Coherent-Coupling-Based Wide-Angle Optical Polarization Splitter 報 告 者 ：陳 嘉 怜 指導教授：王 維 新 博 士

Outline  Introduction  Principle of Operation  Process Steps and Results  Future Work  References

 Introduction  Principle of Operation  Process Steps and Results  Future Work  References

Polarization Splitter Motivation: TE and TM mode have different electrooptic coefficients in birefringence material. Principle: Mode interference Mode sorting Structure: Directional coupler type Y-branch type Material: Ti ; Ni ; PE ; APE ; Zn / Ni In my work: Structure: Y-branch type (simplified coherent couple) Material: Zn / Ni

 Introduction  Principle of Operation  Process Steps and Results  Future Work  References

TE / TM TE TM Ni:LiNbO 3 Z-cut LiNbO 3 Principle of Operation Curved bend Chamfered bend Prism-assisted bend Substrate prism bend Coherently-coupled bend L TE / TM TE TM Ti:LiNbO 3 Ni:LiNbO 3 Z-cut LiNbO 3 Vary the length L can make TM mode coupled to another waveguide. (a) Directional coupler type (b) Y-branch type

Coherently Coupler Bend Θ 2Θ 3Θ 4Θ Phase rocking region Θ 3Θ 4Θ Phase rocking region (a)standard structure (b)new structure

Polarization Splitter With a suitable coupling length, TM wave can be coupled to the S-band but not TE wave. Coherently-coupled Bend (S-band) TE / TM TE TM Zn / Ni:LiNbO 3 Z-cut LiNbO 3 Zn / Ni:LiNbO 3

 Introduction  Principle of Operation  Process Steps and Results  Future Work  References

Process Steps Zn Ni (a) Cr (c) Zn Cr Ni (d) Cr (e) (b) Zn Ni Zn Cr

Coherently-Coupled Y-branch Waveguide Θ 3Θ 5Θ 6Θ 5Θ 3Θ Θ L1 L2 L3 L2 TM L1 = L2+15 / tan (0.5) L2 = coupling length L3 = 1000μm W = 6μm W

Process Parameters Waveguide Width Zn ThicknessNi Thickness Diffusion Time Diffusion Temp. Coupling Length 6μm650 Å200 Å1.5 hr 800 ℃ 200μm 6μm650 Å200 Å1.5 hr 800 ℃ 250μm 6μm650 Å200 Å1.5 hr 800 ℃ 300μm 6μm650 Å200 Å1.5 hr 800 ℃ 350μm For TM Mode

TM Mode Power Splitter TM 2.2  W 0.42  W Laser Wavelength = 1.55  m Pumping Current = 45 mA Coherent Length = 350  m

Straight Waveguide 2.2  W TM mode

S-band Waveguide TM mode Coupling Length = 350  m 0.42  W

 Introduction  Principle of Operation  Process Steps and Results  Future Work  References

Future Work Vary the coupling length to make sure if 350  m is the best coupling length. We have mask for the coupling lengths 400  m, 450  m, 500  m, and 550  m. When the best one is obtained, a new mask is required for the proposed polarization splitter.

References Ruey-Ching Twu, Chia-Chih Huang and Way-Seen Wang “TE-TM Mode Splitter With Heterogeneously Coupled Ti-Diffused And Ni-Diffused Waveguides On Z-cut Lithium Niobate,”Electron. Lett., 3rd, vol. 36, no. 3, pp , Feb Jiun-Yun Li, Wen-Hao Hsu, and Way-Seen Wang, Member, IEEE “A TH-TM Mode Splitter Using Annealed Proton Exchange And Zinc/Nickel Co-Diffusion Waveguides” J.J. Su and W. S. Wang, “Novel coherently-coupled multi-sectional bending optical waveguide,” Photo.Tech. Letters, August 2002.