1. Wu, Q., J. P. Turpin, and D. H. Werner, "Integrated photonic systems based on transformation optics enabled gradient index devices," Nature, Light: Science & Applications, Vol. 1, No. e38, 1-6, Art No. 4700605, November 2012, doi: 10.1038/lsa.2012.38.
2. Zhang, N., W. X. Jiang, H. F. Ma, W. X. Tang, and T. J. Cui, "Compact high-performance lens antenna based on impedance-matching gradient-index metamaterials," IEEE Transactions on Antennas and Propagation, Vol. 67, No. 2, 1323-1328, February 2019, doi: 10.1109/TAP.2018.2880115.
3. Su, Y. and Z. N. Chen, "A flat dual-polarized transformation-optics beamscanning luneburg lens antenna using PCB-stacked gradient index metamaterials," IEEE Transactions on Antennas and Propagation, Vol. 66, No. 10, 5088-5097, October 2018, doi: 10.1109/TAP.2018.2858209.
4. Luque-González, J. M., R. Halir, J. G. Wanguemert-Perez, J. de-Oliva-Rubio, J. H. Schmid, P. Cheben, I. Molina-Fernandez, and A. Ortega-Monux, "An ultracompact GRIN-lens-based spot size converter using subwavelength grating metamaterials," Laser Photonics Reviews, Vol. 13, No. 19001724, 1-7, September 2019, doi: 10.1002/lpor.201900172.
5. Gaufillet, F., S. Marcellin, and E. Akmansoy, "Dielectric metamaterial-based gradient index lens in the terahertz frequency range," IEEE Journal of Selected Topics in Quantum Electronics, Vol. 23, No. 4, 1-5, Art No. 4700605, July/August 2017, doi: 10.1109/JSTQE.2016.2633825.
6. Salami, P. and L. Yousefi, "Far-field subwavelength imaging using phase gradient metasurfaces," IEEE Journal of Lightwave Technology, Vol. 37, No. 10, 2317-2323, March 2019, doi: 10.1109/JLT.2019.2902544.
7. Hajiahmadi, M. J., R. Faraji-Dana, and A. K. Skrivervik, "Far field superlensing inside biological media through a nanorod lens using spatiotemporal information," Nature, Scientific Reports, Vol. 11, 1-8, Art No. 19534, January 2021, doi: 10.1038/s41598-021-81091-0.
8. La Spada, L., T. M. McManus, A. Dyke, S. Haq, L. Zhang, Q. Cheng, and Y. Hao, "Surface wave cloak from graded refractive index nanocomposites," Nature: Scientific Reports, Vol. 6, 29363, July 2016, doi: 10.1038/srep29363.
9. Hadi Badri, S., H. Rasooli Saghai, and H. Soofi, "Multimode waveguide crossing based on a square Maxwell's fisheye lens," Applied Optics, Vol. 58, No. 17, 4647-4653, June 2019, doi: 10.1364/AO.58.004647.
10. Fu, Y., Y. Xu, and H. Chen, "Applications of gradient index metamaterials in waveguides," Nature, Scientific Reports, Vol. 5, Art No. 18223, 1-6, December 2015, doi: 10.1038/srep18223.
11. El-Khozondar, H. J., R. J. El-Khozondar, A. Shama, K. Ahmed, and V. Dhasarathan, "Highly efficient solar energy conversion using graded-index metamaterial nanostructured waveguide," Journal of Optical Communications, eISSN 2191-6322, ISSN 0173-4911, February 2020, doi: 10.1515/joc-2019-0285.
12. Liu, Y. and S. Jian, "Tunable trapping and releasing light in graded graphene-silica metamaterial waveguide," Optics Express, Vol. 22, 24312-24321, October 2014, doi: 10.1364/OE.22.024312.
13. Hu, H.-F., D. Ji, X. Zeng, K. Liu, and Q. Gan, "Rainbow trapping in hyperbolic metamaterial waveguide," Scientific Reports, Vol. 3, 1249-1255, February 2013, doi: 10.1038/srep01249.
14. Yan, B., B. Yu, J. Xu, Y. Li, Z. Wang, Z. Wang, B. Yu, H. Ma, and C. Gong, "Customized metawaveguide for phase and absorption," Journal of Physics D: Applied Physics, Vol. 54, 465102-465112, August 2021, doi: 10.1088/1361-6463/ac1466.
15. Weng, Q., Q. Lin, and H. Wu, "An efficient semianalytical modal analysis of rectangular waveguides containing metamaterials with graded inhomogeneity," International Journal of Antennas and Propagation, Vol. 2021, 1-13, February 2021, doi: 10.1155/2021/6107378.
16. Berneschi, S., S. Soria, G. C. Righini, G. Alombert-Goget, A. Chiappini, A. Chiasera, Y. Jestin, M. Ferrari, S. Guddala, E. Moser, S. N. B. Bhaktha, B. Boulard, C. Duverger Arfuso, and S. Turrell, "Rare-earth-activated glass-ceramic waveguides," Optical Materials, Vol. 32, 1644-1647, May 2010, doi: 10.1016/j.optmat.2010.04.035.
17. Guddala, S., Y. Kawaguchi, F. Komissarenko, S. Kiriushechkina, A. Vakulenko, K. Chen, A. Alu, V. M. Menon, and A. B. Khanikaev, "All-optical nonreciprocity due to valley polarization pumping in transition metal dichalcogenides," Nature Communications, Vol. 12, 1-9, June 2021, doi: 10.1038/s41467-021-24138-0.
18. Estep, N. A., D. L. Sounas, J. Soric, and A. Alu, "Magnetic-free non-reciprocity and isolation based on parametrically modulated coupled-resonator loops," Nature Physics, Vol. 10, 923-927, November 2014, doi: 10.1038/nphys3134.
19. Keshavarz, S. and S. Dimitrios, "Topological transmission line metamaterials for microwave applications,", 194-196, August 2021, doi: 10.1109/Metamaterials52332.2021.9577096.
20. Keshavarz, S., A. Abdolali, A. Mohammadi, and R. Keshavarz, "Design and implementation of low loss and compact microstrip triplexer using CSRR loaded coupled lines," AEU - International Journal of Electronics and Communications, Vol. 111, 152913, August 2019, doi: 10.1016/j.aeue.2019.152913.
21. Keshavarz, S., R. Keshavarz, and A. Abdipour, "Compact active duplexer based on CSRR and interdigital loaded microstrip coupled lines for LTE application," Progress In Electromagnetics Research C, Vol. 109, 27-37, January 2021, doi: 10.2528/PIERC20112307.
22. Dalarsson, M., M. Norgren, T. Asenov, and N. Doncov, "Arbitrary loss factors in the wave propagation between RHM and LHM media with constant impedance throughout the structure," Progress In Electromagnetics Research, Vol. 137, 527-538, March 2013, doi: 10.2528/PIER13013004.
23. Dalarsson, M., "General theory of wave propagation through graded interfaces between positive-and negative refractive-index media," Physical Review A, Vol. 96, 043848, October 2017, doi: PhysRevA.96.043848.
24. Dalarsson, M. and P. Tassin, "Analytical solution for wave propagation through a graded index interface between a right-handed and a left-handed material," Optics Express, Vol. 17, 6747-6752, April 2009.
25. Dalarsson, M. and S. Nordebo, "TE-wave propagation in graded waveguide structures," OSA Continuum, Vol. 3, 67-76, January 2020.