Control over Light Emission in Low-Refractive-Index Artificial Materials Inspired by Reciprocal Design
L. Maiwald, T. Sommer, M.S. Sidorenko, R.R. Yafyasov, M.E. Mustafa, M. Schulz, M.V. Rybin, M. Eich, A.Y. Petrov
Advanced Optical Materials 2, 2100785 (2021).
Reciprocal space engineering allows tailoring the scattering response of media with a low refractive-index contrast. Here it is shown that a quasiperiodic leveled-wave structure with well-defined reciprocal space and random real space distribution can be engineered to open a complete photonic bandgap (CPBG) for any refractive-index contrast. For these structures, an analytical estimation is derived, which predicts that there is an optimal number of Bragg peaks for any refractive-index contrast. A finite 2D or 3D CPBG is expected at this optimal number even for an arbitrarily small refractive-index contrast. Results of numerical simulations of dipole emission in 2D and 3D structures support the estimations. In 3D simulations, an emission suppression of almost 10 dB is demonstrated with a refractive index down to 1.38. The 3D structures are realized by additive manufacturing on millimeter scale for a material with a refractive index of n ≈ 1.59. Measurements confirm a strong suppression of microwave transmission in the expected frequency range.
Efficient optomechanical mode-shape mapping of micromechanical devices
D. Hoch, K.-J. Haas, L. Moller, T. Sommer, P. Soubelet, J. Finley, M. Poot
Micromachines 12, 880 (2021).
Visualizing eigenmodes is crucial in understanding the behavior of state-of-the-art micromechanical devices. We demonstrate a method to optically map multiple modes of mechanical structures simultaneously. The fast and robust method, based on a modified phase-lock loop, is demonstrated on a silicon nitride membrane and shown to outperform three alternative approaches. Line traces and two-dimensional maps of different modes are acquired. The high quality data enables us to determine the weights of individual contributions in superpositions of degenerate modes.
Growth of aluminum nitride on a silicon nitride substrate for hybrid photonic circuits
G. Terrasanta, M. Müller, T. Sommer, S. Geprägs, R. Gross, M. Althammer, M. Poot
Materials for Quantum Technology 1, 21002 (2021).
Aluminum nitride (AlN) is an emerging material for integrated quantum photonics with its excellent linear and nonlinear optical properties. In particular, its second-order nonlinear susceptibility χ(2) allows single-photon generation. We have grown AlN thin films on silicon nitride (Si3N4) via reactive DC magnetron sputtering. The thin films have been characterized using x-ray diffraction (XRD), optical reflectometry, atomic force microscopy (AFM), and scanning electron microscopy. The crystalline properties of the thin films have been improved by optimizing the nitrogen to argon ratio and the magnetron DC power of the deposition process. XRD measurements confirm the fabrication of high-quality c-axis oriented AlN films with a full width at half maximum of the rocking curves of 3.9° for 300 nm-thick films. AFM measurements reveal a root mean square surface roughness below 1 nm. The AlN deposition on SiN allows us to fabricate hybrid photonic circuits with a new approach that avoids the challenging patterning of AlN.
On-chip quantum opticsand integrated optomechanics
D. Hoch, T. Sommer, S. Müller, M. Poot
Turkish Journal of Physics 44, 239 – 246 (2020).
Recent developmentsin quantum computing and the growing interest in optomechanics and quantum opticsneed platforms that enable rapid prototyping and scalability. This can be fulfilled by on-chip integration, as we presenthere. The different nanofabrication steps are explained, and our automated measurement setup is discussed. We presentan opto-electromechanical device, the H-resonator, which enables optomechanical experiments such as electrostaticsprings and nonlinearities and thermomechanical squeezing. Moreover, it also functions as an optomechanical phaseshifter, an essential element for our integrated quantum optics efforts. Besides this, the equivalent of a beam splitter inphotonics-the directional coupler-is shown. Its coupling ratio can be reliably controlled, as we show with experimentaldata. Several directional couplers combined can realize the CNOT operation with almost ideal fidelity.