A new phase matchable nonlinear optical crystal-L-arginine phosphate monohydrate (LAP)

Abstract

In search of new organic nonlinear optic crystals, aromatic compounds with donor and acceptor substituents are extensively studied. Some new crystals with large nonlinear coefficient have been reported. This kind of crystals is usually not useful in ultraviolet region, because the distance between energy levels in conjugated π bonds gets smaller due to the strong conjugation effect. In exploring new organic nonlinear optic crystals used in ultraviolet region, we have discovered a new phase matchable nonlinear optic organic crystal --L-arginine phosphate monohydrate. Of the size 13×35×35 mm~3 LAP single crystals with good optical quality have been grown by the cooling and evaporating methods. LAP crystal belongs to monoclinic system; its space group is P2_1. It shows the following proper ties: (1) transparency range over 10% extends from 230nm to 1940 nm; over 50% extends from 240nm to 1500 nm; (2) when basic wave is 1064 nm and harmonic wave is 532 nm, the calculated phase matching curved surface belongs to Hobden 's ninth type; (3) SHG intensity of LAP crystal in phase matching direction (θ=57°ρ=-13°phase matching type II) is 3.5 times greater than that of KDP crystal (θ=59°ρ=0°type II). It is worth to note that this direction of LAP crystal will not be one of its maximum effective nonlinear coefficient; (4) when basic waves are 1064 nm and 532 nm, the sum-frequency effect has been observed; (5) the optical damage threshold is higher than 1 GW/cm~2·s at 1064 nm; (6) the stability towards atmospheric moisture is excellent. As a result, LAP crystal is a promising nonlinear optic crystal.