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ABSTRACT: We report the spectroscopic characteristics and the laser performances of a low-doped 1% at. Yb:Sc<sub>2</sub>O<sub>3</sub> 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.
Optics Express 09/2012; 20(20):22134-42. · 3.59 Impact Factor
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ABSTRACT: We report the first oscillation achieved on 1 at. % Yb-doped Sc2O3 and Lu2O3 ceramics under quasi-CW pumping at 968 nm. With Sc2O3 we measured a maximum output power of 2.2 W with a slope efficiency of 59% at 1040.5 nm. Comparable results are obtained with Lu2O3 at 1032.5 nm, i.e., 1.8 W with a corresponding slope of 45%, while at 1078 nm we measured 1.5 W with 34% of slope efficiency. Finally, we present the range of tunability, which exceeds 41 nm for both samples. To the best of our knowledge, these are the first measurements reported in literature either in terms of laser emission or continuous tunability range achieved with 1 at. % doping level.
Optics Letters 11/2011; 36(21):4284-6. · 3.40 Impact Factor
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ABSTRACT: A new computational procedure to resolve the contribution of Photosystem I (PSI) and Photosystem II (PSII) to the leaf chlorophyll fluorescence emission spectra at room temperature has been developed. It is based on the Principal Component Analysis (PCA) of the leaf fluorescence emission spectra measured during the OI photochemical phase of fluorescence induction kinetics. During this phase, we can assume that only two spectral components are present, one of which is constant (PSI) and the other variable in intensity (PSII). Application of the PCA method to the measured fluorescence emission spectra of Ficus benjamina L. evidences that the temporal variation in the spectra can be ascribed to a single spectral component (the first principal component extracted by PCA), which can be considered to be a good approximation of the PSII fluorescence emission spectrum. The PSI fluorescence emission spectrum was deduced by difference between measured spectra and the first principal component. A single-band spectrum for the PSI fluorescence emission, peaked at about 735 nm, and a 2-band spectrum with maxima at 685 and 740 nm for the PSII were obtained. A linear combination of only these two spectral shapes produced a good fit for any measured emission spectrum of the leaf under investigation and can be used to obtain the fluorescence emission contributions of photosystems under different conditions. With the use of our approach, the dynamics of energy distribution between the two photosystems, such as state transition, can be monitored in vivo, directly at physiological temperatures. Separation of the PSI and PSII emission components can improve the understanding of the fluorescence signal changes induced by environmental factors or stress conditions on plants.
Photosynthesis Research 08/2011; 108(2-3):225-39. · 3.24 Impact Factor
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ABSTRACT: 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.
Optics Express 08/2010; 18(16):17262-72. · 3.59 Impact Factor
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ABSTRACT: 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.
Optics Express 02/2010; 18(3):2236-41. · 3.59 Impact Factor
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ABSTRACT: We present a high-power, high-efficiency and low threshold laser prototype based on doped ceramic Yb(3+):YAG. We achieved an output power of 9 W with a slope efficiency of 73% and a threshold of 1 W at 1030 nm in quasi-Continuous Wave (QCW). Moreover, we obtained an output power 7.7 W with a slope efficiency of 60% in Continuous Wave (CW). Finally, a characterization of a low losses tunable cavity for several laser wavelengths with an output power exceeding 5 W is reported.
Optics Express 12/2009; 17(25):23344-9. · 3.59 Impact Factor
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ABSTRACT: We report an extensive comparison of the laser performances of diode-pumped Yb(3+):YLF (30% at.) and Yb(3+):CaF(2) (5% at.) crystals, lasing at room-temperature and operating in two different operation mode, i.e. Continuous Wave (CW) and quasi-CW. An in-depth investigation of the crystals behavior by changing the pump power, clearly shows the crystal absorption depends on the lasing conditions. Therefore, we report an unambiguous definition of the slope efficiency calculated taken into account the real measured crystal absorption under laser action. Finally, we present a study of problems related to thermally induced losses which are expected influencing the laser performance.
Optics Express 09/2009; 17(20):18312-9. · 3.59 Impact Factor
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ABSTRACT: 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.
Optics Express 07/2007; 15(13):7994-8002. · 3.59 Impact Factor
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ABSTRACT: This article presents the design criteria, the prototype development, and application results of a low-cost four quadrants infrared (IR) detector. The detector was specifically developed as a position sensor for the alignment of low power IR laser diode beams, especially for spectroscopic applications. The detector consists of a polyvinilidene difluoride pyroelectric radiation sensor of 4×4 mm2 total surface area and of a four-channel high gain transimpedance amplifier, followed by a narrow bandwidth resonant filter for noise rejection. The overall single pixel responsivity resulted 3590 V root mean square / at 5.8 μm, and modulation frequency of 85 Hz. The beam spot centroid of a square-wave modulated laser diode emitting 85 μ was determined using an algorithm evaluating the difference signals between diagonal elements along vertical and horizontal scanning directions. An uncertainty in the centroid position of 6 μm, in both directions, was obtained, mainly limited by the digitizing resolution of the 12-bit acquisition system. © 1999 American Institute of Physics.
Review of Scientific Instruments 01/1999; 70(2):1341-1348. · 1.37 Impact Factor
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ABSTRACT: 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.
Laser and Particle Beams 12/1998; 17(01):59 - 67. · 1.62 Impact Factor
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ABSTRACT: 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 [mu]m, and to a table already
shown we added more nonlinear materials.
Laser and Particle Beams 12/1998; 17(01):109 - 117. · 1.62 Impact Factor
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ABSTRACT: HfO2/SiO2 and Al2O3/SiO2 multilayers to be employed as high reflectance end mirrors in Cerium-doped fluoride solid-state lasers were produced by radio frequency sputtering. The components were designed to have high transmittance at the pumping wavelength and high reflectance in a wavelength band corresponding to the active medium emission. A photoacoustic beam deflection technique and inspection of the irradiated area under a microscope were used to measure the laser induced damage threshold of the mirrors at the pumping wavelength. These coatings were tested in a laser cavity.
Thin Solid Films 517(5):1731-1735. · 1.89 Impact Factor
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ABSTRACT: We report the preparation and characterization of 9.8 at.% Yb3+ doped YAG polycrystalline ceramics for laser applications. Reactive sintering of commercial powders in a clean atmosphere and under high vacuum has been used to achieve the YAG phase. The selected experimental conditions for the powder treatment, shaping and sintering are described and their influence on the optical quality of the obtained samples has been discussed. Microstructural, optical and laser characterization of the ceramics have been performed. In particular the influence of the pre-sintering (calcination) and sintering cycles has been investigated by laser characterization allowing to find unexpected loss mechanisms that cannot be revealed by standard optical characterization.
Optical Materials. 33(2):205-210.
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ABSTRACT: The nonlinear absorption of benzene and toluene solutions of polydiacetylene polyDCHD-HS was measured at λ=1064 and 1500 nm by using Z-scan and picosecond pulses with a trimmed Airy beam configuration. In the data analysis, we took into account both the saturation of the open aperture Z-scan traces occurring for high values of nonlinear absorption and the possible occurrence of cross-talk effects between nonlinear refraction and multiphoton absorption. The polymer exhibits three-photon absorption at both 1064 and 1500 nm. The molecular three-photon absorption coefficient at 1064 nm was and in toluene and benzene, respectively, while at 1500 nm it was in toluene. On this basis, the optical limiting behavior of polyDCHD-HS in the near infrared range is also shown.
Optics Communications.
