Diodes pump dye laser

17 Jun 2002

The first attempt to make a directly-pumped solid-state dye laser will be reported at Photonics West.

Guildford Jones of the Photonics Center at the University of Boston in the US will report the first ever attempt to make a laser based on a benzo-fused pyrromethane dye. Designed for military applications, this solid-state dye laser is directly diode-pumped, and Jones and colleagues believe that it is also ideal for medical applications.

A benzo-fused pyrromethane dye consists of pyrromethane molecules that have been fused with benzene rings. The benzene rings enlarge the pyrromethane-based molecule, which red-shifts the peak absorption wavelength so that direct pumping with a 660 nm diode laser is possible.

When the dye is injected into a solid polymethylmethacrylate matrix its photochemical and lasing properties are better than today's dye lasers, says co-author, Dennis Pacheco of US research firm Physical Sciences Inc.

"Other dyes are notorious for being photochemically unstable, but the benzo-fused pyrromethane dye is robust and can be irradiated," he said. "There are also problems with putting [other dyes] into a solid matrix because they can degrade chemically."

Pacheco claims that the benzo-fused pyrromethane solid laser's 40% fluorescent quantum yield means that lasing is easier to achieve in the near infrared and deep red. "A typical dye laser has a quantum efficiency of between 10 and 30%," he added.

The team believes that it has developed a cheap, efficient and compact way to tune infrared radiation. "Red-emitting laser diodes have a wallplug efficiency of 30%. Efficiencies of up to 80% have been shown for solid-state dye lasers. Therefore, using a laser diode to pump a solid-state dye laser could yield a very efficient tunable source," said Pacheco.

The researchers hope soon to develop an inexpensive throw-away unit for military applications, but Pacheco is keen to extend the laser's uses into a medical environment. "The laser could be used in biological applications such as photodynamic therapy," said Pacheco.

Author
Rebecca Pool is the news editor of optics.org and Opto & Laser Europe magazine.