Investigations on aqueous solution grown L-Arginine Phosphate monohydrate (LAP) single crystals for efficient THz generation

Abstract

Single crystals of L-arginine phosphate monohydrate (LAP) with dimensions of 15 × 10 × 3.5 mm3 were grown by solution cooling method from its aqueous solution. The crystalline phase formation of the synthesized LAP was confirmed using powder X-ray diffraction measurements. Typical morphology of the spontaneously grown LAP crystal was ascertained through optical microscope. The LAP crystal was explored for its ability to generate Terahertz waves by employing a Ti: sapphire laser of 800 nm wavelength, 140 fs pulses, at 80 MHz repetition rate. It is reported, for the first time to the best of our knowledge, that the LAP crystal was capable of generating THz radiation in the range between 0.1 and 2.0 and that there was a gradual enhancement of the THz output power when the input power was increased from 500 to 1200 mW. The optical to THz conversion efficiency of LAP crystal was measured to be about 0.7 × 10−5 which is considerably higher than the well-known inorganic material ZnTe, even with its larger area. Further, the refractive index and absorption coefficient measured for the crystal were found to vary between 1.2 and 1.65 and 5 and40 cm−1 respectively in the range between 0.1 and 2.0 THz. The coherence length of the LAP was theoretically calculated to be about 400 mm at 0.8 THz.