• G Sridhar

      Articles written in Pramana – Journal of Physics

    • Physics and technology of tunable pulsed single longitudinal mode dye laser

      G Sridhar V S Rawat Nitin Kawade Sunita Singh L M Gantayet

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      Design and technology demonstration of compact, narrow bandwidth, high repetition rate, tunable SLM dye lasers in two different configurations, namely Littrow and grazing incidence grating (GIG), were carried out in our lab at BARC, India. The single longitudinal mode (SLM) dye laser generates single-mode laser beams of $\sim 400$ MHz (GIG configuration) and $\sim 600$ MHz (Littrow configuration) bandwidth. Detailed performance studies of the Littrow and GIG dye laser resonators showed that GIG dye laser results in narrower linewidth and broad mode hop free wavelength scanning over 70 GHz. In this paper we present experimental studies carried out on the high repetition rate SLM dye laser system.

    • Cavity ring-down technique for measurement of reflectivity of high reflectivity mirrors with high accuracy

      G Sridhar Sandeep K Agarwalla Sunita Singh L M Gantayet

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      A simple, accurate and reliable method for measuring the reflectivity of laser-grade mirrors ($R$ > 99.5%) based on cavity ring-down (CRD) technique has been success-fully demonstrated in our laboratory using a pulsed Nd:YAG laser. A fast photomultiplier tube with an oscilloscope was used to detect and analyse the CRD signal. The cavity decay times were measured for three cavities formed by a combination of three mirror pairs. The absolute reflectivities $R_{1}$, $R_{2}$, $R_{3}$ were determined to be 99.94%, 99.63%, 99.52% at normal incidence. The reflectivity of mirrors is measured to an accuracy of 0.01%.

    • Temporal dynamics of high repetition rate pulsed single longitudinal mode dye laser

      G Sridhar V S Rawar S Singh L M Gantayet

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      Theoretical and experimental studies of temporal dynamics of grazing incidence grating (GIG) cavity, single-mode dye laser pumped by high repetition rate copper vapour laser (CVL) are presented. Spectral chirp of the dye laser as they evolve in the cavity due to transient phase dynamics of the amplifier gain medium is studied. Effect of grating efficiency, focal spot size, pump power and other cavity parameters on the temporal behaviour of narrow band dye laser such as build-up time, pulse shape and pulse width is studied using the four level dye laser rate equation and photon evolution equation. These results are compared with experimental observations of GIG single-mode dye laser cavity. The effect of pulse stretching of CVL pump pulse on the temporal dynamics of the dye laser is studied.

    • Measurement of flow fluctuations in single longitudinal mode pulsed dye laser

      V S Rawat N Kawade G Sridhar Sunita Singh L M Gantayet

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      A simple technique had been demonstrated for measuring flow-induced fluctuations in the single longitudinal mode (SLM) pulsed dye laser. Two prominent frequency components of 10.74 Hz and 48.83 Hz were present in the output of the Nd:YAG-pumped SLM dye laser. The flow-induced frequency component of 48.83 Hz was present due to the revolution per minute of the motor attached to the magnetically coupled gear pump. The time average bandwidth of 180 MHz has been obtained for this SLM dye laser. The effect of pump pulse energy on the bandwidth of the SLM dye laser was studied. The bandwidth of the SLM dye laser was increased to 285 MHz from 180 MHz, when the pump pulse energy was increased to 0.75 mJ from 0.15 mJ for a constant dye flow velocity of 0.5 m/s.

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