Tunable organic waveguides and microstructured devices

• Autores: Manuel Caño García
• Directores de la Tesis: Xabier Quintana Arregui (codir. tes.), Morten Andreas Geday (codir. tes.)
• Lectura: En la Universidad Politécnica de Madrid ( España ) en 2018
• Idioma: español
• Tribunal Calificador de la Tesis: José Manuel Otón (presid.), Jimena Olivares Roza (secret.), José Miguel López Higuera (voc.), Braulio García Cámara (voc.), Jeroen Missinne (voc.)
• Programa de doctorado: Programa de Doctorado en Tecnologías de la Información y las Comunicaciones: Materiales y Dispositivos por la Universidad Politécnica de Madrid
• Materias:
  • Física
    • Electromagnetismo
    • Óptica
      • Fibras ópticas
      • Óptica física
• Enlaces
  • Tesis en acceso abierto en: Archivo Digital UPM
• Resumen

  • This PhD work is focused on the development of a new research line at the Centro de Materiales y Dispositivos Avanzados para las TIC (CEMDATIC) based on the design, manufacturing, and characterization of photonic integrated circuits (PICs). Moreover, several previous research lines on phase-only devices have been continued, developing new devices and technologies that could be used in PICs with small adjustments. Two instruments have been modified and significantly improved upon PhD realization. A new nano-imprint photolithographic system has been developed, as well as an optical setup for light coupling with nanometer precision for chip characterization; this setup includes the required modules for electronic control. The fabrication methods developed during the PhD Thesis have been • Ablation laser system. The equipment consists of a tripled Nd:YAG 50 kHz-pulsed laser (355 nm) having a 300 mW output, collimation optical system, focusing and a numerical control XYZ system with 0.1µm precision. Two fabrication protocols have been developed for generation of electrodes and waveguides through material evaporation: i) front scribing, i.e. ablation from the upper side, allowing fabrication regardless the material is transparent to UV or not, and ii) back scribing, that shows better performance but can only be used in UV transparent materials; ablation is done focusing the laser through the substrate. • Maskless photolithography through laser direct writing (LDW). This system has been developed on the same laser. It allows selective curing of photoresin for photolithography. This method is particularly suitable for research activities where a high number of different photolithographic designs have to be tested. Replacing mask construction by LDW leads to significant savings of time and money. • Nanoimprint photolithographic system. The full system has been design, fabricated and characterized as a part of the PhD work. The device has successfully manufactured 15×15 mm² replicas of 233 nm feature size. The devices developed during the PhD Thesis have been • Microlenses matrices. Lens matrices whose diameter ranges from 1 to several 100’s µm. Single microlenses are used, for example, for fiber coupling to optical systems, whereas microlenses matrices are often employed to improve light collection in CCD matrices. ◦ Fixed focal distance microlenses. Conventional microlenses matrices, having fixed focal distance, have been developed with nanometric resolution and macroscopic size using nanoimprint photolithography. ◦ Tunable focal distance microlenses. In these microlenses matrices, focal distance varies from infinity (no lens) to a few mm. Several manufacturing approaches have been tested using conventional photolithography and LDW photolithography. • Tunable liquid crystal device for optical vortex generation. An optical vortex is a continuous azimuthal phase variation, leading to a spiral rather than plane propagation. The device is characterized by its topological charge, i.e., number of full turns per wavelength performed by the helical beam. Vortices can be generated by spiral phase plates (SPP), devices where phase delay increases with azimuthal angle in such a way that a full turn is always a multiple of 2π. A liquid crystal flat structure has been developed; it is able to mimic a tunable SPP. A controller (also developed in this work) drives the cell, which arranges phases as required, and allows modifying the topological charge. • Power distribution by intermodal interference (MMI), tunable through liquid crystal interaction with evanescent wave. Several PICs containing different structures have been developed. Among these, some MMIs have been created on hybrid platform SiO2/SU-8/SiO2. Liquid crystal is deposited onto the upper lid, allowing its interaction with the evanescent field of the propagating wave. • Integrated device for switching/splitting orthogonal polarizations of the light coupled to the input waveguide. Another device integrated in PICs. It has been made completely in polymers Epocore/Epoclad. The device is able to modify the optical path of one polarization through the liquid crystal birefringence. The device includes at least one input and two output waveguides –more complex geometries have been created as well. Light coupling from the input to the output waveguides is done through a planar parallel liquid crystal layer. Moreover, the devices are reversible.