Ultrafast Laser Volume Nanostructuring of Transparent Materials: From Nanophotonics to Nanomechanics

Abstract

The capability of ultrashort laser pulses to generate nonlinear absorption in the transparency window of dielectric materials is at the base of volume structuring. The result is a local change of the refractive index, the building block for generating complex embedded optical functions in three-dimensional geometries within a monolith chip. The nonlinearity determines spatial scales on the order of the wavelength. Depending on the rate and the amount of energy deposition, the local refractive index change can be accurately tuned from positive to negative values on variable scales, generating thus new capabilities for processing light within an optical chip in terms of embedded waveguides and micro-optics. New irradiation strategies and engineered glasses permit to go even further in reaching processing super-resolution, i.e. on spatial scales smaller than the optical resolution. The smallest scales achievable nowadays go well bellow the diffraction limit approaching and even surpassing the 100 nm value, a tenth of the wavelength. We will discuss in this chapter the possibility of obtaining structural features much smaller than the electromagnetic wavelength and the associated methods. Direct focusing and self-organization phenomena will be analyzed, as well as the optical functions originating from these processes, namely in transporting and manipulating light. Achieving extreme scales in the range of 100 nm generates an additional capability Razvan Stoian

High-Efficiency Multilevel Volume Diffraction Gratings inside Silicon

“…In recent years, 3D laser lithography has enabled the fabrication of photonic components in Si − and various other materials. − Here, we focus on 3D nonlinear laser lithography exploiting pulsed infrared lasers to create microstructures inside Si, with an optical index contrast on the order of 1 × 10 –3 to 5 × 10 –4 . ,, The magnitude of the index modulation limits the diffraction efficiency (DE) for practical device thickness values. For instance, the power ratio between the zeroth and first diffraction orders of Raman-Nath gratings fabricated with period Λ = 50 μm has been limited to 5–10%, measured at λ = 1310 nm wavelength, depending on the laser polarization .…”

“…In recent years, 3D laser lithography has enabled the fabrication of photonic components in Si 8 − 14 and various other materials. 15 − 18 Here, we focus on 3D nonlinear laser lithography exploiting pulsed infrared lasers to create microstructures inside Si, with an optical index contrast on the order of 1 × 10 –3 to 5 × 10 –4 . 8 , 9 , 19 The magnitude of the index modulation limits the diffraction efficiency (DE) for practical device thickness values.…”