I am trying to measure the linewidth of a diode laser using the self-heterodyne technique. The laser specs says that the linewidth is ~100kHz at 1us. I guess I am confused by the "at 1us" and how exactly that translates to measuring the linewidth myself by looking at the beat note on a spectrum analyzer. If I want to make a comparable measurement to what is cited in the manual, what should I set my sweep time to be? The bandwidth? The resolution? I guess what I don't really understand is how the linewidth changes as you change the measurement time.