Tunable on-chip optical traps for levitating particles based on single-layer metasurface.

Optically levitated multiple nanoparticles have emerged as a platform for studying complex fundamental physics such as non-equilibrium phenomena, quantum entanglement, and light-matter interaction, which could be applied for sensing weak forces and torques with high sensitivity and accuracy. An optical trapping landscape of increased complexity is needed to engineer the interaction between levitated particles beyond the single harmonic trap. However, existing platforms based on spatial light modulators for studying interactions between levitated particles suffered from low efficiency, instability at focal points, the complexity of optical systems, and the scalability for sensing applications.

Free space variable optical attenuator using frustrated total internal reflection with 70 dB dynamic range.

With the advance of high power laser systems, there is an increasing need to dim the corresponding light field power over larger dynamic ranges. The usual means to control the attenuation of directed light use optical filters or coatings with tailored reflectance and transmittance properties. They do not provide the variability that is often required in experiments.