Although aqueous dye lasers are much sought after, they have been of no practical use, as laser dyes show a strong tendency for aggregation in water, thus diminishing their optical output. Contributing towards this shortcoming, we studied the noncovalent interactions of two prominent laser dyes, namely, rhodamine 6G and rhodamine B, with a water soluble macrocyclic host, sulfobutylether-β-cyclodextrin (SBE βCD). Spectral changes in the absorption and fluorescence behavior of dyes in presence of the SBE βCD host indicated adequate complex formation between dye and host (K∼10 M ). A combination of various photophysical parameters evaluated from measurements such as Job plot, changes in the fluorescence lifetime/anisotropy values, and favorable thermodynamic parameters from isothermal titration calorimetric measurements adjudicated a 1 : 1 stoichiometric complex formation between dye and SBE βCD host. Consequently, SBE βCD prevents dye aggregation/adsorption and present rhodamine dyes in their monomeric forms with enhanced fluorescence yield and brightness. These vital parameters were utilized to optimize and demonstrate cost-effective supramolecular broad-band and narrow-band aqueous dye laser systems with improved lasing efficiencies (∼25 % higher for the SBE βCD : RhB system and ∼10 % higher for SBE βCD : Rh6G system), better beam profile, and enhanced durability compared to the respective dyes in optically matched ethanol solutions.

Temporal jitter in a magnetic pulse compression based copper vapor laser (CVL) system is analyzed by considering ripple present in the input dc power supply and ripple present in the magnetic core resetting power supply. It is shown that the jitter is a function of the ratio of operating voltage to the designed voltage, percentage ripple, and the total propagation delay of the magnetic pulse compression circuit. Experimental results from a CVL system operating at a repetition rate of 9 kHz are presented.

In this study, Bi 3+ incorporation in NaYbF 4 :Er lattice and its influence on upconversion luminescence properties have been investigated in detail using techniques such as temperature-dependent luminescence, Fourier transform infrared spectroscopy and X-ray diffraction (XRD). The study was carried out to develop phosphors with improved upconversion luminescence. From photoluminescence and lifetime measurements it is inferred that luminescence intensity from NaYbF 4 :Er increases with Bi 3+ addition. The sample containing 50 at.% Bi 3+ ions exhibited optimum upconversion luminescence. Increased distance between Yb 3+ -Yb 3+ and Er 3+ -Er 3+ due to Bi 3+ incorporation into the lattice and associated decrease in the extent of dipolar interaction/self-quenching are responsible for increase in lifetime values and luminescence intensities from Er 3+ ions. Incorporation of Bi 3+ into NaYbF 4 :Er lattice reduced self-quenching among Yb 3+ -Yb 3+ ions and this facilitated energy transfer from Yb 3+ to Er 3+ . This situation also explains decrease in the extent of temperature-assisted quenching of emission from thermally coupled 2 H 11/2 and 4 S 3/2 levels of Er 3+ . Based on Rietveld refinement of XRD patterns it was confirmed that a maximum of 10 at.% of Bi 3+ added was incorporated into the NaYbF 4 :Er lattice and the remaining complex co-exists as a BiOF phase. These results are of significant interest in the area of development of phosphors based on Yb 3+ -Er 3+ upconversion luminescence. K E Y W O R D SBiOF, lifetime, NaYbF 4 :Er, upconversion, XRD | INTRODUCTIONUpconversion (UC) phosphors give anti-Stokes emission upon irradiation with near-infrared (NIR) light even at low power densities compared with other conventional nonlinear phenomena such as two photon absorption and second harmonic generation. [1][2][3] Such materials are potential candidates for optical thermal sensors [4] , light emitting displays [5,6] , upconversion laser sources [7,8] , cancer treatment [9] , and, most importantly, in solar cells [10] because of its light absorption over extended wavelength regions. Inorganic crystalline materials doped with activators such as Er 3+ , Tm 3+ , or Ho 3+ belong to the category of upconversion luminescent materials and some of these also find application in bio-imaging. [11,12] The abovementioned activators are best suited for the upconversion process because of their ladder-like energy level structure. Such UC materials are also co-doped with Yb 3+ for better absorption of 980 nm