Ultraviolet born in plasma bath
doi:10.1038/nindia.2010.152 Published online 29 October 2010
Researchers have generated extreme-ultraviolet radiation by firing ultrashort laser pulses into plasma plumes of silver nanoparticles. This method relies on high-order harmonic generation (HHG), a technique that has a wide range of applications such as pump–probe studies and soft-X-ray microscopy.
When gas jets, solid surfaces and low-excited plasma plumes interact with ultrashort femtosecond laser pulses, light can be emitted at frequencies that are multiples of the incident laser frequency — known as harmonics. However, targets containing nanoparticles rapidly deplete during this process, causing the harmonic efficiency to fall.
To devise an alternative method of generating HHG, the researchers first hit a silver target with a low-intensity laser pre-pulse, which generated plasma plumes of silver nanoparticles.
After a time delay of ~60 ns, ultrashort femtosecond laser pulses were then made to interact with the plasma plumes of silver nanoparticles, thereby generating extreme-ultraviolet radiation. The generation of coherent extreme-ultraviolet radiation through HHG may also be helpful in low-cost ultrahigh-resolution X-ray microscopy.
"One of the future aims of our research is to make a stable, high-intensity and high-repetition-rate attosecond source that does not have stringent vacuum requirements," says lead researcher Himangshu Singhal. The source will be useful in attosecond metrology and for studying the behaviour of matter at ultrahigh intensities, he adds.
The authors of this work are from: Raja Ramanna Centre for Advanced Technology, Indore, India; and the Institute of Electronics, Tashkent, Uzbekistan.