In this work we present analysis and comparison of two basic operating schemes for praseodymium-doped up-conversion
fiber laser. Single and double wavelength pumped systems were considered, taking into account pumping efficiency and
pump power required for population inversion build-up. Time-dependent rate equation models have been developed for
single and double doped systems, which allow detailed discussion and optimization of pumping parameters. Performed
initial numerical simulations confirm usefulness of model for purposes of up-conversion fiber lasers analysis and design.
An analysis of the spectroscopic properties of trivalent erbium doped Yb3Al5O12 (YbAG) garnet is presented. In this
work, the authors focused attention on the up-conversion processes leading to the short wavelength emission from the
2G9/2, 4S3/2 and 4F9/2 excited states of Er3+ ions. The strong interaction between Yb3+ and Er3+ ions, responsible for the
infra-red (940 nm) induced visible emissions in the 415, 550 and 670 nm range, were observed.
The main concept of molecular computing depends on DNA self-assembly abilities and on modifying DNA with the help of enzymes during genetic operations. In the typical DNA computing a sequence of operations executed on DNA strings in parallel is called an algorithm, which is also determined by a model of DNA strings. This methodology is similar to the soft hardware specialized architecture driven here by heating, cooling and enzymes, especially polymerases used for copying strings. As it is described in this paper the polymerase Taq properties are changed by modifying its DNA sequence in such a way that polymerase side activities together with peptide chains, responsible for destroying amplified strings, are cut off. Thus, it introduces the next level of molecular computing. The genetic operation execution succession and the given molecule model with designed nucleotide sequences produce computation results and additionally they modify enzymes, which directly influence on the computation process. The information flow begins to circulate. Additionally, such optimized enzymes are more suitable for nanoconstruction, because they have only desired characteristics. The experiment was proposed to confirm the possibilities of the suggested implementation.
In this work we present our theoretical investigations on optimization of double doped up-conversion fiber laser, operating in the visible part of spectrum. The developed mathematical model, based on measured spectroscopic parameters, enables analysis of influences of the active fiber and resonator parameters on the threshold and above-threshold laser characteristics. In particular, we discuss the behavior of output power versus the pumping power and mirror reflectances for the basic optical transitions in praseodymium ion, corresponding to the lasing in red, green and blue range.
In this work we focus on an analysis and a comparison of different, both multi-photon and multi-ion excitation mechanisms which can be used for pumping of a short wavelength neodymium doped ZBLAN fiber laser. Spectroscopic properties of Nd:ZBLAN examined under various excitation conditions enabled identification of the involved processes. Rate equation based models have been developed and employed to compare the efficiency of main excitation schemes, giving a good starting point for further optimization and development of Nd:ZBLAN up-conversion fiber laser.
Problems of ultra-violet wavelengths generation in rare-earth doped crystals and glasses are discussed. Examples of UV interconfigurational transitions of praseodymium (Pr3+) ion in different hosts are presented and discussed and UV intraconfigurational transitions of holmium (Ho3+) ion in ZBLAN glass optical fiber after upconversion pumping are reported.
This paper describes efforts taken in Institute of Applied Physics and Institute of Electronic Materials Technology to obtain several single crystals from borate family, namely, CsLiB6)10, Ca4GdO(BO3)3, Li2B4O7, (beta) -BaB2O4, and Yal3(BO3)4, pure and doped with several ions. The main goal of this investigation was to develop technology of these new nonlinear optical materials to create possibility of their applications in higher harmonics generators and self- frequency doubling lasers. Depending on such properties of crystallized borate materials as incongruent melting or high temperature phase transitions, Czochralski technique or high temperature solution growth technique were used. The main aspects of crystallization of these materials as well as their optical properties are discussed.
Rare-earth doped SrLaGa3O7 single crystal are promising laser materials. Also crystal doped with Ho3+ ions could be used as efficient laser in visible and near IR regions. Laser materials, generating in visible and IR regions, can be used for optical data recording in micro photolithography and in medicine. SrLaGa3O7 single crystal doped with 0.3, 1.5 and 2 at percent of Ho3+, respectively were grown by the Czochralski method with use of iridium crucible and after heater. According to EPMA measurements distribution coefficient of Ho3+ in SrLaGa3O7 was estimated to be k approximately equals 0.22. Optical absorption spectra in visible and IR regions were measured at 300K and 12K respectively. Optical quality of single crystals was checked by the use of computerized imaging spectropolarimeter and polariscopic measurements. Temperature dependence of capacitance and conductivity for different dopant concentrations were also measured.
In this communication we report initial results of studies on x-ray and VUV excited luminescence of YAP and YAG crystals activated with Pr3+ and YAP activated with Ce3+. Excitation and luminescence spectra of Pr3+ and Ce3+ d-f and Pr3+ f-f emissions and luminescence time profiles under pulsed synchrotron excitation are presented and analyzed in order to identify and characterize various host-to-ion energy transfer channels. The results support the notion that direct and trap mediated capture and recombination of holes and electrons via Pr3+ or Ce3+ ions provide the dominant mechanism of radio luminescence production in both YAP and YAG crystals.
Liquid phase epitaxy (LPE) is a suitable technique to produce diode laser-pumped solid state lasers with a planar waveguide structure. The thin films of Nd3+, Ga3+ and Lu3+ doped YAG have been grown form a supercooled molten garnet-flux high temperature solution on undoped YAG substrates by the standard LPE dipping technique. The emission spectra and fluorescence lifetimes have been measured for Nd:YAG layers with different concentration of Nd3+ ions. Additionally, the films were investigated versus concentration of neodymium, gallium and lutetium using ESR, x-ray diffraction and micro interferometric techniques. According to above measurements it can be concluded that the obtained epitaxial structures are of good quality.
The effect of the excess quantum noise on statistical properties of light generated by circular grating DFB lasers is discussed. The semiclassical approach based on the Fokker-Planck equation taking into account mode nonorthogonality, the mean laser intensity, the intensity fluctuations and the laser linewidth are obtained.
In this paper we present the systematic numerical studies of nonlinear operation of planar waveguide DBR/DFB lasers with circular grating. An approximate formula relating small signal gain to the output power and the parameters of the structure characteristics for this kind of laser is derived. Laser characteristics obtained revealing gain saturation effects can be used for design optimal structure providing maximal output power for the given pumping rate of the laser medium.
THe spectroscopic properties of trivalent praseodymium doped Be2La2O5 crystals have been investigated at various temperatures. The absorption, emission, excitation and fluorescence lifetime measurements for a sample containing 1 atomic percent of activator have been performed and discussed. The Judd-Ofelt theory has been applied to obtain (Omega) i intensity parameters.
Dysprosium doped inorganic glasses and crystals are reviewed with special emphasis on applications in lasers and optical fiber amplifiers. The results of spectroscopic studies of Dy3+ doped LiNbO3 and SrLaGa3O7 crystals are presented. Absorption, emission, excitation and lifetime measurements have been performed and discussed in the framework of Judd-Ofelt approach. The stimulated emission cross sections of the strongest transitions of Dy3+ ion have been estimated.
An approximate model of light generation in planar waveguide dielectric lasers with Fabry-Perot as well as distributed feedback lasers is presented. In particular the threshold analysis based on the spectral shape of the emission and absorption cross-section of the active medium is developed, which allows us to predict the threshold gain as well as the oscillation wavelength. Moreover, an approximate expression relating the small signal gain to the output power and characteristic parameters of the laser system is derived. It is used for design optimal planar laser structure (i.e., to calculate optical feedback and optimal thin film thickness) providing the maximal power efficiency. Also the dynamic behavior of the planar waveguide laser is discussed. Especially, the influence of the real system parameters on the relaxation oscillations and modulation bandwidth is analyzed. It is shown that the compromise between the optimal power efficiency and maximal modulation bandwidth is required. Furthermore the statistical properties of the generated light are investigated. In particular the effect of the characteristic parameters of the laser structure on the mean laser intensity, variation of the intensity fluctuation and correlation functions of the mode amplitude (which determines laser linewidth), and of the mode intensity fluctuation.
In this paper the basic problems related to active waveguide fabrication, characterization and properties are discussed. We also report the spectroscopic properties of the Er3+:YAG/YAG epitaxial thin films obtained in ITME Laboratory in Warsaw.
Excitation-mission spectra have been measured for Pr3+, Ce3+, Nd3+ and Eu3+ doped YAP, YAG, and SLGO crystals in room temperature. Results of additional absorption measurements and changes in a luminescence after gamma irradiation with dose up to 105 Gy and energy of 2.5 MeV are also presented.
Lithium niobate crystals doped with Pr3+ or Yb3+, as well as double doped with Yb3+ and Pr3+ ions were pulled by the Czochralski method. The doping concentration spread distributions were measured for each ion by the electron microprobe. The optical homogeneity of crystals was investigated using the conoscopic and polarimetric techniques. The absorption characteristics were also investigated. In the absorption spectra a careful attention has been paid to the peak associated with OH group, since from this one can conclude on the location of the doping ions in the crystal lattice.
Single crystals of SrLaGa3O7 doped with 0.5 and 1 at.% praseodymium were grown by the Czochralski technique. A heating system with good thermal insulation and afterheater were applied in order to achieve appropriate radial and axial temperature gradients in the crystallization chamber. Low temperature gradients and flat crystal-melt interface could provide good optical quality crystals free of internal stresses. All single crystals were grown in  direction. The pulling rate was 1.5 - 3 mm/h and the rotation rate 50 rpm. The composition and dopant's distribution in crystals were checked by x-ray microprobe. The obtained crystals up to 25 mm in diameter and up to 80 mm in length were of good quality and the dopant's distribution was uniform. The doped crystals were investigated for their spectral an lasing properties. Absorption spectra in range of 180 - 8000 nm were measured, then laser rods were cut out and their generation properties were evaluated.
Lithium niobate crystals doped with Dy3+ ions were grown by the Czochralski method. The doping concentrations were 0.3, 1, and 1.7 at.%, respectively. The dopant distribution was measured by the electron microprobe 'JOEL-JXA 50 A'-type device, and from these measurements the segregation coefficient has been found to be close to unity (k approximately equals 0.8). Optical homogeneity of crystals was investigated by the conoscopic and polarimetric methods. For the Z-optical axis direction it was found that the maximum residual birefringence (not exceeding 1.5 multiplied by 10-4), involved by residual stresses, occurred at the perimeters of the crystals, and the remaining crystalline areas were almost entirely free from excessive stresses. The absorption characteristics in the wavelength range of 200 - 6000 nm were measured. The photoluminescence characteristics were also measured in the visible part of the spectrum. It has been found that an important feature associated with luminescence of the Dy3+ in LiNbO3 is its high intensity and long decay time. From this it can be concluded that LiNbO3:Dy3+ is particularly well suited for visible lasers.
Growth of Cr4+:YAG crystals as a relatively new laser material and their spectroscopic properties are presented. The possibilities of using these crystals for manufacturing of passive Q-switch modulators are pointed out.
In this lecture several topics relating to the short wavelength solid state lasers are discussed, these include: self doubling crystals, tunable UV and visible lasers, mechanisms of upconversion excitation, upconversion lasing in bulk materials and optical fibers.
Ultra violet and blue wavelengths emission has been observed and studied in Tm3+ doped YAG crystals. Laser, selectively excited fluorescence from 1I6, 1D2 and 1G4 manifolds of Tm3+ ions was observed at cryogenic temperature. These results, together with the decay dynamics and upconversion fluorescence studies, were considered against the possibility of a blue laser.
An approximate analysis of the relaxation oscillations in Fabry Perot laser cavities is presented. A linear smallsignal perturbation solution of the coupled laser rate equations is generalized by including transverse1 as well longitudinal field dependence2. By the threshold field approximation3 we obtain an expression relating the frequency 0 and damping rate X of the relaxation oscillations to the laser parameters such as steadystate output power P0/Pq normaliezed to the saturation power P distributed losses a L'' poin losses at the mirrors a1 and a arbitrary relectivities o the mirrors r1 and r2 spontaneous liftime ''r of the active medium and geometry o the resonator. 2. THEORY The couppled laser rate equations for single mode can be written in the following form dN I(r) N N dQ I(r) N Q --- ---- (1) dt I ''r #r dt I -r 5 S Q where N denotes the inversion density I (r) describes the total intensity of the nmth laser mode in the cavity I is the saturation in tensity p is the exatation rate Q denotes the number of the photons in the nmth laser mode and ''r is the cavity lifetime. An approximate expressions for the spatial dependence of the electric fields for the forward and backward amplitudes of the nmth laser mode in our approach can be written as R AUR(t) f(x e''TZ S A(r) f(x