Femtosecond laser micromachined optical waveguides in LiTaO₃ crystal

Abstract

By using femtosecond laser micromachining, optical wave guides in both depressed cladding and dual‐line configurations have been produced in LiTaO3 crystal. The guiding properties and the thermal stability have been investigated for both geometries, which exhibit different performance. Depressed cladding waveguides support guidance along both extraordinary and ordinary index polarizations, while dual‐line waveguides support only extraordinary index polarization. Thermal annealing has been proved to be an effective method to reduce the propagation losses. For the cladding waveguide, the lowest propagation loss was as low as 0.38 dB/cm after the annealing treatment at 400 °C. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Fabrication of Hierarchical Micro/Nano Compound Eyes

“…In the past few decades, because of significant advantage over a single lens, artificial compound eyes have been studied by many groups, and several fabrication strategies were proposed, including laser direct writing, − Three-dimensional (3D) configurations, ,− or surface wrinkling. , These methods, however, do not render good control of the geometry and shape of a lenslet due to their intrinsic limitations. Moreover, the stereotype lens shape (round) and a larger size of ommatidia (400–1000 μm) of these artificial eyes are much different from those natural ones, which would seriously degrade their optical performance such as resolution and the signal-to-noise ratio.…”

Femtosecond laser hybrid processing strategy of transparent hard and brittle materials

“…By using a temperature higher than the softening point of the amorphous state and lower than the melting point of the crystal, it is possible to give the amorphous layer enough internal energy to soften and volatilize without changing the structure of the crystal body ( He et al, 2013 ). Xu et al (2013) prepared optical waveguides with low cladding and bilinear structure in LiTaO 3 crystals using femtosecond laser ablation combined with annealing. After the thermal annealing process, the propagation loss of the cladding waveguide was reduced and its transmission loss was minimized to 0.38 dB/cm.…”

Fabrication of Artificial Compound Eye with Controllable Field of View and Improved Imaging

“…Because of their unique design and benefits, successful mimicking of, for example, an insect’s eye would be a big step toward an ideal visual system that also offers multifunctional benefits like miniaturization, multiaperture, and a large FOV. A well-functioning artificial compound eye (ACE) may find potential applications in areas like navigation, sensing, biomedical endoscopy, and security cameras. ,− Consequently, the preparation and design of a compound eye has become an active research topic.…”