Photonic crystal nanocavities fabricated from chalcogenide glass fully embedded in an indexmatched cladding with a high Q-factor (>750,000)

We have designed and fabricated a 2-D photonic crystal heterostructure cavity in the chalcogenide glass Ge_11.5As₂₄Se_64.5 that is fully embedded in a cladding with refractive index of 1.44. The low index contrast of this structure (≈ 1.21) means that high-Q resonances cannot be obtained using standard hetero-structure cavity designs based on W1 waveguides. We show that reducing the waveguide width can substantially improve light confinement, leading to high-Q resonances in a heterostructure cavity. Numerical simulations indicate intrinsic Q_v > 107 are possible with this approach. Experimentally, an optical cavity with a high intrinsic Q_v>7.6 × 10⁵ was achieved in a structure with a theoretical Q_v = 1.7 × 10⁶.