Arthur Schawlow talks about coming up with the idea of the dark ruby maser.

Bromberg:

...when it came to working on the dark ruby, Clogston and "Yes, go ahead," but was it already early at the stage when you were working with Townes on the paper that —

Schawlow:

No, it was in between. I guess what it was that, ah, after we finished the paper, I knew that Townes and Cummins and later Abella and Oliver Heavens, were going to work on trying to make a potassium optical maser at Columbia. And I never want to do what anybody else is doing, because I haven't much confidence in my ability to compete, and I don't like competing. And being at Bell Labs in the trasistor era, you felt that if you could do anything in gas, you could do it better in a solid. And so I started trying to learn about solids. And in fact, in that one paragraph in our paper that mentions that solids have broad bands for absorbing and sharp lines to emit it, I had just learned that much; I knew that ruby was that way. Now, ruby was a common material around there because a lot of people were working on microwave masers. So you could go down the hall and find somebody who had a drawer full of rubies or various concentrations, and could borrow a few samples which you'd never return.

So I just thought well, I'll get my feet wet, I'll try and learn something about this stuff, what's it all about. I had no idea of the theory, or anything at all about it. And I got hold of a copy of Pringsheim's book on Fluorescence and Phosplorescence. Which was one of these wonderful, thoroughly Germanic books that had all the references back to the early 1800s. It was very complete, but it didn't have the answers we wanted. At that time, I asked Clogston if Icould work on that, and he said "Fine." Then later there was another incident in the fall of 1958 after, the fall of 1960, rather, after Maiman had published, I was thinking about the dark ruby, and I really knew quite a lot about it, and I knew that those satellite lines, or "N" lines, were really very strong, stronger than the "R" lines, and I just felt that that dark ruby laser that I had proposed really ought to work. So I asked Clogston if he thought I ought to try it out, and he said, "You owe it to yourself." So, we did, and it worked. Right away. And of course, I should have done it sooner.