Solid-State Blue Laser Unveiled

Dan Drollette

Researchers at Coherent Inc., Laser Group, have developed the prototype of a diode-pumped solid-state laser that emits light at 488 nm, addressing what has been a major concern of biologists.

When scientists want to study an individual fragment of DNA, for example, they tag each of its four bases with a different fluorescent dye, or fluorophore. Under a laser's stimulus, each base glows a different color, identifying the fragment's genetic sequence.

Challenge to argon-ion?

Unfortunately, the number of available fluorophores is limited. Most fluoresce near one wavelength -- 488 nm -- most commonly reached by one type of laser, the argon-ion. While well-established, this laser generates excessive heat and is fairly large and heavy for the average laboratory. Researchers lament that there are no commercially available solid-state alternatives to readily reaching this wavelength.

The new laser may change things. "We expect it will go anywhere that a 20-mW argon-ion is used," said manager of business development Paul Ginouves, who unveiled it at a meeting of the International Society for Analytical Cytology in Montpellier, France. "It has 20 mW coming out of it with beam characteristics that mimic or exceed its argon-ion counterpart."

For proprietary reasons, Ginouves was unable to give further details, except to say that the laser operates in TEM₀₀ and emits a continuous wave. It is composed of well-characterized 980- and 808-nm diodes, using chips grown by the Coherent Semiconductor Group. The diodes optically pump a wafer of semiconductor material to emit a fundamental output of 980 nm that is frequency-doubled to 490 nm and tweaked to reach 488 nm, Ginouves said.

The company expects to begin beta testing by late summer and may have the laser available in the commercial marketplace as early as next winter. The device is geared toward makers of laboratory instrumentation. Potential applications include flow cytometry, image analysis, single-photon microscopy and fluorescence-based DNA sequencing.

However, researchers expect that the laser will not outright replace argon-ion, which offers such features as power to spare in the UV and deep-UV.