Richard M. De La Rue

Bio: Richard M. De La Rue is an academic researcher from University of Glasgow. The author has contributed to research in topics: Photonic crystal & Photonics. The author has an hindex of 25, co-authored 150 publications receiving 3397 citations. Previous affiliations of Richard M. De La Rue include Imperial College London & University of Malaya.

Two-dimensional photonic-bandgap structures operating at near-infrared wavelengths

Abstract: PHOTONIC crystals are artificial structures having a periodic dielectric structure designed to influence the behaviour of photons in much the same way that the crystal structure of a semiconductor affects the properties of electrons1. In particular, photonic crystals forbid propagation of photons having a certain range of energies (known as a photonic bandgap), a property that could be incorporated in the design of novel optoelectronic devices2. Following the demonstration of a material with a full photonic bandgap at microwave frequencies3, there has been considerable progress in the fabrication of three-dimensional photonic crystals with operational wavelengths as short as 1.5 μm (ref. 4), although the optical properties of such structures are still far from ideal5. Here we show that, by restricting the geometry of the photonic crystal to two dimensions (in a waveguide configuration), structures with polarization-sensitive photonic band-gaps at still lower wavelengths (in the range 800–900 nm) can be readily fabricated. Our approach should permit the straightfor-ward integration of photonic-bandgap structures with other optical and optoelectronic devices.

Ultra high quality factor one dimensional photonic crystal/photonic wire micro-cavities in silicon-on-insulator (SOI)

Abstract: We present experimental results on photonic crystal/photonic wire micro-cavity structures that demonstrate further enhancement of the quality-factor (Q-factor)--up to approximately 149,000--in the fibre telecommunications wavelength range. The Q-values and the useful transmission levels achieved are due, in particular, to the combination of both tapering within and outside the micro-cavity, with carefully designed hole diameters and non-periodic hole placement within the tapered section. Our 2D Finite Difference Time Domain (FDTD) simulation approach shows good agreement with the experimental results.

Asymmetric split ring resonators for optical sensing of organic materials

Abstract: Asymmetric Split Ring Resonators are known to exhibit resonant modes where the optical electric field is strongest near the ends of the arms, thereby increasing the sensitivity of spectral techniques such as surface enhanced Raman scattering (SERS). By producing asymmetry in the structures, the two arms of the ring produce distinct plasmonic resonances related to their lengths – but are also affected by the presence of the other arm. This combination leads to a steepening of the slope of the reflection spectrum between the resonances that increases the sensitivity of the resonant behavior to the addition of different molecular species. We describe experimental results, supported by simulation, on the resonances of a series of circular split ring resonators with different gap and section lengths – at wavelengths in the mid-infra red regions of the spectrum - and their utilization for highly sensitive detection of organic compounds. We have used thin films of PMMA with different thicknesses, resulting in characteristic shifts from the original resonance. We also demonstrate matching of asymmetric split ring resonators to a molecular resonance of PMMA.

2D Photonic crystal thermo-optic switch based on AlGaAs/GaAs epitaxial structure.

Abstract: The realisation of a thermo-optically controlled symmetric Mach- Zehnder interferometer switch based on an AlGaAs/GaAs epitaxial waveguide structure operating at wavelengths in the region of ? = 1550 nm is reported. The device is based on a very compact two-dimensional photonic crystal channel waveguide structure. The measured and simulated transmission spectra for the devices are in good agreement. The ?-phase shift switching power for the device is as low as 42 mW.

The Fano resonance in plasmonic nanostructures and metamaterials

Abstract: Since its discovery, the asymmetric Fano resonance has been a characteristic feature of interacting quantum systems. The shape of this resonance is distinctively different from that of conventional symmetric resonance curves. Recently, the Fano resonance has been found in plasmonic nanoparticles, photonic crystals, and electromagnetic metamaterials. The steep dispersion of the Fano resonance profile promises applications in sensors, lasing, switching, and nonlinear and slow-light devices.

Photonic crystals: putting a new twist on light

Abstract: Photonic crystals are materials patterned with a periodicity in dielectric constant, which can create a range of 'forbidden' frequencies called a photonic bandgap. Photons with energies lying in the bandgap cannot propagate through the medium. This provides the opportunity to shape and mould the flow of light for photonic information technology.

Photonic crystals

Abstract: The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

The Quantum Theory of Light

Abstract: (b) Write out the equations for the time dependence of ρ11, ρ22, ρ12 and ρ21 assuming that a light field interaction V = -μ12Ee iωt + c.c. couples only levels |1> and |2>, and that the excited levels exhibit spontaneous decay. (8 marks) (c) Under steady-state conditions, find the ratio of populations in states |2> and |3>. (3 marks) (d) Find the slowly varying amplitude ̃ ρ 12 of the polarization ρ12 = ̃ ρ 12e iωt . (6 marks) (e) In the limiting case that no decay is possible from intermediate level |3>, what is the ground state population ρ11(∞)? (2 marks) 2. (15 marks total) In a 2-level atom system subjected to a strong field, dressed states are created in the form |D1(n)> = sin θ |1,n> + cos θ |2,n-1> |D2(n)> = cos θ |1,n> sin θ |2,n-1>

Two-photon polymerization initiators for three-dimensional optical data storage and microfabrication

Abstract: Two-photon excitation provides a means of activating chemical or physical processes with high spatial resolution in three dimensions and has made possible the development of three-dimensional fluorescence imaging, optical data storage, and lithographic microfabrication. These applications take advantage of the fact that the two-photon absorption probability depends quadratically on intensity, so under tight-focusing conditions, the absorption is confined at the focus to a volume of order λ3 (where λ is the laser wavelength). Any subsequent process, such as fluorescence or a photoinduced chemical reaction, is also localized in this small volume. Although three-dimensional data storage and microfabrication have been illustrated using two-photon-initiated polymerization of resins incorporating conventional ultraviolet-absorbing initiators, such photopolymer systems exhibit low photosensitivity as the initiators have small two-photon absorption cross-sections (δ). Consequently, this approach requires high laser power, and its widespread use remains impractical. Here we report on a class of π;-conjugated compounds that exhibit large δ (as high as 1, 250 × 10−50 cm4 s per photon) and enhanced two-photon sensitivity relative to ultraviolet initiators. Two-photon excitable resins based on these new initiators have been developed and used to demonstrate a scheme for three-dimensional data storage which permits fluorescent and refractive read-out, and the fabrication of three-dimensional micro-optical and micromechanical structures, including photonic-bandgap-type structures.