共查询到20条相似文献,搜索用时 93 毫秒
1.
V. Dierolf A.B. Kutsenko A. Ostendorf W. von der Osten W. Sohler H. Suche 《Applied physics. B, Lasers and optics》2001,72(7):803-810
Starting from previous investigations in LiNbO3 bulk crystals, we studied the optical properties of Er3+ ions in Ti:LiNbO3 channel waveguides and investigated the waveguide-specific lattice environment of the Er3+ ions (“sites”) caused by the doping method used and the presence of a large number of Ti4+ ions. For that purpose the method of combined excitation–emission spectroscopy was applied for the first time to waveguides
at low temperatures. Comparing the spectroscopic results obtained for the green, red, and near-IR luminescence (λ≈550, ≈650
and ≈980 nm) under direct (450 nm), 2-step (980 nm), and 3-step (1.5 μm) laser excitation, we found several distinguishable
Er3+ sites which in terms of energy levels and relative numbers are similar to those in bulk material, but exhibit significantly
different up-conversion efficiencies and strongly inhomogeneously broadened transitions. Moreover, we were able to distinguish
isolated and cluster Er3+ sites by their characteristic excitation and emission transition energies and studied the respective excitation/relaxation
channels. The cluster sites are most efficient in the up-conversion process, especially under 3-step excitation. Using accepted
microscopic models for Er3+ and Ti4+ incorporation into the LiNbO3 crystal lattice, the site distribution and up-conversion mechanisms are elucidated and their consequences for laser applications
in different spectral regions are discussed.
Received: 16 November 2000 / Published online: 21 March 2001 相似文献
2.
I. Sokólska 《Applied physics. B, Lasers and optics》2000,71(2):157-162
LaGaO3 crystals doped with Er3+ ions were grown by the Czochralski method and their optical properties were examined. The Er3+ energy levels have been determined from the low-temperature absorption and emission spectra. The results of Judd–Ofelt analysis
are presented and compared with experimental data. The emission cross sections are determined for the 4
I
13/2→4
I
15/2 (1.55 μm) and 4
I
11/2→4
I
13/2 (2.85 μm) transitions of erbium.
Received: 6 December 1999 / Revised version: 10 February 2000 / Published online: 27 April 2000 相似文献
3.
Nonlinear absorption properties of Co2+:MgAl2O4 crystal 总被引:2,自引:0,他引:2
K.V. Yumashev I.A. Denisov N.N. Posnov P.V. Prokoshin V.P. Mikhailov 《Applied physics. B, Lasers and optics》2000,70(2):179-184
The differential absorption spectra of Co2+: MgAl2O4 (MALO) crystal were studied with a picosecond pump-probe technique under excitation of the 4A2→4T1(4P) and 4A2→4T1(4F) transitions of the tetrahedral Co2+ ion. The difference spectra of stimulated emission (SE) and excited state absorption (ESA) were derived from the measured
differential absorption spectra. The 4T1(4P)→4A2 SE band around 660 nm was observed. The ESA bands were assigned to the 4T2→4T1(4P) transition and to transitions from the thermally populated 2E(2G) excited state to doublet levels arising from the 2F free-ion level of the tetrahedrally coordinated Co2+ ion. Absorption saturation measurements were performed at 1.34 μm and 1.54 μm. Passive Q-switching of 1.34-μm Nd3+:YAlO3 and 1.54-μm Er3+:glass lasers was realized using the Co2+:MALO crystal as saturable absorber. The Q-switched laser pulses of 38 ns (110 ns) in duration and up to 2.7 mJ (10 mJ) in
energy at 1.54 μm (1.34 μm) were obtained.
Received: 3 March 1999 / Revised version: 30 June 1999 / Published online: 30 November 1999 相似文献
4.
We demonstrate the advantages of using high levels of rhodium (2000–3200 ppm) to dope barium titanate for achieving finite
absorption coefficients (0.36 cm-1), high two-beam coupling gain (11.5 cm-1), and acceptable response time (7 s) at 1.06 μm. We also report on the mass spectroscopy measurements on Rh:BaTiO3 samples indicating a small segregation coefficient for rhodium (below 0.01) and the presence of a relatively large concentration
(6000 ppm) of unintentionally added strontium.
Received: 20 November 1998 / Revised version: 25 January 1999 / Published online: 12 April 1999 相似文献
5.
4 I13/2 and 4I11/2 of erbium is measured in a fluorozirconate fiber in the wavelength range 780–840 nm. Using a pump- and probe-beam technique
and choosing the pump wavelength such that the perturbation by pump ESA is minimized in the measurement, it is possible to
determine the effective ESA cross sections, despite the fact that the excitation is distributed among two metastable levels.
The derived ESA cross sections at 793 nm of 1.4×10-21 cm2 from the 4I13/2 level and less than 0.1×10-21 cm2 from the 4I11/2 level are in reasonable agreement with former results obtained from a rate-equation simulation of the erbium 3-μm laser.
The corresponding ESA spectrum under 3-μm lasing conditions is derived. At the strongest ground-state absorption around 799 nm,
decreasing ESA from the 4I13/2 level is compensated by increasing ESA from the 4I11/2 level, i.e., ESA losses cannot be avoided when pumping around 800 nm. This result is of relevance for possible high-power
diode pumping of an erbium 3-μm double-clad fiber laser.
Received: 20 January 1998 相似文献
6.
L.E. Batay A.A. Demidovich A.N. Kuzmin A.N. Titov M. Mond S. Kück 《Applied physics. B, Lasers and optics》2002,75(4-5):457-461
A new laser medium – Yb,Tm:KY(WO4)2 – for diode pumped solid state laser applications operating around 1.9 to 2.0 μm has been investigated and the main laser
characteristics are presented. Diode pumping at 981 nm and around 805 nm was realised. For 981-nm pumping, the excitation
occurs into Yb3+ ions followed by an energy transfer to Tm3+ions. A slope efficiency of 19% was realised. For pumping around 805 nm, the excitation occurs directly into the Tm3+ ions. Here a maximum slope efficiency of 52%, an optical efficiency of 40%, and output powers of more than 1 W were realised.
Using a birefringent quartz plate as an intracavity tuning element, the tunability of the Yb,Tm:KY(WO4)2 laser in the spectral range of 1.85–2.0 μm has been demonstrated. The possibility of laser operation in a microchip cavity
configuration for this material has also been shown.
Received: 12 March 2002 / Revised version: 20 May 2002 / Published online: 25 September 2002
RID="*"
ID="*"Corresponding author. Fax: +49-531/592-4116, E-mail: stefan.kueck@ptb.de 相似文献
7.
CW laser performance of Yb and Er,Yb doped tungstates 总被引:2,自引:0,他引:2
N. V. Kuleshov A. A. Lagatsky V. G. Shcherbitsky V. P. Mikhailov E. Heumann T. Jensen A. Diening G. Huber 《Applied physics. B, Lasers and optics》1997,64(4):409-413
Room temperature cw laser action of Yb3+-doped KY(WO4)2 and KGd(WO4)2 crystals at 1.025 μm and Er, Yb : KY(WO4)2 at 1.54 μm has been demonstrated under pumping by both Ti-sapphire laser and InGaAs laser diodes. A slope efficiency of Yb-lasers
up to 78% has been obtained.
Received: 19 June 1996 相似文献
8.
T. Tsuboi 《Applied physics. B, Lasers and optics》1999,69(1):81-83
A stable, free-running LiF:F3
− and LiF:F2
− color center laser oscillation is achieved at room temperature by pumping with the 930-nm laser radiation. The LiF:F3
− laser radiation has a peak at 1100 nm and shifts from the peak wavelength of the F3
− luminescence band because of the absorption of the F3
− luminescence by the F2
− center, which co-exists with the F3
− center.
Received: 2 March 1999 / Revised version: 16 March 1999 / Published online: 12 May 1999 相似文献
9.
Dynamics of the Yb3+ to Er3+ energy transfer in LiNbO3 总被引:1,自引:0,他引:1
The energy transfer dynamics between Yb3+ and Er3+ ions in lithium niobate is investigated after ytterbium-pulsed excitation at 920 nm. The sensitisation of the LiNbO3:Er3+ system with Yb3+ ions does not modify the lifetime of the 4I13/2 erbium level (1.5-μm emission), whereas it induces a marked, concentration-dependent change in the lifetime of the 2F5/2 (Yb3+) and 4S3/2 (Er3+) multiplets (1060-nm and 550-nm emissions, respectively). The results are analysed by using the rate-equation formalism and
cross-relaxation model for the energy transfer.
Received: 15 October 1998 / Revised version: 24 November 1998 / Published online: 24 February 1999 相似文献
10.
Vijay Singh Vineet Kumar Rai S. Watanabe T. K. Gundu?Rao Isabelle Ledoux-Rak Ho-Young Kwak 《Applied Physics A: Materials Science & Processing》2010,100(4):1123-1130
YAG phosphor powders doped/codoped with Er3+/(Er3+ + Yb3+) have been synthesised by using the solution combustion method. The effect of direct pumping into the 4I11/2 level under 980 nm excitation of doped/codoped Er3+/Yb3+−Er3+ in Y3Al5O12 (YAG) phosphor responsible for an infrared (IR) emission peaking at ∼1.53 μm corresponding to the 4I13/2→4I15/2 transition has been studied. YAG exhibits three thermally-stimulated luminescence (TSL) peaks at around 140°C, 210°C and
445°C. Electron spin resonance (ESR) studies were carried out to identify the centres responsible for the TSL peaks. The room
temperature ESR spectrum of irradiated phosphor appears to be a superposition of two distinct centres. One of the centres
(centre I) with principal g-value 2.0176 is identified as O− ion, while centre II with an isotropic g-factor 2.0020 is assigned to an F+ centre (singly ionised oxygen vacancy). An additional defect centre is observed during thermal-annealing experiments and
this centre (assigned to F+ centre) seems to originate from an F-centre (oxygen vacancy with two electrons) and these two centres appear to correlate
with the observed high-temperature TSL peak in YAG phosphor. 相似文献
11.
M. Pollnau W. Lüthy H. P. Weber K. Krämer H. U. Güdel R. A. McFarlane 《Applied physics. B, Lasers and optics》1996,62(4):339-344
The influence of Excited-State Absorption (ESA) on the green laser transition and the overlap of Ground-State Absorption (GSA) and ESA for 970 nm upconversion pumping in erbium is investigated in Er3+ : BaY2F8 and Cs3Er2Br9. Results are compared to Er3+ : LiYF4. In Er3+: BaY2F8, a good overlap between GSA and ESA is found at 969 nm in one polarization direction. The emission cross section at 550 nm is a factor of two smaller than in LiYF4. In Cs3Er2Br9, the smaller Stark splitting of the levels shifts the wavelengths of the green emission and ESA from4
I
1 3/2 off resonance. It enhances, however, ground-state reabsorption. The emission cross section at 550 nm is comparable to LiYF4. Upconversion leads to significant green fluorescence from2
H
9/2. A significant population of the4
I
11/2 level and ESA at 970 nm are not present under 800 nm pumping. 相似文献
12.
C.J. da Silva M.T. de Araujo E.A. Gouveia A.S. Gouveia-Neto 《Applied physics. B, Lasers and optics》2000,70(2):185-188
The temperature effect upon infrared-to-visible frequency upconversion fluorescence emission in Yb3+-sensitized Er3+-doped germanosilicate optical fibers excited with cw radiation at 1.064 μm is investigated. The experimental results revealed
an eightfold enhancement in the visible upconversion emission intensity as the fiber temperature was increased from 17 °C
to 180 °C. The fluorescence emission enhancement is attributed to the temperature-dependent multiphonon-assisted anti-Stokes
excitation process of the ytterbium sensitizer. A theoretical approach that takes into account a sensitizer absorption cross-section,
which depends on the phonon occupation number, has proven to agree very well with the experimental data
Received: 6 April 1999 / Revised version: 27 August 1999 / Published online: 27 January 2000 相似文献
13.
Fluorescence at 3 m and 545 nm in a YAlO3:Er (30 at.%) crystal has been measured as a function of wavelength, intensity and polarization for the excitation in the 800 nm wavelength region. Emission at 545 nm is an indicator of losses for 3 m emission due to excited-state absorption and upconversion. The experimental results allow to determine the excitation mechanisms, the upconversion coefficient W
2 and the optimum pump wavelengths to generate 3 m radiation. 相似文献
14.
G. Franzò V. Vinciguerra F. Priolo 《Applied Physics A: Materials Science & Processing》1999,69(1):3-12
A detailed investigation on the excitation mechanisms of rare-earth (RE) ions introduced in Si nanocrystals (nc) is reported.
Silicon nanocrystals were produced by high-dose 80-keV Si implantation in thermally grown SiO2 followed by 1100 °C annealing for 1 h. Subsequently some of the samples were implanted by 300-keV Er, Yb, Nd, or Tm at doses
in the range 2×1012–3×1015 /cm2. The energy was chosen in such a way to locate the RE ions at the same depth where nanocrystals are. Finally an annealing
at 900 °C for 5 min was performed in order to eliminate the implantation damage. These samples show intense room-temperature
luminescence due to internal 4f shell transitions within the RE ions. For instance, luminescence at 1.54 μm and 0.98 μm is
observed in Er-doped nc, at 0.98 μm in Yb-doped nc, at 0.92 μm in nc and two lines at 0.78 μm and 1.65 μm in Tm-doped nc.
Furthermore, these signals are much more intense than those observed when RE ions are introduced in pure SiO2 in the absence of nanocrystals, demonstrating the important role of nanocrystals in efficiently exciting the REs. It is shown
that the intense nc-related luminescence at around 0.85 μm decreases with increasing RE concentration and the energy is preferentially
transferred from excitons in the nc to the RE ions which, subsequently, emit radiatively. The exact mechanism of energy transfer
has been studied in detail by excitation spectroscopy measurements and time-resolved photoluminescence. On the basis of the
obtained results a plausible phenomenological model for the energy transfer mechanism emerges. The pumping laser generates
excitons within the Si nanocrystals. Excitons confined in the nc can either give their energy to an intrinsic luminescent
center emitting at around 0.85 μm nor pass this energy to the RE 4f shell, thus exciting the ion. The shape of the luminescence
spectra suggests that excited rare-earth ions are not incorporated within the nanocrystals and the energy is transferred at
a distance while they are embedded within SiO2. Rare-earth excitation can quantitatively be described by an effective cross section σeff taking into account all the intermediate steps leading to excitation. We have directly measured σeff for Er in Si nc obtaining a value of ≈2×10−17 cm2. This value is much higher than the cross section for excitation through direct photon absorption (8×10−21 cm2) demonstrating that this process is extremely efficient. Furthermore, the non-radiative decay processes typically limiting
rare-earth luminescence in Si (namely back-transfer and Auger) are demonstrated to be absent in Si nc further improving the
overall efficiency of the process. These data are reported and their implications.
Received: 9 April 1999 / Accepted: 10 April 1999 / Published online: 2 June 1999 相似文献
15.
N.F. Zhuang X.L. Hu S.K. Gao B. Zhao J.L. Chen J.Z. Chen 《Applied physics. B, Lasers and optics》2006,82(4):607-613
GdVO4 single crystal co-doped with Yb3+ and Er3+ was grown by the Czochralski method. The X-ray powder diffraction pattern of Yb,Er:GdVO4 crystal confirms that the as-grown crystal is isostructural with pure GdVO4 crystal. Its polarized absorption spectra and non-polarized fluorescence spectra were measured at room temperature. The absorption band at 984 nm for π-polarization has an FWHM of about 36 nm, which is favorable for InGaAs LD laser pumping. The spectrum properties of Er3+ in Yb,Er:GdVO4 crystal were investigated based on Judd–Ofelt theory. There is strong energy transfer from Yb3+ to Er3+ in this crystal. When excited with 980 nm radiation, this crystal emitted strong fluorescence at about 1529 nm and 552.5 nm. The total energy transfer rate and efficiency from Yb3+ to Er3+ is 3.33 ms-1 and 67%, respectively. The energy transfer between Er3+ and Yb3+ ions is a multistep transfer process, and was investigated based on a random-walk model. The investigation result shows that there is strong cooperative-sensitization effect from Yb3+ to Er3+, which is the main upconversion energy-transfer process in this crystal. PACS 42.70.Hj; 81.10.Fq; 42.55.Rz 相似文献
16.
M. Stanislawki J. Meister T. Mitra M.M. Ivanenko K. Zanger P. Hering 《Applied physics. B, Lasers and optics》2001,72(1):115-120
The Er:YAG and the CO2 laser are competitors in the field of hard tissue ablation. The use of Er:YAG lasers (2.94 μm, pulse length
L of 100 to 200 μs) show smaller areas of thermal defects then ‘‘superpulsed’’ CO2 lasers with pulse lengths of approximately 100 μs. Only the development of a Q-switched CO2 laser (9.6 μm, τL=250 ns) allowed for similar results. In this paper new results for the Er:YAG and the Q-switched CO2 laser under the influence of water spray will be presented. Several parameters are of special interest for these investigations:
the specific ablation energy, which shows a minimum for the CO2 laser at an energy density of 9 J/cm 2 and a broad shallow minimum in the range of 10 to 70 J/cm2 for the Er:YAG laser, and comparison of the cut-shape and depth. Surface effects and cutting velocity are discussed based
on SEM pictures.
Received: 19 July 2000 / Revised version: 1 November 2000 / Published online: 30 November 2000 相似文献
17.
The Er3+ -Yb3+ codoped in Li2O content tungsten -tellurite (TWL) transparent glasses are synthesized and measured the absorption, Raman and upconversion
luminescence (UPL) spectra. At room temperature intense green emission peak at 560 nm ( 4S3/2→4I15/2) and red emission peak at 670 nm ( 4F9/2→4I15/2) of Er3+ observed even at minimum 86 mW pumping power of infrared 980 nm excitation. For structure of the TWL glass, Raman spectrum
result revealed that an important role of WO3 in the formation of glass network linkage with Li2O. Under this influence estimated lifetime of the 4I11/2 of Er3+ was 1.89 μs and due to lower phonon energy of the glass produce strong upconversion signal. The effect of Er2O3 concentration on emission intensity result indicated that green emission intensity initially increase in compare to red emission.
Under the 980 nm pump power variation measured the relatively increases the red emission to the green emission intensity and
analyze the possible upconversion mechanism and process. 相似文献
18.
A thin-disc Nd:GdVO4 laser in multi-pass pumping scheme was developed. Continuous-wave output power of 13.9 W at 1.06 μm for an absorbed power at 808 nm of 22 W was demonstrated from a 250-μm thick, 0.5-at.% Nd:GdVO4 in a 4-pass pumping; the slope efficiency in absorbed power was 0.65, or 0.47 in input power. Output performances were also investigated under diode laser pumping at 879 nm, directly into the emitting 4F3/2 level: maximum power of 3.6 W was obtained at 6.2 W of absorbed power with 0.69 slope efficiency. Compared with pumping at 808 nm, into the highly absorbing 4F5/2 level, improvements of laser parameter in absorbed power (increase of slope efficiency, decrease of threshold) were obtained, showing the advantages of the pumping into the emitting level. However, the laser performances expressed vs. the incident power were modest owing to the low absorption efficiency at 879 nm. Thus, increased number of passes of the medium would be necessary in order to match the performances in input power obtained under 808-nm pumping. 相似文献
19.
Xiaodong Xu Pingxin Song Guoqing Zhou Jun Xu Peizhen Deng 《Solid State Communications》2004,129(11):717-720
Cr4+:YbAG (Cr4+:Yb3Al5O12) crystal with a size up to Φ24 mm×30 mm was grown by the Czochralski method. In the absorption spectrum, there are two absorption bands at 939 and 969 nm, respectively, which are suitable for InGaAs diode laser pumping, and there is an absorption band at 1030 nm, which is suitable for passive Q-switched laser output at 1.03 μm. A broad emission spectrum from 970 to 1100 nm was exhibited from 940 nm wavelength pumping. This crystal is promising as a self-Q-switched laser crystal used for compact, efficient, highly stable, passive self-Q-switched thin chip solid-state lasers. 相似文献
20.
N. Pavel V. Lupei J. Saikawa T. Taira H. Kan 《Applied physics. B, Lasers and optics》2006,82(4):599-605
Laser emission in the 0.94-, 1.06- and 1.34-micron ranges in diluted and concentrated Nd:YAG crystals longitudinally pumped by a 885-nm diode laser on the 4
I
9/2→4
F
3/2 transition is investigated. Continuous-wave operation at watt level in all these wavelength ranges is demonstrated with a 1.0-at. % Nd:YAG crystal; however, the laser performance is impeded by the low pump absorption efficiency. Improved output power and overall efficiency were obtained with a highly doped 2.5-at. % Nd:YAG crystal: 5.5 W at 1.06 μm and 3.8 W at 1.34 μm with 0.38 and 0.26 efficiencies, respectively. Comparative results with traditional pumping at 809 nm into the highly absorbing 4
F
5/2 level are presented, showing the advantage of the direct 4
F
3/2 pumping. The influence of the lasing wavelength and of the Nd concentration on the thermal effects induced by the optical pumping in the laser material is discussed. A clear relation between the heat generated in the Nd:YAG crystals in lasing and non-lasing regimes, a function of the Nd doping, is demonstrated. PACS 42.55.Rz; 42.60.By; 42.60.Da 相似文献