Magneto-Optic Materials for Integrated Photonics Bethanie J. H. Stadler Sang-Yeob Sung, Luis Cruz, Na hyoung Kim, Xiaoyuan Qi, Ryan Cobian, Neal Speetzen Electrical and Computer Engineering University of Minnesota

AIMD Group Bethanie J. H. Stadler Outline n Motivation (isolators) n Garnet Layer – Fabrication – Characterization n Buffer Layers n Permanent Magnets n Photonic Crystals

AIMD Group Bethanie J. H. Stadler Current Isolators Use YIG (Y 3 Fe 5 O 12 ) Garnet Films Polarizer Magnet Laser Beam Garnet Substrate M n Garnet Fabrication – LPE requires garnet substrates and high temperatures. n Bulk permanent magnet  F = V B l V-material constant B- magnetic field l- pathlength

AIMD Group Bethanie J. H. Stadler Integrated Isolators n Garnet Fabrication – MOCVD – MOCLD – Dual-target sputtering – Single-target sputtering n Buffer and cladding layers (MgO, SiO2) n Permanent magnet films (SmCo) Oxide Overlayer / Compliant Layer Garnet Waveguide Buffer layer on semiconductor substrate M PM fiber Device goal: waveguide isolator Permanent Magnet Film

AIMD Group Bethanie J. H. Stadler Advantages n Fully integrating optical isolators on a single wafer n Compact size n Low cost n Low magnetic field required n No focusing optics required n Now: Optical packaging (Laser diode + Isolator) n Later: Photonic integrated circuits (PICs)

AIMD Group Bethanie J. H. Stadler Faraday Rotation n Dispersion 0 Excitation n+n+ n-n- s Absorption Without Magnetic Field With Applied Magnetic Field n Absorption

AIMD Group Bethanie J. H. Stadler Garnet can accommodate half the periodic table! A( ) M a (T)  F (T, ) = C( ) M c (T) + A( ) M a (T) + D( ) M d (T) V. J. Fratello and R. Wolfe, in Magnetic Film Devices, (2000).

AIMD Group Bethanie J. H. Stadler Other materials Low Verdet constants: (longer lengths or stronger magnets) Magneto-optical glasses oxides and fluorides with Ce 3+, Pr 3+, Eu 2+, and Tb 3+ * rare-earth or tranisition-metal doped semiconductors Easy to integrate with semiconductors Potential devitrification lower films due to nonequilibrium fab Rotations as high as –0.569 min/Oe/cm High Absorption: (high optical loss) Maghemite made by pulsed laser deposition at 500C ** High Faraday rotations due to octahedral Fe 2+ * K. Tanaka, K. Fujita, N. Matsuoka, K. Hirao, S. Soga, J. Materials Research (1998) **T. Teper, F. Illievski, C. Ross, R Zaman, R Ram, S Sung, B. Stadler, J. Appl. Phys. 93 (2003).

AIMD Group Bethanie J. H. Stadler Outline n Motivation (isolators) n Garnet Layer – Fabrication – Characterization n Buffer Layers n Permanent Magnets n Photonic Crystals

AIMD Group Bethanie J. H. Stadler Metalorganic Chemical Vapor Deposition (MOCVD) N 2 O O 2 Heater Substrates To Pump Ar Liquid Pump Vaporizer Growth line By pass line Y-, Fe-, Ce-(thd)* *(2,2,6,6-tetramethyl1,3,5-heptanedionate) Collaboration w/ Boston Applied Technologies

AIMD Group Bethanie J. H. Stadler Metalorganic Chemical Liquid Deposition (MOCLD) Solution Dispenser Dipping & Drying Chamber Vertical Tube Furnace Motor& Gear Set Precursors: Y(NO 3 ) 3 and Fe(NO 3 ) 3 in water/ethanol 450 o C Collaboration w/ Boston Applied Technologies

AIMD Group Bethanie J. H. Stadler Specialized Fabrication Potential: Partial Pressure Differential to LN2 trap & pump Rotating substrate holder H 2 O, RF Power, Ar O2O2 All gases conventionally fed in at same location Y Fe

AIMD Group Bethanie J. H. Stadler Outline n Motivation (isolators) n Garnet Layer – Fabrication – Characterization n Buffer Layers n Permanent Magnets n Photonic Crystals

AIMD Group Bethanie J. H. Stadler Composition- MO techniques n Simply add dopant to precursor in MOCVD. n Nonequilibrium techniques allows high dopant level. n Y 1.5 Bi 1.5 Fe 3.8 Al 1.2 O 12 was grown by MOCLD.

AIMD Group Bethanie J. H. Stadler Effect of Composition on Structure Garnet: Y 3 Fe 5 O 12 Fe-poor: Y-O, YFeO 3 Fe-rich: Fe-O, Y 2 Fe 4 O 9

AIMD Group Bethanie J. H. Stadler Oxygen maintains single-phase YIG 1/2 (Y 2 O 3 ) Fe 1/2 (Fe 2 O 3 ) Y 2 Fe 4 O 9 Fe 1-y O Fe 3 O 4 Y 3 Fe 5 O 12 YFeO 3 A B

AIMD Group Bethanie J. H. Stadler Sputtered/Annealed Film

AIMD Group Bethanie J. H. Stadler Structure of MOCLD on glass n MOCLD films were dense, polycrystalline films.

AIMD Group Bethanie J. H. Stadler Optical Properties- Dispersion

AIMD Group Bethanie J. H. Stadler Ce raises the index of YIG

AIMD Group Bethanie J. H. Stadler Magnetic Properties- Sputtered films n Dual-target sputtered and annealed YIG film on MgO. (a) n YIG grown on MgO without anneal with single target sputtering. (b)

AIMD Group Bethanie J. H. Stadler Measuring Faraday Rotation Laser Halfwave Plate Sample Magnet Polarizing Beamsplitter TM TE InGaAs Detectors Lock-In Amplifier Recorder

AIMD Group Bethanie J. H. Stadler Faraday Rotation- MO films %Ce MOCLD sputtered