news Is the line width after frequency doubling twice that of the fundamental frequency light?

 Theoretically, the width of the doubled frequency light is twice that of the fundamental frequency light, so its frequency stability remains unchanged. For scientists studying ultra-stable lasers, this assertion is far from enough, because they need to know at what scale this assertion is true. This time, the frequency-accurate laser technicians searched some literature and immediately obtained the results. Even at the order of 10-20, the 2-fold relationship of the doubled frequency line width still holds true.

However, it should be pointed out that in actual applications, due to the influence of the transmission of a certain size of spatial optical path, the frequency stability may not be as ideal as described in the article. Because the air pressure change and gas flow will cause the frequency stability of the laser to deteriorate during the transmission process, users with extremely high requirements need to pay attention.