Microscale integrated sensor points to cheaper high-throughput displacement sensing

With the rise of applications for atomic force microscopy, mass sensing and accelerometry, demand is growing for smaller and smaller displacement sensors with higher and higher resolution and throughput capabilities. Many of today’s systems operate by measuring the deflection of a cantilever, which can introduce extra bulk to nanoscale devices. One new device looks to provide the integration of sensor read-out for low-cost, compact and parallelizable devices.

Galeotti et al. present a new integrated device for displacement sensing with sub-nanometer resolution. Using a micron-sized double-membrane photonic crystal cavity, the proposed nano-opto-electro-mechanical sensor is with integrated electro-optical read-out and electro-mechanical actuation, which is directly addressed via an on-chip waveguide.

The resulting device features a noise floor comparable with the standard read-out for atomic force microscopy but with an extremely compact footprint of 150 μm² – about one-tenth the cross-section of a human hair.

“The compactness and the level of integration of the read-out and waveguide coupling are surely the key points in this device,” said author Federico Galeotti. “In order to obtain parallelized optical sensing, particularly for AFM application, the development of a displacement sensor which can be massively fabricated on chip is fundamental.”

This sensor displays a noise floor down to 7 fm/Hz and is suitable for the realization of integrated arrays. Because of its fabrication based on semiconductor processing technology, the sensor also has the potential to be integrated into larger sensor arrays.

Galeotti next looks to demonstrate the sensor’s use as an on-chip nanoscale transducer in atomic force microscopy imaging, first by investigating its function with constant force and later expanding to other modes of operation.

Source: “On-chip waveguide-coupled opto-electro-mechanical system for nanoscale displacement sensing,” by Federico Galeotti, Ivana Seršić Vollenbroek, Maurangelo Petruzzella, Francesco Pagliano, Frank W.M. van Otten, Žarko Zobenica, Abbas Mohtashami, Hamed Sadeghian, Rob W. van der Heijden, and Andrea Fiore, APL Photonics (2019). The article can be accessed at https://doi.org/10.1063/1.5131576 .