Optical device having fan-out waveguides and bus waveguide

1. An optical device comprising:

a primary fan-out waveguide;

at least one secondary fan-out waveguide;

a fan-out optical coupler for coupling a light beam between the primary fan-out waveguide and the secondary fan-out waveguide;

at least one bus waveguide associated with the at least one secondary fan-out waveguide and different from each secondary fan-out waveguide; and

a reflecting and coupling structure connecting the secondary fan-out waveguide and the bus waveguide;

wherein the reflecting and coupling structure comprises an optical coupler for coupling a light beam between the secondary fan-out waveguide and the bus waveguide,

wherein the reflecting and coupling structure comprises a bus reflective face for at least partially reflecting a light beam in the bus waveguide and a secondary fan-out reflective face for at least partially reflecting a light beam in the secondary fan-out waveguide,

wherein the optical path length between the optical coupler of the reflecting and coupling structure and the bus reflective face is the same as the optical path length between the optical coupler of the reflecting and coupling structure and the secondary fan-out reflective face.

2. The optical device according to claim 1 , wherein the reflecting and coupling structure is an interferometric structure for coupling a light beam traveling in the secondary fan-out waveguide into the bus waveguide or coupling a light beam traveling in the bus waveguide into the secondary fan-out waveguide such that at least a fraction of the coupled light beam travels in the opposite direction after leaving the interferometric structure.

3. The optical device according to claim 1 , wherein at least a section of the bus waveguide extends alongside at least a section of the secondary fan-out waveguide, substantially parallel to a section of the secondary fan-out waveguide.

4. The optical device according to claim 1 , wherein substantially 50% of the light beam is coupled between the secondary fan-out waveguide and the bus waveguide on passing the optical coupler in one direction.

5. The optical device according to claim 1 , further comprising

an additional primary fan-out waveguide;

at least one additional secondary fan-out waveguide; and

an additional fan-out optical coupler for coupling a light beam between the additional primary fan-out waveguide and the additional secondary fan-out waveguide.

6. The optical device according to claim 1 , further comprising a light source coupled to the primary fan-out waveguide, for projecting a light beam into the primary fan-out waveguide.

7. An optical device comprising:

a primary fan-out waveguide;

at least one secondary fan-out waveguide;

a fan-out optical coupler for coupling a light beam between the primary fan-out waveguide and the secondary fan-out waveguide;

at least one bus waveguide associated with the at least one secondary fan-out waveguide and different from each secondary fan-out waveguide;

a reflecting and coupling structure connecting the secondary fan-out waveguide and the bus waveguide; and

a transparent substrate, wherein the secondary fan-out waveguide and the bus waveguide are provided in the transparent substrate by femtosecond direct laser writing.

8. An optical device comprising:

a primary fan-out waveguide;

at least one secondary fan-out waveguide;

a fan-out optical coupler for coupling a light beam between the primary fan-out waveguide and the secondary fan-out waveguide;

at least one bus waveguide associated with the at least one secondary fan-out waveguide and different from each secondary fan-out waveguide;

a reflecting and coupling structure connecting the secondary fan-out waveguide and the bus waveguide; and

a transparent substrate comprising a facet wherein at least one of a bus reflective face or a secondary fan-out reflective face are provided by at least one of the facet of the transparent substrate or a coating of the facet of the transparent substrate.

9. An optical device comprising:

a primary fan-out waveguide;

at least one secondary fan-out waveguide;

a fan-out optical coupler for coupling a light beam between the primary fan-out waveguide and the secondary fan-out waveguide;

at least one bus waveguide associated with the at least one secondary fan-out waveguide and different from each secondary fan-out waveguide;

a reflecting and coupling structure connecting the secondary fan-out waveguide and the bus waveguide; and at least one pixel waveguide for receiving a light beam from the at least one bus waveguide or for directing a light beam to the at least one bus waveguide, the pixel waveguide bending away from the bus waveguide.

10. An optical device comprising:

a primary fan-out waveguide;

at least one secondary fan-out waveguide;

a fan-out optical coupler for coupling a light beam between the primary fan-out waveguide and the secondary fan-out waveguide;

at least one bus waveguide associated with the at least one secondary fan-out waveguide and different from each secondary fan-out waveguide;

a reflecting and coupling structure connecting the secondary fan-out waveguide and the bus waveguide; and

a phase adjusting element for adjusting the relative optical path length of the secondary fan-out waveguide and of the bus waveguide in the reflecting and coupling structure, wherein the phase adjusting element comprises at least one of a phase shifter or a piezo-mirror.

11. An optical device comprising:

a primary fan-out waveguide;

at least one secondary fan-out waveguide;

a fan-out optical coupler for coupling a light beam between the primary fan-out waveguide and the secondary fan-out waveguide;

at least one bus waveguide associated with the at least one secondary fan-out waveguide and different from each secondary fan-out waveguide;

a reflecting and coupling structure connecting the secondary fan-out waveguide and the bus waveguide; and further comprising

at least a further bus waveguide associated with the secondary fan-out waveguide and different from each secondary fan-out waveguide, wherein the reflecting and coupling structure also connects the secondary fan-out waveguide and the further bus waveguide,

wherein the reflecting and coupling structure comprises a tritter for coupling a light beam between the secondary fan-out waveguide, the bus waveguide and the further bus waveguide.

12. A display, comprising a display panel and a backlight unit formed by an optical device, the optical device comprising:

a primary fan-out waveguide,

at least one secondary fan-out waveguide;

a fan-out optical coupler for coupling a light beam between the primary fan-out waveguide and the secondary fan-out waveguide,

at least one bus waveguide associated with the at least one secondary fan-out waveguide and different from each secondary fan-out waveguide, and

a reflecting and coupling structure connecting the secondary fan-out waveguide and the bus waveguide.