Double Resonance Nanolaser based on Coupled Slit-hole Resonator Structures

This work investigates a kind of metallic magnetic cavity based on slit-hole resonators (SHRs). Two orthogonal hybrid magnetic resonance modes of the cavity with a large spatial overlap are predesigned at the wavelengths of 980 nm and 1550 nm. The Yb-Er co-doped material serving as a gain medium is set in the cavity; this enables the resonator to have high optical activity. The numerical result shows that the strong lasing at 1550 nm may be achieved when the cavity array is pumped at 980 nm. This double resonance nanolaser array has potential applications in future optical devices and quantum information techniques.Comment: 11 pages, 3 figures, http://www.dsl.nju.edu/mp

Diode-pumped Nd : YAG lasers for generation of blue light by frequency doubling

Quasi-three-level lasers in neodymium-doped crystals such asNd:YAG, Nd:YLF and Nd:YVO4have received a great deal of interest becausethey allow generation of blue light by frequency doubling. Forsolid-state blue laser sources, there exist numerousapplications as in high-density optical data storage, colourdisplays, submarine communication and biologicalapplications. Efficient lasing on quasi-three-level transitions at 900-950nm in Nd-doped crystals is considerably more difficult toachieve than on the stronger four-level transitions at 1-1.1µm. The problems with these quasi-three-level transitionsare a significant reabsorption loss at room temperature and avery small stimulated emission cross section. This requires atight focusing of the pump light, which is achieved byend-pumping with high-intensity diode lasers. n this thesis, progress in diode-pumped solid-state lasersfor generation of blue light by frequency doubling has beenmade. Nd:YAG lasers at the 946 nm transition have been builtand a maximum power of 7.0 W was obtained. By inserting a thinquartz etalon in the laser cavity, the938.5 nm laser linecould be selected. An output power of 3.9 W was obtained. By using nonlinear crystals, frequency-doubling of laserlight at both 946 nm and 938.5 nm by second harmonic generation(SHG) was achieved. SHG of the 946 nm transition gives bluelight at 473 nm. Efficient generation of blue light has beenachieved in periodically poled KTP, both in single-passextra-cavity and intracavity configurations. More than 0.5 Wwas obtained at 473 nm by intracavity doubling. Intracavity SHGof the 938.5 nm transition gave slightly more than 200 mW at469 nm. The influence of energy-transfer upconversion (ETU) is adetrimental effect in Nd-doped lasers. An analytical model hasbeen developed for continuous wave quasi-three-level lasersincluding the influence of ETU. The results of the generaloutput modelling are applied to a laser with Gaussian beams,and rigorous numerical calculations have been done to study theinfluence of ETU on threshold, output power, spatialdistribution of population-inversion density and fractionalthermal loading. The model is applied to a laser operating at946 nm in Nd:YAG, where thermal lensing and the dependency oflaser-beam size are investigated in particular. A simple modelfor the degradation of laser beam quality from a transversallyvarying saturated gain is also proposed, which is in very goodagreement with measurements of the laser in a plane-planecavity

Diode-pumped rare-earth-doped quasi-three-level lasers

Many rare-earth-doped materials are suitable for laser operation and this thesis focuses on diode-pumped solid-state lasers employing crystals doped with the trivalent rare-earth ions neodymium (Nd3+), ytterbium (Yb3+) and erbium (Er3+). Especially, the quasi-three-level transitions in Nd and Yb have been studied as well as the eye-safe three-level transition around 1.5 µm in Er. Quasi-three-level laser transitions in neodymium-doped crystals such as Nd:YAG, Nd:YLF and Nd:YVO4 have received a great deal of interest because they allow for generation of blue light by frequency doubling. For solid-state blue laser sources, there exist numerous applications as in high-density optical data storage, colour displays, submarine communication and biological applications. Efficient lasing on quasi-three-level transitions at 900¬–950 nm in Nd-doped crystals is considerably more difficult to achieve than on the stronger four-level transitions at 1–1.1 µm. The problems with these quasi-three-level transitions are a significant reabsorption loss at room temperature and a small stimulated emission cross section. This requires a tight focusing of the pump light, which is achieved by end-pumping with high-intensity diode lasers. Nd:YAG lasers at the 946 nm transition have been built and a maximum power of 7.0 W was obtained. By inserting a thin quartz etalon in the laser cavity, the 938.5 nm laser line could be selected and an output power of 3.9 W was then obtained. By using nonlinear crystals, frequency-doubling of laser light at both 946 nm and 938.5 nm was achieved. Efficient generation of blue light at 473 nm has been obtained in periodically poled KTP, both in single-pass extra-cavity and intracavity configurations. More than 0.5 W was obtained at 473 nm by intracavity doubling. Intracavity second harmonic generation of the 938.5 nm transition gave slightly more than 200 mW at 469 nm. During recent years, Yb-doped double-tungstate crystals like KGW and KYW have shown efficient laser operation. A comparative, experimental study of the laser performance and thermal-lensing properties between standard b-cut Yb:KGW and Yb:KGW cut along a novel athermal direction is presented. The results show that the thermal lens is about two times weaker and less astigmatic in the athermal-direction-cut crystal, for the same absorbed power. Also, Er-Yb-doped KGW and KYW have been investigated and the fluorescence dynamics have been measured for the Yb (2F5/2), Er (4I13/2) and Er (4S3/2) levels around 1 µm, 1.5 µm and 0.55 µm, respectively. The influence of upconversion is a detrimental effect both in Nd-doped and Er-Yb-doped lasers. Analytical models starting from rate equations have been developed for these lasers including the influence of upconversion effects. The results of the general models have been applied to 946 nm Nd:YAG lasers and to Er-Yb-doped double-tungstate crystals in order to find the optimum doping concentrations for high gain for an eye-safe laser at 1.53 µm.QC 2010090

113-W cryogenically-cooled 946-nm Nd:YAG laser

We report a closed-cycle cryogenically-cooled diode-end-pumped continuous-wave Nd:YAG laser operating at 946-nm, generating 113-W of output power (pump power limited) with a slope and an optical-to-optical conversion efficiency of 80% and 76%, respectively

Svenska företagsetableringar i Brasilien : En studie i svenska företags internationaliserings- och etableringsprocess

Med hjälp av denna uppsats avser författarna att visa hur en internationalisering och etableringsprocess kan se ut för ett svenskt företag i Brasilien. Författarna har även undersökt rådgivarnas syn på internationalisering samt etableringsprocess och hur den bör gå till. Med rådgivare menar författarna den Svensk-brasilianska handelskammaren, Exportrådet och SouthPartner konsultföretag

Raman Scattering and Nd3+ Laser Operation in NaLa(WO4)2

The continuous-wave laser operation of Nd-doped tetragonal NaLa(WO4)2 crystal is studied at room temperature by optical pumping in the spectral region overlapping AlGaAs diode laser emission. This crystal has inhomogeneously broadened optical bands. From the room-temperature spectroscopic parameters determined it is found that the optimum Nd concentration for the 4F3/2 --> 4IJ laser channels must be in the 3-5 at.% range. For J=11/2 and 13/2 channels (lambda approximate to 1.06 and 1.3 mum) the most favourable polarization configuration is parallel to the crystallographic c axis, while for J=9/2 little polarization dependence of the laser efficiency is predicted. Laser operation was achieved with a 3.35 at.% Nd-doped sample grown by the Czochralski method. The laser operation was tested in an hemispherical optical cavity pumped by a Ti:sapphire laser. Stimulated emission at lambda=1056 nm was achieved for a wide spectral pumping range, lambda=790-820 nm. Stimulated Raman scattering was achieved in the picosecond regime with an efficiency similar to that of monoclinic KY(WO4)2 reference compoundThis work was supported in part by the Projects DT-CRYS or NMP3-CT-2003-505580 (EU), in part by MAT2004-21113-E, MAT2005-06354-C03-01 (Spanish Science and Education Ministry), and in part by RFBR 06-02-16747 (Russia). The work of M. Rico was supported by the Ramón y Cajal program of the Spanish Science and Education Ministry. The work of A. García-Cortés is supported by the FPU program of the Spanish Science and Education MinistryPeer reviewe