Timmis, R. J. L., Fitzpatrick, C. R. J., Kennedy, J. P., Huddleston, H. M., Denis, E., James, A., Baird, C., Symes, D., McGonegle, D., Atonga, E., Martin, H., Rebenstock, J., Neely, J., Lee, J., Redfern, J., Bourgeois, N., Finlay, O., Ruskov, R., Astbury, S., Hawkes, S., Zhang, Z., Zepf, M., Krushelnick, K., Gumbrell, E., Rajeev, P. P., Yeung, M., Dromey, B., Norreys, P. (2026). Efficiency-optimized relativistic plasma harmonics for extreme fields. Nature. https://doi.org/10.1038/s41586-026-10400-2