1. Armando Cosentino OPT - Optics and Photonics Technology Laboratory (EPFL) Photonic Crystals EDPO PO-014 2009 Photonic crystal slotted guides

2. 03/07/2009A.Cosentino - PhC slotted guides2 Outline Introduction: why slots? Conventional slotted waveguides Photonic crystal slotted guides Green cavity project Conclusion

3. 03/07/2009A.Cosentino - PhC slotted guides3 Outline Introduction: why slots? Conventional slotted waveguides Slotted photonic crystals Green cavity project Conclusion

4. 03/07/2009A.Cosentino - PhC slotted guides4 Technology Introduction Optics Physics Motivation Application Planar integrated photonics QED Quantum dots Nonlinear optics Quantum optics Interaction matter-field Chemical sensing, single atom detection

5. 03/07/2009A.Cosentino - PhC slotted guides5 Motivation Introduction Planar integrated photonics Optics Physics Traditional main limitations in photonic dielectric cavities are due to their size Subwavelength-sized dielectric discontinuities are able to localize strongly the E-field in tiny volumes, that is very narrow slots Photonic crystal slab nanocavities Application Technology SOI free standing membrane, integrated devices Chemical sensing, single atom detection Empty Infiltrated with micro-fluids (air) Low-index materials SLOTS: GEOMETRY REALLY MATTERS Q High Q V eff Small V eff Q High Q V eff Small V eff QED Quantum dots Nonlinear optics Quantum optics Interaction matter-field

6. 03/07/2009A.Cosentino - PhC slotted guides6 Introduction Photonic crystal slab nanocavities SLOTS: GEOMETRY REALLY MATTERS Motivation Guide and enhance light in low-index material Planar integrated photonics Conventional slotted waveguide PhC slotted waveguide

7. 03/07/2009A.Cosentino - PhC slotted guides7 Figure of merit The ratio Q/V is the figure of merit in resonant cavities. It determines the strength of the various cavity interactions, and gives an idea of the cavity size. All the conventional designs conceived so far are not featured by an high Q factor. Neither they are able to enhance the E-field and confine it within a nanometer-sized region. Thus, the new idea is to exploit dielectric discontinuities (that is slots) in order to merge evanescent tails of guided modes. But conventional waveguides are tremendously leaky.

8. 03/07/2009A.Cosentino - PhC slotted guides8 Photonic Crystals By means of only TIR it is impossible to conceive photonic nanocavities featured by a very high figure of merit - the best would be a cavity surrounded by a 3D-PhC, but the fabrication is still prohibitive. Thus, despite the vertical radiation leakage it seems better to employ 2D-PhCs W1. The photonic-bandgap effect gives rise to confinement in the in-plane direction and TIR only concerns the z-direction - Akahane et al. Nature (London) 425, 944 (2003). A.Di Falco, L.O’Faolain, T.F.Krauss Photon. Nanostr. Fundam. Appl. 6, 38-41 (2008)

9. 03/07/2009A.Cosentino - PhC slotted guides9 Outline Introduction: why slots? Conventional slotted waveguides Slotted photonic crystals Green cavity project Conclusion

10. 03/07/2009A.Cosentino - PhC slotted guides10 Evanescent tails merge into high intensity because of the slot discontinuities Conventional slotted waveguides V.R.Almeida, Q.Xu, C.A.Barrios, M.Lipson OPTICS LETTERS 29, 1209 (2004) Infinite height Finite height High index slabs Low index material/air

11. 03/07/2009A.Cosentino - PhC slotted guides11 V.R.Almeida, Q.Xu, C.A.Barrios, M.Lipson OPTICS LETTERS 29, 1209 (2004) Conventional slotted waveguides Silicon-on-insulator (SOI) based samples

12. 03/07/2009A.Cosentino - PhC slotted guides12 Conventional slotted waveguides V.R.Almeida, Q.Xu, C.A.Barrios, M.Lipson OPTICS LETTERS 29, 1209 (2004) I slot (w s =50nm)=6xI Si

13. 03/07/2009A.Cosentino - PhC slotted guides13 J.T.Robinson, C.Manolatou, L.Chen, M.Lipson Phys.Rev.Lett. 95, 143901, (2005) Ultrasmall mode volume in microcavities

14. 03/07/2009A.Cosentino - PhC slotted guides14 J.T.Robinson, C.Manolatou, L.Chen, M.Lipson Phys.Rev.Lett. 95, 143901, (2005) NO SLOT SLOT Ultrasmall mode volume in microcavities

15. 03/07/2009A.Cosentino - PhC slotted guides15 On-chip gas detection J.T.Robinson, L.Chen, and M.Lipson OPTICS EXPRESS 16, 4296 (2008) Limited bending losses (lower than 11dB/cm)

16. 03/07/2009A.Cosentino - PhC slotted guides16 Outline Introduction: why slots? Conventional slotted waveguides Slotted photonic crystals Green cavity project Conclusion

17. 03/07/2009A.Cosentino - PhC slotted guides17 A.Di Falco, L.O’Faolain, T.F.Krauss Photon. Nanostr. Fundam. Appl. 6, 38-41 (2008) Band diagram

18. 03/07/2009A.Cosentino - PhC slotted guides18 T.Yamamoto, M.Notomi et al. OPTICS EXPRESS 16, 13809 (2008)

19. 03/07/2009A.Cosentino - PhC slotted guides19 T.Yamamoto, M.Notomi et al. OPTICS EXPRESS 16, 13809 (2008) Width modulation

20. 03/07/2009A.Cosentino - PhC slotted guides20 Chemical sensing: heterostructured devices SEM inspection reveals slots non-uniformity (narrower in the center with a variation up to 10%) A.Di Falco, L.O’Faolain, T.F.Krauss Appl.Phys.Lett. 94, 063503 (2009) Red lines and yellow shade n=1 Black lines and gray shade n=1.315 Sensitivity maximization: S=  /  n

21. 03/07/2009A.Cosentino - PhC slotted guides21 A.Di Falco, L.O’Faolain, T.F.Krauss Appl.Phys.Lett. 94, 063503 (2009) Slot widths 0.2a=98nm 0.3a=147nm 0.4a=196nm 0.5a=245nm Chemical sensing: heterostructured devices Slot widths 171nm166nm152nm

22. 03/07/2009A.Cosentino - PhC slotted guides22 Quantum and nonlinear optics Interaction matter-field Second harmonic generation (SHG) Optical parametric amplification on integrated photonics (OPA) A.Di Falco, C.Conti, G.Assanto OPTICS LETTERS 31, 3146 (2006)

23. 03/07/2009A.Cosentino - PhC slotted guides23 F.Foubert, L.Lalouat, B.Cluzel, et al. APPLIED PHYSICS LETTERS 94, 251111 (2009) Slotted nanoresonators as PhC nanocavity coupler

24. 03/07/2009A.Cosentino - PhC slotted guides24 Outline Introduction: why slots? Conventional slotted waveguides Slotted photonic crystals Green cavity project Conclusion

25. 03/07/2009A.Cosentino - PhC slotted guides25 Fabrication - access list Vistec EBPG5000, electron beam lithography system Heidelberg DWL200, LASER lithography system EVG150, coater and developer system for positive resist Süss MA6/BA6, double side mask aligner and bond aligner Süss DV10, developer for mask and thick resists Alcatel 601E, dry etcher, fluorine chemistry Tepla 300, dry etcher, oxygen plasma Oxford PRS900, dry etcher, oxygen plasma Coillard Photolithography, wet bench, resist strip and develop Coillard etching, wet bench, oxide and metal etch Idonus HF VPE-100, wet bench, HF vapor phase etcher Zeiss LEO 1550, SEM PHOTOLITHOGRAPHY DRY ETCHING WET ETCHING E-beam LITHOGRAPHY

26. 03/07/2009A.Cosentino - PhC slotted guides26 Green cavity project

27. 03/07/2009A.Cosentino - PhC slotted guides27 Green cavity project green cavity projectcavity 1cavity 2cavity 3cavity 4 period [nm]430 hole diameter [nm]270300 270 w1 [nm]66606660 w2 [nm]90 100 L1 [nm]2600 L2 [nm]1300 Courtesy of Vincent Paeder, OPT - Optics and Photonics Technology Laboratory (EPFL)

28. 03/07/2009A.Cosentino - PhC slotted guides28 Green cavity project E-beam resolutions: Low-res: 100nm High-res: 5nm

29. 03/07/2009A.Cosentino - PhC slotted guides29 Conclusion Conventional slotted waveguides Enhancement of e-field amplitude, power and intensity in low-n materials A strong e-field confinement is localized to a nanometer-sized low-n region Slotted photonic crystals Amazing potentialities of optimization, versatility and functionaliy Green cavity project Conclusion