Tunable ferroelectric photonic crystals

Spectral tuning of photonic band gap (PBG) in photonic crystals is attained due to temperature changes of the refractive index of sodium nitrite infiltrated into the porous silicon template, composed by electrochemical etching of n-type silicon. Optical second harmonic generation measurements prove the ferroelectric state of the infiltrated NaNO
₂
and reveal the ferroelectric behavior different from spinning films of sodium nitrite that is attributed to nanocrystalline and surface effects of NaNO
₂
inside porous silicon matrix. The tuning of PBG up to 15 nm is achieved in the temperature interval from 50degC to 200degC.