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.
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 🔍📉➡️📈💡.