Amplified InGaAs Detector
Chapter 2: Description
Rev M, September 7, 2021
Page 1
Chapter 2 Description
The PDA10DT is an amplified, thermoelectrically cooled, switchable-gain,
switchable-bandwidth, InGaAs photoconductive detector. The detector is DC
coupled. It is sensitive over a wavelength range of 0.9 to 2.57 µm. Two eight-
position rotary switches allow the user to vary the gain in 10 dB steps and select
low-pass filter bandwidth settings from 500 Hz to 1 MHz. A buffered output drives
50
Ω load impedances up to 5 V. The first two gain steps (0 dB and 10 dB) are
biased to -2 V for best high-speed performance while the remaining gain steps are
unbiased for high precision measurements.
The detector is mounted on a thermoelectric cooler and factory set to cool the
detector to -10 °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 acts 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 warm up, causing a higher temperature
drop from the heat sink to the detector element, 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
to, or stop the cooling fan.
The detector housing has an internally SM1-threaded (1.035"-40) mounting
aperture, which is compatible with any SM1-threaded accessory. The device ships
with an SM1RR Retaining Ring allowing convenient mounting of optics, light filters,
apertures, etc. The SM1-threaded mount can be easily integrated into our cage
and lens tube systems.
The PDA10DT(-EC) 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, 47 - 63 Hz power supply.
