Abstract
Scanning micro-mirror actuators are silicon-based oscillatory micro-electro-mechanical systems (MEMS). They enable laser distance measurements for automotive LIDAR applications as well as projection modules for the consumer market. For MEMS applications, the geometric structure is typically designed to serve a number of functional requirements. Most importantly, the mode spectrum contains a single high-Q mode, the drive mode, which per design is expected to yield the only resonantly excited geometric motion during operation. Yet here, we report on the observation of a resonant three-mode excitation via a process known as spontaneous parametric down-conversion. We show that this phenomenon, most extensively studied in the field of nonlinear optics, originates from three-wave coupling induced by geometric nonlinearities. In combination with further Duffing-type nonlinearities, the micro mirror displays a variety of nonlinear dynamical behaviour ranging from stationary state bifurcations to dynamical instabilities observable via amplitude modulations. We are able to explain and emulate all experimental observations using a single fundamental model. In particular, our analysis allows us to understand the conditions for the onset of three-wave down-conversion which if not accounted for in the design of the MEMS structure, can have drastic impact on its functionality even leading to fracture.
Highlights
SPDC has been widely studied in the context of nonlinear optics16
Besides the pronounced energy depletion of the drive mode, above the so called critical point or rather threshold of SPDC, we find its characteristic feature in the response spectrum of the micro mirror
We have observed SPDC processes in a mechanical systems (MEMS) micro mirror and attributed them to non-degenerate three-wave mixing induced by geometric nonlinearities
Summary
SPDC has been widely studied in the context of nonlinear optics16 It has triggered both technological advances, such as tunable lasers or high-quality squeezed light sources, and fundamental insights in the field of quantum optics ranging from quantum information to modern hybrid opto-mechanical devices. We find that the underlying concepts of SPDC apply in full analogy to a complex mechanical system with practical application such as our micro mirror design. Nonlinear dynamics of mechanically coupled oscillators have long been an important field of study with a broad range of engineering applications. As MEMS devices grew smaller in size and more complex in design, their nonlinear dynamic behavior sparked www.nature.com/scientificreports/. Www.nature.com/scientificreports interest and the development of MEMS-specific models emerged and is still ongoing, discussing complex nonlinear dynamic phenomena, such as limit cycles, under various internal resonance conditions. In all measurements, the slow axis is not actuated at all
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
