Characterization of buried photonic crystal waveguides and microcavities fabricated by deep UV-lithography

We present results of the optical characterization of silicon photonic crystal waveguides and microcavities that are completely buried in a silicon dioxide cladding and are fabricated by deep ultraviolet (UV) lithography. The advantages of buried waveguides and deep UV lithography are discussed. Transmission spectra and loss factors for photonic crystal waveguides, as well as quality factors for resonant microcavities, are obtained. The observed characteristics are in good agreement with three-dimensional simulations.

Characterization of Photonic Crystal Waveguides Based on Fabry-Pérot Interference

Hans Peter Herzig, Iwan Märki, Ross Stanley

We present two methods based on the analysis of Fabry-Perot interference for a detailed characterization of a 90degrees corner in a two-dimensional photonic crystal waveguide fabricated in a thin Si membrane. These methods are a means of identifying the critical waveguide elements in the process of improving photonic crystal devices. The effects of the elements forming the photonic crystal waveguide are identified and quantified by means of a stage-by-stage analysis. By Fourier transforming the transmission spectra we observe the amount of light that is back reflected inside the waveguide and based on the fringe contrast of the Fabry-Perot modulation we calculate the loss contribution of each waveguide element, such as the tapers and the 90degrees corner.

2004

Optically tuneable microcavity in a planar photonic crystal silicon waveguide buried in oxide

Hans Peter Herzig, Iwan Märki, Ross Stanley

We present all-optical tuning and switching of a microcavity inside a two-dimensional photonic crystal waveguide. The photonic crystal structure is fabricated in silicon-on-insulator using complementary metal-oxide semiconductor processing techniques based on deep ultraviolet lithography and is completely buried in a silicon dioxide cladding that provides protection from the environment. By focusing a laser onto the micro cavity region, both a thermal and a plasma dispersion effect are generated, allowing tuning and fast modulation of the in-plane transmission. By means of the temporal characteristics of the in-plane transmission, we experimentally identify a slower thermal and a fast plasma dispersion effect with modulation bandwidths of the order of several 100 kHz and up to the gigahertz level, respectively.

2005

Tunable and Broadband Nanostructured Photonic Devices

Pierre-Yves Baroni

The main topic of this thesis is the fabrication and characterization of structures smaller than the wavelength of light, for operation in the visible or near infrared spectral range. In the first part of this thesis, the fabrication of periodic structures in one and two dimensions with an interference photolithography technique is described in detail. The structure periodicities that have been fabricated with this process ranges between 270 nm and a few microns on areas that can be as large as 100 cm2. Typical structure thicknesses are approximately equal to the period. In particular, a square lattice of pillars with a period of 270 nm has been created on the (non-flat) surface of a quartz microlens array and exhibits anti-reflective properties. Experimental results show a 15 % attenuation of the reflectivity and a 3 % enhancement of the transmissivity over the visible spectral range. In the second part of the thesis the structures are fabricated by e-beam lithography to ensure very precise devices shapes. The experimental results are obtained in the infrared range with two different structures, called photonic crystals. The first structure, a superprism, is a triangular lattice of pillars infiltrated by liquid crystals. A displacement of the output light spot is measured to be 20.5 µm for a wavelength variation of 27 nm. The structure length is 70 µm. The device, based on standard silicon technology, should allow integration of the device as a multiplexer/demultiplexer system into optical micro-circuits. The second structure, a tunable resonant cavity, is a wavelength filter working in the near infrared spectrum. The active area is composed of a photonic waveguide with a triangular lattice made of sub-micrometer holes. Additional nanostructuring in the light waveguide acts as a resonant cavity. The tunability of the device is obtained due to the liquid crystals which are infiltrated into the nanostructure. A 32 nm shift of the transmitted light peak inside the photonic band gap is measured by changing the temperature from room temperature to 45 °C.

EPFL2010

Tunable and Broadband Nanostructured Photonic Devices

Pierre-Yves Baroni

EPFL2010