azu_td_1349475_sip1_... - Arizona Campus Repository

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coupling efficiency is that the maximum diffraction efficiency of a binary lens is
less than 41%. Hence more than half the light measured at point A was not
focused onto the fiber core. Another factor influencing coupling efficiency was
the difficulty of mounting and properly aligning the microlenses.
As a final demonstration, a 1x6 array of lenses was used to couple light
into and out of a fiber array. The fiber array was built using silicon V-grooves
(Figure 5-5) with 125 |im pitch. Six single-mode fibers were stripped, cleaved,
and placed using tweezers into every fourth V-groove. Every fourth V-groove
was used to create a fiber array with the same 500 pirn pitch as the diffractive
lenses. This fiber spacing was verified under magnification. A glass cover slip
was then placed against the V-grooves and the fibers were butted up against it
so they would all be flush to the end face. The fibers were then glued into place
and the process was repeated on the other side of the fiber.
Figure 5-6 is a photograph of the experimental setup used to realize the
fiber array coupler. A cylindrical lens focused the output from a HeNe laser into
a thin line which was incident on a 1 x6 array of microlenses. The lens array
coupled the light into the 1x6 fiber array. On the output side of the fiber array
another array of microlenses was used to couple light out of the fibers. The six
output beams were incident onto Fairchild linear CCD array (model CCD-123)
connected to a digitizing oscilloscope. An example of the six output beams from
the array is given in Figure 5-7. The beams are Gaussian in shape as
expected. Variations in spot size are attributed to the difficulty in aligning the
lens and fiber arrays.