Mems-based zerO-power Reconfigurable PHotonic ICs

Project Information

MORPHIC

Grant agreement ID: 780283

DOI

10.3030/780283

Project closed

EC signature date 21 November 2017

Start date 1 January 2018

End date 30 June 2022

Funded under

• INDUSTRIAL LEADERSHIP - Leadership in enabling and industrial technologies - Information and Communication Technologies (ICT)

Total cost

€ 3 982 333,75

EU contribution

€ 3 982 333,75

Coordinated by

INTERUNIVERSITAIR MICRO-ELECTRONICA CENTRUM
Belgium

Periodic Reporting for period 3 - MORPHIC (Mems-based zerO-power Reconfigurable PHotonic ICs)

Reporting period: 2020-07-01 to 2022-06-30

Summary of the context and overall objectives of the project

In the MORPHIC project we have developed silicon photonic MEMS technology for large-scale programmable photonic integrated circuits (PIC) that can be configured in software for different applications. PICs are chips to manipulate light, and today they are used for fibre-optic communications, sensors, spectroscopy and quantum optics. Silicon photonics is a unique PIC technology that leverages the fabrication technologies for CMOS electronics, allowing very compact waveguides and complex circuits.
Developing a new PIC is costly: it takes a year for design, fabrication and test, similar as in electronics. However, in electronics, programmable chips like FPGAs can be purchased off the shelf, providing easy access to the technology.
MORPHIC wants to enable the same model for photonics, creating an optical equivalent of the FPGA. Such a programmable PIC consists of many tunable elements connected by a dense mesh of waveguides, in which the routing of light is controlled electronically. The photonic chip thus requires electronic drivers and the software algorithms to implement a useful function.
As the light passes through many tunable building blocks, these must be efficient, compact and have low power consumption. That is why MORPHIC has extended silicon photonics with micro-mechanical tuning elements (MEMS) consisting of suspended waveguides that can be moved by applying a voltage, affecting the phase delay or the coupling between waveguides. These MEMS consume very little power and, with mechanical latching, can even maintain their state without external power. To protect the exposed MEMS from the environment, we have developed a wafer-scale hermetic sealing procedure for the MEMS.
To enable large-scale circuits, MORPHIC has developed an interposer packaging technology to connect thousands of tunable elements to their driver electronics, specifically developed for the high actuation voltage needed by the MEMS devices. These are wrapped in a software framework that helps the designer to visualize, configure, simulate and test the programmable photonic circuits.
The MORPHIC project targeted three applications to demonstrate its capabilities: optical switches for fiber-optic communication, optical processing of signals for 5G communication, and beamforming for free-space light communication and LiDAR. MORPHIC implemented demonstrator circuits for each application, and also a generic programmable PIC that can be configured for these three applications, testing the viability of this photonic equivalent of the FPGA. These demonstrators are currently under assembly and test.
MORPHIC brings together the full supply chain for programmable PICs, from the silicon photonics and MEMS processing to the packaging schemes, electronics and programming tools, to establish a new way of working with generic PICs that can be customized in software. This lowers the threshold for trying new PIC concepts and can reduce the time for first prototypes from months to weeks.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

In the MORPHIC project, we developed the chip technologies, packaging techniques, driver electronics and software layers in parallel.
At the core, MORPHIC extended IMEC’s established iSiPP50G silicon photonics platform with free-standing waveguide structures that can be electrostatically actuated. We used a vapour etch to locally remove the glass layer under the MEMS phase shifters, tunable couplers and switches. To protect these fragile movable devices from outside effects, a hermetic sealing process using wafer-bonding was developed, placing a cap over every individual cavity, but leaving the other areas of the chip accessible.
Using these MEMS devices, we explored programmable circuits based on meshes of waveguides, and studied how these scale in the presence of losses and imperfections. In large circuits, the effects of small errors accumulate, which also imposes requirements on the electrical control. For this, we developed new circuit algorithms to configure the programmable circuits for optical routing and wavelength filtering.
To interface the MEMS device with their driver electronics, we developed a high-density multi-layer ceramic interposer to interface more than 3000 electrical connections, 24 high-speed microwave connections and 72 parallel fibers. This is definitely one of the most ambitious packaging schemes in silicon photonics.
To control these MEMS devices, MORPHIC developed the necessary driver electronics. MEMS actuation does not consume much power, but requires a high voltage. So we designed custom driver boards that control 64 MEMS devices and read out 32 photodiodes, and these can be combined to control very large circuits. To govern these circuits, we developed a software framework that encapsulates the various aspects of programmable photonic circuits, making it possible for the user to configure its settings, visualize its configuration, run circuit simulations and control the driver electronics.
We executed three fabrication runs to develop and demonstrate the process in different application demonstrators, for which we designed multiple circuits of varying scale. At the end of the project, several demonstrators have been fabricated, but initial tests show that the mechanical MEMS devices in the larger circuits suffer from damage incurred during the packaging process. This is currently being investigated.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

MORPHIC has demonstrated that silicon photonic MEMS can be an integral part of a silicon photonic platform. This has been widely noticed in the community, and we see that other silicon photonics platforms are now exploring similar functionality. Together with the circuit algorithms and the packaging technology, this forms the basis for a new ecosystem for programmable photonic chips powered with MEMS technology. We have demonstrated the basic platform functionality, but have not yet realized the full potential of the generic programmable circuit fully packaged and connected to the driver electronics. These driver electronics, however, show the capability for controlling a large number of actuators.
Our software framework, which interfaces with these electronics, allows us to assess the viability of large-scale circuits, and especially programmable waveguide meshes, in different application settings. We combined this with a mapping of the application spaces, showing great potential for communication, microwave processing, beamforming, and sensing, but also in emerging fields like quantum information processing and artificial intelligence.
The processes and building blocks, the circuit concepts and the packaging strategies were brought together, resulting in many designs that are beyond the state of the art: compact and efficient photonic MEMS actuators, including latched actuators for zero power consumption, large-scale programmable circuits, and a packaging strategy to enable flexible prototyping of large-scale systems.
The impact of MORPHIC is not just in its technology, but in the realization that programmable photonics can become a game-changer in how people use PIC technology. With a software interface to manipulate light on programmable chips, prototyping of new concepts becomes easier, lowering the threshold for product innovation. Also, this new ecosystem can put integrated photonics in the hands of a much larger community, spurring an entirely new range of functionalities.

2. Silicon Photonic MEMS phase shifter with a thin beam that can be moved by a comb drive

Hermetically sealed MEMS cavities on the silicon photonics wafer applied to a full 100 mm

Multi-layer ceramic interposer for large-scale photonic circuits

Programmable waveguide mesh circuit with silicon photonic MEMS tunable couplers and phase shifter

6. Software framework for programmable photonics, combining design, simulation & hardware control

Silicon Photonic MEMS with frees-standing waveguides and movable device