Detection of second-order nonlinear optical magnetization by mapping normalized Stokes parameters

Abstract

A measurable magnetic (nonlocal) contribution to the second harmonic generation (SHG) of nonmagnetic materials is an intriguing issue related to chiral materials, such as biomolecules. Here we report the detection of an intensity-dependent optically induced magnetization of a chiral bacteriorhodopsin film under femtosecond pulse excitation (830 nm) and far from the material's resonance. The analysis of the pump intensity-dependent noncollinear SHG signal, by means of the polarization map of normalized Stokes parameters, allows one to improve the detection of the nonlinear optical magnetization M2ω contribution to the SHG signal.

Second harmonic generation from artificial metasurfaces

“…Several experimental results [ 16,17 ], indicate that magnetic contributions are necessary to accurately explain the nonlinear optical activity [ 17 ]. The second order nonlinear polarization (at 2ω frequency) consists of a series of multipole terms [ 13,14 ]: (1) where represent the electric and magnetic-dipole polarization, electric-quadrupole polarization and nonlinear magnetization, respectively. The electric and magnetic-dipole polarization is given by , where is the nonlinear electrical susceptibility tensor and is the magnetic-dipole tensor.…”

“…Within this context, we recently investigated the nonlinear optical activity of many different materials, one of them was an oriented Bacteriorhodopsin protein film [ 14 ], by means of a noncollinear SHG interaction. We chose BR since it has a well-established structure and its crystal structure is known with a high degree of accuracy.…”

“…Other methods, such as the continuous polarization method [4], reveal very sensitive to detect the nonlinear optical activity of materials in the form of films several wavelength thick; in practice, it consists into the detection of the linear polarization state of the SHG as a function of the polarization state of the pump beam. By using a method based on the linear polarization change of the pump beams under noncollinear configuration, we have analyzed the nonlinear optical activity of a film of chiral material: Bacteriorhodopsin (BR) [13,14].…”