Long-wavelength laser will take better 'fingerprints' of medicines than chemical analysis, research suggests

Dec. 19, 2012 ? A laser capable of working in the terahertz range ? that of long-wavelength light from the far infrared to 1 millimeter ? takes a better 'fingerprint' of, say, a drug under investigation, than a traditional chemical analysis. PhD student Thomas Denis of the University of Twente's MESA+ Institute for Nanotechnology has now combined? a free electron source with photonic crystals. The result: greater flexibility and a compact laser.

A terahertz laser is capable of showing the molecular structure of, say, a drug, because the laser beam it produces is at wavelengths suitable for examining molecular and atomic bonds. This enables more spatial information to be obtained than from chemical analysis, a detailed fingerprint. To date, however, the limitation has been that lasers of this type are restricted to particular wavelengths, e.g. because the source of the laser light is a semiconductor, in which electrons can only take on fixed energy states, hence only a limited number of 'colours' of light can be produced.

Free electrons

In a free electron laser the electrons are not restricted to fixed states, as are electrons in a classic cathode ray tube. So Denis thought, why not combine a free electron source with a 'photonic crystal'? This is a structure with lot of tiny 'posts' that together slow down the incident light and turn it into a coherent beam. Photonic crystals can be created at micro level, e.g. for a lab-on-a-chip, or on a much larger scale. The dimensions and shape of the crystal determine the rough wavelength region, and the precise wavelength can be set and adjusted by changing the speed of the electrons being fired at it. This combination is known as a 'photonic free-electron laser' or pFEL.

Looking inside the crystal

Existing terahertz lasers also have the disadvantage that they are very large, big enough to fill a room. Thanks to the use of photonic crystals the pFEL that Denis has designed is not much bigger than a domestic microwave oven and can still provide high power despite its small size. He has also found a special way of 'looking' inside a photonic crystal -- something that is not normally possible. By interfering slightly with the wavelength pattern in the crystal using a tiny metal ball the actual pattern can be measured.

Thomas Denis (Ahaus, 1981) received his PhD on 14 December for his thesis Theory and Design of Microwave Photonic Free-Electron Lasers. He carried out his research in Prof. Klaus Boller's Laser Physics and Non-linear Optics Group. The thesis, or the summary, is available in digital form on request.

Share this story on Facebook, Twitter, and Google:

Other social bookmarking and sharing tools:

---

Story Source:

The above story is reprinted from materials provided by University of Twente.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

---

Note: If no author is given, the source is cited instead.

Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

Source: http://feeds.sciencedaily.com/~r/sciencedaily/matter_energy/physics/~3/ZEG83A6wCq0/121219101227.htm

soa andy williams andy williams Lady Gaga New Girl Avalanna Gigi Chao