It's interesting to me that Kerr cells were invented so early. I wonder what they were first used for? I know in the '60's and later they were used in lasers fo

It's interesting to me that Kerr cells were invented so early. I wonder what they were first used for? I know in the '60's and later they were used in lasers for Q-switching, but I'm trying to think what else they would have been used for in the 1940's... Also, I wonder if it is more difficult to create a nanosecond pulse using only vacuum tubes...