Surfactant mediated suppression of aggregation and excited state ring puckering process in Pyrromethene 597-Application in water based dye laser.

Water is being considered as an economical, safe and environmental friendly alternative solvent for dye lasers. However, the use of water in dye laser is restricted due to the formation of non-emissive aggregates of dye molecules. In the present study we have explored the possibility of the use of commercially available surfactant molecules for the water based laser of Pyrromethene 597 (PM597) dye, which has emerged as an alternative for more commonly used Rhodamine dyes in dye laser systems. Our studies show that in water, PM597 forms non-emissive aggregates which can be dissociated into monomeric dye molecules by adding common surfactants. Further, the high microviscosity in the micellar media retarded energy wasting ring puckering process in the excited state of the dye leading to the increase in its emission yield and excited state lifetime to a significant extent. It has been demonstrated that the emission yield and excited state lifetime in surfactant solution is relatively higher than in ethanol, the most commonly used organic solvent for dye lasers. Lasing action has been demonstrated in the aqueous solution of dye and lasing efficiency is found to be comparable to ethanol.

Effect of Bi3+ addition on the upconversion luminescence properties of NaYbF4 :Er.

In this study, Bi3+ incorporation in NaYbF4 :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 NaYbF4 :Er increases with Bi3+ addition. The sample containing 50 at.% Bi3+ ions exhibited optimum upconversion luminescence. Increased distance between Yb3+ -Yb3+ and Er3+ -Er3+ due to Bi3+ 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 Er3+ ions. Incorporation of Bi3+ into NaYbF4 :Er lattice reduced self-quenching among Yb3+ -Yb3+ ions and this facilitated energy transfer from Yb3+ to Er3+ . This situation also explains decrease in the extent of temperature-assisted quenching of emission from thermally coupled 2 H11/2 and 4 S3/2 levels of Er3+ . Based on Rietveld refinement of XRD patterns it was confirmed that a maximum of 10 at.% of Bi3+ added was incorporated into the NaYbF4 :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 Yb3+ -Er3+ upconversion luminescence.

Analysis of temporal jitter in a copper vapor laser system.

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.