Cryst. Res. Technol. 42, No. 11, 1110 – 1116 (2007) / DOI 10.1002/crat.200710929 © 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Growth and high frequency dielectric study of pure and thiourea doped KDP crystals S. S. Hussaini 1 , N. R. Dhumane 1 , G. Rabbani 2 , P. Karmuse 3 , V. G. Dongre 3 , and M. D. Shirsat* 1 1 Opto-electronics and Sensor Research Laboratory, Department of Physics, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad-431004, Maharashtra, India 2 Department of Physics and Electronics, Moulana Azad College Aurangabad- 431 001, Maharashtra, India 3 Department of Chemistry, University of Mumbai, Mumbai, Maharashtra, India Received 14 March 2007, revised 3 May 2007, accepted 10 May 2007 Published online 12 June 2007 Key words crystal growth, KDP, NLO Material, dielectric constant, transmission line waveguide method. PACS 42.70.Mp, 78.20.Ci, 74.25.Gz Non linear optical (NLO) materials have acquired new significance with the advent of a large number of devices utilizing solid-state laser sources. Several NLO materials have been used for this kind of technological applications. The Potassium di-hydrogen phosphate (KDP) one of NLO material having superior non linear optical properties has been exploited for variety of applications. In the present investigation we have grown KDP crystals from aqous solution with thiourea, an organic non linear optical material. We could enhance the SHG efficiency of thiourea doped KDP crystal. It was 1.99 times more that of pure KDP. We observed more enhancements in nonlinearity for low concentration of thiourea.The crystal structure and cell parameters of grown crystal were determined from Powder XRD.The incorporation of thiourea in the grown crystals was qualitatively analyzed from FT-IR study. The absorption spectra of pure and thiourea doped KDP crystal reveal that thiourea doped KDP crystals would be a better nonlinear optical (NLO) material for second harmonic generation (SHG) than pure KDP. The thermal decomposition and weight loss of pure and thiourea doped KDP crystal was observed by thermogravimetric (TGA) analysis and Differential Scanning Calorimetry (DSC). The high frequency dielectric study of pure KDP crystal, thiourea doped KDP crystals and organic additive thiourea was carried out using X-band at frequency 8GHz and 12GHz by transmission line wave guide method. We observed low dielectric constant of thiourea doped KDP crystal when it is doped with 2mole% of thiourea. © 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1 Introduction Non linear optics (NLO) has wide applications in the field of telecommunication and information devices [1- 7]. Non linear optics is playing a major role in the emerging photonics and optoelectronics technologies. New non linear optical frequency conversion materials have a significant impact on laser technology, optical communication and optical data storage. Second order nonlinear optical (SONLO) materials have recently attracted much attention because of their potential application in emerging optoelectronics technology [8-13]. Organic NLO materials are attracting a great deal of attention for possible use in optical devices because of their large optical nonlinearity, low cut-off wavelength, short response time and high threshold for laser power [14-15]. The organic materials are being widely used for the development of optical devices, because they posses large nonlinearity. These materials are often formed by weak Vader walls and hydrogen bonds and hence posses a high degree of delocalization [16]. Recent interest in quantum electronics has centered on finding the new materials for efficient second harmonic electro optic modulation [17]. The organic additive ____________________ * Corresponding author: e-mail: mdshirsat_bamu@yahoo.co.in