Electro-thermally tunable silicon photonic crystal lens

We report extremely compact (30 µm × 7 µm) silicon based two-dimensional (2D) thermo-optically tunable photonic crystal lens which operates at around telecommunication wavelength (1.55 µm) with transverse magnetic (TM) like polarized light. A 150 nm thick NiCr micro-heater was placed directly on top of the photonic crystal lens to provide localized heating. The focal length of the photonic crystal lens is modulated through refractive index change caused by thermo-optic effect of silicon. Tuning of the focal length was experimentally demonstrated by applying various current through the heater and the results showed good agreed with the simulation results.