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J. Eur. Opt. Society-Rapid Publ. 22, 53( 2026)
Fig. 9. Power dissipation density profiles for the uncoated, 100 nm PS-coated, and CsPbI 3-coated microresonators on the equator of the microresonator surface.
Fig. 8. Electric-field intensity along the resonator radius at the resonance wavelengths for the uncoated, PS-coated, and CsPbI 3- coated microresonators. The gray area represents the coating region for both PS- and CsPbI 3-coated cases.
( H), borderline( B), and cancerous( C) exosomes are placed in the immediate vicinity of the uncoated, PS-coated, and CsPbI 3-coated microresonators, and the corresponding resonance-wavelength shifts are computed for all three sensor configurations. The resulting shifts are summarized in Table 2. It can already be seen that the CsPbI 3 coating increases the exosome-induced wavelength shift by more than a factor of two compared to the uncoated microresonator.
Figure 10 shows the electric-field intensity distribution for the three microresonators when a single healthy exosome is placed at the sensing position. The field enhancement in the vicinity of the exosome is visibly stronger for the coated cases, with the CsPbI 3-coated microresonator exhibiting the largest local field intensity. Note that for the CsPbI 3-coated case the color scale( vertical) is adjusted, as the peak field is almost twice as large as in the uncoated and PS-coated configurations. The polarization magnitude | P | inside the healthy exosome is also shown in Figure 10 using the horizontal colorbars. The CsPbI 3-coated microresonator yields a significantly larger polarization response inside the exosome, presenting values approximately 3 and 6 times higher than for the PS-coated and uncoated cases, respectively( see the different color scales ranges).
When the exosome health state is changed( healthy, borderline, and cancerous), the induced polarization within the exosome varies. This behavior was observed for all three microresonator configurations. Figure 11 shows the polarization response inside healthy, borderline and cancerous exosomes placed at the sensing location for the CsPbI 3- coated microresonator. A monotonic increase in the polarization magnitude is observed, starting from the healthy case to the borderline case, reaching the largest values for the cancerous case. This trend is consistent with larger resonance wavelength shifts calculated for the borderline and cancerous cases, as shown in Table 2 for all the three microresonators.
Table
2. Resulting resonance-wavelength shifts for a single exosome placed at the immediate vicinity of each microresonator, for healthy( H), borderline( B), and cancerous( C) exosomes.
|
Dk H( pm) |
Dk B( pm) |
Dk C( pm) |
Uncoated |
0.75 |
0.87 |
1.08 |
PS-coated |
1.08 |
1.33 |
1.58 |
CsPbI 3-coated |
1.79 |
2.02 |
2.38 |
Results from Table 2 show that compared to the uncoated microresonator, the PS-coated sensor exhibits increasesof44.0 %, 52.9 %, and46.3 % intheresonancewavelength shift for the healthy, borderline, and cancerous exosomes, respectively. Changing the coating material to CsPbI 3 leads to even larger enhancements: the corresponding shifts increase by 138.7 %, 132.2 %, and 120.4 % for the healthy, borderline, and cancerous exosomes, respectively, relative to the uncoated case. Thus, both coatings improve the absolute sensitivity, with the perovskite nanocoating providing the largest enhancement.
Our main goal, however, is not only to detect the presence of a single exosome but also to discriminate its health state. In this context, the separation between the wavelength shifts associated with different health classes is crucial. For the uncoated microresonator, the difference between the cancerous and healthy cases is Dk C � Dk H = 0.33 pm. This separation increases to 0.50 pm for the PS-coated microresonator and to 0.59 pm for the CsPbI 3-coated microresonator, i. e. an additional increase of about 18 % in the H – C contrast compared to the PS case. Similar trends are observed for the H – B and B – C separations.
These results demonstrate that the presence of the nanocoating not only increases the absolute resonancewavelength shifts but also enhances the contrast between healthy, borderline, and cancerous exosomes. In particular, the CsPbI 3-coated microresonator offers both the largest overall shifts and the largest separation between health states. This validates that our proposed excitonic – photonic hybrid microresonator is capable of identifying the health state of a single exosome and therefore supports liquidbiopsy based, non-invasive, early-stage cancer diagnostics.
In the present work, a single exosome is positioned at the equatorial region of the resonator to maximize