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Coherently Coupled Optical Waveguide

Coherently Coupled Optical Waveguide. 報 告 者 ：陳 嘉 怜 指導教授：王 維 新 博 士. Introduction Paper Review Principle of Operation Experiences and Results Summery References. Outline. Motivation:

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Coherently Coupled Optical Waveguide

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  1. Coherently Coupled Optical Waveguide 報 告 者 ：陳 嘉 怜 指導教授：王 維 新 博 士

  2. Introduction Paper Review Principle of Operation Experiences and Results Summery References Outline

  3. Motivation: Optical bending waveguide are used to change the direction of light propagation in many integrated optical devices such as MZ and directional couplers. In order to reduce the device area and increase the packing density, we must to find bend structures with large bend angles and low loss. Structure: Curved optical waveguide;Conventional bend waveguide; Etched-wall bend waveguide; Coupler bend waveguide; Prism waveguide. Principle of coupler bend waveguide: Coupled-bend transmission can be an oscillatory function of the interconnection length L due to interference between the guided and radiation modes. Material: Ti ; Ni ; Zn and Ni Introduction

  4. Introduction Paper Review Principle of Operation Experiences and Results Summery References

  5. P0 x n1  < 2º Pi n2 z n1 Conventional Bend Waveguide P0: output power Pi: input power 0: radiation and absorb parameter Lo: distance of optical beam propagating in waveguide T: power combine parameter( )

  6. x Pi n1  n2 z P0 n1 /2 Etched-wall Bend Waveguide Wave front in the part is speeded up to make bending easier and reduce the power loss. Advantage: power loss is lower than convention bend waveguide. Disadvantage: As  larger than 20, power loss will be higher and make this bending waveguide not to have the ability of light propagation.

  7. x Pi Wave front in the part is speeded down to make bending easier and reduce the power loss. Wave front in the part is speeded up to make bending easier and reduce the power loss. n1  n2 z P0 n1 /2 Coupler Bend Waveguide d Advantage: power loss is lower with suitable coherent length.

  8. Introduction Paper Review Principle of Operation Experiences and Results Summery References

  9. W X2 X3   L Z2 Z3 Guided mode Radiation mode Electric field: Propagation constant: Principle of Coherent Coupler I 3 1 2

  10. 1 3 2 Electric field: Electric Field parameter: Waveguide 1: Waveguide 2: Waveguide 3: L Principle of Coherent Coupler II

  11. 1 3 2 Electric field: Guided-mode transmission equation: L Principle of Coherent Coupler III Guided mode Radiation mode The equation shows that the coupled-bend transmission can be an oscillatory function of the interconnection length L due to interference between the guided and radiation modes.

  12. Interconnection Length L: 1 3 2 L Neff: guided-mode effective index NeffR:weighted-average effective index of the radiation modes excited after the first bend. If the phase difference between the modes shifts is: light coupled from the guided mode into an unguided mode at a bend can be completely coupled back into the guided mode at a succeeding bend. Principle of Coherent Coupler V

  13. 1 3 2 L=180m L GUIDE-MODE TRANSMISSION PHASE FRONTS L=380m INTERCONNECTING-SEGMENT LENGTH. L(um) Principle of Coherent Coupler VI

  14. Introduction Paper Review Principle of Operation Experiences and Results Summery References

  15. L 4mm L (Relative Transmission) 1/2 2Θ Θ Coherently Coupler Bend SECTION LENGTH, L( m )

  16. 4mm L L 3Θ (Relative Transmission) 1/2 2Θ Θ Coherently Coupler Bend N = 2 NUMBER OF SECTIONS ( N )

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

  18. Transmitted Power with Total Bending Angle

  19. Transmitted Power with Launching Wavelength

  20. Summery • The transmission function of the coupler bend waveguide depends on the interference of guided mode and radiation mode in the interconnection length L. • We study the principle of coupler bend waveguide which is better than conventional bend and etched-wall bend waveguide in being a suitable bending structure with large bend angles and low loss. • Other new structures include prism and new structure couple bend waveguide.

  21. L. M. Johnson and F. J. Leonberger, “Low-loss LiNbO3 waveguide bends with coherent coupling,” Optics Letters, Vol. 8, No. 2, Feb. 1983.” L. M. Johnson and D. Yap, “Theoretical analysis of coherently coupled optical waveguide bends,” Applied Optics, Vol. 23, No.17, 1 Sep.1984. 張文清, “An Investigation of integrated optical waveguide bends, ” 蘇振嘉, “Coherent-coupling-based wide-angle bending optical waveguide design and fabrication, ” References

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