Interference pattern based mode selection for multi modal four wave mixing in silicon waveguides
Abstract
The field of photonics is becoming more and more important in recent years for quantum applications like quantum cryptography and quantum computing. The use of photonics in quantum technologies is motivated by the low noise, high speed transmission and strong correlations exhibited by the quantum states of light. In particular, by moving to integrated silicon photonics, the degree of quantum coherence is even improved, boosting at the same time the widespread diffusion of such technologies. In integrated silicon devices it is possible to create quantum states of light by means of nonlinear optics. One of the most exploited nonlinear processes is Spontaneous Four Wave Mixing (SFWM), that give rise to the generation of entangled photon pairs. In order to maximize the efficiency of SFWM the phase matching condition has to be fulfilled. This condition can be satisfied if the light injected in the waveguide excites particular combinations of waveguide modes. Because of this, a device able to excite selectively the propagating modes in the waveguide is required. We studied a new approach to mode selection in waveguide based on the interference of two coherent tilted beams. By tuning the interference pattern it is possible to select the excited mode in the waveguide by maximizing the overlap integral with the modal optical field. This approach to mode selection is then applied to Multi Modal Four Wave Mixing.