• Yogesh Kumar

      Articles written in Pramana – Journal of Physics

    • Effect of curvature on a statistical model of quark-gluon-plasma fireball in the hadronic medium

      S Somorendro Singh D S Gosain Yogesh Kumar Agam K Jha

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      The free energy of a quark-gluon plasma fireball in the hadronic medium is calculated in the Ramanathan et al statistical model after incorporating the effect of curvature. The result with the inclusion of curvature is found to produce significant improvements in all the parameters we calculated with respect to the earlier results. The surface tension with this curvature effect is found to be $0.17 T_{c}^{3}$ , which is two times the earlier value of surface tension which is $0.078 T_{c}^{3}$ , and this new result is nearly close to the lattice value $0.24 T_{c}^{3}$. As far as transition is concerned, a thermodynamic variable like entropy shows weakly first-order phase transition and it shows continuity in the behaviour of specific heat.

    • Enhancement in the gain recovery of a semiconductor optical amplifier by device temperature control


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      We present a numerical investigation on the temperature dependence of gain recovery, of a semiconductor optical amplifier (SOA). It is shown that the decrease in temperature significantly speed-up the gain recovery of the SOA. Under typical operating conditions, a 20 K reduction in temperature of the SOA results in a decrease of 150 ps in the gain recovery time. A comparative estimation of device temperature and assisted-light power requirements for enhancing the gain recovery has also been carried out. It is found that, a decrease of 8 K in the temperature of the SOA, is as effective in enhancing the gain recovery as injection of 25 dBm assistedlight power in the counter-propagating mode. Our study shows that under moderate current biasing conditions, temperature reduction is a better and convenient option to speed-up the gain recovery of an SOA, than the use of external assisted-light injection, which requires an additional laser source and wavelength division multiplexing(WDM) components for coupling and de-coupling, leading to insertion losses in the communication channel.

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