MID-INFRARED LIGHT PULSES MAY BE CONTROLLED WITH A LEVEL OF PRECISION NEVER BEFORE ACHIEVED
Researchers from the Center for Molecular Fingerprinting, the Max Planck Institute of Quantum Optics,
and Ludwig Maximilians University's attoworld team of laser physicists together with other researchers in the field of quantum optics have achieved unprecedented control over
light pulses in the mid-infrared wavelength region.
Many different technology applications rely on ultra-short infrared light pulses. The oscillating infrared light field can create ultrafast electric currents in semiconductors or excite molecules in a sample to vibrate at particular frequencies. Now that ultrashort mid-infrared pulses have been created and their electric-field waveforms have been precisely controlled, physicists from the attoworld team at the Ludwig-Maximilians-Universitat Munchen (LMU), the Max Planck Institute of Quantum Optics (MPQ), and the Hungarian Center for Molecular Fingerprinting (CMF) have done so. A stabilised laser system that produces light pulses with a carefully specified waveform at near-infrared wavelengths serves as the foundation for the new mid-infrared source.
The pulses are only a few femtoseconds long since they are made up of a single oscillation of the light wave (a femtosecond being one millionth of a billionth of a second, 10-15 s). The team converts the near-infrared pulses into manageable infrared waveforms by using frequency-mixing techniques in nonlinear crystals. This infrared waveform manipulator opens up new avenues for optical control in quantum electronics and medicinal applications.
Anyone looking to use ultrashort light pulses' oscillating waveform to power advanced electro-optical systems, for example, must consider how to manage the waveform most effectively. Different wavelength ranges, such as the UV-visible and the near-infrared, have seen demonstrations of the creation of ultrashort pulses with programmable waveforms. The execution of ultrashort-pulse manipulation in the mid-infrared has proven to be particularly difficult because ideas from other wavelength ranges cannot be easily adapted, despite the huge potential for new applications. This challenge was accepted, and now laser physicists from the attoworld team at the Ludwig Maximilian University, the Max Planck Institute of Quantum Optics, and the Hungarian Center for Molecular Fingerprinting have succeeded in creating a technology that enables the control of the waveform-and thus the electric field-underlying the ultrashort laser pulses in the mid-infrared region. To achieve this, scientists first developed a novel laser platform that generates highly reproducible light pulses in the nearby near-infrared spectral range, with pulse durations of just a few femtoseconds and wavelengths ranging from 1 to 3 micrometres.
By utilising intricate frequency-mixing techniques, long-wavelength infrared pulses can be generated when these pulses are fed into a suitable nonlinear crystal. The team was able to create light pulses with an extraordinarily wide spectral coverage of more than three optical octaves, spanning from 1 to 12 micrometres, in this manner. The researchers were able to precisely regulate the oscillations of the generated mid-infrared light by adjusting the laser input settings in addition to being able to comprehend and replicate the underlying physics of the mixing processes.
In the future, substantially faster electronic signal processing speeds would be possible because to the tunable waveforms that resulted. For instance, they could be used to selectively initiate specific electrical processes in solids. According to researchers in the field of quantum optics - On this basis, one could envision the development of light-controlled electronics. If opto-electronic devices were to operate at frequencies of the generated light, you could speed up today's electronics by at least a factor of 1000.
The physicists of the attoworld are particularly interested in the application of the new light technology for the spectroscopy of molecules. When mid-infrared light passes through a liquid sample, such human blood, the sample's molecules start to oscillate and release distinctive light waves. The precise makeup of the sample determines the specific fingerprint that is produced by molecular response detection. Dr. Nathalie Nagl, who is also the study's first author, explains that "using our laser technology, we have greatly increased the controlled wavelength range in the infrared." She explains, "The additional wavelengths allow us the possibility to investigate a mixture of compounds even more precisely.
Colleagues from the Broadband Infrared Diagnostics (BIRD) team led by Dr. Mihaela Zigman and the CMF Research team lead by Dr. Alexander Weigel in the attoworld group are particularly interested in assessing the precise infrared molecular fingerprints of human blood samples. The goal is to find distinctive markers that make it possible to diagnose diseases like cancer. For instance, the molecular makeup of the blood alters little but significantly when a tumour grows. By detecting the infrared fingerprint of a small drop of human blood, the objective is to identify these changes and enable the early detection of illnesses.
"Our laser method will eventually enable our colleagues to identify modifications in certain biomolecules like proteins or lipids that were previously undetectable. Thus, it improves the accuracy of upcoming medical diagnostics that use infrared laser technology "Dr. Maciej Kowalczyk, the study's first author, notes.