Quantum systems’ integration in chip-scale photonic circuits is the most promising way to succeed in scaling up complex systems for applications ranging from quantum computation to secure communications.
Large systems with many components, especially for scaled all-optical quantum or classical processors, will require improved building blocks with greatly reduced loss, and enhanced bandwidth and robustness to fabrication uncertainties, temperature, etc. In this work, we introduce the concept of rapid adiabatic mode evolution that is the basis of a new family of passive devices with fundamentally improved performance, that we refer to as rapid adiabatic devices. In conventional adiabatic devices, a concept well known in photonics, the waveguide cross-section slowly evolves along the propagation direction, with no particular attention paid to transverse positioning of the cross-section. In contrast, in rapid adiabatic devices, we control the transverse position evolution (taking a tailored off-axis path while advancing along the direction of propagation).
This has a major impact on the dominant crosstalk mechanism, the limiting factor to all performance metrics. By judicious synthesis and design, the dominant crosstalk coupling mechanism can be minimized or even set to zero everywhere along the structure. This concept brings a new paradigm to photonic passives that we stand the test of time as an important tool in the integrated photonics tool-box. We experimentally demonstrate a new integrated 2×2 beam splitter design we call a Rapid Adiabatic Coupler (RAC) in different fabrication platforms. The design is implemented in state-of-the art, field-leading CMOS photonics platforms pioneered in our group, taking into account foundry-imposed limitations on design. It nevertheless shows field-leading, very low-loss and extremely broadband 50:50 splitting ratio over hundreds of nanometers of optical bandwidth. In addition, we also demonstrate other photonic passives based on the concept – Rapid Adiabatic Crossings (RAX), a Rapid Adiabatic Mode Splitter (RAMS) as well as a Polarization Splitter Rotator based on the RAMS. These new high performance, compact components will enable larger-scale systems on chip with a higher number of components, not only for quantum photonics applications but also for other types of systems for sensing, optical AI accelerators, optical “FPGAs”, optical switches and routers, optical communication links and others.
Another key building block for quantum photonic systems is integrated single photon sources. Following the first demonstration of a pair source integrated with pump filters by our group, here we demonstrate a monolithically integrated tunable photon pair source and pump filter on chip in a commercial, advanced 45nm CMOS microelectronics process. Next, we propose electronic-photonic quantum systems on chip, that contain monolithically integrated electronics and photonic components, as a platform to further scale up complexity in, and modularize, quantum systems on chip. As a first demonstration concept, we propose and demonstrate the first experimental step toward a “wall-plug” photon pair source implemented as an electronic-photonic monolithic chiplet. The idea is a CMOS die (or electronic-photonic block on the chip) that takes only electrical DC power, optical CW laser “DC power”, and control signals, and generates high quality photon pairs. The system contains a thermally tunable second-order filter with heater drivers integrated in the chiplet electronics to clean the input pump laser, a self-locking source ring with integrated electronic circuits that allow the ring resonance to automatically align to the pump laser and low-loss, high extinction, high-order thermally tunable filters.
These results taken together show that monolithic integration in CMOS micro-electronics processes does allow high performance photonics, while also supporting scalable complex circuits with electronic control to account for the extreme sensitivity of photonic components and impart reconfigurability and tunability; showing it as a viable approach to build large-scale electronic-photonic systems with a realistic path to commercial technologies.
This work was supported in part by the NSF RAISE-EQuIP program (Award 1842692) and by the Packard Foundation (Award 2012-38222). / 2023-05-23T00:00:00Z
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/44749 |
| Date | 23 May 2022 |
| Creators | Fargas Cabanillas, Josep Maria |
| Contributors | Popovic, Milos A. |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
| Rights | Attribution-NonCommercial-NoDerivatives 4.0 International, http://creativecommons.org/licenses/by-nc-nd/4.0/ |
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