• K P J Reddy

      Articles written in Pramana – Journal of Physics

    • Review of theoretical gain-optimization studies in 10.6µm CO2-N2 gasdynamic lasers

      K P J Reddy N M Reddy

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      A comprehensive theoretical analysis of optimization of gain in CO2-N2 gasdynamic laser employing wedge or conical or hyperbolic nozzles with either H2O or He as the catalyst is presented. After a review of previous work, the usual governing equations for the steady inviscid quasi-one-dimensional flow in a supersonic nozzle of a gasdynamic laser are used to obtain similar solutions for the various flow quantities, which variables are subsequently used to optimize the small-signal gain on theP(20) line of the (001) → (100) transition of CO2 at wavelength 10.6µm. The corresponding optimum values like reservoir pressure and temperature and nozzle area ratio also have been predicted and presented in the form of graphs. The analysis predicts that employing of 2D-wedge nozzle results in higher gain values and the CO2-N2-H2O gasdynamic laser employing 2D-wedge nozzle is operationally the best laser system for which the optimum value as high as 3.1 m−1 gain can be obtained.

    • Study of synchronously mode-locked and internally frequency-doubledcw dye laser

      K P J Reddy

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      The analysis of the characteristics of a synchronously mode-locked and internally frequency-doubled dye laser is presented. Dependence of dye laser pulse characteristics on the cavity length mismatch of the pump laser and dye laser is studied. Variation of the minimum pulsewidth with intracavity bandwidth and the harmonic conversion efficiency is presented in the form of graphs.

    • Evaluation of downstream-mixing scheme for 9.4-µm CO2 gasdynamic laser

      P Chakravarty N M Reddy K P J Reddy

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      A theoretical analysis of a downstream-mixing 16-µm CO2 gasdynamic laser revealed the possibility of utilizing the downstream-mixing scheme for the generation of 9.4-µm radiation using a CO2 gasdynamic laser. The flow-field has been analyzed using complete two-dimensional, unsteady laminar form of Navier-Stokes equations coupled with the finite rate vibrational kinetic equations. The analysis showed that integrated small-signal gain of 11.5m−1 for Lorentzian broadening and 4.8m−1 considering Voigt function can be obtained for N2 reservoir temperature of 2000°K and velocity ratio 1:1 between the CO2 and N2 mixing streams. These results (presented in graphs) clearly highlight the large potential of downstream-mixing CO2 gasdynamic laser for 9.4-µm laser generation.

    • Spatial light modulation characteristics of reverse saturable absorber

      K P J Reddy P K Barhai

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      Construction of a spatial light modulator (SLM) using reverse saturable absorber molecules is suggested. The SLM characteristics are derived using a recently proposed steady-state kinetic analysis. Results are presented for the rhodamine 6G dye molecules.

    • Analysis of mode-locked internally frequency doubled broad-band continuous wave lasers

      H K T Kumar K Appaji Gowda K P J Reddy

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      Closed-form analysis of pulse evolution in the transient regime in an actively modelocked internally frequency doubled broad-band continuous wave laser is presented. The analysis enables investigation of the effect of nonlinear crystal inside the laser cavity on mode-locked pulse parameters at the fundamental frequency. It is shown that the presence of internal second harmonic crystal broadens the fundamental mode-locked pulse while accelerating the approach of the system to steady-state. The dependence of pulse parameters on the bandwidth of the tuning element, modulation depth of the active mode-locker and conversion efficiency of the frequency doubler is presented in detailed graphical form.

    • Self-similar solutions of laser produced blast waves

      K P J Reddy

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      The aerodynamics of the blast wave produced by laser ablation is studied using the piston analogy. The unsteady one-dimensional gasdynamic equations governing the flow are solved under assumption of self-similarity. The solutions are utilized to obtain analytical expressions for the velocity, density, pressure and temperature distributions. The results predict all the experimentally observed features of the laser produced blast waves.

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