THORLABS LCC3111, User Manual

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Liquid Crystal Noise Eater
Page 7
Rev C, Dec 8, 2015
Chapter 5 Operation
5.1. Selecting the Power Range
The LCC3112H and LCC3113H have two selection switches at the top of the
case which are used to select the input power range. When the high/low power
switch is set to “LOW”, the input power range can be set from 1 mW to 30 mW,
and when the status switch set to “HIGH”, the input power range can be set from
100 mW to 500. The LCC3111H and LCC3111L have only one selection switch
which can set the input power range from 1 mW to 30 mW or 100 mW to 500
mW. The power selector should be set to the lowest value that is still higher than
the actual power of the laser. For example, if the LCC3111L is being used with a
beam power of 8 mW at 635 nm, the selector should be set to 10 mW.
Figure 4 Top View of the LCC3111L (Left), LCC3111H (Center) and
LCC3112H/LCC3113H (Right) Noise Eaters
The LCC3111H and LCC3112H noise eaters use a Silicon detector, while the
LCC3113H uses a Germanium detector, as part of the feedback loop. The
responsivity of the detector is different for different wavelengths, and so the
power settings on the selector only correspond to the design wavelength of the
detector (635 nm for LCC3111H and LCC3111L, 780 nm for LCC3112H, 1550
nm for LCC3113H). The power range at a given wavelength is inversely
proportional to the responsivity (higher responsivity value will result lower power
range value). The graph below shows the relative responsivity of both detectors
at a range of wavelengths. The tables below show a rough estimate of the power
settings at various wavelengths for each model.