Optical coherence tomography (OCT) light sources will shrink to one-fifth the size of conventional devices with the help of a tapered laser being developed by the European Union project FAMOS (Functional Anatomical Molecular Optical Screening). Seventeen partners have joined forces under the FAMOS project to bring OCT — a key technology displaying structures located a few millimeters inside the tissue — to the forefront. The approach pursued for OCT requires white laser light that emerges when a special glass fiber is irradiated with a femtosecond laser. As these lasers generate heat, they must be cooled with water, making the equipment needed for operation bulky and difficult to transport. FAMOS — a four-year project begun in October 2012 and composed of laser and medical technology manufacturers and of scientists from universities in Vienna and St. Andrews (Scotland), London University College, Weizmann Institute (Israel), Technical University of Denmark and Ferdinand Braun Institute (FBH) in Germany — will address these issues to develop a smaller, more compact light source. Under the FAMOS project, a tapered laser that combines excellent beam quality with very high output power will be developed. It will serve as a pump source for OCT light sources. Courtesy of FBH/schurian.com. Positron emission tomography, magnetic resonance imaging and CT scans are the standard in today’s diagnostics for diseases that require sophisticated imaging methods while also taking samples for precise diagnosis and therapy control. More cost-effective and noninvasive laser optical diagnosis methods, however, could be the technique of choice for examining surface tissues such as human skin, retina and intestine, which have, up until now, been far less prevalent. “Our task at FBH is to develop a semiconductor laser with very high beam quality,” said Bernd Sumpf, head of the FAMOS project at FBH. “Colleagues from Denmark will then frequency-double the light, thus bisecting the wavelength.” The laser will be used by a Vienna-based industrial partner to pump a femtosecond Ti:sapphire laser, which will excite the white-light OCT source. If this works, only ambient air will be needed for cooling — requiring only a little ventilator, as in computers. This will potentially shrink the equipment to one-fifth of the size of current devices, making it portable and cost-efficient. Within the ridge waveguide (RW section) high-quality radiation is generated, which is amplified within the tapered section (TA section) — this tapered laser thus combines excellent beam quality with very high output power. Courtesy of ©FBH/D. Feise. To achieve this, Sumpf and colleagues will develop a tapered laser with excellent beam quality and high focusability as the pump source. Ti:sapphire lasers can be stimulated at wavelengths around 500 nm, but until now, mostly water-cooled solid-state lasers with an emission wavelength of 532 nm have been used. “We decided to use a more efficient, shorter wavelength of 515 nm,” Sumpf said. The aim is to generate 10 W of optical output power at 1030 nm. The wavelength will then be halved to 515 nm using a specific crystal. With overall efficiency higher, no sophisticated cooling will be necessary, the investigators say, making this the key part of the new technology. For more information, visit: www.famos-fp7.eu