Analysis of Slanted Gratings for Lightguide Coupling

Transcription

1 Analysis of Slanted Gratings for Lightguide Coupling

2 Abstract Slanted gratings are commonly used for coupling light into optical lightguides due to their high efficiency in a certain diffraction order. Nowadays, they are often applied in the augmented and mixed reality applications. It will be shown how VirtualLab Fusion can be used to analyze certain slanted grating geometries from literature, with specific parameters like slant angle, fill factor, and modulation depth. In addition, the effect of different incidence angles on the diffraction efficiency is investigated. 2

3 Modeling Task to be varied slanted grating period: nm relative depth fill factor slant angle diffraction efficiency =? How to calculate the diffraction efficiencies of the coupling grating, with varying grating parameters? T+1 st R+0 th incidence R+1 st R+2 nd air n = 1.5 diffraction efficiency =? input plane wave wavelength: 633 nm angle of incidence: -45 TE polarized 3

4 Diffraction Efficiency vs. Relative Depth simulation by Fourier modal method (FMM), also known as RCWA, in VirtualLab Fusion φφ c/p =fill factor c p Grating Parameter Value & Unit x relative depth to be varied y z h slant angle φφ -30 fill factor c/p 50% Reference: J. Michael Miller, Nicole de Beaucoudrey, Pierre Chavel, Jari Turunen, and Edmond Cambril, "Design and fabrication of binary slanted surface-relief gratings for a planar optical interconnection," Appl. Opt. 36, (1997) 4

5 Diffraction Efficiency vs. Slant Angle simulation by Fourier modal method (FMM), also known as RCWA, in VirtualLab Fusion φφ c/p =fill factor c p Grating Parameter Value & Unit x relative depth λλ y z h slant angle φφ to be varied fill factor c/p 50% Reference: J. Michael Miller, Nicole de Beaucoudrey, Pierre Chavel, Jari Turunen, and Edmond Cambril, "Design and fabrication of binary slanted surface-relief gratings for a planar optical interconnection," Appl. Opt. 36, (1997) 5

6 Diffraction Efficiency vs. Fill Factor simulation by Fourier modal method (FMM), also known as RCWA, in VirtualLab Fusion φφ c/p =fill factor c p Grating Parameter Value & Unit x relative depth λλ y z h slant angle φφ -30 fill factor c/p to be varied Reference: J. Michael Miller, Nicole de Beaucoudrey, Pierre Chavel, Jari Turunen, and Edmond Cambril, "Design and fabrication of binary slanted surface-relief gratings for a planar optical interconnection," Appl. Opt. 36, (1997). 6

7 Diffraction Efficiency vs. Varying Incidence Angle diffraction efficiency T+1 st fixed grating parameters (taken from reference) period: nm relative depth 1.058λλ fill factor 50% slant angle -30 Incidence input plane waves wavelength: 633 nm varying incidence angle: -45 ±10 Grating diffraction efficiency is usually sensitive to the angle of incidence. 7

8 Peek into VirtualLab Fusion convenient definition for slanted gratings rigorous diffraction efficiency calculation and visualization 8

9 Workflow in VirtualLab Fusion Configuration of lightguide coupling grating structure Advanced Configuration of Slanted Grating [Use Case] Configuration of Grating Structures by Using Special Media [Use Case] Configuration of Grating Structures by Using Interfaces [Use Case] Analyze coupling grating diffraction efficiency Customized Detector for Lightguide Coupling Grating Evaluation [Use Case] Check efficiency by scanning over specific parameter 9

10 VirtualLab Fusion Technologies crystals & anisotropic components nonlinear components free space 2 prisms, plates, cubes,... 2 waveguides & fibers lenses & freeforms 1 scatterer Field Solver apertures & boundaries 2 diffusers 1 gratings diffractive beam splitters SLM & adaptive components micro lens & freeform arrays diffractive, Fresnel, meta lenses HOE, CGH, DOE 10

11 Document Information title document code version 1.0 toolbox(es) VL version used for simulations category Analysis of Slanted Gratings for Lightguide Coupling LGC.0001 Starter Toolbox, Grating Toolbox Application Use Case further reading - Customized Detector for Lightguide Coupling Grating Evaluation 11