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.