------Question for MTPD2601SL-100 Please Put your question below------
Hi,
I have bought these two type of PD’s up to 2600 but compared to other photodetectors I can only measure very small amount of current resulting in 0.1 A/W peak Responsivity at 2350nm then goes to 0 A/W at 2400. This is not the responsivity thats advertised and if it was a problem of my light source that doesn’t illuminate enough in the region 2000-2500nm I should be able to see that with the commercial photodector I use to calibrate.
@k.t.tersis
Would you have images of the light sensing side of both items that you have on hand?
From the chart in the datasheet I’d expect responsivity in the range of 2350~2400nm to be nearly constant; not 12x less than indicated and varying by 100% over that limited range of wavelength.
There are numerous opportunities for error in regard to such measurements, not least because the quantities in question aren’t directly perceptible without instrumentation. A description of the test method and apparatus used to obtain the reported measurements would be helpful.
I used these two tight clamps which normally hold two needles which I use to probe phototetectors specifically. I measure the voltage drop over a resistor and then with simple math I calculate the current. I change the wavelenghts of my white lamp with a monochromator and use special optics for this range up to 2.5um. Below you will see how much current I get from the 2-pin marktech photodetector which if compared to my other two photodetectors (one from Artifex up to 2.5um and one from Nova up to 1.7um) you will see that the current is low. I suppose it has to do with the way I clamp it but I also tried soldering and the result was the same. Also played with the alignment but didn’t try to get the cap off yet.
I assume the calibration devices have an average 1 A/W responsivity since they are InGaAs based.
And this is the 2.5 um calibration detector. So If I assume 1 to 1 Watt to Amp and devide the 12 nA with 250nW @1400 for example then the responsivity is indeed low.
I’ll politely but very firmly suggest that one should not assert that the performance of a product like this is other than advertised, if the word “assume” appears anywhere in the same postal code as one’s explanation of their test method.
The three plots above cover different wavelength ranges, with intersection over the 1300-1700nm span. Within this span, the shapes of the three curves appear to be quite similar, decreasing with values at 1700 roughly half of those measured at 1300. If we’re speaking of detectors based on the same materials and working principles and expecting similar responses, this is good news.
The vertical axis for the MTPDxxxx device is labeled in units of current, while those for the other (unspecified) detectors appear with units of power; these are not the same thing. If the two reference detectors are calibrated to read out in units of incident optical power, there is a very big question at hand in regard to the active sensor area of these detectors, compared to the device being tested; the larger the active area, the larger the magnitude of the response produced.
Also, the plot for the MTPDxxxx device appears to show the response magnitude changing sign at roughly 2000nm. This is not expected behavior, though it may easily arise from an offset error present in the measurement apparatus. If present, such an error would invalidate magnitude measurements until accounted for and corrected.
@k.t.tersis
I have heard back from the supplier on this an they indicated that the measurements provided in the data-sheet for the SL type were done without the cap(as the data-sheet does say).
They also indicate that this sensor is suited for fiber optic / narrow beam light sources(ie lasers).
They also ask if you have put any Bias on the device?
