New method will make it easier to generate extremely short laser pulses

In a new research project researchers aim to find more efficient methods for generating extremely short femtosecond laser pulses in the important visible and near-infrared regimes. These pulses can today only be generated in research laboratories with bulky, fickle state-of-the-art lasers operating complex setups. A simpler and more efficient method is needed in order for these pulses to be used in the industry and for medical purposes. Of possible applications are ultra-fast spectroscopy of molecular vibrations and non-invasive surgery on living cells.
Soliton compression

Numerical simulation showing the compression of a 250 femtosecond pulse at 1030 nm wavelength from a commercial fiber amplifier system to 7 fs (2.0 optical cycles). The compression occurs on propagation in a short quadratic nonlinear crystal.

Ultra-short femtosecond laser pulses challenge the limits in optics. Since they can be as short as a single optical cycle they can be incredibly intense while carrying very little energy. With these pulses extremely weak and exotic nonlinear phenomena can be studied. It is said that ultra-short optical pulses are as hard to measure as they are to generate, and that they are hard to generate is beyond any doubt. This project aims to change that: starting from cheap fiber lasers and only a single active component it is the goal to generate ultra-short high-energy laser pulses in the visible and near-infrared (VINIR) areas. This is possible when exploiting unique properties of femtosecond nonlinear optical solitons in well-known optical frequency conversion processes.

 

Possible applications: ultrafast spectroscopy and nanosurgery

Ultra-short femtosecond laser pulses can be used to film, e.g., chemical reactions and molecular vibrations real time: exactly as a person standing in a stroboscope light, it is possible to get a unique insight into how the processes evolve step-by-step. The pulses can also be used for nanosurgery, where non-invasive surgery of living cells is possible, and micromachining of materials with nanometer resolution. Finally, few-cycle pulses are an essential component in the emerging field of atto-physics: with few-cycle pulses even shorter laser pulses are generated (on the time-scale of electronic orbital motion) that can be used to monitor and ultimately manipulate electron motion on an atomic level.

 

Generating ultra-short laser pulses using nonlinear optical solitons

No lasers can directly generate ultra-short femtosecond laser pulses with duration of just a few optical cycles (5-20 fs). Today one has therefore to use very complicated setups and expensive equipment, especially in the VINIR areas, which are so important in medicine and biophysics. The goal of the project is to use nonlinear optical solitons: starting from longer laser pulses – generated by cheap, stable, effective and compact pulsed high-energy fiber lasers – the solitons can be used to compress these to few-cycle duration in an ordinary nonlinear crystal commonly used for frequency conversion processes. The combination of a cheap laser source and simple equipment will lead to a much more wide-spread and commercial use of ultra-short pulses: femtosecond laser pulses will become common to everybody.

 

The Research project “Few-cycle femtosecond optical pulses in the visible and near-infrared” (Femto-VINIR) is funded with 5.4 million DKK by the Danish Research Council for Technology and Production Sciences (Forskningsrådet for Teknologi og Produktion) over 3 years. It is a collaboration between DTU Fotonik (headed by associate professor Morten Bache), Cornell University (professor Frank Wise) and Australian National University (professor Wieslaw Krolikowski). The project is based on theory and numerical simulations done at DTU Fotonik in collaboration with ongoing experimental work at Cornell University.

 

For more information contact:
Associate professor Morten Bache, DTU Fotonik
moba@fotonik.dtu.dk
+45 4525 3775