
Simulating Optical Single Event Transients on Silicon Photonic Waveguides for Satellite Communication
G. Terrasanta, M. W. Ziarko, N. Bergamasco, M. Poot, J. Poliak
Ieee Transactions on Nuclear Science 71 (2), 176-183 (2024).
Photonic integrated circuits (PICs) are a promising platform for space applications. In particular, they have the potential to reduce the cost, size, weight, and power (C-SWaP) consumption of satellite payloads that employ free-space optical communication. However, the effect of the space environment on such circuits has yet to be fully understood. Here, a simulation framework to investigate the impact of heavy ions on a silicon photonic waveguide is presented. These high-energy particles temporarily increase the waveguide losses, resulting in a drop of the transmitted power, commonly defined as either optical single event transient (OSET) or single event effect (SEE). The magnitude and rate of such transients are simulated. The framework is based on three open-source tools: OMERE, Geant4, and Meep. First, the heavy ion fluxes are modeled for commonly used satellite orbits. Afterward, Monte Carlo simulations are used to generate realistic ion tracks and their effect is evaluated with 3-D finite-difference time-domain simulations. The results show that SEEs have only a small impact on the transmission properties of silicon waveguides in the simulated orbits, thus indicating the potential of using silicon PICs in the space environment. Furthermore, the importance of having realistic carrier distributions, compared to using only an analytical model, is discussed.

Efficient adiabatic-coupler-based silicon nitride waveguide crossings for photonic quantum computing
T. Sommer, N. Mange, P. Wegmann, M. Poot
Optics Letters 48 (11), 2981-2984 (2023).
Optical integrated quantum computing protocols, in partic-ular using the dual-rail encoding, require that waveguides cross each other to realize, e.g., SWAP or Toffoli gate oper-ations. We demonstrate efficient adiabatic crossings. The working principle is explained using simulations, and sev-eral test circuits are fabricated in silicon nitride (SiN) to characterize the coupling performance and insertion loss. Well-working crossings are found by experimentally varying the coupler parameters. The adiabatic waveguide crossing (WgX) outperforms a normal directional coupler in terms of spectral working range and fabrication variance stability. The insertion loss is determined using two different meth-ods: using the transmission and by incorporating crossings in microring resonators. We show that the latter method is very efficient for low-loss photonic components. The lowest insertion loss is 0.18 dB (4.06%) enabling high-fidelity NOT operations. The presented WgX represents a high-fidelity (96.2%) quantum NOT operation. © 2023 Optica Publishing Group

Relaxation and dynamics of stressed predisplaced string resonators
X. Yao, D. Hoch, M. Poot
Physical Review B 106 (17), 174109 (2022).
Predisplaced micromechanical resonators made from stressed materials give rise to new static and dynamic behavior, such as geometric tuning of stress. Here, an analytical model is presented to describe the mechanics of such predisplaced resonators. The bending and tension energies are derived and a modified Euler-Bernoulli equation is obtained by applying the least action principle. By projecting the model onto a cosine shape, the energy landscape is visualized, and the predisplacement dependence of stress and frequencies is studied semianalytically. The analysis is extended with finite-element simulations, including the mode shapes, the role of overhang, the stress distribution, and the impact of film stress on beam relaxation.