In an intensive three-week push, researchers from the Center for Research and Education in Optics and Lasers at the University of Central Florida in Orlando cranked up the power of their diode-pumped, self-frequency- doubled Nd:YCOB laser. Using a 2-W diode, the group achieved 60 mW of continuous-wave laser power at 530 nm.
The drive was an effort to extend the system's power beyond 2 mW in time to present the results -- and a working device -- at the 1998 Conference on Lasers and Electro-Optics held in May in San Francisco. The eleventh-hour success depended heavily on relationships between the laboratory and companies such as Newport, Polaroid and Quality Thin Films, which provided product support and quick turnaround times.
"Our friends in these companies helped us to meet this three-week deadline," said Martin Richardson, director of the laser plasma laboratory at the center where the laser was developed.
The oxyborate group of crystals, including YCOB and GdCOB, have been the focus of friendly investigative competition by the Florida researchers and separate research teams at the Institut d'Optique Théoretique et Appliqué in Orsay, France, and at the University of Osaka in Japan. Doped and undoped crystals can be used as frequency doublers; however, when doped with neodymium and cut at the correct angle, the crystals lase at 1060 nm and automatically double that for green laser output.
The crystals, grown by Crystal Photonics of Orlando, have a peak absorption at 812 nm, making them ideally suited for diode pumping. The neodymium-doped crystals have laser emission at three main wavelengths, 936, 1060 and 1331 nm, opening the door to frequency-doubled devices in the red, green and blue ranges. The researchers also have demonstrated flashlamp pumping, which has the potential to greatly increase the laser power.
A commercial device
Laser Energetics of Mercerville, N.J., funded the laboratory's work on the laser and will commercialize the technology. "We are fairly confident that powers over 100 mW are achievable in a commercial device," Richardson said, "and we have every intention of bringing out a commercial device very soon."
He added that the laser crystals are comparable to other neodymium host crystals in terms of manufacturing and efficiency. They have a high damage threshold (estimated at 1 GW/cm2), are not affected by moisture and can be grown in very large boules.
Richardson said he expects the oxyborate group of crystals to become a "whole suite of materials that will find applications in several different areas: as host materials, self-frequency-doubling materials and harmonic converters."
Along those lines, the Florida researchers also created a laser with Yb:YCOB, which they said is tunable from 1020 to 1090 nm. The group plans to continue to investigate the oxyborate materials and to optimize the Nd:YCOB system for diode and flashlamp pumping in hopes of introducing additional commercially viable devices.