Dye laser action at 330 nm using benzoxazole: A new class of lasing dyes

Dye laser action has been observed without dispersion elements at 330 nm in phenyl-benzoxazole, the shortest wavelength observed so far in these experimental conditions. Quantum efficiency of laser emission point to benzoxazole as a new class of dye lasers.     

OSL from BeO ceramics: new observations from an old material

In BeO ceramics, exposed to ionizing radiation, an intense OSL signal was observed. The properties of the signal and its behavior under various experimental conditions were investigated. It was found that the OSL signal is a composite signal and exhibits strong thermal quenching. The quenching energy was estimated as 0.5 eV. The excitation spectrum of the OSL signal was obtained as a broad peak in the region 420–550 nm with maximum around 435 nm. The possible correlation between the OSL signal and the peaks in the TL glow curve was also examined. It was interesting to observe that the highly light sensitive TL peak near 220°C does not contribute to the OSL signal. The OSL signal was found to originate from a trap near 340°C.

To check the possibility of using the material for radiation dosimetry the dose response and thermal stability of the OSL signal were also investigated. The dose response was found to be quite linear up to 10 Gy. The thermal activation energy of the OSL trap was determined as 1.7 eV using isothermal annealing and heating rate methods thus proving the suitability for dosimetry.     

Search for efficient,near UV lasing dyes. I. Substituent effects on bicyclic dyes

Methods of blue-shifting the lasing wavelengths of coumarin and quinolone-2 dyes are examined and are evaluated by new synthetic materials. Methoxy substitution at the 4 position is found to be effective. This study was supported under contract SANL 284 from the Lawrence Livermore Laboratory.     

Dual-band lasing of benzopyran dyes in the red region of the spectrum

We have studied the spectral and energy characteristics of lasing for two benzopyran dyes in a dispersive cavity with a diffraction grating when the dyes are excited at several different wavelengths using an additional flashlamp-pumped dye laser. These dyes have high fluorescence quantum yield and lase efficiently in the red region of the spectrum. The tuning range of their lasing spectrum is greater than 100 nm. We discuss the characteristic features of conversion of the selective excitation energy by these dye molecules. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 3, pp. 401–404, May–June, 2006.     

Nonlinear optical characteristics and lasing ability of merocyanine dyes having different solvatochromic behaviour

Lasing characteristics and two-photon absorption (TPA) of merocyanine dyes with solvatochromism of different types are first investigated. Efficient lasing is excited in solutions pumped by radiation of the 2nd harmonic of a Nd-YAG laser (532 nm) with the lasing efficiency exceeding 40% and by XeCl laser radiation (308 nm) with the lasing efficiency up to 19%. The TPA cross-section at a wavelength of 1064 nm is determined. It is established that for merocyanines possessing the highest positive and negative values of solvatochromism, the TPA cross-section reaches maximum values of 115 and 125 GM, respectively. Influence of the special features of the electronic structure, spectral and luminescent properties, solvatochromic behavior, and nature of the medium on the lasing characteristics and nonlinear absorption of merocyanine dyes is investigated. Prospects for merocyanine application in modern optical technologies are demonstrated.     

Spectroscopic and lasing properties of Xanthene dyes encapsulated in silica and polymeric matrices

The photo-physical properties of Xanthene dyes: Basic Rhodamine Yellow (BRY), Rhodamine590perchlorate (R590p), SulforhodamineB (SRB) doped in tetramethylorthosilicate (TMOS) and poly-methylmethacrylate (PMMA) are observed. The various parameters viz. full-width at half-maxima (FWHM), peak emission wavelength, quantum yield and excited state lifetime at different concentrations ranging from ∼0.05 to ∼1 mM of the dye under excitation by Copper Vapor Laser (CVL) of high repetition rate (∼5.6 kHz) of are investigated. In order to identify photostability in dyes, normalized photostability has been studied and found that silica gel samples containing dye are more stable than that of polymeric samples. This has been further understood in terms of number density of unbleached dye molecules that infers that photobleaching of dye molecules is not prominent at higher concentrations in glassy solid matrices. Pump intensity dependent optical gain of the samples has also been reported and efforts have been made to study the efficiency of solid-state laser samples in a cavity for the performance of the dye laser.     

Investigation of lasing of dyes under the influence of the radiation of copper-vapor lasers

A study is made of the possibility of improving the laser properties of dyes pumped by the radiation of a copper-vapor laser, the choice of dye mixtures optimal from the point of view of producing stimulated emission, and the influence of the solvent on these properties, the aim being to obtain optimal energy parameters in an instrument based on a copper-vapor laser and an optical attachment.Translated from Izvestiya Vysshikh Uchebnhykh Zavedemii, Fizika, No. 10, pp. 44–48, October, 1980.     

An investigation into the possibility of lasing directly from an isomeric level

A conceptual realization of a γ-ray laser is described, which is based on thermal neutron pumping of long-lived Mössbauer isotopes to obtain inversion, and the simultaneous application of techniques that destroy the effect of inhomogeneous broadening, to attain resonance. Three long-lived isotopes with the required characteristics are identified. The results of a study, using the nuclear properties of these isomers and the solid state properties of the bulk materials, are presented. Threshold conditions and pumping requirements for such a device are discussed.     

The development of an X-ray lasing oscillator

An X-ray lasing oscillator is being developed which uses visible laser irradiation of solid targets in multipulse, multipass, operation to produce dramatic, rather than incremental, improvement in almost any X-ray lasing scheme. Hydrodynamic code simulations indicate reproducible plasma conditions are possible with multiple pulses, while ray trace simulations define mirror cavity configurations in a refracting carbon plasma under multipass operation.     

Effect of stimulated raman scattering on the formation of the random lasing spectrum of dyes

The nature of the line structure of the random lasing spectrum of vesicular films activated by dyes (rhodamine 6G, pyrromethene 597) has been analyzed. The spectral lines appear above the random lasing threshold and are manifested only within the spectrum of the amplified spontaneous radiation of dye molecules against the continuous-pedestal background. Their intensities are proportional to the product of the intensities of the pump and continuous spectrum at the frequencies of these lines, and the frequencies are exactly reproduced from pulse to pulse. The shifts of the lines are strongly correlated with the pump frequency and the frequencies of these lines coincide with the frequencies of the Raman scattering lines of dye molecules. Using these properties, it has been shown that the observed lines are due to stimulated resonant Raman scattering by dye molecules, which occurs simultaneously with the stimulated emission of these molecules. These two processes affect each other and jointly form a united nonlinear process where all of the oscillations active in Raman scattering are manifested.     

The phenoxazones: A new class of laser dyes

A promising new class of laser dyes for the red and near infrared with extended tuning range and high photo-chemical stability is described. Results are given for nitrogen laser pumping, long-pulse flashlamp pumping and cw- operation of one of these dyes.     

A new exotic state in an old material: a tale of SmB6

We review current theoretical and experimental efforts to identify a novel class of intermetallic 4f and 5f orbital materials in which strong interactions between itinerant and predominately localized degrees of freedom give rise to a bulk insulating state at low temperatures, while the surface remains metallic. This effect arises due to inversion of even-parity conduction bands and odd-parity very narrow f-electron bands. The number of band inversions is mainly determined by the crystal symmetry of a material and the corresponding degeneracy of the hybridized f-electron bands. For an odd number of band inversions, the metallic surface states are chiral and therefore remain robust against disorder and time-reversal invariant perturbations. We discuss a number of unresolved theoretical issues specific to topological Kondo insulators and outline experimental challenges in probing the chiral surface states in these materials.