What are the parts in a diode?

Answer 1

That depends on the diode, however I will talk about a very basic one. Simple version: One side is called the anode, the other is the cathode. Current only flows from the anode to toward the cathode. It is blocked from traveling in the other direction. Less simple version: I am including this since you asked about the parts "in" a diode and not the parts "of" a diode. Diodes are semiconductor devices and are constructed with two pieces of semiconductor material (silicon, germanium, etc), one of which has been designed with extra electrons in it (cathode side) and one with extra spots for electrons to occupy (anode side) . Remember current flowing in one direction means electrons are traveling in the opposite direction. Now, if you apply enough positive voltage to the cathode, current will flow to the anode, but it will damage the diode if it is not designed to handle it. Some diodes are even designed to be used this way (look up zener diodes). To really understand the physics of what is happening in these materials, you need some knowledge of quantum mechanics (not joking) but that is beyond this question. Hope you got what you needed.

Answer 2

A laser diode is a laser where the active medium is a semiconductor similar to that found in a light-emitting diode. The most common and practical type of laser diode is formed from a p-n junction and powered by injected electric current. These devices are sometimes referred to as injection laser diodes to distinguish them from (optically) pumped laser diodes, which are more easily produced in the laboratory.