Faster-than-light effects and negative group delays in optics and electronics, and their applications

Recent manifestations of apparently faster-than-light effects confirmed our predictions that the group velocity in transparent optical media can exceed c. Special relativity is not violated by these phenomena. Moreover, in the electronic domain, the causality principle does not forbid negative group delays of analytic signals in electronic circuits, in which the peak of an output pulse leaves the exit port of a circuit before the peak of the input pulse enters the input port. Furthermore, pulse distortion for these “superluminal” analytic signals can be negligible in both the optical and electronic domains. Here we suggest an extension of these ideas to the microelectronic domain. The underlying principle is that negative feedback can be used to produce negative group delays. Such negative group delays can be used to cancel out the positive group delays due to “transistor latency” (e.g., the finite RC rise time of MOSFETS caused by their intrinsic gate capacitance), as well as the “propagation delays” due to the interconnects between transistors. Using this principle, it is possible to speed up computer systems. ∗ On leave from the Department of Physics, Universidade Federal de Alagoas, Brazil; supported by the Brazilian agency CNPq.