We report efficient cw laser operation of laser diode pumped Pr(3+)-doped LiYF4 crystals in the visible spectral region. Using two InGaN laser diodes emitting at λ(P)=443.9?nm with maximum output power of 1?W each and a 2.9-mm-long crystal with a doping concentration of 0.5%, output powers of 938?mW, 418?mW, 384?mW, and 773?mW were achieved for the laser wavelengths 639.5?nm, 607.2?nm, 545.9?nm, and 522.6?nm, respectively. The maximum absorbed pump powers were approximately 1.5?W, resulting in slope efficiencies of 63.6%, 32.0%, 52.1%, and 61.5%, as well as electro-optical efficiencies of 9.4%, 4.2%, 3.8%, and 7.7%, respectively. Within these experiments, laser diode-pumped laser action at 545.9?nm was demonstrated for what is believed to be the first time. 相似文献
We consider a continuous time stochastic individual based model for a population structured only by an inherited vector trait and with logistic interactions. We consider its limit in a context from adaptive dynamics: the population is large, the mutations are rare and the process is viewed in the timescale of mutations. Using averaging techniques due to Kurtz (in Lecture Notes in Control and Inform. Sci., vol. 177, pp. 186–209, 1992), we give a new proof of the convergence of the individual based model to the trait substitution sequence of Metz et al. (in Trends in Ecology and Evolution 7(6), 198–202, 1992), first worked out by Dieckman and Law (in Journal of Mathematical Biology 34(5–6), 579–612, 1996) and rigorously proved by Champagnat (in Theoretical Population Biology 69, 297–321, 2006): rigging the model such that “invasion implies substitution”, we obtain in the limit a process that jumps from one population equilibrium to another when mutations occur and invade the population. 相似文献
We show experimental evidence of surface phonon scattering in the high-/spl kappa/ dielectric being the primary cause of channel electron mobility degradation. Next, we show that midgap TiN metal-gate electrode is effective in screening phonon scattering in the high-/spl kappa/ dielectric from coupling to the channel under inversion conditions, resulting in improved channel electron mobility. We then show that other metal-gate electrodes, such as the ones with n+ and p+ work functions, are also effective in improving channel mobilities to close to those of the conventional SiO/sub 2//poly-Si stack. Finally, we demonstrate this mobility degradation recovery translates directly into high drive performance on high-/spl kappa//metal-gate CMOS transistors with desirable threshold voltages. 相似文献
The singly excited functions satisfying Brillouin theorem are expressed as linear combinations of configuration-state functions for any spin and spatial symmetries (atomic or molecular) and for any reference wave function. The generality of the formulation is ensured by the use of the irreducible tensor method that can be adapted to any symmetry point group of interest. The expansion coefficients are simply written as products of fractional parentage coefficients, spin- and orbit-recoupling coefficients, and phase factors. The formalism is illustrated for some atomic (Kh) and molecular (C∞v, C3v, and Td) configurations. Group theoretical techniques are also used to correlate the Brillouin conditions within a chain of groups. 相似文献
Pamamycins are macrodiolides of polyketide origin with antibacterial activities. Their biosynthesis has been proposed to utilize succinate as a building block. However, the mechanism of succinate incorporation into a polyketide was unclear. Here, we report identification of a pamamycin biosynthesis gene cluster by aligning genomes of two pamamycin‐producing strains. This unique cluster contains polyketide synthase (PKS) genes encoding seven discrete ketosynthase (KS) enzymes and one acyl‐carrier protein (ACP)‐encoding gene. A cosmid containing the entire set of genes required for pamamycin biosynthesis was successfully expressed in a heterologous host. Genetic and biochemical studies allowed complete delineation of pamamycin biosynthesis. The pathway proceeds through 3‐oxoadipyl‐CoA, a key intermediate in the primary metabolism of the degradation of aromatic compounds. 3‐Oxoadipyl‐CoA could be used as an extender unit in polyketide assembly to facilitate the incorporation of succinate. 相似文献
The rise of semiconductor‐based pump sources such as InxGa1‐xN‐laser diodes or frequency‐doubled optically pumped semiconductor lasers with emission wavelengths in the blue encourages a revisitation of the rare‐earth ions Pr3+, Sm3+, Tb3+, Dy3+, Ho3+ and Er3+ with respect to their properties as active ions in crystalline solid‐state laser materials with direct emission in the visible spectral range. Nowadays, some of these blue‐pumped visible lasers compete with Nd3+‐lasers in terms of efficiency and direct lasing at various colors from the cyan‐blue to the deep red can be addressed in very simple and compact laser setups. This paper highlights the spectroscopic properties of suitable rare‐earth ions for visible lasing and reviews the latest progress in the field of blue‐pumped visible rare‐earth doped solid‐state lasers.