CLEO, May 7-12, 7 2000, San Francisco Propagation of Photons Through Localized Coupled Cavity Modes in Photonic Band Gap Structures: A New Type of Waveguiding Mechanism Mehmet Bayındır Burak Temelkuran and Ekmel Özbay Bilkent University, Department of Physics
Outline Review of layer-by by-layer three-dimensional photonic crystals Tight binding description of the coupled cavities Experimental observation of the eigenmode splitting Determination of the tight-binding parameters Observation of a new type of waveguiding mechanism: Coupled-cavity waveguides (CCW) Straight CCWs Bent CCWs Zig-zag CCWs Observation of heavy photons at the CCW band edges Group velocity tends towards to zero Photon lifetime increases drastically Possible applications of the CCWs
Layer-by by-layer Three-Dimensional Photonic Crystals Power (db) -5-15 -25-35 -45-55 Reflection Transmission 9 10 11 12 13 14 15 16 17 18 Frequency (GHz) Symmetry: Face centered tetragonal (fct) Material: Alumina of refractive index ε =3.1 at microwave frequencies Dimensions: 0.32 cm 0.32 cm 15.25 cm Three-dimensional stop band: from 10.6 GHz to 12.8 GHz E. Ozbay, J. Opt. Soc. Am. B 13, 1945 (1996)
Tight-Binding Description of Localized Coupled Defect Modes Tight-binding parameters can be directly determined from experiments N. Stefanou and A. Modinos, Phys. Rev. B 57, 12127 (1998) A. Yariv et al., Opt. Lett. 24, 711 (1999) Mehmet Bayindir, B. Temelkuran, and E. Ozbay, Phys. Rev. Lett. 82, 2140 (2000)
Experimental Setup HP 8510C
Localized Coupled-Cavity Cavity Modes: Splitting Transmission (arb. units) Q=1000 Ω =12.150 GHz ω 1 =11.831 GHz ω 2 =12.402 GHz Γ 1 =11.708 GHz Γ 2 =12.153 GHz Γ 3 =12.506 GHz 11.0 11.5 12.0 12.5 13.0 Frequency (GHz) 13.5 The tight-binding parameter can be determined from the splitting of two coupled-cavity cavity modes Mehmet Bayindir, B. Temelkuran, and E. Ozbay, Phys. Rev. Lett. 82, 2140 (2000)
Straight CCW: Transmission Characteristics Propagation of the electromagnetic waves through localized coupled-cavity cavity modes: A new type of waveguiding mechanism The tight-binding parameter can also be determined from the bandwidth of CCW band Transmission (db) 0-20 -40-60 Perfect Crystal Coupled-Cavity Waveguide 10 11 12 13 14 15 Frequency (GHz) No loss, No backreflections Full transmission was measured throughout the CCW band
Straight CCW: Dispersion Relation 1.10 1.05 Experiment Theory ω k / Ω 1.00 0.95 0.90 0.00 0.25 0.50 0.75 1.00 Tight-binding approximation: k Λ / π
Straight CCW: Group Velocity and Photon Lifetime v g / c 0.04 0.03 0.02 0.01 Experiment Theory Photon Lifetime (ns) 40 30 20 10 0 Experiment Theory 0.00 0.00 0.25 0.50 0.75 1.00 k Λ / π 11.50 11.75 12.00 12.25 12.50 12.75 Frequency (GHz) at the CCW band edges heavy photon Mehmet Bayindir and E. Ozbay, Phys. Rev. B 62, R2247 (2000)
40 o Bent CCW: Transmission Characteristics The problem of how to guide light around small structures seems s to be a difficult task when conventional waveguides are used. 0 Possibility of constructing lossless and reflectionless bends in optical circuits Transmission (db) -10-20 -30-40 -50-60 -70 10 11 12 13 14 15 Frequency (GHz) Nearly 100 % transmission was measured throughout the CCW band
Nearly 100 % transmission was measured throughout the CCW band Zig-Zag Zag CCW: Transmission Characteristics Arbitrarily shaped path with a constant intercavity distance 0 Transmission (db) -10-20 -30-40 -50-60 -70 10 11 12 13 14 15 Frequency (GHz)
Zig-Zag Zag CCW: Dispersion Relation and Group Velocity 1.10 0.05 1.05 Experiment Theory 0.04 Experiment Theory ω k / Ω 1.00 v g / c 0.03 0.02 0.95 0.01 0.90 0.00 0.25 0.50 0.75 1.00 k Λ / π 0.00 0.00 0.25 0.50 0.75 1.00 k Λ / π Mehmet Bayindir, B. Temelkuran, and E. Ozbay, Phys. Rev. B 64, 11855 (2000)
Possible Applications of CCWs Small group velocity and long photon lifetime: Increasing efficiency of nonlinear optical process, second harmonic generation, stimulated emission,... Sharp transitions in the transmission spectrum: Switching applications,... A new propagation mechanism: Lossless and reflectionless guiding and bending of light around sharp corners in optical circuits,... Coupled-cavity RCE photodetectors: High efficiency for wide range of resonance wavelengths
What about optical wavelengths? Our experimental and theoretical results for coupled-cavity cavity optical waveguides (CCOW) will be presented at OSA Annual Meeting 2000.
Acknowledgments These works are supported by Turkish Department of Defence Grant No. KOBRA-01 Turkish Scientific and Technical Research Council of TURKEY (TUBITAK) under Contract No. 197-E044 NATO Grant No. SfP971970 National Science Foundation Grant No. INT-9820646 NATO-Collaborative Research Grant No. 950079