Tailoring chiral optical properties by femtosecond laser direct writing in silica

Abstract

An object that possesses chirality, that is, having its mirror image not overlayed on itself by rotation and translation, can provide a different optical response to a left- or right-handed circular polarized light. Chiral nanostructures may exhibit polarization-selective optical properties that can be controlled for micro-to-nano optical element engineering. An attractive way to induce such complex nanostructures in three-dimension in glass is femtosecond laser direct writing. However, the mechanism of femtosecond laser induced chirality remains to be unveiled due to complex physical and chemical processes occurring during the ultrashort light-matter interaction. Here, a phenomenological model is proposed and is built on two-layers phase shifters to account for this laser-induced optical chirality in an initially achiral material (silica glass). This model is based on the observation that femtosecond laser induced nanogratings own two principal contributions to its aggregate birefringent response: a form and a stress-related one. By refining this formalism, a multilayer approach is developed to imprint on demand optical rotation. Values up to +/-60° at 550 nm within an optimal 80 μm thickness in silica glass are possible, corresponding to the highest value in a glass to date. These results provide new insights of circular-optical control in micro-nano optical manufacturing and open new opportunities for photonics applications.

Femtosecond‐laser micromachining fork gratings in LN crystal with different mechanisms

“…According to the induced index changes (Δ n ) of the laser irradiated region, the femtosecond‐laser written filaments can be classified into two types: type‐I modification (which is located inside the laser‐write tracks with positive Δ n ) and type‐II modification (which is located in the vicinal regions of the laser written tracks with negative Δ n ). These two different mechanisms have been demonstrated in kinds of optical crystals, glasses, and ceramics 26–30 …”

“…These two different mechanisms have been demonstrated in kinds of optical crystals, glasses, and ceramics. [26][27][28][29][30] Vector beam is a kind of special structured light beam with an anisotropy space distribution of polarization state. 31 Recently, vector beams have been widely used in kinds of applications, such as laser processing, 32 optical trapping, 33 and optical communication.…”

Multiple degrees‐of‐freedom programmable soft‐matter‐photonics: Configuration, manipulation, and advanced applications

“…The laser direct writing system supplies a straight‐forward approach for LC alignment, which is usually composed of a focused UV laser and a pair of translational scanning stages (Figure 2c). [42] In a direct‐writing setup, the sample is put in the focal plane of the optical system to expose the photoalignment materials. The exposed region is moved by translating the stages.…”

Femtosecond Laser Fabrication of Refractive/Diffractive Micro‐Optical Components on Hard Brittle Materials

“…The chiral optical properties are also attributed to the coexistence of two phenomena, stress birefringence, and nanograting birefringence. [ 142 ]…”

“…The chiral optical properties are also attributed to the coexistence of two phenomena, stress birefringence, and nanograting birefringence. [142] The Dammann grating is a typical example of a binary optical beam splitter, a new type of diffraction grating with a unique aperture function. [143] The incident light wave passed through the Dammann grating and produced a uniform-intensity beam array.…”