R.S. Quimby -- Research Interests

Rare earth ions doped in glass

My current research interests are in the optical properties of rare earth and transition metal ions doped in glassy hosts. Of particular interest are new types of hosts for the dopant ion, such as fluoride glass and sulfide glass. These novel glasses exhibit superior fluorescence properties for dopant rare earth ions, and are presently under active investigation for possible applications.

One important application of rare earth doped glasses is in generating or amplifying laser light travelling down an optical fiber. The "Erbium- doped Fiber Amplifier" (EDFA) amplifies light around a wavelength of 1530 nm, and it has now become a standard component of fiber optic communications systems. The EDFA does not amplify light in the second telecommunications window around 1300 nm, however, due to the particular location of the energy levels in the erbium ion. There has been on ongoing effort to employ alternative rare earth ions such as praseodymium, neodymium, dysprosium, and thulium, as possible dopant ions for use as a 1300-nm amplifier material. Recently there has been increasing interest in wavelengths outside the conventional 1.3 and 1.5 micron regions, and the search for alternative amplifier media for these other wavelength regions is one focus of my current research.

Another growing application of rare earth doped glasses is in fiber lasers, which are efficient and compact. New types of low-phonon energy hosts such as the fluorides and chalcogenides allow a much wider range of laser wavelengths, including in the infrared up to ~3.5 um. A primary focus of my current research is exploring the ultimate potential of these glasses for wavelengths as far as possible into the infrared.

Another type of material that I have studied is the Transparent Glass Ceramic. These novel materials have properties of both a glass and a crystal. They consist of small fluoride nanocrystals embedded in an oxide glass matrix (sort of like jello, with the nanocrystals being the fruit pieces and the oxide glass the gel). The advantage of this material is that when it is doped with rare earth ions, they go preferentially into the fluoride nanocrystals, where the optical emission efficiency is higher than it would be in an oxide glass host. On the other hand, the glass ceramic behaves mechanically like an oxide glass, and the processing and drawing into a fiber can be accomplished easier than it would be for fluoride and sulfide glasses.