Invited Talks :
(1) Plenary talk on "Solid State Lasers" at "PhotoSMART", A summer school organized by Institute of Radio Physics and Electronics, University of Calcutta, 1-18th June 2010.(2) "Silicon Carbide Quantum Dots" at Dept. of ECE at George Mason University, Fairfax, VA, USA, Dec. 16, 2011.
(3) "Quantum Well Intermixed Lateral Grating Assisted Weighted Directional Coupler" at School of ECE, University of Oklahoma, Norman, OK, USA, Dec. 09, 2009.
(4) "Refractive Index and Absorption in Interdiffused Nano-Structures", R. K. Sonkar, T. Bhowmick and U. Das, Intl. Conf.-cum-workshop on Nanoscience and Nanotechnology, Ansal Inst. Of Technol., Delhi, Dec. 17-21, 2007.
(5) "CWDM Bragg Gratings using F Implanted QW Intermixing", R. K. Sonkar, A. K Srivastava and U. Das, International Conference on Electronic and Photonic Materials, Devices and Systems - EPMDS 2006, Jan. 04-06, 2006, Kolkata. Not included in proceedings due to delayed submission.
(6) "Quantum Well Disordered Integrated Photonic Devices", Photonics 2006 Conference, Dec. 13-16, 2006, Univ. of Hydrabad, Hydrabad.
(7) "Impurity Induced Disordering of Quantum Wells and Applications", Conference on Horizons of Telecommunications, Feb. 3-5, 2003, Kolkata, India.
(8) "Anodic Oxides on GaAs for Photodiode insulation masks", 10th International Workshop on the Physics of Semiconductor Devices, Dec. 14 - 18, 1999, New Delhi, India.
(9) "Models for waveguide DBRs by F induced disordering of MQWs", INDO-FRENCH workshop on Quantum Structures : Modern Developments, Dec. 01 - 07, 1999, Calcutta University, Kolkata.
(10) "F induced disordering of InGaP/GaAs and strained AlGaAs/GaAsP QWs", Dec. 17, 1999, Arizona State University, Tempe, AR, USA.
(11) "QW Impurity Induced Disordering Applications in Optoelectronic Integration, Tutorial series on Nanostructures- Applications And Goals (NAG), 12-13 Jan. 1998, Calcutta University, Kolkata.
(12) "Fluorine impurity induced layer disordered AlGaAs/GaAsP strained Quantum wells : Experiment and model" 9th International Conference on Physics of Semiconductor Devices, Dec. 16-20, 1997, New Delhi, India.
(13) "Fluorine Induced Group V Inter-diffusion in III-V Quantum Wells", Dept of EE, Mar. 9, 1996, Oregon State University, OR, USA.
(14) "Band Gap Engineering for Semiconductor lasers", National Laser Symposium, BARC, Bombay, Jan 17-19, 1996.
(15) "Photoluminescence Spectroscopy of (111)B III-V semiconductors --- Peculiarities and Applications", U. Das, Workshop on Advanced Laser Spectroscopy, Feb. 25 - 28 (1995), IIT Kanpur, Kanpur 208016, India.
(16) "Proposal for an integrated Photo diode-HBT amplifier using impurity induced layer disordering of QWs" , U. Das, Intl. Conf. on Emerging Optoelectronic Technologies, July 18-22 (1994), Bangalore, India.
(17) "F Impurity Induced Disordering of Quantum Wells", TIFR, Bombay, May 1994.
(18) "Optoelectronic Integration using Fluorine Impurity Induced Disordering", CEERI, Pilani, April 1994.
(19) "Fluorine Impurity Induced Disordering of InGaP/GaAs Quantum Wells", IIT Kharagpur, Kharagpur, July 1994.
(20) "MBE Growth of natural Quantum Dot Structures on (111)B GaAs", Colloquium on Physics and Technol., University of South Florida, Tampa, FL, USA, Aug 24 (1993). (21) "Semiconductor Strained Quantum Wells : Properties and Applications", Naval Research Laboratory, Washington DC, USA, May (1992).