Periodic Reporting for period 4 - STARCHIP (Microphotonics-based frequency combs for habitable exoplanet detection)
Période du rapport: 2024-11-01 au 2025-10-31
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.
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.
Our work addresses several key challenges of microresonator technology that need to be solved before they can be applied for either for astronomy or their many other applications. Specifically, these challenges include:
• Identifying ways to extend the operating regime towards longer rand shorter wavelength.
• Achieving robust operation on similar to current commercial mode-locked laser systems.
To address these challenges, we develop novel microresonator geometries, based on novel nano-structured geometries; importantly we use fabrication processes that can be readily scaled to large volume, which is critical for a high impact technology.
Our key results include
- the first soliton pulses in a chip-integrated Fabry-Perot microresonator, demonstrating photonic-crystal reflector-based dispersion engineering as a viable approach for ultra-short on chip pulse generation, beyond the usual near-infrared wavelength
- the first demonstration of synthetic reflection as a novel approach to ensure low-noise frequency comb generation with the desired characteristics in a deterministic way and in every sample by design of a nano-structured photonic crystal structure.
- the first demonstration of up-conversion of microresonator frequency combs from the infrared to visible and ultraviolet wavelength.
- the first demonstration of an astronomical spectrograph in the ultraviolet wavelength regime.
Key to this result was the interplay between large scale numeric simulations on DESY's Maxwell computing cluster and GHz-mode-locked laser frequency comb-based broadband dispersion measurements to calibrate and validate the designs with high precision. Surprisingly, we found that through careful process calibration the nano-structuring can be achieved in a scalable ultra-violet lithographic process, indicating that this new approach can also become relevant for large-scale applications in sensing, data transfer, and generally resonant integrated photonics.
These results provide a clear pathway for extending the spectral operating range of microresonator combs with a level of complexity that is compatible with operation outside a specialized photonics lab at an astronomical observatory.
• Identifying ways to extend the operating regime towards longer rand shorter wavelength.
• Achieving robust operation on similar to current commercial mode-locked laser systems.
To address these challenges, we develop novel microresonator geometries, based on novel nano-structured geometries; importantly we use fabrication processes that can be readily scaled to large volume, which is critical for a high impact technology.
Our key results include
- the first soliton pulses in a chip-integrated Fabry-Perot microresonator, demonstrating photonic-crystal reflector-based dispersion engineering as a viable approach for ultra-short on chip pulse generation, beyond the usual near-infrared wavelength
- the first demonstration of synthetic reflection as a novel approach to ensure low-noise frequency comb generation with the desired characteristics in a deterministic way and in every sample by design of a nano-structured photonic crystal structure.
- the first demonstration of up-conversion of microresonator frequency combs from the infrared to visible and ultraviolet wavelength.
- the first demonstration of an astronomical spectrograph in the ultraviolet wavelength regime.
Key to this result was the interplay between large scale numeric simulations on DESY's Maxwell computing cluster and GHz-mode-locked laser frequency comb-based broadband dispersion measurements to calibrate and validate the designs with high precision. Surprisingly, we found that through careful process calibration the nano-structuring can be achieved in a scalable ultra-violet lithographic process, indicating that this new approach can also become relevant for large-scale applications in sensing, data transfer, and generally resonant integrated photonics.
These results provide a clear pathway for extending the spectral operating range of microresonator combs with a level of complexity that is compatible with operation outside a specialized photonics lab at an astronomical observatory.
We expect to have demonstrated novel microresonator comb generators that can provide widely spaced frequency comb lines in spectral regions that are currently not accessible by this technology. With astronomical spectrograph calibration as a challenging application, we will further have explored the potential of these novel light sources for high-precision optical metrology. Importantly, we will also work towards easier schemes of operation, an important requirement for this technology to impact out-of-lab applications. These results and the generated insights will also be transferrable to other potential applications ranging from optical spectroscopy to optical channel generation for broadband optical communication.