Photodetector based on TI OPA818 transimpedance amplifier followed by a second stage noninverting amplifier. Both AC (high bandwidth) and DC (low bandwidth) outputs using SMA connectors. Requires bipolar power-supply, e.g. +/-12V, and uses low-noise voltage regulators LT3042 and LT3093. Fits thru-hole photodiodes with TO-18/TO-46 pinout. Two-sided PCB 45mm x 34mm. Enclosure designed to fit optical table and 25mm beam-height.
Measurement data overlaid with TIASim predictions show a parasitic feedback-capacitance of ca 0.15-0.17 pF when no Cf (C126 in shematic) capacitor is installed.
See also One-Inch-Photodetector if you don't need a second stage of gain.
Hamamatsu S5793 Si photodiode, 33 kOhm transimpedance, 20 dB postgain, ca 38 MHz bandwidth. Used for 674nm/30cm ultra-stable cavity PDH laser-lock since 2022-06.
Wideband view of PDH-locking signal spectrum. EOM frequency 25 MHz. 674nm power at photodetector ca 10 uW. Traces SA-floor (green), Detector Dark (Red), Bright (laser unlocked, Blue), Laser locked (yellow). Note 2nd harmonic at 50 MHz, and shot noise in blue trace at low frequencies.
Narrowband view of PDH-signal around 25 MHz.
FGA015 InGaAs phototdiode, 30 kOhm transimpendance, 20 dB postgain.
Gain vs. frequency for 2nd stage gain using OPA818.
PCB front. 2-sided PCB, height 45mm x width 34mm.
PCB back. Note the through-hole photodiode is installed on the backside of the PCB.
Aluminium enclosure with photodetector PCB and FGA015 photodiode, ca 2022-10.
CNC machined Aluminium enclosure with 5mm hole for photodiode at 25mm height from optical table. M6 holes on 25mm grid for mounting to optical breadboard. Overall height 68mm x width 66 mm x depth 28mm. 4pcs M3 threads for mounting the top/PCB.
Enlcosure top with holes for SMA-connectors and power-supply wires. The top could be made from PCB-material also?
