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Shedding more light on medical diagnosis

27 March 2013

PET, CT and MRI are common clinical diagnostic tools but laser-optical diagnosis methods are, up to now, far less prevalent. FAMOS is aiming to change this.

The FAMOS tapered laser: combining excellent beam quality with very high output power (photo: FBH/
The FAMOS tapered laser: combining excellent beam quality with very high output power (photo: FBH/

Some diseases, like cancer, call for sophisticated imaging methods and also sample taking for precise diagnosis and therapy control. For examinations of surface tissue such as skin, retina and so on, optical methods could become the technique of choice. It is more cost-effective, non-invasive, and involves neither ionising radiation nord contrast agents. Only high-energy laser light is needed.
In order to further advance the technique of 'Functional Anatomical Molecular Optical Screening' (FAMOS), 17 partners have joined forces, including manufacturers of lasers and medical technology as well as scientists from the universities in Vienna  and St. Andrews (Scotland), University College London, Weizmann Institute (Israel), Technical University of Denmark and the German Ferdinand-Braun-Institut (FBH).

The FAMOS project concentrates on optical coherence tomography (OCT), a key technology precisely displaying structures which are located at just a few millimeters depth within the tissue.

The approach requires white laser light, created when a special glass fibre is irradiated by a femto-second laser. As these lasers generate a lot of heat they need to be cooled, so the equipment is bulky and, in addition, requires an expert to operate it.
“Our task at FBH is to develop a semiconductor laser with very high beam quality," says  Bernd Sumpf, head of the FAMOS project at FBH. "Colleagues from Denmark will then frequency-double the light, thus bisecting the wavelength."

This laser will be used by an industrial partner in Vienna to pump a femto-second titanium-sapphire laser, which will excite the white light OCT source. If everything works out as planned, ambient air will be sufficient for cooling – requiring possibly only a cooling fan similar to those used in computers.

As a result, the team believes it can shrink the OCT to a fifth of its current size. To achieve this, Bernd Sumpf and his team are developing a 'tapered laser' as the pump source. This offers both excellent beam quality and focusing.
A titanium-sapphire laser can be stimulated at wavelengths around 500nm. Up to now, mostly water-cooled solid-state lasers with an emission wavelength of 532nm have been used. “We decided to use a more efficient shorter wavelength of 515nm," says Sumpf. The aim is to generate 10W optical output power at 1,030nm; the wavelength will then be halved to 515nm using a specific crystal.

This tiny FBH laser will be key to the success of this project.

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