The picotector is a sensitive and accurate instrument for low level optical power measurements. Itīs design is based on a unique new technology. I have been developing this instrument for some time now and have finished a second version of it.

I tested the instrument with a simple red LED placed at different distances from the instrument in a dark room. As a reference I used a commercial power meter (Garseby Optronics model 371R with a 1cm2 silicon photodiode). The distance from the LED to the instrument was measured with a ruler and might be accurate to a couple of centimeters. The measurement results of this simple measurement are listed in the following table:

DistancepicotectorGraseby 371R
20 cm
40 cm
80 cm
150 cm
4.97 V
1.31 V
0.352 V
0.115 V
0.0003 V
34.9 nW
8.80 nW
2.45 nW
0.84 nW
0.03-0.06 nW

The results are plotted in the following figure:

This simple test proves that the new technology works and is very sensitive. It remains to test the long-time stability of the instrument. The measurement noise is very low compared to the Graseby meter. The voltmeter (a Metex handheld 4.5 digit multimeter was used) reading was very stable while the Graseby meter reading fluctuated a lot. The sensitivity of the instrument allows measurements of tens of picowatts, and perhaps even picowatts of optical powers per square centimetres.

Tom Ahola Metrology Research Institute, March 26, 1997