{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,22]],"date-time":"2026-04-22T18:23:20Z","timestamp":1776882200128,"version":"3.51.2"},"reference-count":54,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2025,6,18]],"date-time":"2025-06-18T00:00:00Z","timestamp":1750204800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"National Natural Science Foundation of China (NSFC)","award":["12204214"],"award-info":[{"award-number":["12204214"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Symmetry"],"abstract":"<jats:p>High-order harmonic generation in atomic systems driven by laser fields with tailored symmetries provides a powerful approach for producing structured ultrafast light sources. In this work, we theoretically investigate the ellipticity control of high-order harmonics emitted from helium atoms exposed to orthogonally polarized two-color laser pulses with a 1:3 frequency ratio. The polarization properties of the harmonics are governed by the interplay between the spatial symmetry of the driving field and the atomic potential. By numerically solving the time-dependent Schr\u00f6dinger equation, we show that fine-tuning the relative phase and amplitude ratio between the fundamental and third-harmonic components enables selective symmetry breaking, resulting in the emission of elliptically and circularly polarized harmonics. Remarkably, we achieve near-perfect circular polarization (ellipticity \u2248 0.995) for the 5th harmonic, as well as highly circularly polarized 17th (0.945), 21st (0.96), and 23rd (0.935) harmonics, demonstrating a level of polarization control and efficiency that exceeds previous schemes. Our results highlight the advantage of using a 1:3 frequency ratio orthogonally polarized two-color laser field over the conventional 1:2 configuration, offering a promising route toward tunable attosecond light sources with tailored polarization characteristics.<\/jats:p>","DOI":"10.3390\/sym17060967","type":"journal-article","created":{"date-parts":[[2025,6,18]],"date-time":"2025-06-18T04:08:06Z","timestamp":1750219686000},"page":"967","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Tuning the Ellipticity of High-Order Harmonics from Helium in Orthogonal Two-Color Laser Fields"],"prefix":"10.3390","volume":"17","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-0504-987X","authenticated-orcid":false,"given":"Shushan","family":"Zhou","sequence":"first","affiliation":[{"name":"School of Physics and Electronic Technology, Liaoning Normal University, Dalian 116029, China"}]},{"given":"Hao","family":"Wang","sequence":"additional","affiliation":[{"name":"School of Physics and Electronic Technology, Liaoning Normal University, Dalian 116029, China"}]},{"given":"Yue","family":"Qiao","sequence":"additional","affiliation":[{"name":"School of Physics and Electronic Information, Yantai University, Yantai 264005, China"}]},{"given":"Nan","family":"Xu","sequence":"additional","affiliation":[{"name":"School of Physics and Electronic Technology, Liaoning Normal University, Dalian 116029, China"}]},{"given":"Fuming","family":"Guo","sequence":"additional","affiliation":[{"name":"Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012, China"}]},{"given":"Yujun","family":"Yang","sequence":"additional","affiliation":[{"name":"Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012, China"}]},{"given":"Muhong","family":"Hu","sequence":"additional","affiliation":[{"name":"School of Physics and Electronic Technology, Liaoning Normal University, Dalian 116029, China"}]}],"member":"1968","published-online":{"date-parts":[[2025,6,18]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"023408","DOI":"10.1103\/PhysRevA.97.023408","article-title":"Symmetry in circularly polarized molecular high-order harmonic generation with intense bicircular laser pulses","volume":"97","author":"Yuan","year":"2018","journal-title":"Phys. Rev. A"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"443","DOI":"10.1126\/science.1132838","article-title":"Isolated Single-Cycle Attosecond Pulses","volume":"314","author":"Sansone","year":"2006","journal-title":"Science"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"376","DOI":"10.1126\/science.1071718","article-title":"Generation of Spatially Coherent Light at Extreme Ultraviolet Wavelengths","volume":"297","author":"Bartels","year":"2002","journal-title":"Science"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"L31","DOI":"10.1088\/0953-4075\/21\/3\/001","article-title":"Multiple-harmonic conversion of 1064 nm radiation in rare gases","volume":"21","author":"Ferray","year":"1988","journal-title":"J. Phys. B At. Mol. Opt. Phys."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"053402","DOI":"10.1103\/PhysRevA.98.053402","article-title":"Control of the helicity of high-order harmonic radiation using bichromatic circularly polarized laser fields","volume":"98","author":"Gopal","year":"2018","journal-title":"Phys. Rev. A"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"073007","DOI":"10.1088\/1367-2630\/aa732f","article-title":"Attosecond control of spin polarization in electron\u2013ion recollision driven by intense tailored fields","volume":"19","author":"Ayuso","year":"2017","journal-title":"New J. Phys."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"253201","DOI":"10.1103\/PhysRevLett.133.253201","article-title":"Observation of Laser-Assisted Dynamic Interference by Attosecond Controlled Photoelectron Spectroscopy","volume":"133","author":"Li","year":"2024","journal-title":"Phys. Rev. Lett."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"108190","DOI":"10.1016\/j.rinp.2025.108190","article-title":"Regulation of helium atom higher harmonic emission and attosecond pulse angle in inhomogeneous fields","volume":"72","author":"Xu","year":"2025","journal-title":"Results Phys."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"053417","DOI":"10.1103\/PhysRevA.85.053417","article-title":"Laser-induced electron diffraction: A tool for molecular orbital imaging","volume":"85","author":"Peters","year":"2012","journal-title":"Phys. Rev. A"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"822","DOI":"10.1038\/nphys2029","article-title":"Generalized molecular orbital tomography","volume":"7","author":"Vozzi","year":"2011","journal-title":"Nat. Phys."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"053003","DOI":"10.1103\/PhysRevLett.105.053003","article-title":"Mapping Molecular Orbital Symmetry on High-Order Harmonic Generation Spectrum Using Two-Color Laser Fields","volume":"105","author":"Niikura","year":"2010","journal-title":"Phys. Rev. Lett."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"867","DOI":"10.1038\/nature03183","article-title":"Tomographic imaging of molecular orbitals","volume":"432","author":"Itatani","year":"2004","journal-title":"Nature"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"381","DOI":"10.1038\/nphys620","article-title":"Attosecond science","volume":"3","author":"Corkum","year":"2007","journal-title":"Nat. Phys."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"163","DOI":"10.1103\/RevModPhys.81.163","article-title":"Attosecond physics","volume":"81","author":"Krausz","year":"2009","journal-title":"Rev. Mod. Phys."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"447","DOI":"10.1146\/annurev-physchem-032511-143702","article-title":"Attosecond Science: Recent Highlights and Future Trends","volume":"63","author":"Gallmann","year":"2012","journal-title":"Annu. Rev. Phys. Chem."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"023421","DOI":"10.1103\/PhysRevA.94.023421","article-title":"Inversion of strong-field photoelectron spectra for molecular orbital imaging","volume":"94","author":"Peters","year":"2016","journal-title":"Phys. Rev. A"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"041401","DOI":"10.1103\/PhysRevA.98.041401","article-title":"Multiple-orbital effects in laser-induced electron diffraction of aligned molecules","volume":"98","author":"Wopperer","year":"2018","journal-title":"Phys. Rev. A"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1038\/s41566-024-01607-8","article-title":"Measuring the quantum state of photoelectrons","volume":"19","author":"Laurell","year":"2025","journal-title":"Nat. Photonics"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"043271","DOI":"10.1103\/PhysRevResearch.6.043271","article-title":"Influence of final state interactions in attosecond photoelectron interferometry","volume":"6","author":"Luo","year":"2024","journal-title":"Phys. Rev. Res."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"043201","DOI":"10.1088\/0256-307X\/42\/4\/043201","article-title":"The Role of Multi-Electron and Multi-Orbital Effects in High-Order Harmonic Generation of Benzonitrile Molecules","volume":"42","author":"Xing","year":"2025","journal-title":"Chin. Phys. Lett."},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Zhou, S., Wang, H., Hu, M., Sun, Y., and Zhao, X. (2025). Review of the Generation, Regulation, and Applications of High-Order Harmonic Generation in Gases Studied Using Time-Dependent Density Functional Theory. Symmetry, 17.","DOI":"10.3390\/sym17030359"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"013501","DOI":"10.1103\/PhysRevA.111.013501","article-title":"Modulation of harmonics from solids by laser pulses with a small chirp","volume":"111","author":"Qiao","year":"2025","journal-title":"Phys. Rev. A"},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Wang, J., Gao, S., Liu, A., He, L., and Zhao, X. (2025). Non vertical ionization-dissociation model for strong IR induced dissociation dynamics of D2O2+. Sci. Rep., 15.","DOI":"10.1038\/s41598-024-83209-6"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"1994","DOI":"10.1103\/PhysRevLett.71.1994","article-title":"Plasma Perspective on Strong-Field Multiphoton Ionization","volume":"71","author":"Corkum","year":"1994","journal-title":"Phys. Rev. Lett."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"1187","DOI":"10.1103\/PhysRevLett.86.1187","article-title":"Asymmetry in Photoelectron Emission from Chiral Molecules Induced by Circularly Polarized Light","volume":"86","author":"Lischke","year":"2001","journal-title":"Phys. Rev. Lett."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"4553","DOI":"10.1063\/1.1651474","article-title":"Photoelectron circular dichroism in core level ionization of randomly oriented pure enantiomers of the chiral molecule camphor","volume":"120","author":"Hergenhahn","year":"2004","journal-title":"J. Chem. Phys."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"325","DOI":"10.1039\/C6FD00113K","article-title":"Probing ultrafast dynamics of chiral molecules using time-resolved photoelectron circular dichroism","volume":"194","author":"Samuel","year":"2016","journal-title":"Faraday Discuss."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"133206","DOI":"10.1103\/PhysRevLett.120.133206","article-title":"Optical Chirality in Nonlinear Optics: Application to High Harmonic Generation","volume":"120","author":"Neufeld","year":"2018","journal-title":"Phys. Rev. Lett."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"621","DOI":"10.1038\/nphys3395","article-title":"Drive round the twist","volume":"11","author":"Cho","year":"2015","journal-title":"Nat. Phys."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"179","DOI":"10.1080\/10408439508241252","article-title":"Spin- and angle-resolved photoelectron spectroscopy from solid surfaces with circularly polarized light","volume":"20","author":"Schneider","year":"1995","journal-title":"Crit. Rev. Solid State Mater. Sci."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"3900","DOI":"10.1021\/nl300512q","article-title":"Graphene sublattice symmetry and isospin determined by circular dichroism in angle-resolved photoemission spectroscopy","volume":"12","author":"Isabella","year":"2012","journal-title":"Nano Lett."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"93","DOI":"10.1038\/nphoton.2014.314","article-title":"A table-top ultrashort light source in the extreme ultraviolet for circular dichroism experiments","volume":"9","author":"Handschin","year":"2015","journal-title":"Nat. Photonics"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"205","DOI":"10.1038\/nature09901","article-title":"Transient ferromagnetic-like state mediating ultrafast reversal of antiferromagnetically coupled spins","volume":"472","author":"Radu","year":"2011","journal-title":"Nature"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"124016","DOI":"10.1088\/2040-8986\/aa9673","article-title":"Circularly polarized attosecond pulse generation and applications to ultrafast magnetism","volume":"19","author":"Bandrauk","year":"2017","journal-title":"J. Opt."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"042509","DOI":"10.1103\/PhysRevA.91.042509","article-title":"Attosecond-magnetic-field-pulse generation by coherent circular molecular electron wave packets","volume":"91","author":"Yuan","year":"2015","journal-title":"Phys. Rev. A"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"043410","DOI":"10.1103\/PhysRevA.98.043410","article-title":"Generation of ultrafast magnetic fields from molecular coherent electron currents","volume":"98","author":"Yuan","year":"2018","journal-title":"Phys. Rev. A"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"011401","DOI":"10.1103\/PhysRevA.86.011401","article-title":"Dependence of high-order-harmonic-generation yield on driving-laser ellipticity","volume":"86","author":"Cheng","year":"2012","journal-title":"Phys. Rev. A"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"R3433","DOI":"10.1103\/PhysRevA.51.R3433","article-title":"Polarization of high-intensity high-harmonic generation","volume":"51","author":"Weihe","year":"1995","journal-title":"Phys. Rev. A"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"063404","DOI":"10.1103\/PhysRevA.96.063404","article-title":"Generation of circularly polarized XUV and soft-x-ray high-order harmonics by homonuclear and heteronuclear diatomic molecules subject to bichromatic counter-rotating circularly polarized intense laser fields","volume":"96","author":"Heslar","year":"2017","journal-title":"Phys. Rev. A"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"0066","DOI":"10.34133\/ultrafastscience.0066","article-title":"Strong Field Ionization Dynamics Resolved by Two-Color Elliptical Phase-of-Phase Spectroscopy","volume":"4","author":"Jin","year":"2024","journal-title":"Ultrafast Sci."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"14205","DOI":"10.1088\/0256-307X\/41\/1\/014205","article-title":"Modulation of High-Order Harmonic Generation from a Monolayer ZnO by Co-rotating Two-Color Circularly Polarized Laser Fields","volume":"41","author":"Qiao","year":"2024","journal-title":"Chin. Phys. Lett."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"2262","DOI":"10.1103\/PhysRevA.52.2262","article-title":"Model calculations of polarization-dependent two-color high-harmonic generation","volume":"52","author":"Long","year":"1995","journal-title":"Phys. Rev. A"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"R3414","DOI":"10.1103\/PhysRevA.51.R3414","article-title":"Polarization-dependent high-order two-color mixing","volume":"51","author":"Eichmann","year":"1995","journal-title":"Phys. Rev. A"},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"543","DOI":"10.1038\/nphoton.2014.108","article-title":"Spin angular momentum and tunable polarization in high-harmonic generation","volume":"8","author":"Fleischer","year":"2014","journal-title":"Nat. Photonics"},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"2692","DOI":"10.1103\/PhysRevLett.73.2692","article-title":"Two-Color Phase Control in Tunneling Ionization and Harmonic Generation by a Strong Laser Field and Its Third Harmonic","volume":"73","author":"Watanabe","year":"1994","journal-title":"Phys. Rev. Lett."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"031401","DOI":"10.1103\/PhysRevA.100.031401","article-title":"X-ray harmonic generation by orthogonally polarized two-color fields: Spectral shape and polarization","volume":"100","author":"Becker","year":"2019","journal-title":"Phys. Rev. A"},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"043202","DOI":"10.1088\/0256-307X\/32\/4\/043202","article-title":"Generation of Linear Isolated Sub-60 Attosecond Pulses by Combining a Circularly Polarized Pulse with an Elliptically Polarized Pulse","volume":"32","author":"Xia","year":"2015","journal-title":"Chin. Phys. Lett."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"605","DOI":"10.1080\/00387010.2014.938757","article-title":"Broadband-Isolated Attosecond Pulse Generation by Two-Color Elliptically Polarized Laser Pulses","volume":"48","author":"Xia","year":"2015","journal-title":"Spectrosc. Lett."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"053116","DOI":"10.1103\/PhysRevA.103.053116","article-title":"Elliptical high-order harmonic generation from H2+ driven by orthogonally polarized two-color laser fields","volume":"103","author":"Huo","year":"2021","journal-title":"Phys. Rev. A"},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"063428","DOI":"10.1103\/PhysRevA.100.063428","article-title":"High-order harmonic generation from H2+ irradiated by a co-rotating two-color circularly polarized laser field","volume":"100","author":"Qiao","year":"2019","journal-title":"Phys. Rev. A"},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"053407","DOI":"10.1103\/PhysRevA.101.053407","article-title":"Ellipticity control of high-order harmonic generation with nearly orthogonal two-color laser fields","volume":"101","author":"Zhai","year":"2020","journal-title":"Phys. Rev. A"},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"033410","DOI":"10.1103\/PhysRevA.100.033410","article-title":"Controlling polarization of high-order harmonic generation by molecular alignment in a bicircular laser field","volume":"100","author":"Li","year":"2019","journal-title":"Phys. Rev. A"},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"1027","DOI":"10.1364\/OL.42.001027","article-title":"Ellipticity-tunable attosecond XUV pulse generation with a rotating bichromatic circularly polarized laser field","volume":"42","author":"Zhang","year":"2017","journal-title":"Opt. Lett."},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"053416","DOI":"10.1103\/PhysRevA.92.053416","article-title":"Bicircular-laser-field-assisted electron-ion radiative recombination","volume":"92","year":"2015","journal-title":"Phys. Rev. A"}],"container-title":["Symmetry"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2073-8994\/17\/6\/967\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,9]],"date-time":"2025-10-09T17:54:00Z","timestamp":1760032440000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2073-8994\/17\/6\/967"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,6,18]]},"references-count":54,"journal-issue":{"issue":"6","published-online":{"date-parts":[[2025,6]]}},"alternative-id":["sym17060967"],"URL":"https:\/\/doi.org\/10.3390\/sym17060967","relation":{},"ISSN":["2073-8994"],"issn-type":[{"value":"2073-8994","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,6,18]]}}}