TFLN platform for QKD and telecom applications

Satellite telecommunications are a currently developing technological field in which there is a need for the optimization of several characteristics, such as high-speed modulation performance, low transmission losses and reducing the size, weight and power (SWaP) of the communications payload. Optical communications can leverage the physical security layer provided by quantum principles, making use of technologies such as quantum key distribution (QKD), which promises a certain security level against eavesdroppers. In gaussian states, such as the ones coming from laser sources, it is common to encode the signal in continuous variables (CV-QKD). The main appeal of photonic circuit integration is the possibility to have a whole communications processor in a device as small as some mm², plus the implications it has: scalability, high design flexibility, SWaP reduction... For high-end applications, a novel material is emerging as a promising solution due to its exceptional electrooptical capabilities, which allows for a really high (> 100GHz) modulation speed, while maintaining a really low power consumption (reporting down to V_π ∼ 2.2 V · cm). In this work, we experimentally characterize the behavior of different passive elements, and both thermo-optic phase shifters for bias stabilization and electrooptic modulators for high-speed modulation, validating its use for an integrated transceiver. Results reveal a good agreement with its desired functionality sending an IQ modulated signal. Further implementation of a QKD transceiver system in a chip is proposed based on simulations performed using experimental data, validating its security and optimizing parameters in the range they achieve a positive secret key rate (SKR).