In 1962, Willard Boyle, working at Bell Labs, produced the first continuous output from a ruby laser. Unlike the usual side-pumping method, the light from a mercury arc lamp was pumped into the end of a very small rod, to achieve the necessary population inversion. The laser did not emit a continuous wave, but rather a continuous train of pulses, giving scientists the opportunity to study the spiked output of ruby. The continuous ruby laser was the first laser to be used in medicine. It was used by Leon Goldman, a pioneer in laser medicine, for treatments such as tattoo removal, scar treatments, and to induce healing. Due to its limits in output power, tunability, and complications in operating and cooling the units, the continuous ruby laser was quickly replaced with more versatile dye, , and argon lasers.