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Lars Zimmermann

Publications and source records attributed to Lars Zimmermann.

7 recordsLinked to original sources
arXiv2026

Validation and extension of the PAWS Zemax model as a first step in the development of a Compact Arrayed Waveguide Stacked Multi-Object Spectrograph (CAWSMOS)

The linear size of a bulk optical astronomical spectrograph scales with the diameter of the primary mirror of the corresponding telescope. As modern telescopes continue to increase in aperture size, miniaturization of the spectrograph becomes crucial beyond the offered advantages in terms of multifunctional integration and photon efficiency. The presented concept of development for a Compact Arrayed Waveguide Stacked Multi-Object Spectrograph (CAWSMOS) includes the design of the Arrayed Waveguide Grating (AWG) chips, the stacking frame and cross-dispersion optics for the imaging of multiple spectral orders per AWG. It aims to reduce the cost and size of astronomical spectrographs while also improving efficiency. This will bring the AWG technology closer to the realization of its full potential for ground based, airborne and spaceborne astronomical applications. Part of this development is an extension of the Potsdam Arrayed Waveguide Spectrograph (PAWS). To do that, the Zemax model is compared to PAWS calibration data, finding that the position can be matched with the measurement within 28 px in x and 18 px in y-direction. It also shows a discrepancy between the measured PSF size and the Zemax model of around factor five, and that the detector area can only partially accommodate a second chip.

astro-ph.IM↗
arXiv2026

On-chip semi-device-independent quantum random number generator exploiting contextuality

We present a semi-device-independent quantum random number generator (QRNG) based on the violation of a contextuality inequality, implemented by the integration of two silicon photonic chips. Our system combines a heralded single-photon source with a reconfigurable interferometric mesh to implement qutrit state preparation, transformations, and measurements suitable for testing a KCBS contextuality inequality. This architecture enables the generation of random numbers from the intrinsic randomness of single-photon interference in a complex optical network, while simultaneously allowing a quantitative certification of their security without requiring entanglement. We observe a contextuality violation exceeding the classical bound by more than 10{\sigma}, unambiguously confirming non-classical behavior. From this violation, we certify a conditional min-entropy per experimental round of Hmin = 0.077 +- 0.002, derived via a tailored semidefinite-programming-based security analysis. Each measurement outcome therefore contains at least 0.077 +- 0.002 bits of extractable genuine randomness, corresponding to an asymptotic generation rate of 21.7 +- 0.5 bits/s. These results establish a viable route towards general-purpose, untrusted quantum random number generators compatible with practical integrated photonic quantum networks.

quant-ph↗
arXiv2022

Dual-polarization multiplexing amorphous Si:H grating couplers for silicon photonic transmitters in the photonic BiCMOS backend of line

We report on polarization combining 2D grating couplers (2D GCs) on amorphous Si:H, fabricated in the backend of line of a photonic BiCMOS platform. The 2D GCs can be used as an interface of a hybrid silicon photonic coherent transmitter, which can be implemented on bulk Si wafers. The fabricated 2D GCs operate in the telecom C-band and show an experimental coupling efficiency of -5 dB with a wafer variation of +/-1.2 dB. Possibilities for efficiency enhancement and improved performance stability in future design generations are outlined and extension towards O-band devices is investigated as well.

physics.app-ph↗
arXiv2020

Cross-polarization effects in sheared 2D grating couplers in a photonic BiCMOS technology

We investigate numerically and experimentally sheared 2D grating couplers in a photonic BiCMOS technology with a focus on their splitting behavior. Two realization forms of a waveguide-to-grating shear angle are considered. The cross-polarization used as a figure-of-merit is shown to be strongly dependent on the grating perturbation strength and is a crucial limitation not only for the grating splitting performance, but also for its coupling efficiency.

physics.optics↗
arXiv2019

A BaTiO3-Based Electro-Optic Pockels Modulator Monolithically Integrated on an Advanced Silicon Photonics Platform

To develop a new generation of high-speed photonic modulators on silicon-technology-based photonics, new materials with large Pockels coefficients have been transferred to silicon substrates. Previous approaches focus on realizing stand-alone devices on dedicated silicon substrates, incompatible with the fabrication process in silicon foundries. In this work, we demonstrate monolithic integration of electro-optic modulators based on the Pockels effect in barium titanate (BTO) thin films into the back-end-of-line of a photonic integrated circuit (PIC) platform. Molecular wafer bonding allows fully PIC-compatible integration of BTO-based devices and is, as shown, scalable to 200 mm wafers. The PIC-integrated BTO Mach-Zehnder modulators outperform conventional Si photonic modulators in modulation efficiency, losses, and static tuning power. The devices show excellent V{\pi}L (0.2 Vcm) and V{\pi}L{\alpha} (1.3 VdB), work at high speed (25 Gbps), and can be tuned at low static power consumption (100 nW). Our concept demonstrates the possibility of monolithic integration of Pockels-based electro-optic modulators in advanced silicon photonic platforms. {\c} 2019 Optical Society of America. Users may use, reuse, and build upon the article, or use the article for text or data mining, so long as such uses are for non-commercial purposes and appropriate attribution is maintained. All other rights are reserved. https://www.osapublishing.org/jlt/abstract.cfm?URI=jlt-37-5-1456 Publication date: March 1, 2019 This work was supported in part by the European Union (EU) under Horizon 2020 grant agreements no. H2020-ICT-2015-25-688579 (PHRESCO) and H2020-ICT-2017-1-780997 (plaCMOS).

physics.app-ph↗
arXiv2015

Vertical optical ring resonators fully integrated with nanophotonic waveguides on silicon-on-insulator substrates

We demonstrate full integration of vertical optical ring resonators with silicon nanophotonic waveguides on silicon-on-insulator substrates to accomplish a significant step towards 3D photonic integration. The on-chip integration is realized by rolling up 2D differentially strained TiO2 nanomembranes into 3D microtube cavities on a nanophotonic microchip. The integration configuration allows for out of plane optical coupling between the in-plane nanowaveguides and the vertical microtube cavities as a compact and mechanically stable optical unit, which could enable refined vertical light transfer in 3D stacks of multiple photonic layers. In this vertical transmission scheme, resonant filtering of optical signals at telecommunication wavelengths is demonstrated based on subwavelength thick walled microcavities. Moreover, an array of microtube cavities is prepared and each microtube cavity is integrated with multiple waveguides which opens up interesting perspectives towards parallel and multi-routing through a single cavity device as well as high-throughput optofluidic sensing schemes.

physics.optics↗