Flat focusing mirrors
- Autores: Yu Chieh Cheng
- Directores de la Tesis: Kestutis Staliunas (dir. tes.), Diederik S Wiersma (codir. tes.), José Francisco Trull Silvestre (codir. tes.)
- Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2015
- Idioma: español
- Tribunal Calificador de la Tesis: Francesca Intonti (presid.), Ramon Herrero Simon (secret.), Víctor José Sánchez Morcillo (voc.)
- Materias:
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- Resumen
The work of flat focusing mirrors with transversal invariance has been numerically and experimentally demonstrated in different configurations such as multilayer thin film structures and subwavelength gratings. One of the important properties of flat focusing mirrors is to keep the transversal invariance for building of corresponding micro-size focusing devices as integrated components into photonic integrated circuits.
The principle of flat focusing mirror with transversal invariance is based on anomalous diffraction, similar to the idea of flat lens or superlens. In a primary design, a chirped mirror was initially proposed the physical principle of flat lensing and the focusing in reflection was demonstrated. To increase usability, their advanced designs for further focal lengths have also been demonstrated by a chirped mirror with a defect layer and an optimized mirror. Finally, a promising and new near field focusing mirror which can successfully bring a near field focusing to the far field is demonstrated numerically and experimentally by optimized structures.
Different configurations of flat focusing mirror are also proposed with periodic SWGs in this thesis. Beam focalization at normal incidence can be obtained with subwavelength gratings by considering the phase shift between the primary and secondary scattering. Such configuration of subwavelength gratings can be extended to two-dimensional (2D) square symmetry and quasi-symmetry which can bring 2D focusing in reflection for more applications. Another type of waveguide-like SWGs can also perform beam focusing in reflection with an accompany of negative Goos-Hänchen effect. Two parallel subwavelength diffraction gratings are assumed to support the forward or backward wave and, surprisingly, their the slope of lateral shifts depending on angle of incidence can be negative which results in beam focusing in reflection.Importantly, all flat focusing mirrors in this work do not have optical axes and this noticeable feature opens a new field for the ultra-compact focusing micro devices. In addition, the flat focusing mirror with a long focal length could even bring the near field focusing to the far field zone. One of the applications of such strong focusing mirrors can be applied for a non-dispersive waveguide, composed of two parallel flat focusing mirrors. The beam experience multiple reflection and focusing during propagation in the waveguide and, eventually, obtain a focusing in the output of such non-dispersive waveguide.
