Reconfigurable microfluidic photonic crystal slab cavities

Abstract

We demonstrate the spectral and spatial reconfigurability of photonic crystal double-heterostructure cavities in silicon by microfluidic infiltration of selected air holes. The lengths of the microfluidic cavities are changed by adjusting the region of infiltrated holes in steps of several microns. We systematically investigate the spectral signature of these cavities, showing high Q-factor resonances for a broad range of cavity lengths. The fluid can be removed by immersing the device in toluene, offering complete reconfigurability. Our cavity writing technique allows for tolerances in the infiltration process and provides flexibility as it can be employed at any time after photonic crystal fabrication.

In situ optofluidic control of reconfigurable photonic crystal cavities

“…With only a small section of the waveguide infiltrated (roughly 10 periods), a fluid-induced double heterostructure (DHS) cavity is created. [12][13][14][15]19 This DHS cavity is also observed in the present experiments as follows from curves 1 and 2 of Fig. 4(b).…”

“…8 By careful local evaporation of infiltrated water, an accurate tuning mechanism for pre-existing PhC cavities was realized, 9 which enabled detailed studies of coupled cavities. 10,11 Selective liquid infiltration of planar PhCs was not merely used to tune pre-existing cavities and devices but also proposed 12 and demonstrated [13][14][15] as a way to create liquidinduced double heterostructure cavities. While reconfigurability is an important motivation for the local liquid infiltration, 16 whether it is applied to tuning or liquid-induced devices, the associated demonstrations still lack flexibility and do not take full advantage of the mobile nature of the liquids.…”

“…The selective local liquid infiltration is performed using the method reported earlier. [13][14][15] An optical fiber is pulled to a diameter less than 1 lm in a microflame and after breaking is mounted in an independent piezo-controlled nanomanipulator near the sample. 18 The tip is wetted in the liquid from a macroscopic ($1 mm 3 ) drop somewhere on the chip.…”

Temperature stabilization of optofluidic photonic crystal cavities

“…We have shown previously that the quality factor associated with the modes of optofluidic cavities decreases with decreasing wavelength. 9 This phenomenon is based on the fact that the modes at shorter wavelengths experience a lower effective refractive index and thus the vertical confinement in the slab is less, reducing the quality factor of that specific mode. The depth of the Fabry-Pérot dip for the various modes varies with temperature due to the change of coupling efficiency between tapered fiber and optofluidic cavity with temperature.…”

“…1 PhC cavities may exhibit high quality factors, 2 suggesting great potential for realizing compact and high-resolution refractive index sensors, 3,4 including sensor arrays for biomolecular detection. 5 In this context, the combination of PhC components with microfluidics-a subset of optofluidics 6 -has attracted much attention because it allows hybrid architectures that offer tunable 7,8 or reconfigurable 9 optical properties and double-heterostructure PhC cavities with high quality factors of the order of Q Ϸ 60 000. 10 In many sensor applications, a major challenge is the susceptibility of the sensing system to environmental changes.…”