Integrated photonic microresonators are a key emerging photonic technology. They are expected to enable ground-breaking science and disruptive technological advances from astronomical searches for life beyond Earth to high-capacity optical communication.
Within STARCHIP, based on integrated photonic microresonator technology, a novel type of laser frequency comb for astronomical spectrograph calibration is developed, potentially contributing to the challenging search for habitable exoplanets. Generally, laser frequency combs provide a large set of well-defined, narrow laser lines that are equally spaced in optical frequency. Such frequency comb sources are well established and key to optical precision measurements. However, for astronomy, the individual comb lines need to be widely separated in optical frequency in order to be resolvable by the astronomical spectrograph. This is challenging to achieve with conventional laser systems.
Developing novel types of scientific instrumentation is key to making discoveries and advancing our knowledge about the world. This included in particular the fascinating question on whether (and/or where) there are other habitable planets similar to Earth. At the same time, the technology developed in this project, although geared towards a fundamental research application, can directly be transferred to other areas of application that are more ‘down to earth’; these include optical spectroscopy for environmental monitoring or for medical diagnostics.
While widely spaced frequency combs (‘astrocombs’) are challenging to achieve in conventional laser systems, this is naturally the case in photonic chip-integrated microresonator-based sources. The aim of STARCHIP is to establish a new class of photonic chip-integrated microresonator comb sources of broadband spectra of resolvable lines, in particular in the difficult to access ultraviolet wavelength domain.
Achieving a core objective, project STARCHIP has led to the first frequency-comb-based calibration of an astronomical spectrograph in the ultraviolet wavelength range. To reach this goal, several milestone results in integrated photonics were accomplished. Importantly, pathways toward self-starting and reliable operation of microresonator frequency combs were identified and implemented, and their suitability for precision measurements was demonstrated.
Beyond microresonators, an ecosystem of photonic components and functionalities was developed and demonstrated, including on-chip optical amplifiers and nonlinear frequency converters to achieve broadband comb spectra for astronomy in previously inaccessible wavelength domains. These developments have far-reaching implications well beyond their initial astronomical application, impacting optical data transfer, precision sensing for health and materials science, as well as emerging technologies such as photonic computing. Overall the action has not only delivered on core goals but opened up new research opportunities and application scenarios that were not anticipated before.
