Beam reflections from one-dimensionally modulated photonic structures

Summary form only given. We explore reflections of narrow beams from one-dimensionally modulated photonic structures, where the modulation period varies across the structure (the so called chirped dielectric mirrors). It is known, that the plane waves reflected in a normal direction from the chirped mirrors, can show modified temporal dispersion [1]. Different frequency components reflect from the different depth of the structure, as illustrated in Fig. 1a. As a consequence the pulses reflected from such mirrors can obtain a chirp, or contrarily, a pulse chirp of opposite sign can be compensated and eliminated by reflection. We argue, that the character of reflection of narrow beams can be also peculiar from such a chirped structure. The plane wave components of the beam also reflect from the different depth of the structure (see illustration in Fig. 1b), which can result in modification of the spatial dispersion. The beam, in this way could obtain important spatial transformations during reflections. In particular a focalisation of the beam could be possible under particular conditions, as illustrated in Fig. 1c.