It is a well known fact that light can have an impact on the conduction of some types of diodes. LEDs have been used as photodiodes in certain circuits.
I theorized that light could be used possibly control the clipping point and/or the knee of the diode conduction curve. A quick search through my parts bin yielded some glass 1N4148 silicon diodes and a few clear 1N34a germanium diodes, which were perfect for the experiment.
I arranged a selected diode on a breadboard with a red LED positioned to illuminate the glass body of the diode. A small black opaque 35mm film can was used as a cover to shield the setup from ambient light. The LED could be activated from outside the film can shield by applying power to the breadboard.
With the LED off, I measured the forward voltage (Vf) of the silicon diode at 550mv. Then I powered up the LED and measured the Vf… still 550mv.
Next I put the germanium 1N34a into place in front of the LED. It measured 265mv with the LED off and 265mv with the LED on. So far, it’s a bust.
I tried both diodes with a bright yellow LED, then a green one and finally a really bright blue LED. In no case did the Vf change from the 550mv and 265mv values! I switched meters and measured the Vf with a different meter and then with a diode tester. No change.
Bottom line is that light does not seem to have any influence on the conduction of the diode.
Not all good ideas work out