• Udit Chatterjee

      Articles written in Pramana – Journal of Physics

    • Highly efficient deep ultraviolet generation by sum-frequency mixing in a BBO crystal pair

      Gopal C Bhar Pathik Kumbhakar Udit Chatterjee Anil K Chaudhary Alexander Kokh

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      Generation of deep ultraviolet radiation at 210 nm by Type-I third harmonic generation is achieved in a pair of BBO crystals with conversion efficiency as high as 36%. The fundamental source is the dye laser radiation pumped by the second harmonic of a Q-switched Nd: YAG laser. A walk-off compensated configuration with the BBO crystal pair has enabled us to realize such a high conversion efficiency in the interaction.

    • Development of coherent tunable source in 2–16 𝜇m region using nonlinear frequency mixing processes

      Udit Chatterjee

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      A very convenient way to obtain widely tunable source of coherent radiation in the infrared region is through nonlinear frequency mixing processes like second harmonic generation (SHG), difference-frequency mixing (DFM) or optical parametric oscillation (OPO). Using commonly available Nd:YAG laser and its harmonic pumped dye laser radiation as parent beams, we have been able to generate coherent tunable infrared radiation (IR) in 2–16 𝜇m region using different nonlinear crystals by DFM and OPO. We have also generated such IR source in the 4–5 𝜇m region through SHG of CO2 laser in different infrared crystals. In the process we have characterized a large number of nonlinear crystals like different borate group of crystals, KTP, KTA, LiIO3, MgO:LiNbO3, GaSe, AgGaSe2, ZnGeP2, AgGa$_{1−x}$In$_x$Se2, HgGa2S$_4$ etc. To improve the conversion efficiencies of such frequency conversion processes, we have developed some novel schemes, like multipass configuration (MC) and positive optical feedback (POF). The significance of the obtained results lies in the fact that to get the same conversion in SHG or DFM, one now requires fundamental input radiation with much lower intensity.

    • Observation of two-photon absorption at UV radiation in ZnS quantum dots

      Manajit Chattopadhyay Pathik Kumbhakar Udit Chatterjee

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      Research studies on quantum dots (QDs) of semiconductor materials are of potential interest in present days having promising applications in different optoelectronic devices. Among other materials, ZnS is a direct bandgap semiconductor material having a wide bandgap of 3.6 eV for its cubic phase at room temperature and it shows excellent optical properties. However, here the nonlinear optical (NLO) properties of chemically synthesized ZnS QDs of average size of ∼ 1.5 nm have been reported which are measured by using an indigenously developed Z-scan technique. The pump radiation is 355 nm which is the third harmonic of the Q-switched Nd:YAG laser radiation having pulsed duration of 10 ns with the repetition rate of 10 Hz. The measured experimental data have been analysed by using analytical models and two-photon absorption coefficients of the ZnS QDs at 355 nm have been extracted.

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