Periodic Reporting for period 1 - POLYNICES (POLYmer based electro-optic PCB motherboard integration with Si3N4 Chiplets, InP Components and Electronic ICs enabling affordable photonic modules for THz Sensing and quantum computing applications)
Période du rapport: 2023-01-01 au 2024-06-30
POLYNICES goal is to design and produce a low cost, scalable, high-performing electro-optic PCB platform that will drive the development of the next generation photonic modules. POLYNICES will heterogeneously integrate FhG-HHI’s PolyBoard hybrid photonic integration platform on PCBs, to realize a low-cost Electro-Optic PCB (EOPCB) motherboard with low-loss single mode waveguides, micro-optical functionalities and etched recesses to host chiplets from other photonic integration technologies such as silicon nitride and InP, as well as high-frequency elements such as rod-antennas.
In the first 18 months, the project made considerable advances in several critical areas. The team successfully identified and tested appropriate materials and processes for developing the electro-optical printed circuit board (EO-PCB). After a thorough investigation of commercially available PCB substrates, two suitable materials—FR4 and Rogers 6002—were chosen. A reliable method for planarizing optical polymer layers on these substrates was also developed. This paved the way for fabricating the first optical waveguides on the FR4 substrate, achieving promising propagation losses of 2.19 dB/cm for TE polarization and 1.6 dB/cm for TM polarization, marking a significant milestone in the project.
In parallel, progress was made on the design and fabrication of etched recesses in the motherboard to support flip-chip integration. This process will enable the passive alignment of the InP and TriPleX PICs. Ongoing simulations are determining the geometry of recesses for Si rod antennas, with further design parameters expected to be finalized soon.
At the system-level, the consortium defined the high-level functional layouts of prototypes in line with system requirements. A major accomplishment was the mathematical analysis of four different architectures for FMCW THz spectrometers, focusing on performance metrics like link gain and noise. This analysis ensured that the designs meet the required system specifications. In order to evaluate the system performance of the individual components and provide useful feedback on the design and fabrication activities, four precursor prototypes will be developed. Within the reporting period, • the TriPleX PIC of Precursor-0A (external cavity laser sources with PZT-based phase actuators), • the InP-based THz transceivers of Precursor-1A (fiber pigtailed THz transceivers), • the PolyBoard PIC for Precursor-2A (fiber-pigtailed ppKTP crystal), • the laser sources of QIP have been designed.
The project also undertook extensive modeling efforts to optimize PZT-based phase actuators. These actuators, which are critical for high-speed and low-voltage performance, were evaluated in various configurations. Several parameters, such as electrode structure, material type, and waveguide width, were tested, leading to the identification of the most promising configuration for further development.
For the THz antenna elements, three different designs were modeled, compatible with the POLYNICES integration process. These designs aimed to provide adequate bandwidth for the FMCW THz spectrometer prototypes. The project selected a ground signal pad structure and defined an integration approach for the THz antenna with the InP photodiodes, which form the key components of the THz transmitter and receiver.
In the area of flip-chip integration, key parameters were defined, including the use of alignment marks, circular fiducials for horizontal alignment, and stop pillars for vertical alignment. Various soldering methods were explored for integrating POLYNICES prototypes, with a dedicated "short loop" set up for evaluating flip-chipping techniques on TriPleX PICs. Daisy chains on FR-4 PCB substrates were designed and fabricated to test these soldering methods, with experiments scheduled for the beginning of the next period.
In the domain of communication and dissemination activities, a comprehensive communication toolkit has been developed and released, featuring the launch of the project website, initiation of social media accounts, creation of a video, and preparation of presentation materials. This multifaceted toolkit is designed and developed to serve effective dissemination, ensure a diverse and engaging outreach to various stakeholders. The project website acts as a central hub for information, while the use of social media platforms enhances visibility and interaction. The video serves as a dynamic visual representation of the project's objectives offering a concise overview. Additionally, presentation materials provide a versatile resource for conveying the project's essence during various engagements and interactions. Combined these components, form a cohesive communication tools aiming at enhancing overall project impact. Lastly, the key metrics of the exploitation, dissemination, and communications activities have been identified and all partners have defined an initial exploitation strategy that will continuously being updated.
In parallel, progress was made on the design and fabrication of etched recesses in the motherboard to support flip-chip integration. This process will enable the passive alignment of the InP and TriPleX PICs. Ongoing simulations are determining the geometry of recesses for Si rod antennas, with further design parameters expected to be finalized soon.
At the system-level, the consortium defined the high-level functional layouts of prototypes in line with system requirements. A major accomplishment was the mathematical analysis of four different architectures for FMCW THz spectrometers, focusing on performance metrics like link gain and noise. This analysis ensured that the designs meet the required system specifications. In order to evaluate the system performance of the individual components and provide useful feedback on the design and fabrication activities, four precursor prototypes will be developed. Within the reporting period, • the TriPleX PIC of Precursor-0A (external cavity laser sources with PZT-based phase actuators), • the InP-based THz transceivers of Precursor-1A (fiber pigtailed THz transceivers), • the PolyBoard PIC for Precursor-2A (fiber-pigtailed ppKTP crystal), • the laser sources of QIP have been designed.
The project also undertook extensive modeling efforts to optimize PZT-based phase actuators. These actuators, which are critical for high-speed and low-voltage performance, were evaluated in various configurations. Several parameters, such as electrode structure, material type, and waveguide width, were tested, leading to the identification of the most promising configuration for further development.
For the THz antenna elements, three different designs were modeled, compatible with the POLYNICES integration process. These designs aimed to provide adequate bandwidth for the FMCW THz spectrometer prototypes. The project selected a ground signal pad structure and defined an integration approach for the THz antenna with the InP photodiodes, which form the key components of the THz transmitter and receiver.
In the area of flip-chip integration, key parameters were defined, including the use of alignment marks, circular fiducials for horizontal alignment, and stop pillars for vertical alignment. Various soldering methods were explored for integrating POLYNICES prototypes, with a dedicated "short loop" set up for evaluating flip-chipping techniques on TriPleX PICs. Daisy chains on FR-4 PCB substrates were designed and fabricated to test these soldering methods, with experiments scheduled for the beginning of the next period.
In the domain of communication and dissemination activities, a comprehensive communication toolkit has been developed and released, featuring the launch of the project website, initiation of social media accounts, creation of a video, and preparation of presentation materials. This multifaceted toolkit is designed and developed to serve effective dissemination, ensure a diverse and engaging outreach to various stakeholders. The project website acts as a central hub for information, while the use of social media platforms enhances visibility and interaction. The video serves as a dynamic visual representation of the project's objectives offering a concise overview. Additionally, presentation materials provide a versatile resource for conveying the project's essence during various engagements and interactions. Combined these components, form a cohesive communication tools aiming at enhancing overall project impact. Lastly, the key metrics of the exploitation, dissemination, and communications activities have been identified and all partners have defined an initial exploitation strategy that will continuously being updated.
Within the first period of the project, a reproducible planarization method for the optical polymer stack has been successfully developed, followed by the successful planarization on both FR4 and Rogers-6002 PCB substrates. A significant milestone was the fabrication of the first optical PolyBoard waveguides on FR-4 PCB substrate. The propagation loss was in the order of 2.19 dB/cm for TE polarization and 1.6 dB/cm for TM. However, it was identified that the high losses in comparison to the ones expected from PolyBoard waveguides (typically ~ 0.7 dB/cm at 1550 nm), as well as the polarization dependence was due to a misadjustment in one the machines used in the fabrication and was not related to the use of the FR4-PCB substrate. This issue is expected to be solved in the next fabrication iteration.
Additionally, in Period 1, external cavity laser sources operating at 1550 nm were designed and fabricated. These laser sources incorporate an InP gain section and a TriPleX cavity, and for the first time, they utilize PZT-based phase actuators. These actuators are crucial for achieving high-speed and low-voltage performance. The fast wavelength tunability provided by these actuators is particularly desirable for FMCW THz spectrometers, as it enables precise control over the spectral range, enhancing the overall performance and flexibility of the spectrometer systems. The experimental evaluation of the laser source is subject for Period 2.
Regarding the development of the driving electronics, the ICs for the InP gain section of the laser sources, semiconductor optical amplifiers and PZT-based phase shifters have been identified and a first precursor laser diode driver integrated with ucontroller and safety features has been designed. The next step would be the integration of the laser source drivers together with the PZT-drivers and offer a complete solution for the PZT-based laser sources.
Another significant result was the modeling of four architectures for the FMCW THz spectrometers. A comprehensive mathematical analysis was performed for the first time to clarify the operational principles, link gain, and noise performance of these architectures. The results of this analysis were used to provide valuable feedback on the system design activities. To validate these theoretical findings and refine the models with experimental data, dedicated experiments have been scheduled for Period 2.
Additionally, in Period 1, external cavity laser sources operating at 1550 nm were designed and fabricated. These laser sources incorporate an InP gain section and a TriPleX cavity, and for the first time, they utilize PZT-based phase actuators. These actuators are crucial for achieving high-speed and low-voltage performance. The fast wavelength tunability provided by these actuators is particularly desirable for FMCW THz spectrometers, as it enables precise control over the spectral range, enhancing the overall performance and flexibility of the spectrometer systems. The experimental evaluation of the laser source is subject for Period 2.
Regarding the development of the driving electronics, the ICs for the InP gain section of the laser sources, semiconductor optical amplifiers and PZT-based phase shifters have been identified and a first precursor laser diode driver integrated with ucontroller and safety features has been designed. The next step would be the integration of the laser source drivers together with the PZT-drivers and offer a complete solution for the PZT-based laser sources.
Another significant result was the modeling of four architectures for the FMCW THz spectrometers. A comprehensive mathematical analysis was performed for the first time to clarify the operational principles, link gain, and noise performance of these architectures. The results of this analysis were used to provide valuable feedback on the system design activities. To validate these theoretical findings and refine the models with experimental data, dedicated experiments have been scheduled for Period 2.