FAMOS aims to make OCT light sources more compact

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.

The FAMOS project will develop a tapered laser combining excellent beam quality with very high output power. It will serve as a pump source for OCT light sources. Courtesy of FBH/schurian.com.

FAMOS – a four-year project begun in October 2012 and composed of laser and medical technology manufacturers and scientists from Austria, Scotland, England, Denmark, Israel and Germany – will address these issues to develop a smaller, more compact light source.

Positron emission tomography, magnetic resonance imaging and CT scans are the standard in today’s diagnostics for diseases that require sophisticated imaging methods while taking biopsies. Laser methods could become the techniques of choice, particulary for examining the skin, the retina and the intestines, if the devices were portable and cost-efficent.

“Our task at [Ferdinand Braun Institute] 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.”

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. DBR = distributed Bragg reflector. Courtesy of ©FBH/D.Feise.

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 the size of current devices, making it portable and cost-efficient.

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.