Characterization of Photonic Structures with CST Microwave Studio. CST UGM 2010 Darmstadt

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1 Characterization of Photonic Structures with CST Microwave Studio Stefan Prorok, Jan Hendrik Wülbern, Jan Hampe, Hooi Sing Lee, Alexander Petrov and Manfred Eich, Institute of Optical and Electronic Materials CST UGM 2010 Darmstadt

2 1. Overview 2. Ring Resonators 3. 3D Photonic Crystals 4. 2D Photonic Crystals 5. Summary 2

3 A wide range of topics is covered by our institute CURRENT RESEARCH TOPICS Waveguides: Four-wave mixing Gyrotropic waveguides Ring resonators: Tunable filters Optical circulators Electrooptical modulation 2D Photonic crystals: Slow light Strong light confinement, high Q cavities (Q > 1e6) Electrooptical modulation 3D Photonic crystals: Thermal barrier coatings Thermophotovoltaich 3

4 Strip waveguides and slotted waveguides serve as basic building blocks for integrated photonic devices E-FIELD PATTERN OF STRIP AND SLOT WAVEGUIDES Strip waveguide Slot waveguide Polymer y Polymer x Si Si Si BOX BOX SOI wafers with 2 µm bouried oxide 220 nm silicon core. Polymer cladding q-tm E y -component q-te E x -component 4

5 1. Overview 2. Ring Resonators 3. 3D Photonic Crystals 4. 2D Photonic Crystals 5. Summary 5

6 Slotted waveguides can be used to build highly resonant structures NORMAL H-FIELD COMPONENT AND RADIAL E-FIELD COMPONENT OF A RING RESONATOR AT RESONANCE Logarithmic E r field Polymer Logarithmic H y field BOX Normal H-field and radial E-field of ring resonator at resonance 6

7 Quality factor can be extracted from the E-field intensity spectrum in the ring E-FIELD INTENSITY IN THE RING FROM CST SIMULATION E-field Inte ensity [db V/m] Q~ Wavelength [nm] 7

8 Complete resonator including segmented part for electrical contact was simulated SIMULATION AND EXPERIMENTAL RESULTS 0 Polymer 400 nm db] Trans smission [ Simulation Experiment Input y x Si 220 nm SiO 2 TM mode -20 Output x y ,8 190,9 191,0 191,1 191,2 191,3 19 z Frequency [THz] 8

9 1. Overview 2. Ring Resonators 3. 3D Photonic Crystals 4. 2D Photonic Crystals 5. Summary 9

10 3D photonic crystal structures can be used as efficient infrared reflectors CONCEPT FOR THERMAL BARRIER COATINGS Self assembled dielectric i spheres Heat reflection High reflectivity for infrared radiation Low thermal conductivity 10

11 Inverse structure provides a wider bandgap and greater suppression than the direct opal TRANSMISSION SPECTRA OF DIRECT & INVERSE OPAL STRUCTURE Δn = layers Direct opal Inverse opal 11

12 Hemispherical broadband illumination of multilayer structure can be simulated APPLICATION OF DIFFERENT CST MWS SOLVERS FOR 3D PhC Infinite Single stack normal & angle Multistack incl. FCC incidence defects lattice, Periodic boundry Nickel alloy Eigenmode solver Frequency domain solver, Time domain solvers Frequency domain solver, Time domain solvers 12

13 Experimental results are shifted by 3 % due to deviations in the diameter of spheres TRANSMISSION SPECTRA OF SIMULATION & MEASUREMENT λ center = 922 nm FWHM = 112 nm r ~ 180nm λ center = 950 nm FWHM = 90 nm Simulation: 10 layers Measurement: ~ 60 layers 13

14 1. Overview 2. Ring Resonators 3. 3D Photonic Crystals 4. 2D Photonic Crystals 5. Summary 14

15 Symmetry planes are used to reduce the simulation volume MODEL FOR A 2-D POINT DEFECT CAVITY IN A HEXAGONAL LATTICE EXCITED BY A DISCRETE PORT CST MWS model with symmetry planes and boundary conditions Normal H-field distribution inside the cavity at resonance frequency 15

16 AR-filter can reduce the simulation time in highly resonant structures significantly ENERGY DECAY IN TRANSIENT SIMULATION AND H-FIELD MAGNITUDE AR-filter is used to compensate for truncation errors in prematurely aborted transient simulations 16

17 CST reproduces previously reported results on PhC heterostructure cavities CST MODEL AND RESULTS FOR HETEROSTRUCTURE CAVITY C Asano: * Q Sim = 2*10 6 ν res = THz 1,0 CST: Q Eng = 2.1*10 6 Q AR = 1.9*10 6 ν res = THz Sim parameters: C = 12a, N 2 = 20a 152,950 Meshcells t Sim = 20 ps t Comp = 1h 50 min 0,8 N 2 0,6 17 d [a.u] Probe Fiel 0,4 0,2 0,0 192, , , , , ,760 frequency [THz] *Asano et al., IEEE Jour. of Sel. Top. in Quan. Elec., 2006

18 A slotted PhC heterostructure cavity incl. injector and coupler sections was realized DESIGN AND SEM OF A SLOTTED PHC HETEROSTRUCTURE CAVITY Injector Reflector Cavity Reflector Injector Fabrication by HHI and TU Berlin 18

19 Resonance with Q = 2600 has been observed in a NLOpolymer infiltrated slotted PhC heterostructure TRANSMISSION OF A SLOTTED PHC HETEROSTRUCTURE CAVITY 0.5 Trans smission [a a.u.] Q = 2600 λ 0 = nm Δλ = 0.58 nm Fabrication by HHI and TU Berlin Wavelength [nm] Wülbern, Eich et al., Opt. Exp. 17, (2009) 19

20 Slotted cavity increases sensitivity to index changes RESONANCE SPECTRA AT MODIFIED REFRACTIVE INDICIES TE-Polarization -> Δn = 05n 0.5n 3 r 13 E -> Δn = => U < 1 V r 33 = 100 pm/v d = 3µm W slot = 150 nm Δn = => Δν = 40 GHz, Δλ = 0.32 nm 20

21 . Photonic crystal provides optical isolation and electrical contact for 100 GHz EO modulation bandwidth SLOTTED PhC EQUIVALTENT RF CIRCUIT ρ = 0 1 Ω cm Rslot WSiρ / Fd Si l C / 2 slot = ε 0n polyd Sil W slot with ρ = 0.1 Ωcm (N doping = cm -3 ) * f3db = 1/(2π 2RslotCslot ) 100 GHz U mod < 1V for r 33 = 100 pm/v Losses due to doping: ~ 2 db/cm (Soref et al., IEEE JQE. 23, 1987) Wülbern, Eich et al., Opt. Exp. 17, (2009) 21

22 First realization of modulator with 40 GHz bandwidth and µm footprint MODULATION SIDE BANDS IN OPTICAL SPECTRUM ical Power [db Bm] GHz 20 GHz ical Power [db Bm] GHz 40 GHz Opti -80 Opti Frequency [GHz] Frequency [GHz] Wülbern et al., APL (submitted) 22

23 1. Overview 2. Ring Resonators 3. 3D Photonic Crystals 4. 2D Photonic Crystals 5. Summary 23

24 Summary Simulation of strip and slot waveguides with CST MWS has been shown Q-factor extraction from time domain simulations is demonstrated for ring resonators and 2D photonic crystals Frequency solver is used to determine angle dependent transmission spectra of 3D photonic crystals A photonic crystal cavity for GHz amplitude modulation is discussed 24