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A conical tip made out of good conductive metal can be used to efficiently localize the optical field at the apex of the tip. For a tip of finite length both a field singularity (lightning rod effect) and a surface plasmon resonance contribute to the E-field enhancement. A strongly absorbing superconducting nanodetector placed in the optical near-field of the tip shows enhanced optical absorption. The design of an optimal tip- detector system is non-trivial because the strong damping by the detector shifts the resonance wavelength of the tip and significantly lowers the quality factor of the resonance. We compare calculations of the field enhancement of a bare tip to the absorption enhancement in the detector in the presence of the tip as a function of tip length, apex radius and semi-angle of the cone. The resonance of a 225 nm long gold tip in the presence of a detector occurs at 1000 nm and is red-shifted by 150 nm compared to the resonance of a bare tip.

We have studied surface-plasmons on metal hole arrays combined with gain and observe surface plasmon laser action. We will discuss the feedback mechanism, angular beam profile, and spatial emission profile of this surface plasmon laser.

Silicon nitride (Si3N4) optical ring resonators provide exceptional opportunities for low-loss integrated optics. Here we study the transmission through a multimode waveguide coupled to a Si3N4 ring resonator. By coupling single-mode fibers to both input and output ports of the waveguide we selectively excite and probe combinations of modes in the waveguide. Strong asymmetric Fano resonances are observed and the degree of asymmetry can be tuned through the positions of the input and output fibers. The Fano resonance results from the interference between modes of the waveguide and light that couples resonantly to the ring resonator. We develop a theoretical model based on the coupled mode theory to describe the experimental results. The large extension of the optical modes out of the Si3N4 core makes this system promising for sensing applications.

We experimentally characterize sources of frequency degenerate down-converted photons at 826.4 nm generated in 2 mm, 5 mm and 10 mm long periodically-poled KTP crystals. The crystals are pumped by 413.2 nm laser pulses with 2 ps duration. The dispersion D=1.3 ps/mm puts a limit to the length over which phase matching is efficient for a 2 ps pulse and provides a lower limit for the angular width of SPDC in the far-field. We investigate the far-field distribution of SPDC produced by periodically-poled KTP crystals and compare this with the calculated intensity distribution and find good agreement with theory. We also discuss the performance of PPKTP in terms of nonlinearity and group velocity walk-off compared to other available materials.

We explore four-photon spatial entanglement created by stimulated emission of photon pairs in a 2 mm long periodically poled KTP crystal. We vary the experimental conditions to explore and optimize the visiblity of stimulated pairs.

We present a method to transfer free standing photonic crystal membranes to a low refractive index substrate. These structures are optically flat and we compare the optical properties with the properties of free standing membranes.

Photonic graphene is a two-dimensional photonic crystal structure that is analogous to graphene. We use 5 mm diameter ${\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ rods placed on a triangular lattice with a lattice constant $a=8\text{ }\text{ }\mathrm{mm}$ to create an isolated conical singularity in the photonic band structure at a microwave frequency of 17.6 GHz. At this frequency, the measured transmission of microwaves through a perfectly ordered structure enters a pseudodiffusive regime where the transmission scales inversely with the thickness $L$ of the crystal ($L/a\ensuremath{\gtrsim}5$). The transmission depends critically on the configuration of the edges: distinct oscillations with an amplitude comparable to the transmission are observed for structures terminated with zigzag edges, while these oscillations are absent for samples with a straight edge configuration.

Although very desirable for detector applications and photovoltaic cells, thin film materials that absorb all incoming light are extremely hard to find. In this work, we introduce a metamaterial consisting of a meandering wire of only a few nanometer thickness that can absorb all incident radiation when the film is illuminated at the critical angle for total internal reflection. The observed effect occurs for s-polarized radiation in very lossy metals or dielectrics for which the imaginary part of the dielectric constant is much larger than the real part.

The reflection and transmission spectra of two-dimensional photonic crystal slabs show several asymmetric Fano resonances. The asymmetry is due to interference of a direct reflection from the slab with a resonant contribution due to coupling of light to a leaky waveguide mode [1]. In this work, we study the resonances in a photonic crystal slab by imaging the near-field of the propagating modes. This technique allows a separation of the direct and resonant contributions in the reflection and gives an unambiguous measure of the propagation length of the modes.

We propose an experiment to directly probe the local response of a superconducting single photon detector using a sharp metal tip in a scattering scanning near-field optical microscope. The optical absorption is obtained by simulating the tip-detector system, where the tip-detector is illuminated from the side, with the tip functioning as an optical antenna. The local detection efficiency is calculated by considering the recently introduced position-dependent threshold current in the detector. The calculated response for a 150 nm wide detector shows a peak close to the edge that can be spatially resolved with an estimated resolution of ∼ 20 nm, using a tip with parameters that are experimentally accessible.

We report on the demonstration of a high finesse micro-optomechanical system and identify potential applications ranging from optical cooling to weak force detection to massive quantum superpositions. The system consists of a high quality $30\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ diameter flat dielectric mirror cut from a larger substrate with a focused ion beam and attached to an atomic force microscope cantilever. Cavity ring-down measurements performed on a 25 mm long Fabry-P\'erot cavity with the $30\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ mirror at one end show an optical finesse of 2100. Numerical calculations show that the finesse is not diffraction limited and that orders of magnitude higher finesse should be possible. A mechanical quality factor of more than ${10}^{5}$ at pressures below ${10}^{\ensuremath{-}3}\text{ }\text{ }\mathrm{mbar}$ is demonstrated for the cantilever with a mirror attached.

We investigate numerically the existence of photonic band gaps in woodpile crystals. We present a numerical method specifically developed to solve Maxwell's equations in such photonic structures. It is based upon a rigorous mathematical formulation and leads to a considerable improvement of the convergence speed as compared to other existing numerical methods. We tested our method by comparing the calculated reflectivity with measurements on an actual sample, i.e., a silicon woodpile photonic crystal designed for 1.5 microm wavelength. Excellent agreement is obtained, provided the main structural imperfections of the sample are taken into account. We show that the existence of photonic band gaps in woodpile crystals requires an index contrast higher than 2.05 +/- 0.01. The effects of imperfections of such structures with an index contrast equal to 2.25 are also investigated. Thus, the relative band gap width falls from 3.5% to 2.2% with structurals imperfection similar to those of the sample.

We investigate the use of a superconducting nano-detector as a novel near-field probe. In contrast to conventional scanning near-field optical microscopes, the nano-detector absorbs and detects photons in the near-field. We show that this absorption-based probe has a higher collection efficiency and investigate the details of the interaction between the nano detector and the dipole emitter. To this end, we introduce a multipole model to describe the interaction. Calculations of the local density of states show that the nano-detector does not strongly modify the emission rate of a dipole, especially when compared to traditional metal probes.

We observe a 104 times enhancement of the second harmonic generation of 1.535 μm laser light in a two-dimensional AlGaAs photonic crystal at normal incidence. The linear properties of the optical modes that are resonant with the fundamental frequency are well described by a Fano model and have a typical quality factor of 100. We present an extended version of the Fano interpretation to quantitatively analyze the second harmonic signal using the measured linear properties as input and find good agreement with the data.