An apparatus includes a chamber, an electro-mechanical driver, a window, and a mechanical cantilever. The chamber has an interior in which the mechanical cantilever is located. The mechanical cantilever has a first end that is attached to the electro-mechanical driver and has second end that is free. The driver is configured to drive the mechanical cantilever to perform an oscillatory motion. The window is located along a wall of the chamber to enable external light to enter the chamber and illuminate a portion of the mechanical cantilever. The mechanical cantilever is configured to mechanically respond to being illuminated by the external light entering the chamber via the window.