Picture of PhCreflector
The image shows an artistic impression of a freely suspended mechanical resonator that reflects a focused laser beam. Illustration: Alexander Ericson​​

Experimental platform for shaping the interaction between micromechanical motion and light

Researchers from Chalmers University of Technology have developed a novel experimental platform for the field of cavity optomechanics. The findings are a crucial step towards increasing light-matter interactions further in order to access new possibilities in the field of quantum technology. The work also shows the ability to fabricate two mechanical resonators on top of each other with a gap smaller than one micrometer. "This ability is an important ingredient for the next step of the project", says Witlef Wieczorek, head of the group at MC2.
Picture of deviceHow can light interact with matter? A rather evident way is via the radiation pressure force. However, this force is tiny. Or, have you already been pushed back by a laser pointer hitting you? But when we consider much smaller systems in the micro- and nano world, this force becomes appreciable and can actually be used to manipulate tiny objects. The radiation pressure force can even be enhanced in so-called cavity optomechanical devices. These devices exploit the interaction between light and micro- or nanomechanical resonators to alter the dynamical properties of either of the two systems.

The figure above shows a scanning electron microscope image
of a fabricated device: a 100 nanometer thin slab of GaAs is
freely suspended and hold by four strings above a GaAs substrate.
The holes in the device are a photonic crystal pattern that yield
high optical reflectivity at telecom wavelengths.
Image: Sushanth Kini Manjeshwar

"Cavity optomechanical devices open the door to a world of possibilities such as studying quantum mechanical behavior on larger scales or as transducing microwave to optical photons, which could prove invaluable in superconducting-based quantum computing", says Witlef Wieczorek.

In Witlef Wieczorek’s research group, the cavity optomechanics project deals with increasing the light-matter interaction even further to access novel possibilities for the field of quantum technology. The present work reports a crucial step in this direction and presents a novel experimental platform based on specifically tailored AlGaAs heterostructures.

Picture of Sushanth KiniSushanth Kini Manjeshwar (to the right), PhD student in the lab of Witlef Wieczorek at MC2 and the lead author of the article, fabricated high-reflectivity mechanical resonators in AlGaAs heterostructures in the world-class nanofabrication cleanroom at MC2. The raw material, an epitaxially grown heterostructure on a GaAs wafer, was supplied by the group of professor Shu Min Wang at the Photonics Laboratory at MC2.
"We patterned the mechanical resonators with a so-called photonic crystal, which can alter the behavior of light. Here, the photonic crystal enables an increase of the optical reflectivity of the mechanical resonator, which is a crucial requirement for the project", explains Sushanth Kini Manjeshwar.
The design of the photonic crystal pattern was developed by the group of associate professor Philippe Tassin at the Department of Physics at Chalmers.
The work also shows the ability to fabricate two mechanical resonators on top of each other with a gap smaller than one micrometer. This ability is an important ingredient for the next step of the project, where the researchers plan to integrate the presented devices in a chip-based optomechanical cavity. Their grand goal is then to access the elusive regime of strong interaction between a single photon and a single phonon, which is indispensable for realizing novel hardware for the field of quantum technology.

This is the first experimental work from the Wieczorek Lab at the Quantum Technology Laboratory at MC2, and it has been published as Editor’s Pick in the special topic on Hybrid Quantum Devices in the scientific journal Applied Physics Letters.

The research was driven by a newly established collaboration amongst researchers from Chalmers comprising the groups of Witlef Wieczorek and Shu Min Wang, both at MC2, and of Philippe Tassin at the Department of Physics.

The work was jointly supported by Chalmers Excellence Initiative Nano, the Swedish Research Council (VR), the European QuantERA project C’MON-QSENS! and the Wallenberg Centre for Quantum Technology (WACQT).

Text: Witlef Wieczorek and Michael Nystås
Illustration: Alexander Ericson, Swirly Pop AB
Image of device: Sushanth Kini Manjeshwar
Photo of Sushanth Kini Manjeshwar: Michael Nystås

Witlef Wieczorek, Assistant Professor, Quantum Technology Laboratory, Department of Microtechnology and Nanoscience – MC2, Chalmers University of Technology, Sweden, witlef.wieczorek@chalmers.se, wieczorek-lab.com

Read the article in Applied Physics Letters >>>
Suspended photonic crystal membranes in AlGaAs heterostructures for integrated multi-element optomechanics

Published: Tue 14 Jul 2020.