Ultrahigh-Q optomechanical crystal cavities fabricated in a CMOS foundry

Abstract

Photonic crystals use periodic structures to create frequency regions where the optical wave propagation is forbidden, which allows the creation and integration of complex optical functionalities in small footprint devices. Such strategy has also been successfully applied to confine mechanical waves and to explore their interaction with light in the so-called optomechanical cavities. Because of their challenging design, these cavities are traditionally fabricated using dedicated high-resolution electron-beam lithography tools that are inherently slow, limiting this solution to small-scale or research applications. Here we show how to overcome this problem by using a deep-UV photolithography process to fabricate optomechanical crystals in a commercial CMOS foundry. We show that a careful design of the photonic crystals can withstand the limitations of the photolithography process, producing cavities with measured intrinsic optical quality factors as high as Q i = (1.21 ± 0.02) × 106. Optomechanical crystals are also created using phononic crystals to tightly confine the GHz sound waves within the optical cavity, resulting in a measured vacuum optomechanical coupling rate of g 0 = 2π × (91 ± 4) kHz. Efficient sideband cooling and amplification are also demonstrated since these cavities are in the resolved sideband regime. Further improvements in the design and fabrication process suggest that commercial foundry-based optomechanical cavities could be used for quantum ground-state cooling.

High-extinction-ratio TE/TM selective Bragg grating filters on silicon-on-insulator

“…Similar figures in terms of maximum ER were measured when a TM polarised input beam was coupled to the device. It is worth noting that, although challenging, the 160 nm diameter of the top waveguide holes can be fabricated by DUV lithography [21]. 9.…”

Designing of strongly confined short-wave Brillouin phonons in silicon waveguide periodic lattices

“…We also opted to work around minimal support thickness since the Brillouin optomechanical gain would approach the one from the ideal floating silicon nanowire. So we considered for our simulations a Si thickness of 220 nm and a etching depth of 160 nm (𝑡 = 60 nm), as well as other dimensions compatible with commercial foundries rules, which already proven to produce ultra-high optical and mechanical quality factor devices [37,43].…”

Ar/Cl2 etching of GaAs optomechanical microdisks fabricated with positive electroresist

“…Other ingredients in the optomechanical enhancement are the cavity or waveguide material properties. Although silicon is widespread in many optomechanical devices [14,[24][25][26][27] due to its mature fabrication, the interest in III-V materials for optomechanical devices has increased [28][29][30][31][32] due to their unique optical, electronic and mechanical properties. Gallium Arsenide (GaAs), for instance, is advantageous because of its very high photoelastic coefficient [33], which leads to large electrostrictive forces and optomechanical coupling [18,34].…”