Michael D. Wheeler
Barely a month after Nichia Chemical Industries Ltd. announced the first shipments of its blue laser diodes, a second company has rushed to incorporate the diodes into a laser system touted as a more powerful blue light source for spectroscopy.
In the past, researchers who performed experiments in atomic physics and chemistry had limited options in achieving a continuous-wave (CW), tunable blue light source. Usually they resorted to one of two options: a frequency-doubled dye laser or a Ti:sapphire laser. These systems are bulky and require an expensive, high-power pump source. They also additional problems with output power and stability. And they require nonlinear crystals for frequency doubling and enhancement cavities to store and magnify light, both of which require high maintenance and complicated designs.
Even with these limitations, the lasers cost a minimum of $100,000. In a research environment, this might be acceptable, but for chemical trace analysis in high-volume markets (chemical trace analysis or atomic absorption spectroscopy), it is prohibitive.
When the blue diodes were made commercially available in January, researchers at TuiOptics GmbH had the enabling technology at hand to develop an external-cavity diode system that would address the needs of chemists and physicists requiring a CW, tunable blue light source.
Important for research
The system has an output beam centered between 390 and 410 nm, and an individual tuning range of 2.5 nm. The laser operates not only in a single transversal mode, but also at a single frequency that is tunable with megahertz precision. (Using a light source with two frequencies will skew spectroscopy results.) It also has higher intensity (5 mW) and offers improved amplitude stability over other blue laser sources, including fixed-frequency gas lasers.
"The blue wavelength region is not only critical for research," said Wilhelm Kaenders, president of TuiOptics. "With our external-cavity setup we add reliable single-frequency operation and tunability to the diodes from Nichia."
Blue light is suitable for fluorescence detection and working with organic dyes. The laser should also be useful for detecting or manipulating chemical elements that have resonant lines in the blue region of the spectrum, including aluminum, erbium, gallium, gadolinium, titanium, tungsten, indium and holmium.
Although initially marketing its laser system to the research community, Kaenders said the company is exploring its uses in other applications, including Raman spectroscopy, microscopy, interferometry and holography, as well as optical data storage and printing. It has received two orders for the system since its debut at Photonics West in late January. The device carries a price tag of $17,000 to $20,000.