Novel thin film optical modulator/tunable retarder
MetadataShow full item record
A reflection retarder is a device that induces a change in the phase between the parallel and perpendicular components, of the electric field, to the plane of incidence while maintaining the relative amplitudes. A film-substrate reflection retarder is a reflection retarder that only consists of a film-substrate system. Film-substrate reflection retarders have been previously studied in the negative, zero, and positive systems. The type of system is determined by the relationship between the refractive index of the ambient N0, film N1, and substrate N2: if N1<(N0*N2)^(1/2) , the system is negative; if N1=(N0*N2)^(1/2), the system is zero; if N1>(N0*N2)^(1/2), the system is positive. It has been determined that is the condition required to achieve reflection retarders, in general. Angle-of-incidence tunable (AIT) retarder designs have not been investigated for the zero system, but have been studied in the negative system. An exact retarder in the zero system only exists at a single angle of incidence and a corresponding single film thickness. By approximating the retarder condition to allow the relative amplitudes to be within 5% of the exact value of unity, it is possible to realize unique AIT retarders in the zero system: retarders that can be operated over a continuous range of angles of incidence resulting in a large range of phase shifts approaching 360°. It is possible to have multiple angles of incidence with a difference of between their respective phase shifts. By inducing a phase shift of, it is possible to modulate the polarization of light. By employing an approximation of the retarder condition, AIT retarder designs were developed. The design’s tolerance to changes in design parameters is analyzed and discussed.