P.1 Circuit diagram
Added components are indicated by red symbols.
- The diode on the board is HAMAMATSU S3399. It is a Si PIN diode with φ3.0 mm.
- Based on prototype version of aLIGO BBPD D1002969-v8 (although the board says v7, It is v8.)
- The input impedance of the MAR-6SM amplifier (50Ohm) provides the transimpedance.
- The first notch (Lres and Cresa/b) is actually not notch but a LF rejection with DC block.
- The second and third notches are tuned to 11MHz and 55MHz.
- Another notch is implemented between the RF amps. The 33MHz signal is weak so I expected
to have no saturation at the first amplifier.
- As you see from the DC path, the transimpedance of the DC path is 2k V/A. If this is too high,
we need to replace R9 and R11 at the same time. TP1 is providing +10V such that the total
reverse bias becomes 25V without bringing a special power supply.
The transimpedance is measured with an amplitude modulated diode laser.
The transimpedance is 1k V/A ish. It is already at the edge of the bandwidth.
If we need more transimpedance at 165MHz, we should replace
the PD with FFD-100 (I have one) and apply 100V of reverse bias.
P.3 Current noise spectrum
The measured dark noise voltage spectrum was converted to the equivalent current noise at the diode.
The measured transimpedance is ~1.2kV/A.
The reduction of the transimpedance above 100MHz has been seen as 165MHz is already at the edge of the bandwidth.
If we need more transimpedance at 165MHz, we should replace the diode with FFD-100 (I have one) and apply 100V of reverse bias.
P.4 Shot-noise intercept current
Shot-noise intercept current was measured with a white light from a light bulb.
This measurement suggests the shot-noise intercept current of 1mA, and transimpedance of 1.5kV/A.