Enhancement of the indistinguishability of single photon emitters coupled to photonic waveguides.

One of the main steps towards large-scale quantum photonics consists of the integration of single photon sources (SPS) with photonic integrated circuits (PICs). For that purpose, the PICs should offer an efficient light coupling and a high preservation of the indistinguishability of photons. Therefore, optimization of the indistinguishability through waveguide design is especially relevant. In this work we have developed an analytical model that uses the Green's Dyadic of a 3D unbounded rectangular waveguide to calculate the coupling and the indistinguishability of an ideal point-source quantum emitter coupled to a photonic waveguide depending on its orientation and position. The model has been numerically evaluated through finite-difference time-domain (FDTD) simulations showing consistent results. The maximum coupling is achieved when the emitter is embedded in the center of the waveguide but somewhat surprisingly the maximum indistinguishability appears when the emitter is placed at the edge of the waveguide where the electric field is stronger due to the surface discontinuity.

Low-cost and large-size nanoplasmonic sensor based on Fano resonances with fast response and high sensitivity.

We have developed a low-cost, fast and sensitive plasmonic sensor with a large-size for easy handling. The sensor is formed by a Au nanobelt grating fabricated by soft lithography with a period of 780 nm and a width of 355 nm in an even and uniform area of ~2 × 2 cm2. The sensor uses the Fano-shaped third order mode localized plasmon resonance of the Au nanobelts, which appears in the visible part of the transmission spectrum. We have found a detection resolution of 1.56 × 10-5 refractive index units with a temporal resolution of 1 s in a sensing area of 0.75 × 0.75 mm2. The high uniformity and size of the sensor permit the detection using a simple optical system, which provides the device with the potential to be used as an easy to handle, portable and disposable sensor.

Emission polarization control in semiconductor quantum dots coupled to a photonic crystal microcavity.

We study the optical emission of single semiconductor quantum dots weakly coupled to a photonic-crystal micro-cavity. The linearly polarized emission of a selected quantum dot changes continuously its polarization angle, from nearly perpendicular to the cavity mode polarization at large detuning, to parallel at zero detuning, and reversing sign for negative detuning. The linear polarization rotation is qualitatively interpreted in terms of the detuning dependent mixing of the quantum dot and cavity states. The present result is relevant to achieve continuous control of the linear polarization in single photon emitters.

Optofluidic chips with nanochannels for dynamic molecular detection using enhanced fluorescence.

The fabrication of a novel optofluidic chip using nanochannels optimized for DNA-stretched molecules and optical detection by enhanced fluorescence is reported. The chips are composed of a series of microchannels that allow the transport of molecules in the femto-liter per second inside a fluid or gas. The nanochannels are surrounded by a photonic crystal structure to enhance the emission of fluorescent light from the molecules, which can travel along the nanochannel, allowing for enhanced optical detection of the molecules in motion. The photonic crystal structure provides an enhancement up to 2.5 times in the light emitted from fluorescent molecules inside the nanochannels which increases to around 250 when normalized to the area of the nanochannels emitting fluorescence. The results may help to the detection of fluorescent molecules (like marked-DNA) in series by speeding it and allowing the use of less sophisticated equipment.