I assume by diode you mean photodiode and you want to control it’s output power using pulses (voltage). In this case yes you can using pulse width modulation (PWM).Photodiodes response is usually slow therefore it takes the average of the input train of pulses, if the pulses are short enough. For example, consider a train of pulses with (0 as GND) and (1 as 5V) and the pulse width is short enough. In this case, if the input sequence is (111111), then the output from the diode will be equivalent to (5V input “the average of the sequence”). And if the input sequence is 101010 which corresponds to (5V-0V-5V-0V-5V-0V), then the diode will average this sequence and give you an output corresponding to this ~2.5V. I hope this answers your question.