Apparatus and method for coupling light to a thin film optical waveguide
View Patent ↗An optical waveguide comprises a core guiding layer; a cladding layer positioned adjacent to the core guiding layer; a reflective layer positioned adjacent to the cladding layer; and a grating for coupling light into the core guiding layer; wherein the cladding layer has a thickness such that a ray reflected from the reflective layer is phase matched to an incident ray at the grating. A method of coupling electromagnetic radiation into the optical waveguide is also described.
1. An optical waveguide comprising:
a core guiding layer;
a cladding layer positioned adjacent to the core guiding layer;
a reflective layer positioned adjacent to the cladding layer; and
a grating for coupling light into the waveguide;
wherein the cladding layer has a thickness such that a ray reflected from the reflective layer is phase matched to an incident ray at the grating.
2. The optical waveguide of claim 1 , wherein consecutive leaky rays from the guiding layer at the grating are in-phase or have a phase difference of multiple 2π.
3. The optical waveguide of claim 1 , wherein the grating is positioned on a surface of the core guiding layer opposite the cladding layer.
4. The optical waveguide of claim 1 , wherein the grating is positioned at an interface of the core guiding layer and the cladding layer.
5. The optical waveguide of claim 1 , wherein the grating comprises a plurality of rectangular grooves in the core guiding layer.
6. The optical waveguide of claim 1 , wherein the grating comprises a plurality of rectangular ridges on the core guiding layer.
7. A magneto-optical recording head comprising:
a magnetic write pole; and
the optical waveguide of claim 1 positioned adjacent to the magnetic write pole.
8. A disc drive comprising:
means for supporting a storage medium;
the magneto-optical recording head of claim 7 ; and
means for positioning the magneto-optical recording head adjacent to the storage medium.
9. An optical waveguide comprising:
a core guiding layer;
a cladding layer positioned adjacent to the core guiding layer; and
a grating having a period Λ of
λ
n
eff
<
Λ
<
2
λ
n
eff
+
n
s
,
for coupling light into the waveguide, wherein n eff is the effective refractive index of the guiding layer, n s is the refractive index of the cladding layer, and λ is the wavelength of an electromagnetic wave.
10. The optical waveguide of claim 9 , wherein the grating is positioned on a surface of the core guiding layer opposite the cladding layer.
11. The optical waveguide of claim 9 , wherein the grating is positioned at an interface of the core guiding layer and the cladding layer.
12. The optical waveguide of claim 9 , wherein the grating comprises a plurality of rectangular grooves in the core guiding layer.
13. The optical waveguide of claim 9 , wherein the grating comprises a plurality of rectangular ridges on the core guiding layer.
14. A magneto-optical recording head comprising:
a magnetic write pole; and
the optical waveguide of claim 9 positioned adjacent to the magnetic write pole.
15. A disc drive comprising:
means for supporting a storage medium;
the magneto-optical recording head of claim 14 ; and
means for positioning the magneto-optical recording head adjacent to the storage medium.
16. The disc drive of claim 15 , wherein the means for supporting a storage medium comprised a spindle motor; and
the means for positioning the magneto-optical recording head adjacent to the storage medium comprises an arm.
17. A method of coupling electromagnetic radiation into optical waveguide including a core guiding layer, a cladding layer positioned adjacent to the core guiding layer, a reflective layer positioned adjacent to the cladding layer, and a grating for coupling light into the core guiding layer, the method comprising:
directing first and second rays onto the grating, wherein the first and second rays are in phase with each other and wherein the cladding layer has a thickness such that the first ray reflected from the reflective layer is phase matched to the second ray at the grating.
18. A method of coupling electromagnetic radiation into optical waveguide including a core guiding layer, a cladding layer positioned adjacent to the core guiding layer, a reflective layer positioned adjacent to the cladding layer, and a grating for coupling light into the core guiding layer, the method comprising: directing electromagnetic radiation onto the grating to create a guided mode in the guiding layer, wherein radiated rays from the guided mode into the cladding layer are in-phase or have a phase difference of multiple 2π.