Ultracompact nanophotonic device for signal processing and biosensing applications

The technology is based on single channel interferometers combined with periodic photonic structures that allow significantly increasing the device performance and its compactness by reducing the propagation velocity of light. The proposed technology allows deploying functional photonic devices being more sensitive, more efficient and more compact in comparison with other approaches thus also leading to a cost reduction. The technology can be used to create, among others, ultracompact switching matrices and modulators (for optical networks, data centers, mobile services, etc.) and ultrasensitive biosensing devices (for medical diagnosis, food safety, environmental monitoring, etc.). The fields of application of optical interferometers are innumerable, with the main focus on communications and sensing applications. Photonics is rapidly evolving in order to become the substitute of electronics in those applications where this technology is limited in terms of bandwidth, processing speed, power consumption, etc. Additionally, photonic technology also exhibits a huge potential in the field of advanced biomolecular analysis for application in medical diagnosis, food control, environmental monitoring, etc. Traditionally, research on interferometric devices aims to meet two main outcomes: maximising the accumulation of phase difference between the two interfering signals and achieving the smallest possible size. To address these challenges, the usual solution is to lengthen the optical paths in order to improve performance by achieving larger phase shifts even though the size is larger. Another common approach is the design of spiral-shaped optical paths in order to obtain long optical paths that produce large phase shifts occupying as little space as possible. Despite these improvements, the size and performance of optical interferometers still has to be further improved to ease its use. The proposed invention allows the measurement of the phase shift produced between two of the propagating modes by the same waveguide. The proposed invention is composed of a single-mode waveguide at the input and another one at the output, while in its central part, the system is composed of a periodic bimodal photonic crystal structure. Thanks to this photonic crystal, the modes can be designed in such a way that the phase shift obtained between them after a certain optical path is as large as possible due to the group velocity reduction obtained for one of the interfering modes. As a result, a larger phase shift accumulates than in conventional interferometers and the optical path lengths are considerably reduced, making it possible to integrate multiple devices on small chips. The idea can be extrapolated to all kinds of photonic structures and applications: two- and three-dimensional photonic crystals, multi-mode photonic crystal fibres or free-space optics.