Periodic Reporting for period 1 - CSOC (Chip-scale Optical Atomic Clock)
Reporting period: 2022-10-01 to 2023-09-30
Optical atomic clocks play a pivotal role in modern technology, influencing timekeeping, navigation, and global positioning systems. This project is dedicated to pioneering the world's first chip-scale all-optical atomic clock. It leverages recent breakthroughs in Kerr soliton micro-comb technology, chip-integrated picosecond mode-locked lasers, and highly efficient on-chip frequency doublers. It will create this based on recent advances in Kerr soliton micro-comb technology, ps mode-locked lasers that are heterogeneously integrated on a chip, and using novel on-chip frequency doublers with vastly improved efficiency. Exploitation of the Rb85 two-photon transition enables to obtain a clock signal that is two orders of magnitude improved compared to today’s radio frequency transition-based clocks. This clock can revolutionize timekeeping in mobile, airborne or space applications and used in future GPS networks such as Galileo. Moreover the underlying clockwork - a chipscale comb - can have applications ranging from distance measurements to time and frequency metrology.
Realizing this ambitious endeavor presents a multitude of challenges. To begin, the development of a Silicon Nitride (SiN) platform capable of integrating III-V materials is imperative. The theoretical models and designs are needed for achieving an octave-spanning Kerr soliton comb. The creation of a comprehensive set of new processes is essential, including the fabrication of a GaAs quantum dot amplifier and an AlGaAs second harmonic generation (SHG) device. Furthermore, the miniaturization of the rubidium-based spectroscopy setup to chip-scale dimensions is a task that requires meticulous engineering. This consortium brings together the leading groups in Europe in the domain of Frequency combs, micro-comb technology, and photonic chipscale laser integration. Their collective expertise is instrumental in addressing these formidable challenges and advancing the frontiers of optical atomic clock technology.
Realizing this ambitious endeavor presents a multitude of challenges. To begin, the development of a Silicon Nitride (SiN) platform capable of integrating III-V materials is imperative. The theoretical models and designs are needed for achieving an octave-spanning Kerr soliton comb. The creation of a comprehensive set of new processes is essential, including the fabrication of a GaAs quantum dot amplifier and an AlGaAs second harmonic generation (SHG) device. Furthermore, the miniaturization of the rubidium-based spectroscopy setup to chip-scale dimensions is a task that requires meticulous engineering. This consortium brings together the leading groups in Europe in the domain of Frequency combs, micro-comb technology, and photonic chipscale laser integration. Their collective expertise is instrumental in addressing these formidable challenges and advancing the frontiers of optical atomic clock technology.
From the begining of this project, the consortium meet together at kickoff meeting to clarify the main goal, and divided into seperate modules. Within the first project year, many activities and achievements were reached. Notably, it has achieved a 93% optical coupling efficiency in simulation from SiN waveguides to GaAs amplifiers, designed various mode-lock laser cavities, and investigated GaAs process flow alongside in-house coupon fabrication. Two types of high-efficiency second harmonic generation in AlGaAsOI waveguides were observed. The first octave-spanning frequency comb has been characterized by using external electro-optic comb pulse-pumping. An improved design, particularly for the bus waveguide coupler, was submitted for internal fabrication. A process flow was drafted for implementing the modified LoCA module, and showcased the feasibility of integrating III-V components at 1310 nm and 1550 nm. Material models for poly-Silicon were developed to optimize process conditions for uniform properties, and a breadboard spectroscopy setup was designed with the necessary components ordered. These accomplishments collectively represent significant strides in photonics research.