arXiv subjects

Paul Muellner

Publications and source records attributed to Paul Muellner.

3 recordsLinked to original sources

arXiv2020

Multi-channel swept source optical coherence tomography concept based on photonic integrated circuits

In this paper, we present a novel concept for a multi-channel swept source optical coherence tomography (OCT) system based on photonic integrated circuits (PICs). At the core of this concept is a low-loss polarization dependent path routing approach allowing for lower excess loss compared to previously shown PIC-based OCT systems, facilitating a parallelization of measurement units. As a proof of concept for the low-loss path routing, a silicon nitride PIC-based single-channel swept source OCT system operating at 840 nm was implemented and used to acquire in-vivo tomograms of a human retina. The fabrication of the PIC was done via CMOS-compatible plasma-enhanced chemical vapor deposition to allow future monolithic co-integration with photodiodes and read-out electronics. A performance analysis using the results of the implemented photonic building blocks shows a potential tenfold increase of the acquisition speed for a multi-channel system compared to an ideal lossless single-channel system with the same signal-to-noise ratio.

physics.app-ph↗

arXiv2020

Broadband low loss and ultra-low crosstalk waveguide crossings based on multimode interferometer for 840 nm operation

Broadband low loss and ultra-low crosstalk waveguide crossings are a crucial component for photonic integrated circuits to allow a higher integration density of functional components and an increased flexibility in the layout. We report the design of optimized silicon nitride waveguide crossings based on multimode interferometer structures for intersecting light paths of TE/TE-like, TM/TM-like and TE/TM-like polarized light in the near infrared wavelength region of 790 nm to 890 nm. The crossing design for diverse polarization modes facilitates dual polarization operation on a single chip. For all configurations the loss of a single crossing was measured to be 0.05 dB at 840 nm. Within the 100 nm bandwidth losses stayed below 0.16 dB. The crosstalk was estimated to be on the order of -60 dB by means of 3D finite difference time domain simulations.

physics.optics↗

arXiv2019

Broadband SiN asymmetric directional coupler for 840 nm operation

Silicon nitride based photonic integrated circuits offer a wavelength operation window in the near infrared down to visible light, which makes them attractive for life science applications. However, they exhibit significantly different behavior in comparison with better-established silicon on insulator counterparts due to the lower index contrast. Among the most important building blocks in photonic integrated circuits are broadband couplers with a defined coupling ratio. We present silicon nitride broadband asymmetric directional coupler designs with 50/50 and 90/10 splitting ratios with a central wavelength of 840 nm for both TE- and TM-like polarization. We show that silicon nitride broadband asymmetric directional couplers can be designed accurately in a time efficient way by using a general implementation of the coupled mode theory. The accuracy of the coupled mode theory approach is validated with finite difference time domain simulations and confirmed with measurements of four coupler configurations.

physics.optics↗