Photodiodes not sensitiv enough / How to amplify?

Projects General Guidance
31 
 if (timingFlag == false && digitalRead(diode1) == LOW ) {
    Start1 = micros();
    timingFlag = true;
  }
  if (timingFlag == true && digitalRead(diode1) == HIGH ) {
    Stop1 = micros();
    timingFlag = false;
  }

the code really doesnt seem to make any problems