New method for tuning lasers gives potential for nanosurgery
16 April 2010
Researchers at the Technische Universität Darmstadt have found
a new method for generating tunable wavelengths, as well as more easily
switching back and forth between two wavelengths, employing quantum-dot
lasers.
Prospective applications are in the fields of biomedicine and
nanosurgery.
Darmstadt physicists have discovered an effect that turns the
physics of semiconductor lasers upside down. Laser action in
semiconductor lasers usually starts off with emission of photons
corresponding to transitions originating from the lowest energy
level. Emission of high energetic, ie short-wavelength, photons does
not normally commence until the pumping current has been increased
to well above the lasing threshold.
Under the EU’s FAST-DOT project, researchers from the
Semiconductor Optics Group at the Technische Universität Darmstadt’s
Institute for Applied Physics headed by Prof. Dr. Wolfgang Elsäßer
have recently discovered that, under some circumstances, quantum-dot
lasers do emit first short-wavelength photons and then
long-wavelength photons.
Elsäßer explained that “this inverted hierarchy of emission
states that we are the first to discover effectively allows
generating intentionally custom-tailored wavelengths covering a
wavelength range of interest in many applications. Furthermore, the
method not only allows switching back and forth between two
wavelengths and but also exploiting beneficially effects occurring
in the laser systems involved for improving pulse parameters.”
Following up on that work, the Darmstadt researchers engaged in
the FAST-DOT project plan to explore applications of the easier
means for switching between wavelengths, whose underlying physics
they have discovered.
Medical applications of nanostructured quantum-dot lasers
Quantum-dot lasers operable at high pulse-repetition rates are
capable of reaching pulse energies that will allow modification of
living cells, eg making accurately controlled incisions in cell
structures, while minimizing the attendant effects on cellular
environments.
Summarizing their capabilities, Elsäßer said that, “They may be
employed as high-precision scalpels, with which cell structures may
be parted in controlled manners.”
In addition, certain cell organelles might be deactivated or
individual intracellular or extracellular molecules activated, which
would open up unforeseen opportunities in molecular surgery, which
allows making incisions two-thousand times finer than a human hair.
In the future, these qauntum dot lasers might allow destroying
cancer cells very specifically or applying them simultaneously
either for corneal surgery or diagnostics.