Physics-Informed Surrogate for Sb2S3 Dispersion Trimming in Thin-Film Lithium Niobate
Abstract
A film-thickness error of 8 nm, within the tolerance of commercial thin-film lithium niobate wafers, shifts the group-velocity dispersion β2 at 1550 nm by about 28 ps2 km−1. We study numerically whether a segmented, non-volatile phase-change cladding can correct this error after fabrication. In mode solves of 3012 geometries, Sb2S3 switches β2 by a median of 181 ps2 km−1 at a 40 nm strip thickness with no material absorption under the adopted optical constants, whereas Sb2Se3 reaches a comparable contrast at a median modal loss of 5.6 dB cm−1. Because phase adds along the guide, four independently switched binary segments reach a two-dimensional region of the (β2,β3) plane; eigenmode expansion supports this description at the junctions. Full-wave solves at 65 die geometries show that the segment states move with the die error, so the bit pattern is chosen from a per-die model: a spectral surrogate constrained by exact identities of the lossless Maxwell problem. Its accuracy within the training domain is similar to that of unconstrained baselines; it keeps β2 and β3 consistent, and its error at an unseen film thickness is 8.3 rather than 13.0 ps2 km−1. With a bare test ring and a second ring carrying a crystalline strip already on the mask, 96.8% of the dies are trimmed into ±25 ps2 km−1, scored on full-wave solutions. A thermal model gives a candidate write window for a 532 nm beam.
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BibTeX
@misc{debnath2026physicsinformed,
title = {{Physics-Informed Surrogate for Sb2S3 Dispersion Trimming in Thin-Film Lithium Niobate}},
author = {Shoumik Debnath and Anup Kumar Modak and Sudipta Saha},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.02652},
eprint = {2611.02652},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.02652},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Physics-Informed Surrogate for Sb2S3 Dispersion Trimming in Thin-Film Lithium Niobate
AU - Shoumik Debnath
AU - Anup Kumar Modak
AU - Sudipta Saha
PY - 2026
DA - 2026/11/02
PB - arXiv
DO - 10.48550/arxiv.2611.02652
UR - https://arxiv.org/abs/2611.02652
AB - A film-thickness error of 8 nm, within the tolerance of commercial thin-film lithium niobate wafers, shifts the group-velocity dispersion β_2 at 1550 nm by about 28 ps^2 km^−1. We study numerically whether a segmented, non-volatile phase-change cladding can correct this error after fabrication. In mode solves of 3012 geometries, Sb_2S_3 switches β_2 by a median of 181 ps^2 km^−1 at a 40 nm strip thickness with no material absorption under the adopted optical constants, whereas Sb_2Se_3 reaches a comparable contrast at a median modal loss of 5.6 dB cm^−1. Because phase adds along the guide, four independently switched binary segments reach a two-dimensional region of the (β_2,β_3) plane; eigenmode expansion supports this description at the junctions. Full-wave solves at 65 die geometries show that the segment states move with the die error, so the bit pattern is chosen from a per-die model: a spectral surrogate constrained by exact identities of the lossless Maxwell problem. Its accuracy within the training domain is similar to that of unconstrained baselines; it keeps β_2 and β_3 consistent, and its error at an unseen film thickness is 8.3 rather than 13.0 ps^2 km^−1. With a bare test ring and a second ring carrying a crystalline strip already on the mask, 96.8% of the dies are trimmed into ±25 ps^2 km^−1, scored on full-wave solutions. A thermal model gives a candidate write window for a 532 nm beam.
ER -