This family of OPM™ detectors presented here is based on Si, InGaAs, and Ge photodiodes operated in photovoltaic mode for best DC and low frequency performance. We offer both room temperature and TE cooled models. The calibrated models allow you to take spectroradiometric measurements over the useful detection ranges of these devices. The OPM™ Readout downloads the PROM stored calibration data and utilizes it to calculate the incident power for display and for PC communications (RS-232 and IEEE-488). The RMS mode of operation of the OPM™ allows you to measure AC signals up to the 100 kHz bandwidth limit.
Fig. 1 Typical responsivities of Si and InGaAs Detectors.
Why Photovoltaic Operation?
We have chosen to operate this family of photodiodes in a photovoltaic, unbiased mode. The photovoltaic mode of operation offers the lowest noise for DC and low frequency operation since it avoids the shot noise associated with bias currents.
Spectral Ranges
Fig. 1 shows the typical spectral responsivities of the very popular Si and InGaAs detectors. Choose the UV versions of Si detector if your work takes you below 400 nm. These Si detectors are sensitive down to 180 nm and offer calibrated performance down to 200 nm. The VIS-NIR version of Si detectors give you the best performance between 400 nm and 1.0 µm and useful performance to 1.1 µm. Use the InGaAs units for wavelengths up to the 1.7 µm long wavelength cut off point. Ge extends the IR response, as compared to InGaAs, by ~0.1 µm.
We offer TE cooled detectors for improved stability of response and to allow you to reach lower noise level performance, especially for InGaAs and Ge. Cooling also has an effect on spectral responsivity, most significantly at longer wavelengths. The detector's cut-off wavelength shifts to slightly lower values as the temperature is lowered. It can change by about 0.1 µm for InGaAs or Ge when going from room temperature to 243 K.
What Else do I Need?
These detectors include all necessary cables to connect to the Oriel OPM™ (Optical Power Meter). To build a complete system you simply need:
Room temperature or TE Cooled Detector
OPM™ (Optical Power Meter)
77055 TE Cooler Controller (if using a TE cooled detector)
