Design and modeling of optomechanical cavities

Treballs Finals de Grau de Física, Facultat de Física, Universitat de Barcelona, Curs: 2021, Tutor: Daniel Navarro Urrios We have designed a silicon optomechanical crystal (OMC) nanobeam with a cavity in the center that enables to confine the light through an optical trap. The OMC is constructed on the basis of a unitary cell that is repeated several times to create a mirror region that is placed on the sides and a defect region in between. The latter consists of a set of cells whose dimensions have been reduced towards the center so that in varying the sizes of the cell through a one-dimensional chain of these cells using the gaps in the optical bands it is possible to achieve optical modes confined to the center of the chain. Regarding the mechanical modes, we have focused our study on string-type mechanical modes oscillating outside the plane of the sample, that are well coupled to photonic cavity modes. Our work has consisted of optimizing the optomechanical (OM) coupling by introducing an angle (α) in the walls of the cell so that we have been able to break its vertical symmetry and achieve modes with large OM coupling coefficient g.