NKT Photonics A203-000-001, Product Manual

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Output beam quality
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Optimum RF power
RF power
When operating the AOTF, RF power is one important factor to consider. As RF
power is increased, the central peak of the selected wavelength increases
gradually up to a point. Beyond this point, increasing RF power causes side band
power to increase instead of the central peak power. This is illustrated in
Figure 24
. The RF power level beyond which the central peak does not increase
is called the optimum RF power.
Note: The systems shipped from NKT Photonics A/S, have their optimum RF pow -
er mapped as a function of wavelength. Your SELECT system RF level is already
optimally mapped at the NKT Photonics factory and unless you swap-out certain
hardware, no further optimization is required.
Figure 24 AOTF transmission spectrum for varying RF powers
In
Figure 24
, the red curve is optimum, whereas the green and blue curves
illustrate the result when RF power level is increased beyond the optimum. Side
band power increases and the amplitude of the central peak decreases.
In summary, the power ratio between the sidebands and the primary
transmission (central) peak is determined by the selected configuration and the
operational parameters. For example, the selected wavelength, RF power and RF
cable lengths used.
Fiber coupled
In an application where the beam does not need to be perfectly single mode, you
can gain some output power increasing the RF power level beyond the optimum.
However, when single mode operation is needed, such as when using a fiber
delivery system, going beyond the optimum RF power level results in decreasing
output power. This is illustrated in
Figure 25
where for a specific wavelength the
fiber coupled power is plotted as a function of RF power. Once the RF driver
power reaches a level between 40 and 50 percent, no further output optical
power is achieved by further increasing the RF driver power.
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