共查询到20条相似文献,搜索用时 15 毫秒
1.
A.-H. Li Z.-R. Zheng T.-Q. Lü L. Sun W.-L. Liu W.-Z. Wu 《Applied physics. B, Lasers and optics》2010,98(1):149-158
Four near-stoichiometric lithium niobate (NSLN) crystals codoped with Er3+ (1 mol%) and MgO (0, 0.5, 1.0, and 2.0 mol%) were grown from K2O-based flux in air using top seeded solution growth technique. The [Li]/[Nb] ratio, estimated from the blueshift of ultraviolet
absorption edge, is 97.2% in NSLN:Er. MgO; codoping can increase the segregation coefficient of Er3+ in NSLN:Er:MgO crystal. The photorefractive damage threshold is enhanced by three orders of magnitude for NSLN:Er codoped
with 1 mol% MgO, it coincides with the peak shift of OH− absorption spectrum from 3481 to 3535 cm−1. Judd–Ofelt theory based on absorption spectra is used to analyze the influence of MgO concentration on the Judd–Ofelt intensity
parameter, transition strength, fluorescence branching ratio, and stimulated emission cross section. From the time-resolved
emission spectra and the comparison among emission spectra, two Er3+ crystal-field sites are ascertained in NSLN:Er codoped with 2 mol% MgO, this coincides with the bimodal structure in X-ray
photoelectron spectrometry spectra. The upconversion processes under pulse excitation is proposed based on the pump energy
dependence and decay kinetics. The distribution of Er3+-clustered sites in NSLN:Er:MgO series is discussed based on the nonexponential decay curves monitored at 550 nm under two-photon
excitation. 相似文献
2.
A. N. Tuchak G. N. Gol’tsman G. Kh. Kitaeva A. N. Penin S. V. Seliverstov M. I. Finkel A. V. Shepelev P. V. Yakunin 《JETP Letters》2012,96(2):94-97
The possibility of the generation of quasi-cw terahertz radiation by the optical rectification method for broad-band Fourier unlimited nanosecond laser pulses has been experimentally demonstrated. The broadband radiation of a LiF dye-center laser is used as a pump source of a nonlinear optical oscillator. The energy efficiency of terahertz optical frequency conversion in a periodically polarized lithium niobate crystal is 4 × 10−9 at a pump power density of 7 MW/cm2. 相似文献
3.
K. C. Cossel F. Adler K. A. Bertness M. J. Thorpe J. Feng M. W. Raynor J. Ye 《Applied physics. B, Lasers and optics》2010,100(4):917-924
Cavity-enhanced direct frequency comb spectroscopy (CE-DFCS) has demonstrated powerful potential for trace-gas detection based
on its unique combination of high bandwidth, rapid data acquisition, high sensitivity, and high resolution, which is unavailable
with conventional systems. However, previous demonstrations have been limited to proof-of-principle experiments or studies
of fundamental laboratory science. Here, we present the development of CE-DFCS towards an industrial application—measuring
impurities in arsine, an important process gas used in III–V semiconductor compound manufacturing. A strongly absorbing background
gas with an extremely complex, congested, and broadband spectrum renders trace detection exceptionally difficult, but the
capabilities of CE-DFCS overcome this challenge and make it possible to identify and quantify multiple spectral lines associated
with water impurities. Further, frequency combs allow easy access to new spectral regions via efficient nonlinear optical
processes. Here, we demonstrate detection of multiple potential impurities across 1.75–1.95 μm (5710–5130 cm−1), with a single-channel detection sensitivity (simultaneously over 2000 channels) of ∼4×10−8 cm−1 Hz−1/2 in nitrogen and, specifically, an absorption sensitivity of ∼4×10−7 cm−1 Hz−1/2 for trace water doped in arsine. 相似文献
4.
De-Long Zhang Zhen Wang Ping-Rang Hua Edwin Yue-Bun Pun 《Applied Physics A: Materials Science & Processing》2010,100(4):1073-1081
Li-rich (Li-poor) vapor transport equilibration (VTE) treatments on a number of Z-cut 0.47 mm thick congruent MgO (5 mol%
in melt) : LiNbO3 crystals were carried out at 1100°C over different durations ranging in 1–172 (40–395) h. Neutron activation analysis shows
that neither Li-rich nor Li-poor VTE-induced Mg and Nb loss from the crystal occurred. The Li2O content in the crystal was measured as a function of VTE duration by the gravimetric method. The Li-rich/Li-poor VTE effects
on OH− absorption were studied in comparison with the as-grown crystal. The study shows that the Li-rich VTE results in OH− absorption band annihilation. After further oxidation treatment the band reemerges and peaks at the same wavenumber as that
of the as-grown crystal (∼3535.6 cm−1), showing that the MgO concentration in the Li-rich VTE crystal is still above the optical-damage threshold. The Li-poor
VTE causes OH− band shift to 3486.3–3491.6 cm−1, indicating that the MgO concentration in all Li-poor VTE crystals is all below the optical-damage threshold. Further successive
Li-rich VTE and oxidation treatments on the Li-poor VTE-treated crystal lead the band to shift back to 3535.6 cm−1, showing that the post Li-rich VTE brought the Li-poor VTE-treated crystal above the optical-damage threshold again. It is
found that the peaking position, band width, peaking absorption and band area of the absorption at ∼3486 cm−1 all increase monotonously with the decrease of the Li2O content arising from prolonged Li-poor VTE, and quantitative relationships to the Li2O content are established for the latter two parameters. The VTE effects on the OH− absorption are conducted with the VTE-induced OH− content alteration and charge redistribution. 相似文献
5.
J.R. Schwesyg H.A. Eggert K. Buse E. Śliwińska S. Khalil M. Kaiser K. Meerholz 《Applied physics. B, Lasers and optics》2007,89(1):15-17
Stable suspensions of iron- or copper-doped lithium niobate nanocrystals in heptane are prepared by high-energy ball milling
of iron- and copper-doped bulk crystals for 25 h. The distribution of particle sizes is determined by means of dynamic light
scattering with more than 90% of the crystals in the range of 10–25 nm. The optical absorption of the suspensions suggests
a changed environment of the dopants.
PACS 77.84.Nh; 78.67.Bf; 81.07.-b 相似文献
6.
L. Kovács M. Mazzera E. Beregi R. Capelletti 《Applied physics. B, Lasers and optics》2009,94(2):273-277
Several weak absorption bands have been observed in the optical absorption spectra of pure and rare-earth-doped YAl3(BO3)4 single crystals in the 3350– 3650 cm−1 wave number region. Two of them, peaking at about 3377 cm−1 and 3580 cm−1 in the 8 K spectra, appear in most of the samples. They are tentatively attributed to the stretching mode of OH− ions incorporated in the crystal during the growth. An additional absorption band at about 5250 cm−1 at 8 K has also been detected in almost all samples. The temperature and polarization dependences of these bands, and their
possible origin, are discussed. 相似文献
7.
L. Ciaffoni R. Grilli G. Hancock A. J. Orr-Ewing R. Peverall G. A. D. Ritchie 《Applied physics. B, Lasers and optics》2009,94(3):517-525
Diode laser technology coupled with a wavelength-conversion unit to produce mid-infrared narrow bandwidth laser light applicable
to trace-gas detection and with the potential for high-resolution spectroscopy is described. Quasi-phase-matched difference-frequency
generation (QPM-DFG) in a compact and fibre-coupled periodically poled lithium niobate (PPLN) waveguide module mixing 1063
and 1525-nm radiations has been adopted for generating 34 μW of 3.5-μm wavelength laser light. Optical detection methods,
including sensitive wavelength modulation spectroscopy and a rapid wavelength chirp technique, have been employed with a single-pass
cell to investigate methane and formaldehyde absorption profiles around 2855 cm−1, as proof of principle experiments for high sensitivity and resolution spectroscopy on atmospherically important molecules. 相似文献
8.
Light pulses of 240 fs duration and 388-nm wavelength generate in lithium niobate crystals transient absorption. The absorption changes are observed with delayed ultra-short pulses (wavelength 776 nm) and with continuous-wave light (wavelength 785 nm) over 10 decades from 400 fs up to 10 s after the pump pulse. The decay is well described by one stretched-exponential function over the entire temporal range. We attribute the absorption changes to small bound polarons because of the temporal, spectral, and polarization fingerprints. The polarons are formed in less than 400 fs after the pump illumination, ruling out that phonons with wavenumbers below 100 cm-1 are the main cause for polaron generation and indicating that the breathing mode of the oxygen octahedra is of relevance. An upper limit of the generated polaron concentration is estimated as ≈4.4×1018 cm-3 with an intensity of ≈220 GW/cm2. PACS 71.38.Ht; 78.47.+p; 77.84.Dy; 42.50.Gy; 42.70.Mp; 72.20.Jv 相似文献
9.
H. G. Demirkhanyan 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2011,46(6):274-278
Possibilities of using lithium niobate crystals, doped with ytterbium (LN:Yb3+) as materials for optical temperature sensor (OTS), are discussed. We consider both the radiative and absorptive characteristics
of the crystals, assuming that their temperature dependences are caused by the Boltzmann factor of the initial population
of Stark sublevels of the ion. It is shown that the crystals can be used as materials for OTS in the temperature range 150–400
K. 相似文献
10.
High-power distributed-feedback (DFB) lasers for the wavelength range near 940 nm (i.e. about 10,600 cm−1) were used for line-broadening measurements of individual rotational-vibrational absorption lines of water vapour at atmospheric
pressure using a minimalist set-up. The laser has a maximum output power larger than 500 mW. Over the whole power range from
threshold to maximum power, it operates in single mode operation with a tuning range of 4.7 nm, i.e. 50 cm−1, at 20°C. With an emission line-width ≤2 MHz (0.66×10−4 cm−1), the device is well suited for high-resolution spectroscopy. 相似文献
11.
We describe the application of a long-wavelength vertical-cavity surface-emitting laser (VCSEL) with extended tuning range
to the detection of benzene vapor at atmospheric pressure. A benzene absorption feature centered at 1684.24 nm was accessed
by reducing the heat sink temperature of a VCSEL designed for room-temperature operation to −55°C. This allowed us to increase
the injection current and thus to extend a single-scan tuning interval up to 46.4 cm−1 or 13.2 nm around a central wavelength of 1687.4 nm. Five absorption lines of methane in the 5903–5950 cm−1 range could be acquired within single laser scans at a repetition rate of 500 Hz. A benzene absorption feature between 5926
and 5948 cm−1 was recorded for concentration measurements at atmospheric pressure using a single-pass 1.2 m absorption cell. A 50 ppmv
mixture of CH4 in N2 was introduced into the cell along with benzene vapor to calibrate benzene concentration measurements. Benzene mixing ratios
down to ∼90 ppmv were measured using a direct absorption technique. The minimum detectable absorbance and detection limit
of benzene were estimated to be ∼10−4 and 30 ppmv, respectively. Using the wavelength modulation technique, we measured a second harmonic sensor response to benzene
vapor absorption in air at atmospheric pressure as a function of modulation index. We conclude that a low-temperature monolithic
VCSEL operating near 1684 nm can be employed in compact benzene sensors with a detection limit in the sub-ppm range. 相似文献
12.
A. C. Busacca R. L. Oliveri A. C. Cino S. Riva-Sanseverino A. Parisi G. Assanto 《Laser Physics》2007,17(6):884-888
The compatibility of low concentration (α-phase) proton exchange channel waveguides with electric field surface periodic poling of congruent lithium niobate (SPPLN) crystals has been experimentally demonstrated. With such waveguides, we obtained ultraviolet second harmonic generation (SHG) by first order quasi-phase-matching (QPM), a result made possible by the fabrication, on Z-cut LN crystals, of periodic structures with a pitch down to 750 nm. Nonlinear copropagating QPM-SHG measurements have been carried out on such structures. The pump source was a Ti:sapphire laser with a tunability range of 700–980 nm and a 40 GHz linewidth. We have measured UV continuous wave light at 390 nm by means of a lock-in amplifier and a photodiode with an enhanced response in the UV. The measured conversion efficiency was about 1% W?1 cm?2. 相似文献
13.
Single crystals of gadolinium orthosilicate Gd2SiO5 containing 0.5 at% and 5 at% of Sm3+ were grown by the Czochralski method. Optical absorption spectra, luminescence spectra and luminescence decay curves were
recorded for these systems at 10 K and at room temperature. Comparison of optical spectra recorded in polarized light revealed
that the anisotropy of this optically biaxial host affects the intensity distribution within absorption and emission bands
related to transitions between multiplets rather than the overall band intensity. It has been found that among four bands
of luminescence related to the 4G5/2→6HJ (J=5/2–11/2) transitions of Sm3+ in the visible and near infrared region the 4G5/2 →6H7/2 one has the highest intensity with a peak emission cross section of 3.54×10−21 cm2 at 601 nm for light polarized parallel to the crystallographic axis c of the crystal. The luminescence decay curve recorded
for Gd2SiO5:0.5 at% Sm3+ follows a single exponential time dependence with a lifetime 1.74 ms, in good agreement with the 4G5/2 radiative lifetime τ
rad=1.78 ms calculated in the framework of Judd-Ofelt theory. Considerably faster and non-exponential luminescence decay recorded
for Gd2SiO5:5 at% Sm3+ sample was fitted to that predicted by the Inokuti-Hirayama theory yielding the microparameter of Sm3+–Sm3+ energy transfer C
da=1.264×10−52 cm6×s−1. 相似文献
14.
Optical absorption in MnGaInS4 single crystals has been studied. Direct and indirect optical transitions are found to occur in the range of photon energies
of 2.37–2.74 eV and in the temperature range of 83–270 K. The temperature dependence of the band gap has been determined;
its temperature coefficients E
gd
and E
gi
are −5.06 × 10−4 and −5.35 × 10−4 eV/K, respectively. MnGaInS4 single crystals exhibit anisotropy in polarized light at the absorption edge; the nature of
this anisotropy is explained. 相似文献
15.
We report experimental observation of ultra-long lifetime UV-induced absorption in undoped and 5 mol.% Mg-doped congruent lithium niobate crystals between 400 nm and 2500 nm wavelength range. The saturated absorption coefficient change in undoped congruent lithium niobate was about 3 to 7 times that in Mg-doped congruent lithium niobate in the mid-infrared spectrum. The UV-illuminated LiNbO3:Mg was fully recovered in the dark after 2 days, whereas the undoped congruent LiNbO3 still exhibited nontrivial infrared absorption. We attribute the cause of the UV-induced absorption to the creation of hole-trapped intermediate states O− near lithium vacancies. 相似文献
16.
In the paper the dependence of the photorefraction (PhR) in LiNbO3 and LiNbO3−Fe (0.1 wt%, 0.3wt%) crystals on light intensity (within 1016–1023 quanta·cm−2·s−1 at wavelengths 496.5 nm and 600 nm) and temperature (in the region 100–500 K) is studied. For all the crystals the limiting
values of PhR are similar and atT=293 K Δn
sat
lim
≈3·10−3. In LiNbO3 the temperature dependence of PhR in the range 100–500 K requires to take into account at least two trapping centres. 相似文献
17.
A new phenomenon — intense luminescence of noncolored lithium fluoride (LiF) crystals excited by an electrodeless pulsed microwave
discharge at the prebreakdown stage of development — is observed. This luminescence consists of the luminescence of short-lived
aggregate F2 and F
3
+
color centers at room temperature. It is shown that the density of short-lived color centers induced in the surface layer
of LiF crystals by a microsecond microwave discharge reaches values of ∼1019−1020 cm−3.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 3, 163–167 (10 August 1997) 相似文献
18.
M. Jubera J. Villarroel A. García-Caba?es M. Carrascosa J. Olivares F. Agullo-López A. Méndez J. B. Ramiro 《Applied physics. B, Lasers and optics》2012,107(1):157-162
The propagation losses (PL) of lithium niobate optical planar waveguides fabricated by swift heavy-ion irradiation (SHI),
an alternative to conventional ion implantation, have been investigated and optimized. For waveguide fabrication, congruently
melting LiNbO3 substrates were irradiated with F ions at 20 MeV or 30 MeV and fluences in the range 1013–1014 cm−2. The influence of the temperature and time of post-irradiation annealing treatments has been systematically studied. Optimum
propagation losses lower than 0.5 dB/cm have been obtained for both TE and TM modes, after a two-stage annealing treatment
at 350 and 375∘C. Possible loss mechanisms are discussed. 相似文献
19.
P. Galinetto M. Marinone D. Grando G. Samoggia F. Caccavale A. Morbiato M. Musolino 《Optics and Lasers in Engineering》2007,45(3):380
In this work we report on micro-Raman analysis on lithium niobate (LN) substrates in order to study the compositional homogeneity of the crystals and to clear up the effects of etching and polishing processes on the surface of wafers and crystals.The fact that the linewidth of some Raman modes scale with the composition of LN crystals, together with the use of a confocal microscope, allowed a three-dimensional determination of the sample stoichiometry and of the crystalline quality. This local tool can supply additional information, which can be complementary to the electro-optic coefficients, carefully measured as well in order to check functional parameters.Raman spectra from buried regions were obtained on as-grown, etched and polished crystals and wafers. The depth profile of the peak energy and the linewidth of the Raman mode at 872 cm−1 indicate that mechanical processing of surfaces causes, in some cases, structural modifications till a depth of 15 μm. 相似文献
20.
We present detailed investigations of a femtosecond green-pumped optical parametric oscillator (OPO) based on lithium triborate.
As pump source, a frequency-doubled Yb-fiber laser-amplifier system is used. The OPO generates signal pulses tunable over
a spectral range from 780 to 940 nm and idler pulses tunable from 1630 to 1190 nm. More than 250 mW are generated in the signal
beam and more than 300 mW in the idler beam. Without dispersion compensation chirped signal pulses with a pulse duration between
100 and 250 fs are measured. Using this system for coherent anti-Stokes Raman scattering spectroscopy, vibrational resonances
between 1110 and 6760 cm−1 can be excited. Due to the chirped pulses, a spectral resolution of 100 cm−1 is achieved, which is 2.5 times higher compared to an excitation with time-bandwidth limited pulses. 相似文献