  We present a microcavity structure with a shifted photonic stop-band to
enable efficient non-resonant injection of a polariton condensate with
spectrally broad femtosecond pulses. The concept is demonstrated theoretically
and confirmed experimentally for a planar GaAs/AlGaAs multilayer
heterostructure pumped with ultrashort near-infrared pulses while
photoluminescence is collected to monitor the optically injected polariton
density. As the excitation wavelength is scanned, a regime of polariton
condensation can be reached in our structure at a consistently lower fluence
threshold than in a state-of-the-art conventional microcavity. Our microcavity
design improves the polariton injection efficiency by a factor of 4, as
compared to a conventional microcavity design, when broad excitation pulses are
centered at a wavelength of 740 nm. Most remarkably, this improvement factor
reaches 270 when the excitation wavelength is centered at 750 nm.

Mesoscale and Nanoscale Physics;Optics