Excitonic polaritons in Fibonacci quasicrystals.

The fabrication and characterization of light-emitting one-dimensional photonic quasicrystals based on excitonic resonances is reported. The structures consist of high-quality GaAs/AlGaAs quantum wells grown by molecular-beam epitaxy with wavelength-scale spacings satisfying a Fibonacci sequence. The polaritonic (resonant light-matter coupling) effects and light emission originate from the quantum well excitonic resonances. Measured reflectivity spectra as a function of detuning between emission and Bragg wavelength are in good agreement with excitonic polariton theory. Photoluminescence experiments show that active photonic quasicrystals, unlike photonic crystals, can be good light emitters: While their long-range order results in a stopband similar to that of photonic crystals, the lack of periodicity results in strong emission.