Optical combs for photonic waveform synthesiser and frequency control – PhotoSynth

Since the development of the laser, emulating the numerous breakthroughs achieved in electronics with optical waves has been a major goal in science and technology. This is the realm of photonics. Despite the huge progress made towards the fulfilment of the photonics “raison d’être” and its potential embodiment in what would be a photonic computer or a multifunction photonic device, the field has yet to take up a number of scientific challenges needed for a leap from an electronics based technology to an all “photonic era”. Among the challenges that would bring photonics to the degree of maturity of electronics, we count optical waveform synthesis and integrated solutions for optical frequency reference and control. The present proposal aims to address these challenges in a radically new approach to set the required technological and scientific foundations to synthesise optical waveforms in an analogous manner to an electronic function generator. The proposal entails the use of an emerging gas-phase integrated-photonic technology to develop highly innovative photonic devices for ultra-broad optical frequency comb generation, photonic resonators and photonic based atomic clocks.
Synthesis of electronic waveforms and their frequency control with high accuracy and stability clocks are an integral part of electronic technology and a basic building block for data processing, synchronisation and dissemination. These capabilities underpin all aspects of today’s human activities or scientific and technological endeavours. For example, nearly all kinds of modern instruments and devices are run thanks to the capability of processing and exchanging date using electronic oscillators and clocks that are either embedded in the devices themselves or linked to them through telecommunication networks such as global positioning system (GPS). In contrast, and despite their success and rapid development, photonics technologies haven’t yet reached the degree of maturity in wave synthesis as the one we find in electronics. As a matter of fact, synthesis of optical waves is synonym of either phase modulation through electro-optical components and dielectric micro-resonators, or shaping of ultra-short pulses. Such a seemingly “misleading” terminology mirrors the infancy of waveform synthesis in photonics and ultra-fast optics. The pre-requisite of a “rigorously-speaking” synthesis of arbitrary optical waveforms is a coherent (phase-locked) spectral comb of CW spectral components that span several octaves from UV to mid-IR. To date, such a multi-octave CW optical comb has yet to be achieved, as all the routes, such as high harmonic generation (HHG), which have been extensively explored so far for the generation of such broad combs are based on optical pulses.
Harnessing optical waves with a similar degree of control as in electronics would radically transform the photonics field as the advent of this comb represents the foundation stone for what would be photonic function generator and its ensuing photonic computer. In addition, the generation of CW coherent multi-octave optical combs would have impact on ultra-high time and spectral resolution spectroscopy, quantum optics and computing, and ultra-fast optical processing, including the emerging attoscience. The project builds on recent developments in coherent nonlinear optics and photonics and photonic materials to take on the challenge of synthesising and atomic-clock referencing arbitrary optical waveforms.