Femit

Femit is a speculative concept in nano-optoelectronics describing a nanoscale device capable of emitting and routing ultrafast particles or photons under the control of femtosecond-scale excitation. The term blends femto- (10^-15) with emit, indicating ultrafast emission. In theoretical discussions, femit devices are imagined as integrated emitters that can be switched on and off with femtosecond precision and produce single photons or electron packets with defined energy, timing, and polarization.

Most proposals describe a heterostructure that combines a quantum emitter (such as a quantum dot or defect center) with a nanophotonic or plasmonic element to enhance emission and directivity. Excitation is provided by ultrashort optical pulses or fast electrical gating, with the emission characterized by extremely short duration and tunable spectrum. Realizations would rely on advanced fabrication of clean interfaces, precise alignment of resonators, and low-temperature operation, though some designs aim for room-temperature compatibility.

Potential applications include ultrafast spectroscopy, high-bandwidth optical communications, and interfaces for quantum information processing, where control of emission timing at the femtosecond scale is advantageous. Limitations cited in the literature include decoherence, noise, heat management, fabrication scalability, and integration with conventional electronics.

At present, femit remains a theoretical or speculative concept with limited experimental demonstration, used mainly to illustrate possibilities in ultrafast nanophotonics and quantum emitter engineering.

See also: femtosecond pulse, quantum emitter, nanophotonics, ultrafast optics, plasmonics.