Fraunhofer aims for better surgical laser

Researchers at the Fraunhofer Institutes for Laser Technology (ILT) and for Applied Solid State Physics have developed a surgical diode laser for soft tissue surgery that is easier for surgeons to aim.

Laser surgery for snoring involves surgically removing part of the palate and the uvula using a relatively cheap CO₂ laser. But its light cannot be directed along a waveguide, so an articulated arm has to be used to direct the beam to the correct position inside the patient’s mouth, which can prove unwieldy.

The new diode laser has has a wavelength of two micrometers which gets round this problem, while at the same time being compact and inexpensive. A typical diode laser costs less than a third of the price of other types of laser.

‘The laser output can be routed through a very fine light-conducting fibre,’ said ILT project manager Dr Konstantin Boucke. ‘Instead of laboriously positioning a mirror at the correct angle, the surgeon merely has to introduce a flexible optical fibre into the patient’s mouth.’

‘Light at this wavelength is readily absorbed by biological tissue, and the laser beam doesn’t penetrate far. Surgical incisions can be controlled much better with this laser. It can also be switched to a second operating mode in which it emits radiation at 800 to 980 nanometres, the ideal wavelength for arresting bleeding. This makes the new laser highly suitable for any type of soft tissue surgery – including prostate resection, which involves inserting an optical fibre in the urethra,’ said Boucke.

In order to produce a diode laser operating at this wavelength, the researchers had to work with an unconventional material – gallium antimonide – and adapt the optical setup accordingly. The cameras normally used to calibrate the laser beam were not sufficiently sensitive for a wavelength of two micrometers.

The laser will also allow transparent plastic objects to be processed. A plastic material that appears transparent to the human eye allows conventional types of laser beam to pass through without obstruction, and without producing any melting effect. Until now, in order to weld transparent plastics with a laser, it was necessary to add coloured pigments to the material, which added to the cost, changed the properties, and tainted the colour of the resulting product.

‘The new laser permits transparent plastics to be joined without having to add pigments,’ said Boucke.