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Entry  Sat May 18 22:25:30 2019, Anjali, Update, 2micronLasers, Characterization of new detector setup.pngbeat_note.pdfNoise_floor.pdf
    Reply  Thu May 23 02:53:19 2019, Anjali, Update, 2micronLasers, Characterization of new detector 
Message ID: 2346     Entry time: Sat May 18 22:25:30 2019     Reply to this: 2350
Author: Anjali 
Type: Update 
Category: 2micronLasers 
Subject: Characterization of new detector 

The new photo detector has arrived (https://www.newport.com/p/818-BB-51F) . We did the DC and AC characterization of the same.

  • Following table shows the results from DC characterisation            
  • Laser diode current (mA) Input power (mW) Output voltage(mV)
    50 0.5 7.2
    70 0.9 13.6
    90 1.3 19.7
  • In this case, the input power was measured after the isolator.The power to voltage conversion is linear. The voltage levels are very low because this is a non-amplified detector. Also, the detector is coupled to a FC/UPC patch cord and we have all FC/APC fiber connectors. So, there could be some coupling loss from FC/APC to FC/UPC. FC/APC to FC/UPC conversion patch cord is ordered. We can check the performance again after it is arrived.

  • We then assembled the Mach-Zehnder interferometer (MZI) for the 2-micron laser source. Attachment #1 shows the schematic of the same. We measured a power level of 0.37 mW when the AOM was not turned on (RF power to AOM off). When AOM is turned ON, the power level measured at the output of MZI is 0.5 mW. Power meter was then replaced with the new photodetector and the beat note was observed on spectrum analyser.

  • Attachment # 2 shows the RF beat note at 78.8 MHz on spectrum analyser. So, the band width of the detector is enough to work at this frequency range. The signal to noise ratio is about 37 dB. There are some small peaks appearing at around 77 MHz and 80 MHz, but they are about  29 dB below the main peak.
  • Attachment # 3 shows the noise floor. There are no other RF interferences at this frequency range.
Attachment 1: setup.png  59 kB  | Hide | Hide all
Attachment 2: beat_note.pdf  14 kB  | Hide | Hide all
Attachment 3: Noise_floor.pdf  15 kB  | Hide | Hide all
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