If you are measuring very low powers, you’ll want a photodiode power sensor. These come in various models, with physically different detectors. Some are made from Silicon, some are Germanium, etc.
Different detectors act differently at different wavelengths. For example, a silicon detector absorbs visible light but is transparent at other laser wavelengths. In short, no one detector can be used for all wavelengths, which is why various types are used.
Here’s a graph of the wavelengths that each photodiode laser sensor is calibrated for:
Ophir Photodiode Sensor Wavelength Range (IS stands for Integrating Sphere)
So, what have we learnt so far?
If you have a UV laser you need to use the UV sensor (duh) and if your laser is right in between 1700 and 1800 nanometers, your only choice is a Germanium detector.
For all other visible or near infrared lasers, though, you have a few options. That means you will need to whittle down the list of sensor candidates through other means, such as maximum power. (You can also check out our sensor finder program.)
What about other wavelengths?
I cleverly ended the graph around the end of these detectors’ range of calibration. But you’re clever, so you know that there’s a whole world of IR lasers with wavelengths well past the range of these photodiodes.
Of course, you’ll usually want a thermal sensor for those lasers, unless their power is quite low. For example, the 3A-FS is Ophir’s most sensitive thermals sensor and it can measure accurately down to 30 μW.
(However, if you do have the perfect storm laser that doesn’t quite fit the photodiode wavelength spectrum or the thermal power range, let us know and see if that’s not a challenge our OEM engineers can find a solution for!)
You might also like to read:
How to Measure Different Wavelengths with a Laser Power Meter
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