THORLABS PDB440A, Operation Manual, Page: 9 / 29

© 2019 Thorlabs
3 Operating Instruction
7
Note
Do not exceed a maximum power density of 4 W/cm
2
for maximum linearity performance when
measuring focused or small diameter beams. Always try to illuminate the whole detector active
area to prevent nonlinearities. Equal power densities on both detectors are important for max-
imum common mode noise suppression (CMRR).
The PDB440x and PDB450x detectors can be used in balanced mode (both inputs are illumin-
ated) as well as in single detector mode. In single detector mode, the RF OUTPUT swing de-
pends on which INPUT is used: it is positive for INPUT+ and negative for INPUT-. Please be
aware that PDB440 and PDB450 have opposite optical input connectors for + and - (see draw-
ings).
In single detector mode, the optical input power should be below the specified CW saturation
power (see
Technical Data ) to avoid saturation of the RF OUTPUT amplifier.
In balanced mode the power difference between the optical inputs should be less than the CW
Saturation Power. If necessary, use external neutral density filters or attenuators to reduce the
input light level.
Attention
The optical damage threshold is 20 mW. Exceeding this value will permanently damage the
photodiodes!
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