High efficiency waveguide-based near-eye displays
Systems and methods to improve efficiency of in-coupling electromagnetic waves, such as in a visible light wavelength range, into a waveguide system arrangement are disclosed. The waveguide system includes: a display or an illumination assembly; a waveguide substrate; a polarization volume grating or a spin-dependent bifacial metasurface as in-coupler, which efficiently couples electromagnetic waves, such as in a visible light wavelength range, into the waveguide substrate. An out-coupler can couple the electromagnetic waves, such as in a visible light wavelength range, out of the waveguide substrate.
1. A waveguide assembly, comprising:
in-coupler optically coupled to a waveguide substrate; and
wherein the in-coupler includes at least one high-efficiency polarization volume grating (PVG) optically coupled to a surface of the waveguide substrate, a thickness of the PVG selected to satisfy a half-wave plate phase-retardation condition of an in-coupled circularly polarized (CP) light, which in response to a first interaction of an in-coupled CP light incident with the PVG the CP light deflects and propagates in the waveguide substrate, and thereafter during a second interaction of the CP light incident with the PVG the CP light experiences a circular polarization conversion without changing its propagation direction.
2. A method for a waveguide assembly including a waveguide substrate and a high-efficiency polarization volume grating (PVG) optically coupled with a surface of the waveguide substrate as an in-coupler of circularly polarized light (CPL) into the waveguide substrate, a thickness of the PVG selected to satisfy a half-wave plate condition for a wavelength range of an in-coupled CPL incident on the PVG, the method comprising:
in-coupling into the waveguide substrate a right-handed or left-handed circularly polarized light (CPL);
during a first interaction of the in-coupled CPL incident on the PVG, deflecting the in-coupled CPL to propagate the CPL in the waveguide substrate by total internal reflections; and
during a second interaction with the PVG, after the first interaction with the PVG, converting a circular polarization of the CPL incident on the PVG without changing the propagation direction of the CPL.
3. A waveguide apparatus in a head-mounted display or in an illumination system, comprising:
a display assembly or an illumination assembly;
a waveguide assembly comprising a waveguide substrate and an in-coupler disposed on a surface of the waveguide substrate;
one or more high-efficiency polarization volume gratings (PVG), or one or more spin-dependent bifacial metasurfaces, as the in-coupler disposed on a surface of the waveguide substrate, wherein the PVG being
optically coupled to a surface of the waveguide substrate, a thickness of the PVG selected to satisfy a half-wave plate phase-retardation condition of an in-coupled circularly polarized (CP) light, which in response to a first interaction of an in-coupled CP light incident with the PVG the CP light deflects and propagates in the waveguide substrate, and thereafter during a second interaction of the CP light incident with the PVG the CP light experiences a circular polarization conversion without changing its propagation direction; and
an out-coupler.
4. The waveguide apparatus according to claim 3 , wherein light in-coupled from the display assembly or the illumination assembly comprises circularly polarized light.
5. The waveguide apparatus according to claim 3 , wherein the display assembly comprises:
a display component; and
a circular polarizer, which converts light from the display component into circular polarization light.
6. The waveguide apparatus according to claim 3 , wherein the display assembly comprises:
a display component;
a collimation lens; and
a circular polarizer, which converts light from the display component into circularly polarized light.
7. The waveguide apparatus according to claim 3 , wherein the illumination assembly comprises:
a light source and a circular polarizer, which converts light from the light source into circular polarization light.
8. The waveguide apparatus according to claim 3 , wherein the illumination assembly comprises:
a light source;
a lens component; and
a circular polarizer, which converts light from the light source into circularly polarized light.
9. The waveguide apparatus according to claim 3 , wherein the waveguide assembly includes one or multiple waveguide substrates that support propagation of red, green, and blue lights either individually or collectively.
10. The waveguide apparatus according to claim 3 , wherein the waveguide substrate comprises suitable transparent material including at least one of glass material, plastic material, or a combination thereof.
11. The waveguide apparatus according to claim 3 , wherein the PVG includes one layer or a plurality of layers combined in a structure, with thickness of each layer selected for achieving polarization conversion of in-coupled circularly polarized light during a second interaction with the PVG.
12. The waveguide apparatus of claim 11 , wherein the waveguide assembly includes one or multiple waveguide substrates, optically coupled with a plurality of film layers combined in a structure of the PVG to support in-coupling and propagation of red, green, and/or blue, lights either individually or collectively.
13. The waveguide apparatus according to claim 3 , wherein the PVG comprises a gradient pitch structure with optimized thickness selected for achieving polarization conversion during a second interaction with the polarization volume grating.
14. The waveguide apparatus according to claim 3 , wherein the PVG comprises a right-handed structure or a left-handed structure.
15. The waveguide apparatus according to claim 3 , wherein a plurality of polarization volume gratings is laminated on a plurality of surfaces of a waveguide substrate, and in-coupled light comprises linearly polarized light or un-polarized light.
16. The waveguide apparatus according to claim 3 , wherein a mirror is combined with a spin-dependent bifacial metasurface on two surfaces of the waveguide substrate for achieving more efficient reverse polarization during reflection at a boundary of the waveguide substrate.
17. The waveguide apparatus according to claim 3 , wherein the out-coupler includes a type of gratings, mirror, or partial mirror array, which couple light out of the waveguide substrate.
18. The waveguide apparatus according to claim 3 , wherein the out-coupler comprises multiple gratings.
19. The waveguide apparatus according to claim 3 , wherein the waveguide substrate comprises multiple out-couplers, or extra turning couplers, for 2-dimensional beam expansion.