SciPost Submission Page
THz Higher-Order Topological Photonics in Ge-on-Si Heterostructures
by Ian Colombo, Pietro Minazzi, Emiliano Bonera, Fabio Pezzoli, and Jacopo Pedrini
Submission summary
| Authors (as registered SciPost users): | Ian Colombo · Jacopo Pedrini · Fabio Pezzoli |
| Submission information | |
|---|---|
| Preprint Link: | scipost_202311_00045v2 (pdf) |
| Date submitted: | 2024-03-28 19:06 |
| Submitted by: | Pedrini, Jacopo |
| Submitted to: | SciPost Physics |
| Ontological classification | |
|---|---|
| Academic field: | Physics |
| Specialties: |
|
| Approach: | Computational |
Abstract
We design germanium-based higher-order topological cavities for terahertz applications by breaking the symmetry of a two-dimensional photonic crystal following the Su-Schrieffer-Heeger model. Calculations demonstrate the parity inversion of the electric field in differently deformed unit cells. The interface between domains of opposite topology presents edge and corner modes. The former are chiral, locking light propagation to its helicity. The latter prove that Ge-based structures can be used as high-order topological photonic crystals. These findings can accelerate the development of Si-photonic components working in a spectral range of high technological interest.
Author comments upon resubmission
we thank you for providing us with the referee report. We thoroughly answered to each of their questions. We modified the work by following their report and we believe that this allowed us to improve the quality of our work.
Best regards,
Jacopo Pedrini
List of changes
1. We added the supplementary materials in the form of appendices.
2. We added the following paragraph to the main text (starting at line 117):
"The topological invariant in SSH-like 2D photonic crystals like those described in this work can be classified by the Zak phase [40, 56], which is basically the integral of the Berry connection on the Brillouin Zone. In some works [40] the bulk polarization P is discussed instead of the Zak phase φZ, but the two are simply related by φZ = 2πP. The values of the Zak phase form a Z2 index in C4-symmetric topological crystals such as the one described in our work and can only take the values 0 or π for each direction for trivial or non-trivial topologies, respectively. [41, 57] It is known from the literature [40, 41] that in structures akin to those described in this work, the Zak phase for the directions (x , y) is (0, 0) for the compressed structure and (π, π) for the expanded structure, meaning that the structures are topologically trivial and nontrivial, respectively."
We also added references [40,41].
3. We corrected a small mistake in Figure 2g and h, where the electric field distribution maps were inverted.
4. We changed the sentence starting at line 136 with: “One of the fingerprints of a topological transition is the so-called bulk, edge correspondence, that is the emergence of spatially confined guided modes at the boundary between two domains with different band topology”.
5. We added reference [1] to the list of references found at line 138, that is now "[1, 5, 7, 58, 59]"
6. We added a section in the Appendices describing the role of the {111} facets and added at line 63 "The {111} facets are sub-wavelength and their role on determining the photonic bandstructure of the crystal is negligible, as shown in Figure 5 in Appendix A."
7. We added a section in the Appendices describing the computational methods in detail, and we added at line 75: "Further details on the simulation methods are reported in Appendix B."
8. We corrected some typos as suggested by the reviewer.