Here we present a method and structures for mid-infrared, free-space optical communication using unmodified, commercially available complementary metal-oxide semiconductor integrated circuits. The modulator is based on
the free carrier absorption in parasitic PN junction structures under reverse bias. Measured results demonstrate the proof-of-concept with speeds of 100bps (1.55um wavelength), but at least two orders of magnitude improvement can be achieved. This technology will enable non-galvanic chip-to-chip and chip-to-package communication as an alternative to wirebonding in applications that benefit from a planar top chip surface, such as chemical sensing lab-on-chip systems as well as general sensors
and mid-infrared communication.