THORLABS PDA10JT, User Manual

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Amplified MCT Detector Chapter 3: Description
Rev G, March 11, 2019 Page 3
Chapter 3 Description
The PDA10JT is an amplified, TEC-cooled, switchable-gain, switchable-
bandwidth, HgCdTe photoconductive detector. The detector is AC coupled and
requires a chopped or pulsed input detection of light signals over a wavelength
range from 2.0 to 5.4 µm. Two eight-position rotary switches allow the user to vary
the gain in 6 dB steps and select low pass filter bandwidth settings from 1.25 to
160 kHz. A buffered output drives 50
Ω load impedances up to 5 volt. A constant
2.5 mA bias current is provided to the detector via a Howland current pump for
improved stability and low noise operation.
The detector is mounted on a thermoelectric cooler and factory set to cool the
detector to -30 °C with a thermistor providing feedback to maintain a constant
temperature. This cooling provides higher detectivity (D*), which results in a lower
offset at the output and allows higher gains. It also reduces thermally generated
noise. The housing is used as a heat sink and includes a fan to increase the cooling
capacity. It is important to note that the cooling fan will keep the heat sink at room
temperature. Without it, the heat sink will heat up causing a higher temperature
drop between the detector element and the heat sink, resulting in larger TEC
currents. Without the fan, the TEC current will operate at its limit (~820 mA) and
the detector element will no longer be temperature stabilized. Offsets will increase
and fluctuate, and output noise will increase. For best results do not block, limit
airflow, or stop the cooling fan.
The detector housing has a threaded mounting aperture around the diode, which
is compatible with any SM1-threaded accessory. The devices ships with an
SM1RR Retaining Ring allowing convenient mounting of external optics, light
filters, apertures, etc. The SM1-threaded mount can be easily integrated into our
cage and lens tube systems.
The PDA10JT has two 8-32 (M4) tapped holes for mounting the detector on a
Ø1/2" optical post in one of two perpendicular directions. The detector includes a
100 - 240 V, 50 - 60 Hz power supply.