the doping concentration. In particular, an output power as high as 8.9 W with a corresponding slope efficiency of 52% with respect to the injected pump power was reached with the 20% at. sample. Conversely, at high population inversion densities, the 20% doped sample shows a sudden decrease of the laser output for increasing pump power, due to the onset of a nonlinear loss mechanism. Finally, we report a comparison of the experimental results with numerical simulations for the evaluation of the inversion density and of the temperature distribution
Experimental evidence of a nonlinear loss mechanism in highly doped Yb:LuAG crystal
We report a rigorous study of the spectroscopic, laser and thermal properties of a 10at.% and a 15at.% Yb:LuAG crystals. A loss mechanism is observed in the medium with the highest doping, pumped at 936 nm and 968 nm, as a sharp and dramatic decrease of the laser output power is measured at higher excitation densities. The nonlinearity of the loss mechanism is confirmed by the fluorescence data and by the thermal lens. In particular, the dioptric power of the thermal lens acquired at different pumping levels shows a strong deviation of the expected linear trend. Here we report the influence of both the concentration and the ion excitation density of Yb3+ on the output powers, the slope efficiencies and the thresholds. Conversely excellent results are achieved with the 10at.%, which does not show any loss mechanism as at 1046 nm it delivers 11.8 W with a slope efficiency of eta(s) = 82%, which is, to the best of our knowledge, the highest value reported in literature for this material. (C) 2014 Optical Society of Americ
Spectroscopy and CW first laser operation of Yb-doped Gd_3(Al_05Ga_05)_5O_12 crystal
We present the spectroscopic characterization and laser operation of a 2%at. Yb doped Gd3(Al0.5Ga0.5)5O12 (Yb:GAGG) crystal, grown with the Czochralski method. We determined the absorption and the emission spectrum, the upper level lifetime, and the thermal conductivity. The internal disordered structure determines a significant broadening of the emission band (12.1 nm FWHM) with respect to the parent composition Yb:GGG (8 nm FWHM). The laser performances were evaluated on an end pumped cavity, using a CW semiconductor laser as the pump source. We obtained a maximum slope efficiency of 60.8% and an optical to optical efficiency of 46.0%, with a maximum output power of 4 W, limited only by the available pump power. The tuning range extends from 995 nm to 1050 nm. To our knowledge this is the first spectroscopic investigation and the first assessment of the laser performance of an Yb:GAGG crystal with this composition (i.e. Al/Ga balance = 0.5/0.5)
High efficiency room temperature laser emission in heavily doped Yb:YLF
We report the tunable, CW and quasi CW laser operation at room temperature of an highly doped (30% at.) Yb:YLF crystal longitudinally pumped by a fiber coupled laser diode array. The CW output power is 1.15 W vs. an absorbed pump power of 6 W, with a slope efficiency of 31%. In quasi-CW operation (20% duty factor @10 Hz) an output power of 4 W with an absorbed power of 9.5 W, and a slope efficiency of 62.8% were obtained. The tuning range spans from 1022 to 1075 nm. To our knowledge, these are among the best experimental results obtained at room temperature with Yb doped YLF
A fluorescence LIDAR sensor for hyper-spectral time-resolved remote sensing and mapping
In this work we present a LIDAR sensor devised for the acquisition of time resolved laser induced fluorescence spectra. The gating time for the acquisition of the fluorescence spectra can be sequentially delayed in order to achieve fluorescence data that are resolved both in the spectral and temporal domains. The sensor can provide sub-nanometric spectral resolution and nanosecond time resolution. The sensor has also imaging capabilities by means of a computer-controlled motorized steering mirror featuring a biaxial angular scanning with 200 mu radiant angular resolution. The measurement can be repeated for each point of a geometric grid in order to collect a hyper-spectral time-resolved map of an extended target. (C)2013 Optical Society of Americ
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