Thermally induced self-phase modulation and optical limiting application of l-arginine hydrochloride (LAHCl) solutions

l-arginine hydrochloride (LAHCl) solutions of 1 M (A) and 2 M (B) concentrations have been investigated for optical nonlinearity under a continuous wave (CW) diode laser of wavelength 670 nm. Nonlinear absorption (β), nonlinear refraction (n2) and third-order nonlinear optical susceptibility (χ(3)) of LAHCl solutions (A and B) have been measured. Excited state absorption (ESA) assisted reverse saturable absorption (RSA) has been observed to be the reason for nonlinearity in the material. The nonlinear absorption has been observed to increase with increase in concentration of the solution. Thermal aberration rings have been formed by tightly focused Gaussian laser beam and also the beam suffered a self-phase modulation. The observed RSA has been effectively used to verify the optical limiting behaviour of LAHCl solutions. Theoretically predicted third-order nonlinear polarizability has a negative value that further conform the self-defocusing behaviour of LAHCl.