How to use an IR photo diode or similar in this circuit?

The circuit that I am designing starts with an IR emitter, which is just a basic circuit with an IR LED, a resistor and a power supply, that fires a constant IR pulse. The next part is a 555 bistable circuit, which when receives an input from a switch or such and turns the whole circuit high, thus I have it triggering another circuit. However, I have not really come across infrared and photo diodes in electronics before, so I was wondering how a photo diode actually works and whether I could use it as the switch (input) for the bistable circuit or not?