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A photonic crystal L3 nanocavity, consisting of only three missing neighboring holes, is coupled to a large multimode 60 missing holes cavity, both made in an InGaAsP membrane. The coupling was studied in detail by the photothermal tuning of the small cavity over about three Free Spectral Ranges of the large cavity. A single mode from the L3 cavity is shown to couple simultaneously to at least three cavity modes of the large cavity as concluded from level anticrossing data when the small cavity was tuned. The observations are excellently reproduced by a model of coupled Fabry Perot resonators.

Planar photonic crystal nanocavities, made in a thin semiconductor membrane and suspended by breakable tethers, are released after fabrication. The cavity spectrum can be read out remotely by detecting the photoluminescence of embedded Quantum Dots. Both transfer printing and deterministic positioning of the cavities on foreign substrates by individual micromanipulation is demonstrated. The microscopic environment of the particles, including their bonding to the substrate, determines the cavities' resonance spectrum, which can be exploited in applications. As the first application, we demonstrate a novel fiber-optic sensor with a PhC cavity chiplet attached to the tip of a single-mode optical fiber.

The conventional optical detectors operate in a linear mode, but their sensitivity is limited due to the noise in the readout electronics. Single photon detectors, on the other hand, have the highest sensitivity, but are strongly nonlinear. Photon number resolving detectors, which can precisely determine the number of photons in weak optical pulses, are potential candidates to fill the gap between these two detection modes. We present the design of photon number resolving detectors with large dynamic range, based on spatial multiplexing of superconducting single photon detectors, with excellent timing resolution and very high sensitivity at the telecommunication wavelength range.