Optical Transmission In The Spectral Changes And Spectral Switches

In the spectral analysis of the radiation, it is assumed that the normalized spectrum is the same on propagation of the light in free space. This assumption, which is referred as to the assumption of spectral invariance on propagation in free space, has proven by experiment to be justified in the vast majority of circumstance. However, in 1986, Prof. Wolf had proven that only when the source satisfies a certain scaling law, the normalized spectrum radiated from the source will be the same on propagation. If the source violates the scaling law, the normalized spectrum will be changed on propagation, even through free space. People refer to this phenomenon as the correlation-induced spectral changes or"Wolf shift". The recent research shows that the normalized spectrum of light diffracted by an aperture will also be changed. This phenomenon is sometimes called the diffraction-induced spectral changes, because it is the diffraction effect that results in the spectral changes.By using the fundamental theory of the partially coherent light and the general diffraction theory, we investigate the phenomena of spectral changes and spectral switch of the polychromatic partially coherent light after passing through a certain optical system both theoretically and experimentally. The mainly tasks in this paper include:1. The spectral changes of polychromatic partially coherent light diffracted by a slit in the geometrical-imaging system of an achromatic lens are studied both theoretically and experimentally. Furthermore, the influence of the chromatic aberration of the lens on the spectral changes of the diffraction field is researched experimentally.2. The phenomena of spectral changes and spectral switch of polychromatic partially coherent light in Young's double-slit interference experiment are studied both theoretically and experimentally. The phenomena of spectral changes and spectral switch are observed successfully in Young's double-slit interference experiment.3. We investigate the phenomena of spectral changes and spectral switch of polychromatic partially coherent light at the geometrical-imaging plane of a chromatic lens experimentally, and the phenomenon of spectral switch with high intensity is observed experimentally.4. The spectral changes of polychromatic partially coherent light diffracted by a grating are researched experimentally, and the theoretical analysis is also given.The results show that the normalized spectrum is different from that of the source after passing through the four kinds of optical systems mentioned above. And the phenomena of spectral changes are varied with the spectral degree of coherence, the width of the slit, the chromatic aberration, the bandwidth of the incident beam and so forth. The spectral changes take on spectral blueshift or redshift, and in some special circumstances, the spectral shift is changed rapidly from blueshift (redshift) to redshift (blueshift), i.e. the spectral switch occurs. This phenomenon is verified by Prof. Kandpal experimentally.Furthermore, the theoretical research shows that the phenomena of spectral anomalies are in close link to the singular optics. In modern physical optics, the point of the light field at which the intensity has zero value is referred to as singularity. In 2002, Gbur, Visser and Wolf, in their study, illustrate that drastic spectral change takes place in the vicinity of singularity in the focal region of polychromatic, spatial coherent light. In this paper, we discuss the phenomena of spectral changes and spectral switch in the vicinity of singularity of polychromatic, spatial coherent light diffracted by a Fresnel zone plate. The theoretical research shows that in the vicinity of singularity of the diffraction field, the normalized spectrum is blueshifted or redshifted, and at the certain position of the singularity, the phenomenon of spectral switch occurs. And these results are similar with Gbur's description of the phenomena of spectral anomalies. Furthermore, the phenomena of the spectral anomalies and the on-axis intensity distribution of light diffracted by different kinds of Fresnel zone plates are also discussed.Finally, according to the theoretical and experimental results, we propose the potential applications of spectral changes and spectral switch in information encoding and transmission, and give a description in detail.