Photonic Wire Micro Cavities

Contacts:

Lars Hagedorn Frandsen, DTU Fotonik, 4525-6359 (lhfr@fotonik.dtu.dk)

Torben Roland Nielsen, DTU Fotonik, 4525-6367 (trn@fotonik.dtu.dk)

Jesper Mørk, DTU Fotonik, 4525-5765 (jm@fotonik.dtu.dk)

http://www.fotonik.dtu.dk

(top) Scanning electron microscope picture of a photonic wire with microcavities fabricated in silicon-on-insulator material in the DANCHIP cleanroom. (Middle, bottom) 3D Finite Difference Time Domain simulation of a light pulse propagating in the wire and approaching the micro cavity.

The combination of narrow optical waveguides and one-dimensionally periodic photonic crystal structures in high refractive index semiconductors such as silicon, in the form of silicon-on-insulator and epitaxial structures based on the III-V semiconductors, has been a topic of interest for a number of years. Designing high quality-factor performance in this kind of structure is useful for telecoms applications such as all-optical (non-linear) switching and dense wavelength division multiplexing.

Recent work has led to demonstrations of quality-factor (Q-factor) values approaching 60,000 together with a normalised transmission coefficient of nearly 90%. Observations using various versions of scanning near-field optical microscopy have also verified that such structures can exhibit optical confinement in very small volumes, resulting in extremely large Purcell-factor values. Key factors in achieving such high values of Q-factor and normalised transmission are the incorporation of hole diameter tapering, careful displacement of hole position in transition sections (both within and outside the cavity) and careful adjustment of the length of the cavity spacer section, aided by numerical modelling.

In this project, you will take part in the research carried out at DTU Fotonik on planar photonic wire micro cavities fabricated in silicon at DANCHIP. The project will focus on the modelling and optimization of the Q-factor and transmission of the cavities using state-of-the-art user-friendly simulation tools. Based on the knowledge gained from this modelling work you will (if time permits) have the chance to fabricate your own novel photonic wire component in the DANCHIP cleanroom and characterize it in the optical lab at DTU Fotonik.