Method and device for light coupling
An interconnect system for coupling light from a laser light source to an optical fiber having a fiber aperture, the interconnect system including a 2-dimensional array of laser light sources, a 2-dimensional array of micro lenses disposed between 10-200 μm distance from the laser light source, between the laser light source and the optical fiber and in registration therewith, each micro lens comprising a micro lens back surface, a micro lens body, a micro lens front surface, and a clear aperture, the micro lens front surface and back surface being shaped to provide a laser beam in the micro lens body of smaller diameter than the clear aperture for focusing the beam onto the fiber aperture.
1. An interconnect system comprising:
a 2-dimensional array of optical light sources;
a 2-dimensional array of light transmission elements;
a 2-dimensional array of micro lenses;
said array of micro lenses being disposed between 10-200 μm distance from said optical light sources and aligned in registration with said array of optical light sources,
said array of micro lenses being disposed between the array of optical light sources and the array of light transmission elements;
each micro lens comprising an optical light source facing surface, a micro lens body, a light transmission element-facing surface, and a clear aperture;
said optical light source facing surface and said light transmission element-facing surface being shaped to provide a laser beam in said micro lens body of smaller diameter than said clear aperture for focusing said beam onto said fiber aperture;
said optical light source facing surface having a radius of curvature (Rc) of about 0.1 mm±5%, a conic constant (k) of about −1.8, and lens sag of about 0.056 mm, to create a collimated beam less than said clear aperture; and
said light transmission element-facing surface having an Rc of about 0.27 mm±5%, k of about −5.0±10% and a sag of about 0.023 mm.
2. The interconnect system according to claim 1 , wherein:
said array of optical light sources include a 2-dimensional array of VCSELs; and
said array of light transmission elements include a two-dimensional array of optical fibers, each of said fibers disposed in registration with an associated VCSEL.
3. The interconnect system according to claim 1 , wherein values for the radius of curvature (Rc) and conic constant (k) for said optical light source facing surface are calculated by:
h
=
1
R
C
·
r
2
1
+
1
-
(
k
+
1
)
·
r
2
R
C
2
where h is the lens sag and r (=D/2) is the lens radius.
4. A micro lens for coupling light from an optical light source to a light transmission element, the micro lens comprising:
an optical light source facing surface, a micro lens body, a light transmission element-facing surface, and a clear aperture;
wherein said optical light source facing surface has a radius of curvature (Rc) of about 0.1 mm±5%, a conic constant (k) of about −1.8±10%, and a lens sag of about 0.056 mm, to create a collimated beam less than said clear aperture; and
wherein said light transmission element-facing surface has an Rc of about 0.27 mm±5%, k of about −5.0±10% and a sag of about 0.023 mm.
5. The micro lens according to claim 4 , wherein values for the radius of curvature (Rc) and conic constant (k) for said optical light source facing surface are calculated by:
h
=
1
R
C
·
r
2
1
+
1
-
(
k
+
1
)
·
r
2
R
C
2
where h is the lens sag and r (=D/2) is the lens radius.
6. A method for optimizing coupling between an optical light source and a light transmission element, the method comprising:
forming a micro lens having a clear aperture, an optical light source facing surface and a light transmission element-facing surface;
shaping said optical light source facing surface with a radius of curvature (Rc) of about 0.1 mm±5%, a conic constant (k) of about −1.8±10%, and a lens sag of about 0.056 mm, to create a collimated beam less than said clear aperture;
shaping said light transmission element-facing surface with Rc of about 0.27 mm±5%, k of about −5.0±10% and sag of about 0.023 mm, to create an incidence angle of a focused beam less than an acceptance angle of the optical light transmission element;
disposing said micro lens between the optical light source and the optical light transmission element at a distance between 10-200 μm from said optical light source.
7. The method according to claim 6 , further comprising:
providing a 2-dimensional array of said optical light source;
providing a 2-dimensional array of said light transmission element;
providing a 2-dimensional array of said micro lens;
disposing said array of light transmission elements in registration with said array of optical light sources; and
disposing said array of micro lenses between said array of optical light sources and said array of light transmission elements at a distance Z 1 between 10-200 μm from said array of light sources, said array of micro lenses being aligned in registration with said array of optical light sources to form an optical interconnect system.
8. The method according to claim 7 , wherein said distance (Z 1 ) is calculated as follows:
Z
1
=
D
2
-
L
·
tan
[
sin
-
1
(
NA
n
GaAs
)
]
tan
[
sin
-
1
(
NA
n
freespace
)
]
≤
0.21
mm
where D is the micro lens clear aperture; L is the substrate thickness, and n GaAs , n freespace are the refractive indices of a substrate and the free space, respectively.
9. The method according to claim 6 , wherein the optical light source is a laser light source and the light transmission element is an optical fiber.
10. The method according to claim 6 , wherein values for the radius of curvature (Rc) and conic constant (k) for said optical light source facing surface of each micro lens are calculated by:
h
=
1
R
C
·
r
2
1
+
1
-
(
k
+
1
)
·
r
2
R
C
2
.