@article{80bc23a183c74c86af036eb536b64307,
title = "On-chip beam rotators, adiabatic mode converters, and waveplates through low-loss waveguides with variable cross-sections",
abstract = "Photonics integrated circuitry would benefit considerably from the ability to arbitrarily control waveguide cross-sections with high precision and low loss, in order to provide more degrees of freedom in manipulating propagating light. Here, we report a new method for femtosecond laser writing of optical-fiber-compatible glass waveguides, namely spherical phase-induced multicore waveguide (SPIM-WG), which addresses this challenging task with three-dimensional on-chip light control. Fabricating in the heating regime with high scanning speed, precise deformation of cross-sections is still achievable along the waveguide, with shapes and sizes finely controllable of high resolution in both horizontal and vertical transversal directions. We observed that these waveguides have high refractive index contrast of 0.017, low propagation loss of 0.14 dB/cm, and very low coupling loss of 0.19 dB coupled from a single-mode fiber. SPIM-WG devices were easily fabricated that were able to perform on-chip beam rotation through varying angles, or manipulate the polarization state of propagating light for target wavelengths. We also demonstrated SPIM-WG mode converters that provide arbitrary adiabatic mode conversion with high efficiency between symmetric and asymmetric nonuniform modes; examples include circular, elliptical modes, and asymmetric modes from ppKTP (periodically poled potassium titanyl phosphate) waveguides which are generally applied in frequency conversion and quantum light sources. Created inside optical glass, these waveguides and devices have the capability to operate across ultra-broad bands from visible to infrared wavelengths. The compatibility with optical fiber also paves the way toward packaged photonic integrated circuitry, which usually needs input and output fiber connections.",
keywords = "Physics - Applied Physics, Physics - Optics",
author = "Bangshan Sun and Fyodor Morozko and Salter, {Patrick S.} and Simon Moser and Zhikai Pong and Patel, {Raj B.} and Walmsley, {Ian A.} and Mohan Wang and Adir Hazan and Nicolas Barr{\'e} and Alexander Jesacher and Julian Fells and Chao He and Aviad Katiyi and Tian, {Zhen Nan} and Alina Karabchevsky and Booth, {Martin J.}",
note = "Funding Information: B.S. acknowledges valuable discussions with Prof. Robert R. Thomson in Heriot-Watt University, Dr. Josh Nunn in University of Bath, Prof. Dong Wu in University of Science and Technology of China, as well as valuable suggestions from all the anonymous reviewers. All their comments greatly helped to improve the paper. This project was partially supported by the European Research Council Advanced Grants AdOMiS (695140), UK Engineering and Physical Sciences Research Council grants EP/T001062/1, EP/R004803/01, EP/T00326X/1, Austrian Science Fund (FWF) I3984-N36. A.K. acknowledges Israel Innovation Authority KAMIN #69073 {\textquoteleft}Development of mode converters technology with twisted waveguides on a chip{\textquoteright}. C.H. acknowledges Junior Research Fellowship of St John{\textquoteright}s College in Oxford. Funding Information: B.S. acknowledges valuable discussions with Prof. Robert R. Thomson in Heriot-Watt University, Dr. Josh Nunn in University of Bath, Prof. Dong Wu in University of Science and Technology of China, as well as valuable suggestions from all the anonymous reviewers. All their comments greatly helped to improve the paper. This project was partially supported by the European Research Council Advanced Grants AdOMiS (695140), UK Engineering and Physical Sciences Research Council grants EP/T001062/1, EP/R004803/01, EP/T00326X/1, Austrian Science Fund (FWF) I3984-N36. A.K. acknowledges Israel Innovation Authority KAMIN #69073 {\textquoteleft}Development of mode converters technology with twisted waveguides on a chip{\textquoteright}. C.H. acknowledges Junior Research Fellowship of St John{\textquoteright}s College in Oxford. Publisher Copyright: {\textcopyright} 2022, The Author(s).",
year = "2022",
month = jul,
day = "7",
doi = "https://doi.org/10.1038/s41377-022-00907-4",
language = "American English",
volume = "11",
journal = "Light: Science and Applications",
issn = "2095-5545",
publisher = "Nature Publishing Group",
number = "1",
}