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(a) SEM image of a fabricated structure in which , , and . (b) Schematic diagram of the modified H1 defect cavity. The photonic crystal consists of a triangular lattice of air columns (or holes) with a lattice spacing and a radius . A defect cavity is created by removing a single hole and modifying the radius, , of the surrounding six nearest neighbors.
A typical photoluminescence spectrum from a structure with ; exhibits a resonant peak, M, at a wavelength of . The emission from an exciton is labeled X. The dashed lines show Lorentzian fits to the two peaks, from which a quality factor for the cavity of can be determined. A comparison of the intensity of the exciton line X with that from a quantum dot not in a photonic crystal cavity is shown in the inset, the former being two orders of magnitude more intense at saturation.
The PL spectrum for device A at (top panel) shows two excitons, and , detuned from the optical mode, , by and , respectively. The time resolved data for is shown in the inset and a lifetime of was calculated. In device B (bottom panel) the mode, is on resonance with an exciton, . A streak camera was used to measure a lifetime of (inset).
As the temperature is increased, the detuning of (closed squares) from (open squares) decreases until they come onto resonance at (left panel). This has the effect of reducing the exciton lifetime to below the temporal resolution of the system (dashed line). This trend is compared (right panel) to structures with a much larger (closed circles) and with a smaller (closed triangles) detuning at . In the former case, the exciton lifetime is approximately independent of temperature up to . In the latter case, as the temperature is increased above the lifetime begins to increase as the detuning is increased.
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