More light for medicine

March 26, 2013
Tapered laser (FAMOS project) - combines excellent beam quality with very high output power. Credit: FBH/

PET scan, CT and MRI are almost standard in today's diagnostics – highly developed and very sophisticated. Although more capable and less cost-intensive, laser-optical diagnosis methods are, up to now, far less prevalent. FAMOS is aiming to change this.

Some diseases like cancer call for sophisticated imaging methods and also sample taking for precise diagnosis and therapy control. In the future, in case of examinations of surface tissue such as human skin, retina, and intestine, optical methods could be the technique of choice to clarify the matter – more cost-effective, non-invasive, and without requiring and . For examinations, only high-energy laser light is used.

In order to further advance Functional Anatomical Molecular Optical Screening, 17 partners joined forces within the EU project FAMOS. Among them, manufacturers of lasers and medical technology as well as scientists from the universities in Vienna (Austria) and St. Andrews (Scotland), the London University College, Weizmann Institute (Israel), Technical University of Denmark and the German Ferdinand-Braun-Institut (FBH). The project builds up on OCT – optical – a key technology precisely displaying structures which are located a few millimeters inside the tissue. The approach pursued for OCT requires white laser light that emerges when a special glass fiber is irradiated with a femto-second laser. As these lasers generate a lot of heat they need to be cooled with water. Thus, the equipment is rather massive, not portable, and, in addition, so complicated that it requires an expert for operation.

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. Credit: FBH/D. Feise

FAMOS is addressing these features: with it, the light sources shall become smaller and more compact. "Our task at FBH is to develop a semiconductor laser with very high beam quality. Colleagues from Denmark will then frequency-double the light, thus bisecting the wavelength", outlines Bernd Sumpf, head of the FAMOS project at FBH. This laser will be used by an industrial partner in Vienna to pump a femto-second titanium-sapphire laser, which will excite the white OCT source. If everything works out as planned, ambient air will be sufficient for cooling – requiring only a little ventilator as in computers. Thus, the equipment will shrink to a fifth of its current size and accordingly be portable and cost-efficient. To achieve this, Bernd Sumpf and his team will develop a tapered laser as pump source that features an excellent beam quality and is highly focusable at the same time.

A titanium-sapphire laser can be stimulated at wavelengths around 500 nanometers (nm). Up to 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", explains Sumpf. The aim is to generate 10 Watt optical output power at 1030 nm, the wavelength will then be halved to 515 nm using a specific crystal. As the overall efficiency shall be so high that no sophisticated cooling will be necessary, this tiny FBH will be the key part of the new technology.

Explore further: A silicon chip with integrated laser and optical grating offers new possibilities for telecommunications

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