Engineering optical anisotropy in nonlinear crystals with ultrafast light

Abstract

Photonic technology is widely based on anisotropic (and) nonlinear materials, which allow light modulation and parametric light conversion. Because the number of naturally occurring crystals is limited, there is a growing demand for artificial metamaterials with optical properties specifically tailored to a given application. Here, we utilize the top-down method to synthesize sub-wavelength periodic nanostructures inside a uniaxial optically nonlinear crystal (lithium niobate, LiNbO 3 ) by irradiating it with multiple femtosecond laser pulses. By superimposing form-birefringence associated with the light-induced nanostructures onto natural birefringence of the host crystal we create macroscopic domains of a biaxial metamaterial embedded into otherwise uniaxial medium.

Recent Advances in Vertically Aligned Nanocomposites with Tunable Optical Anisotropy: Fundamentals and Beyond

“…Optical anisotropy can be defined as the differences of complex refractive indices along the principal axes when light propagates through media [1]. Photonic crystals possessing birefringence or dichroism phenomena are considered as natural anisotropic media, but are either too bulky or present with limited birefringence [2][3][4]. Research continue developing structures with broken symmetry, such as layered two-dimensional crystals or transition metal dichalcogenides (TMDs) [5][6][7], as well as artificially constructed nanostructures or the so-called metamaterials that surpass the conventional limit in achieving extreme anisotropy at controlled frequencies [8][9][10].…”

Polarization controlled femtosecond laser induced birefringence in isotropic crystals

“…Nanogratings were written by fs laser in crystals, such as tellurium dioxide (TeO2) [1], sapphire [2] and quartz [3]. Nanogratings produced polarization dependent birefringence has been reported only in magnesium-oxide-doped lithium niobate (MgO:LiNbO3) crystal along optical axis [4], However, the strong natural birefringence prevents observation of induced birefringence along arbitrary direction, which limits the applications. Here, we demonstrate new type of polarization controlled birefringent modification in the bulk of isotropic crystal, i.e.…”