  On the heels of metamaterial absorbers (MAs) which produce near perfect
electromagnetic (EM) absorption and emission, we propose a universal
electromagnetic energy conversion adapter (UEECA) based on MA. By choosing the
appropriate energy converting sensors, the UEECA is able to achieve near 100%
signal transfer ratio between EM energy and various forms of energy such as
thermal, DC electric, or higher harmonic EM energy. The inherited subwavelength
dimension and the EM field intensity enhancement can further empower UEECA in
many critical applications such as energy harvesting, solar cell, and nonlinear
optics. The principle of UEECA is understood with a transmission line model,
which further provides a design strategy that can incorporate a variety of
energy conversion devices. The concept is experimentally validated at a
microwave frequency with a signal transfer ratio of 96% by choosing an RF diode
as the energy converting sensor.
