Armando Cosentino OPT Optics and Photonics Technology Laboratory

Armando Cosentino OPT - Optics and Photonics Technology Laboratory (EPFL) Photonic Crystals EDPO PO-014 2009 Photonic crystal slotted guides 03/07/2009 A. Cosentino - Ph. C slotted guides

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

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

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

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

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

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. 03/07/2009 A. Cosentino - Ph. C slotted guides 7

Photonic Crystals A. Di Falco, L. O’Faolain, T. F. Krauss Photon. Nanostr. Fundam. Appl. 6, 38 -41 (2008) 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 3 D-Ph. C, but the fabrication is still prohibitive. Thus, despite the vertical radiation leakage it seems better to employ 2 D-Ph. Cs W 1. 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). 03/07/2009 A. Cosentino - Ph. C slotted guides 8

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

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

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

Conventional slotted waveguides Islot(ws=50 nm)=6 x. ISi V. R. Almeida, Q. Xu, C. A. Barrios, M. Lipson OPTICS LETTERS 29, 1209 (2004) 03/07/2009 A. Cosentino - Ph. C slotted guides 12

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

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

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

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

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

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

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

Chemical sensing: heterostructured devices Sensitivity maximization: S= / n Red lines and yellow shade n=1 Black lines and gray shade n=1. 315 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) 03/07/2009 A. Cosentino - Ph. C slotted guides 20

Chemical sensing: heterostructured devices Slot widths 0. 2 a= 98 nm 0. 2 a=98 nm 171 nm 0. 3 a=147 nm 0. 4 a=196 nm 166 nm 0. 5 a=245 nm 152 nm A. Di Falco, L. O’Faolain, T. F. Krauss Appl. Phys. Lett. 94, 063503 (2009) 03/07/2009 A. Cosentino - Ph. C slotted guides 21

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) 03/07/2009 A. Cosentino - Ph. C slotted guides 22

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

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

Fabrication - access list • Vistec EBPG 5000, electron beam lithography system • • • Heidelberg DWL 200, LASER lithography system EVG 150, coater and developer system for positive resist Süss MA 6/BA 6, double side mask aligner and bond aligner Süss DV 10, developer for mask and thick resists Alcatel 601 E, dry etcher, fluorine chemistry Tepla 300, dry etcher, oxygen plasma Oxford PRS 900, 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 03/07/2009 A. Cosentino - Ph. C slotted guides E-beam LITHOGRAPHY PHOTOLITHOGRAPHY DRY ETCHING WET ETCHING 25

Green cavity project 03/07/2009 A. Cosentino - Ph. C slotted guides 26

Green cavity project green cavity project cavity 1 cavity 2 cavity 3 cavity 4 period [nm] 430 430 hole diameter [nm] 270 300 270 w 1 [nm] 66 60 w 2 [nm] 90 90 100 L 1 [nm] 2600 L 2 [nm] 1300 Courtesy of Vincent Paeder, OPT - Optics and Photonics Technology Laboratory (EPFL) 03/07/2009 A. Cosentino - Ph. C slotted guides 27

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

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 03/07/2009 A. Cosentino - Ph. C slotted guides 29