Optical device having nonmonotonic transfer function and applications using same
View Patent ↗An entirely passive all-optical device, referred to as an optical hard limiter, includes alternating layers of materials having oppositely signed Kerr coefficients and substantially different linear indices of refraction, wherein the higher linear index material has the negative Kerr coefficient and the lower index material has the positive Kerr coefficient. The optical device has two distinct transmittance curves. Various optical devices and systems can be built from such optical hard limiters.
1. An entirely passive all-optical device comprising
a stack of a plurality of alternating layers of a first medium and a second medium, each medium characterized by a Kerr coefficient having one of a negative nonlinear coefficient and a positive nonlinear coefficient, each medium further characterized by a linear index of refraction, the Kerr coefficients of the first and second media being of opposite sign and substantially equal magnitude, the linear indices of refraction of the first and second media having substantially different magnitudes, the alternating layers arranged such that the medium having the higher linear index of refraction has the negative nonlinear coefficient and the medium having the lower linear index of refraction has the positive nonlinear coefficient.
2. An optical hard limiter comprising an entirely passive all-optical device consisting of alternating layers of materials having oppositely signed Kerr coefficients and substantially different linear indices of refraction, wherein the higher linear index material has the negative Kerr coefficient and the lower linear index material has the positive Kerr coefficient.
3. The optical hard limiter of claim 2 , wherein transmitted characteristics of the optical hard limiter comprise:
a first range bounded by input signals in the range of approximately zero to I 1 in which the transmitted output signal of the stable, non-absorbing optical hard limiter is approximately zero;
a second range bounded by input signals in the range approximately from I 1 to I 2 in which the transmitted output signal of the stable, non-absorbing optical hard limiter increases from zero to I 2 ; and
a third range bounded by input signals in the range above approximately I 2 in which the transmitted output signal of the stable, non-absorbing optical hard limiter is approximately I 2 , where I 1 is approximately half of I 2 .