Conicity and depth effects on the optical transmission of lithium liobate photonic crystals patterned by focused ion beam

We report on novel focused ion beam fabrication techniques that can greatly improve the optical performance of photonic crystal structures. The finite depth and conicity effects of holes and trenches in Lithium Niobate (LN) photonic crystals have been theoretically analyzed, showing that the conicity causes refraction into the bulk sample, resulting in high transmission loss and no useful spectral features. The techniques for reducing the conicity angle from 25° to 5° were explained for the focused ion beam (FIB) milled structures. ©2011 Optical Society of America OCIS codes: (130.3730) Lithium niobate; (160.5298) Photonic crystals; (230.2090) Electrooptical devices. References and links 1. S. Sriram and S. A. Kingsley, “Sensitivity enhancements to photonic electric field sensor,” SPIE Defense & Security Symposium, Orlando, FL, 12–16 April 2004. 2. H. Hu, R. Ricken, W. Sohler, and R. B. Wehrspohn, “Lithium niobate ridge waveguides fabricated by wet etching,” IEEE Photon. Technol. Lett. 19(6), 417–419 (2007). 3. H. Hu, A. P. Milenin, R. B. Wehrspohn, H. Hermann, and W. Sohler, “Plasma etching of proton-exchanged lithium niobate,” J. Vac. Sci. Technol. A 24(4), 1012–1015 (2006). 4. F. Chen, “Photonic guiding structures in lithium niobate crystals produced by energetic ion beams,” J. Appl. Phys. 106(8), 081101 (2009). 5. G. Si, E. J. Teo, A. A. Bettiol, J. Teng, and A. J. Danner, “Suspended slab and photonic crystal waveguides in lithium niobate,” J. Vac. Sci. Technol. B 28(2), 316–320 (2010). 6. Y. K. Kim, A. J. Danner, J. J. Raftery, and K. D. Choquette, “Focused ion beam nanopatterning for optoelectronic device fabrication,” IEEE J. Sel. Top. Quantum Electron. 11(6), 1292–1298 (2005). 7. M. Roussey, M. P. Bernal, N. Courjal, and F. I. Baida, “Experimental and theoretical characterization of a lithium niobate photonic crystal,” Appl. Phys. Lett. 87(24), 241101 (2005). 8. A. Farjadpour, D. Roundy, A. Rodriguez, M. Ibanescu, P. Bermel, J. D. Joannopoulos, S. G. Johnson, and G. W. Burr, “Improving accuracy by subpixel smoothing in the finite-difference time domain,” Opt. Lett. 31(20), 2972– 2974 (2006). 9. J. Ouyang, X. Wang, and M. Qi, “Meep,” DOI: 10254/nanohub-r2954.6 (2011). 10. A. F. Oskooi, D. Roundy, M. Ibanescu, P. Bermel, J. D. Joannopoulos, and S. G. Johnson, “MEEP: A flexible free-software package for electromagnetic simulations by the FDTD method,” Comput. Phys. Commun. 181(3), 687–702 (2010). 11. Srico Inc., 2724 Sawbury Blvd., Columbus, OH 43235, USA. 12. N. J. Bassom and T. Mai, “Modeling and optimization XeF2-enhanced FIB milling of Silicon,” in Proc. 25th International Symposium for Testing and Failure Analysis, Santa Clara, CA, 255–261 (1999). 13. H. Nakamura, H. Komano, and M. Ogasawara, “Focused ion beam assisted etching of quartz in XeF2 without transmittence reduction for phase shifting mask repair,” Jpn. J. Appl. Phys. 31(Part 1, No. 12B), 4465–4467 (1992). 14. J. Kettle, R. T. Hoyle, and S. Dimov, “Fabrication of step-and-flash imprint lithography (S-FIL) templates using XeF2 enhanced focused ion-beam etching,” Appl. Phys., A Mater. Sci. Process. 96(4), 819–825 (2009). 15. G. W. Burr, S. Diziain, and M. P. Bernal, “The impact of finite-depth cylindrical and conical holes in lithium niobate photonic crystals,” Opt. Express 16(9), 6302–6316 (2008). 16. D. Runde, S. Brunken, C. E. Rüter, and D. Kip, “Integrated optical electric field sensor based on a Bragg grating in lithium niobate,” Appl. Phys. B 86(1), 91–95 (2006). 17. A. Suzuki, T. Iwamoto, A. Enokihara, H. Murata, and Y. Okamura, “Fabrication of Bragg gratings with deep grooves in LiNbO3 ridge optical waveguide,” Microelectron. Eng. 85(5-6), 1417–1420 (2008). #154084 $15.00 USD Received 9 Sep 2011; revised 9 Oct 2011; accepted 10 Oct 2011; published 17 Oct 2011 (C) 2011 OSA 1 November 2011 / Vol. 1, No. 7 / OPTICAL MATERIALS EXPRESS 1262 18. K. Ghoumid, R. Ferriere, B. E. Benkelfat, B. Guizal, and T. Gharbi, “Optical performance of Bragg gratings fabricated in Ti:LiNbO3 waveguides by focused ion beam milling,” J. Lightwave Technol. 28, 3488–3493 (2010). 19. L. Pierno, M. Dispenza, A. Secchi, A. Fiorello, and V. Foglietti, “A lithium niobate electro-optic tunable Bragg filter fabricated by electron beam lithography,” J. Opt. A, Pure Appl. Opt. 10(6), 064017 (2008). 20. D. Grobnic, S. J. Mihailov, C. W. Smelser, F. Genereux, G. Baldenberger, and R. Vallee, “Bragg gratings made in reverse proton exchange lithium niobate waveguides with a femtosecond IR laser and a phase mask,” IEEE Photon. Technol. Lett. 17(7), 1453–1455 (2005). 21. J. Hukriede, D. Runde, and D. Kip, “Fabrication and application of holographic Bragg gratings in lithium niobate channel waveguides,” J. Phys. D Appl. Phys. 36(3), R1–R16 (2003). 22. M. W. Pruessner, T. H. Stievater, and W. S. Rabinovich, “Integrated waveguide Fabry-Perot microcavities with silicon/air Bragg mirrors,” Opt. Lett. 32(5), 533–535 (2007).