Light control by nanostructured metal surfaces and photonic crystals in nanobeams and freestanding membranes

B. Wang

Research output: ThesisPhd Thesis 1 (Research TU/e / Graduation TU/e)

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Abstract

The work presented in this thesis aims at studying the properties of photonic crystals (PhCs) and developing their applications, such as slow light waveguide, superlens, modulator and sensor. PhCs are periodic nanostructures, which affect the motion of photons in a similar way that periodicity of a semiconductor crystal affects the motion of electrons. In this thesis, both simulation and experimental studies are presented. For the simulations, the plane wave expansion and finite difference time domain methods are used to calculate the band structures of PhCs and obtain the field distribution of a finite PhC, respectively. The fabrication is done in the clean room with the state of the art technology. Exploiting the incorporated quantum dots, the optical characterization was performed with a micro-photoluminescence (µPL) experiment. At terahertz frequencies, tailoring the topography of metal surface allows to localize the evanescent parts of surface waves to a distance significantly smaller than the wavelength. The propagation loss is discussed, when the metal is used as a waveguide. Normally, the loss is large when the group velocity is small. A new type of metal waveguide is designed for slow light with a small propagation loss and small group velocity dispersion by applying two thin metal slabs with subwavelength periodic corrugations on their inner boundaries. Several dielectric PhC configurations are designed and analyzed for different applications. A PhC superlens is designed with a resolution of 0.164¿ which beats the diffraction limit. The effect of disorder in the PhC on the extraction efficiency of a Light Emitting Diode is also studied by modelling the disordered PhC. A PhC waveguide is designed to make a fast modulator as an optical circuit component. A liquid crystal is used to tune the degeneracy of cavity modes of a PhC cavity. The latter design was verified experimentally. A major part of the thesis is concerned with sensing. Miniaturization of label-free optical sensors is of particular interest for realizing ultracompact lab-on-a-chip applications with dense arrays of functionalized spots for multiplexed sensing, which may lead to portable, low cost and low power devices. A PhC is very promising as a sensing element. A record high sensitivity PhC nanobeam is realized experimentally with a sensitivity of about 900 nm per refractive index unit. Simulations show that the quality factor can be substantially increased by tapering the two ends. Spectrally encoded PhC nanocavities by independent lithographic mode tuning are experimentally demonstrated for identification. The PhC nanocavities are taken from the chip to serve as autonomous devices for (bio)sensing. The properties of these free PhC nanocavities are studied by nano-manipulation and µPL experiments. The possibility of attaching one PhC nanocavity to the end of a fibre to make a fibre sensor is shown. The feasibility of an alignment procedure by precise nano-manipulation is demonstrated, which will enable to make three dimensional nanophotonic structures.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Applied Physics
Supervisors/Advisors
  • Fiore, Andrea, Promotor
  • He, S., Promotor, External person
  • van der Heijden, Rob W., Copromotor
Award date10 Oct 2011
Place of PublicationEindhoven
Publisher
Print ISBNs978-90-386-2660-4
DOIs
Publication statusPublished - 2011

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