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2
Chapter 1. Introduction
stability. Finely threaded tubes control the lens positions along the axis
of propagation. The U-chassis allows simple user replacement of the
TA
diode (see chapter 8).
Flexure alignment screws Focus tools Lens focus
& lock ring
Figure 1.2:
TA
diode block (U-chassis), showing flexure alignment and focus
adjustments for input and output lenses and tools for focus adjust and locking.
The
TA
diode emits from both input and output facets. Emission from the
input-side waveguide can be used for seed laser alignment. A tapered
engraving on the side of the U-chassis shows the
TA
diode orientation,
with the small area ridge waveguide on the input side and large area
tapered waveguide on the output side.
The input lens focuses the seed laser onto the input waveguide of the
TA
diode. The output lens collimates the amplified
TA
laser beam emitted from
the output waveguide.
In normal operation, the seed laser should provide a collimated beam of 10
to 60 mW. The minimum seed power requirement depends on the specific
TA
diode, and will be specified in the laser test report. The seed laser
beam should propagate through an input isolator (we recommend
>
38dB
isolation) and is deflected by mirrors
M1
and
M2
into the
TA
diode, with an
optional input isolator between
M1
and
M2
. For the
MSA
,
M1
is a fixed beam
splitter (or polarising beam splitter (
PBS
) with a half-wave plate before the