ULTRAPURE · INTEGRATED SOURCES FOR ULTRAPURE OSCILLATIONS FROM ACOUSTICAL TO LIGHT WAVES

Many high-performance photonics applications with immense potential such as quantum sensing, atomic clocks and THz communications are hindered in their translation from academic research into real-world solutions by the absence of methods to generate oscillations of sufficiently narrow linewidth, high spectral purity and long-term stability in small integrated devices. ULTRAPURE will enable the generation of ultrapure waves in the radiofrequency, microwave, terahertz and optical domain enabled by stimulated Brillouin scattering (SBS) in an integrated thin-film lithium tantalate (TFLT) platform to realise these solutions.Compared to other state-of-the-art materials, TFLT is the first material that promises simultaneous realisation of high SBS gain, narrow linewidth, minimal propagation losses, high integration density and high potential for scalability due to intrinsic material properties such as absence of birefringence, as well as very high optical damage threshold and thermal stability. The high SBS gain in TFLT will be exploited to design chip-scale Brillouin lasers at different wavelengths that achieve a linewidth of around 1 Hz and a side-mode suppression ratio > 40dB, together with additional features such as modulation on-chip. These lasers constitute the basis of the ULTRAPURE applications: A coherent population trapping (CPT) atomic clock that will achieve a stability of <5x10^-13 at 1 s and <2x10^-14 at 1 h, and a volume of 1-3 L, thus overcoming the trade-off between stability and size of current alternatives, and a THz source with linewidths of around 1 Hz, a continuous tuneability from 300GHz to 1 THz, SMSR >50 dB and a precise stabilisation of the generated frequencies. These advances will facilitate breakthroughs in various photonics applications, e.g., leading to the realisation of smart cities, promising substantial benefits for economy, society and environment through high data rate communication and satellite-independent network synchronisation.