New light source with unprecedented sensitivity to molecular finger prints of cancer cells
Researchers from the Attoscience and Ultrafast Optics Group led by ICREA, in collaboration with the Laboratory for Attosecond Physics at the Max Planck Institute for Quantum Optics (MPQ) and the Ludwig-Maximilians-Universität (LMU) in Munich, have developed a worldwide unique broadband and coherent infrared light source. The record peak brilliance of the light source makes it an ultrasensitive detector for the infrared molecular finger print region, ideal to detect minute changes in the spectral features from cells or tissue which are tell-tale signs of DNA mutation or the presence of cellular malfunctions such as cancer.
The mid-wave infrared is an extremely important range of the electromagnetic spectrum since the wavelength of the light can resonantly excite molecular vibrations. Consequently, shining light through a sample leaves the resonant fingerprints in the spectrum allowing identification. The absence of light sources that cover enough of the infrared spectrum with sufficient brilliance to detect minute concentrations originating from onco-metaboloids has been the main challenge in cancer detection.
Now, ICFO researchers have collaborated with colleagues from MPQ/LMU to develop a light source which addresses this need. Their light source exerts extreme control over mid-wave infrared laser light with unrivalled peak brilliance and single-shot spectral coverage between 6.8 and 16.4 micron wavelength. The emitted radiation is fully coherent and emitted 100 million times per second. Each laser pulse has a duration of 66 fs which is so short that the electric field oscillates only twice. These characteristics, in combination with its coherence, make the light source a compact and ultrasensitive molecular detector.
Professors at ICFO are currently investigating molecular sensitivity for the identification of cancer biomarkers on the single cell level using all optical techniques in the mid-wave infrared wavelength range.
Materials provided by ICFO-The Institute of Photonic Sciences. Note: Content may be edited for style and length.
Pixel-array quantum cascade detector paves the way for portable thermal imaging devices
The primary source of infrared radiation is heat -- the radiation produced by the thermal motion of charged particles in matter, including the motion of the atoms and molecules in an object. The higher the temperature of an object, the more its atoms and molecules vibrate, rotate, twist through their vibrational modes, the more infrared radiation they radiate. Because infrared detectors can be "blinded" by their own heat, high-quality infrared sensing and imaging devices are usually cooled down, sometimes to just a few degrees above absolute zero. Though they are very sensitive, the hardware required for cooling renders these instruments less-than-mobile, energy-inefficient and limits in-the-field applications.
A paper published this week in the journal Optics Express, from The Optical Society (OSA), describes a new type of portable, field-friendly, mid-infrared detector that operates at room temperature. Room-temperature operation, notes Andreas Harrer of the TU-Wien Center for Micro- and Nanostructures, Austria and the first author of the paper, "is essential for detectors to be energy-efficient enough for portable and handheld applications. We want to pave the way to an infrared-detection technology which is flexible in design and meets all requirements for compact integrated field-applicable detection systems."
The type of instrument developed by Harrer and his colleagues is known as a quantum cascade detector, or QCD. A QCD is a high-speed detector composed of semiconductor devices that sense specific wavelengths of infrared light and convert that light into proportionate electrical signals. A unique aspect of the design described by Harrer and his colleagues is that it consists of an 8 x 8 array of pixels, each approximately 110 microns square. Tuning is achieved by specifically adjusting the well and the barrier dimensions to a wavelength of 4.3 microns.
The number of pixels used in the QCD, Harrer says, can be easily scaled up. "The growth and processing technology used can be adapted and extended to larger array dimensions and smaller pixel sizes," he says. "This is essential to achieve cost-effective high resolution imaging devices in the future."
The 4.3-micron wavelength detected by the QCD elements represents one of the three narrow wavelengths at which CO2 molecules absorb infrared radiation. Future applications envisioned for the device is with "unmanned search and rescue robots that detect disaster victims, for example, based on the CO2 content of their exhaled breath," Harrer said.
The 4.3-micron wavelength also falls within the so-called mid-infrared regime, which is also referred to as the chemical "fingerprint" region of the electromagnetic spectrum. The rotational-vibrational absorption spectra of many chemical compounds are found within this wavelength range. In other words, when molecules absorb infrared radiation that falls within this wavelength range, they excite these molecules to a higher state of vibration, wherein they rotate and vibrate in distinctive, characteristic patterns -- "fingerprint" patterns that can be used to identify particular chemical species. This identification is very exact, and will be enhanced through the use of these QCD detectors. The potential for enhanced detection in remote sensing at 4.3 microns is promising with the spectrally narrowed QCDs described by Harrer and colleagues.
Materials provided by The Optical Society. Note: Content may be edited for style and length.
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