Dual logarithmic photodetector
Koheron PD10R is a dual logarithmic photodetector for general purpose optical power measurements.
In addition to two analog outputs log(A) and log(B), the PD10R gives the log-ratio log(A/B) with an adjustable offset and two gain settings (x1 and x10). The PD10R provides a fully-analog solution for direct absorption measurement in spectroscopy setups.
For free-space measurements, see Koheron PDX10R free-space logarithmic photodetector.
|Detector type||Dual InGaAs photodiodes|
|Active diameter||300 µm|
|Wavelength range||900 nm to 1700 nm|
|Optical input power(0 dBm = 1 mW)||-67 dBm to 7 dBm|
|Peak responsivity(1550 nm)||0.9 A/W|
|Small signal bandwidth(at 3 dB, input current > 100 µA)||1.2 MHz|
|Logarithmic slope||300 mV/decade|
|Intercept photocurrent||100 pA|
|Output impedance||1 kΩ|
|Supply voltage||3.3 V to 13 V|
|Quiescent current||11 mA|
|Maximum current||40 mA|
|Outside dimensions||38 mm x 53 mm x 12 mm|
|Operating temperature||0 °C to 50 °C|
Output voltage vs Optical power
Optical source is a Koheron LD101 1550 nm DFB laser followed by a variable optical attenuator and measured with a Thorlabs PM100D / S155C power meter.
We observe a linear behavior between -50 dBm (10 nW) and 7 dBm (5 mW).
Frequency response of the logarithmic amplifier for several input optical powers:
The PD10R can perform accurate absorption measurements with small amounts of optical power. We used the setup below to observe the absorption lines of a HCN gas cell with 200 nW of total optical power. Optical source is a DFB laser whose temperature is increased linearly from 10 to 25 °C in 60 s. The absorption path and the reference path are connected respectively to the A and B inputs of the PD10R.
The three outputs log(A), log(B) and log(A/B) have been recorded simultaneously during the 60 s temperature sweep. Intensity variation observed on the log(A) and log(B) channels are nicely rejected on the log(A/B) output. Numerical computation of log(A/B) from log(A) and log(B) is represented in the cyan curve.
|PD10R||InGaAs photodiodes mounted|
|REFERENCE||COUNTRY OF ORIGIN||HS CODE||HTSUS||ECCN|