Topology optimization is used to design a planar photonic crystal waveguide component resulting in significantly enhanced functionality. Exceptional transmission through a photonic crystal waveguide Z-bend is obtained using this inverse design strategy. The design has been realized in a silicon-on-insulator based photonic crystal waveguide. A large low loss bandwidth of more than 200 nm for the bandgap polarization is experimentally confirmed.

No abstract

Structural characterization of the third polymorph of silicon nitride, synthesized under high-pressure and high-temperature conditions, has been obtained by Rietveld structure refinements of X-ray powder diffraction data recorded using synchrotron radiation. The material has a cubic spinel structure at 295 K with a space group Fd-3m, Z = 8, a unit cell of a = 7.7339±0.0001 Å, nitrogen position x = 0.2583±0.0001, and density ρ = 3.75±0.02 g cm −3 . The complete structural data obtained should offer a firm basis for understanding the properties of the novel material. One example is present for the Raman spectroscopy data of the material.

Thermal nanoimprint lithography (NIL) of the cyclic olefin copolymeric thermoplast Topas® is demonstrated. Topas® is highly UV-transparent, has low water absorption, and is chemically resistant to hydrolysis, acids and organic polar solvents which makes it suitable for lab-on-a-chip applications. In particular, Topas® is suitable for micro systems made for optical bio-detection since waveguides for UV-light can be made directly in Topas®. In this article full process sequences for spin coating Topas® onto 4 in. silicon wafers, NIL silicon stamp fabrication with micro and nanometer sized features, and the NIL process parameters are presented. The rheological properties of Topas® are measured and the zero shear rate viscosity is found to be 2.16×104 Pa s at 170 °C and 3.6×103 Pa s at 200 °C while the dominant relaxation time is found to be 4.4 s and 0.9 s, respectively. The etch resistance of Topas® to two different reactive ion etch processes, an oxygen plasma, and an anisotropic silicon etch, is found to be 12.6 nm/s and 0.7 nm/s, respectively. The etch rates are compared to the similar etch rates of 950 k PMMA, cross-linked SU-8, and standard AZ5214E photoresist. Finally, UV-lithography (UVL) followed by metal deposition and lift-off on top of a Topas® film patterned by NIL is demonstrated. This exploits the chemical resistance of Topas® to sodium hydroxide and acetone. The demonstrated UVL and lift-off on top of an imprinted Topas® film opens new possibilities for post-NIL processing.