Astrid Honc-Gruber

I am pleased to share that I successfully coupled the laser radiation into the chip.

After two weeks of learning about the concepts of the micro-ring resonators (#MRR) and attempting to capture the resonances, I finally achieved my goal.

The main challenge I faced was accurately cutting the optical fiber and determining the optimal distance and angle between the fiber and the #waveguide for effective coupling. This process required a significant amount of trial and error. Additionally, for an entire week, I unknowingly worked with a chip that had broken couplers. When I adjusted the z-axis, I accidentally damaged the couplers with the fiber. Fortunately, I have a sufficient number of chips available for multiple trials.

#biosensor #bioelectronic #microelectronic @JLBe @tuberlin

Jul 29, 2025 at 8:50amWeb
Show threadAstrid Honc-GruberAug 4, 2025

How would a signal look like from our micro-ring resonator #MRR #biosensor?

We observe a spectrum in a wavelength range around 1.55 µm by coupling the laser radiation into an array of five MRRs, see bottom figure. It is notable that each MRR has a curved triangular shape of different size this causes the resonance peak of each MRR to occur at different positions in the spectrum.

In the spectrum range investigated, we observed four groups of resonance peaks corresponding to four standing waves occurring to each of the five rings.

Determining the perimeter of the ring was challenging. I used #ImageJ to draw a polygon that approximated the triangular shape and measured the perimeter. Then, with the use of the formulas obtained from P. Steglich, et al(https://ieeexplore.ieee.org/abstract/document/9568878), it was possible to determine the effective refractive index nff and the order m of the standing wave.

#microelectronic #bioelectronic

Show threadAstrid Honc-GruberAug 13, 2025

What would the spectrum look like with an #analyte on the #microring resonator (#MRR) chip?

This can easily be demonstrated by depositing 💧 water on the MRRs’ surfaces. The result is shown in the plot 📊. While the blue curve shows the resonance peaks for a measurement in air, the red curve was measured for the rings covered with water 💧. It can clearly be seen that the resonance peaks were shifted . This is caused by the different refractive index of water that is probed by the evanescent field ⚡."

How these shifts can be evaluated will be explained in the next post 🔍📉➡️📈💡.

Show threadAstrid Honc-GruberAug 21, 2025

For our sensor array with a few microrings various resonance peaks are observed in a measured spectrum. How can each microring resonator (#MRR) be matched to a resonance peak? 🔍

This is done by selecting a particular ring using a #water droplet 💧 that causes the particular peak to shift to a new position in the #spectrum. In the graph below 📊, the blue line represents the resonance peaks in air 🌬️, while the red curve shows the measurements taken when a water droplet was placed on MRR number 5 of the array.

It can be observed that four of the five resonance peaks shift to the left , while the first peak shifts to the right. This indicates that MRR 5 corresponds to the identified resonance peak. 🎯

This method successfully allowed for assigning each MRR to a particular spectral peak.