Ultrashort Flashes of Light under Optical Control

Light pulses can form pairs in ultra-short pulse lasers. The pulse intervals can be precisely adjusted by making certain changes to pump beam. (Source: UBT)

Ultrashort laser pulses have enabled scientists and physicians to carry out high-precision material analyses and medical procedures. Physicists from the Univer­sity of Bayreuth and the University of Göttingen have now discovered a new method for adjusting the extremely short time intervals between laser flashes with excep­tional speed and precision. The intervals can be increased or decreased as needed, all at the push of a button. Potential appli­cations range from laser spectro­scopy to micro­scopy and materials processing.

Laser pulses have long been utilized in research labora­tories, industrial production, and medical therapies. In these appli­cations it is often crucial that the pulses – the optical solitons – occur at certain intervals. Using a special high-speed measure­ment technique, the researchers have now been able to show how a short-pulse laser widely applied in research can be made to auto­matically generate pairs of light pulses separated by the desired interval. All that is required are small distur­bances in the green pump beam, which generates the laser pulses, triggered by electric signals.

The new process centres on the targeted mani­pulation of solitons, wave packets that can occur in pairs in ultrashort laser pulses. “The resonance excitation and the short disturbance of soliton pairs trigger effects that can be used to speci­fically control ultrashort laser pulses. This opens up an exciting new area of research with a yet unfore­seeable range of possible appli­cations,” said Georg Herink. “At the right frequency, a tiny external modu­lation of the laser is all you need, and ultrashort laser pulses are set into reciprocal, resonant oscil­lation. Similar phenomena can be observed in water molecules heated in the microwave,” added his colleague Felix Kurtz from Göttingen. The findings show that in the future, ultra-short pulse lasers will not only be considered as a tool, but also remain a fascinating object of research. (Source: U. Bayreuth)

Reference: F. Kurtz et al.: Resonant excitation and all-optical switching of femtosecond soliton molecules, Nat. Phot., online 14. Oktober 2019; DOI: 10.1038/s41566-019-0530-3

Links: Ultrafast Dynamics Lab (G. Herink),Dept. of Physics, University of Bayreuth, Bayreuth, GermanySolid State & Nanostructures, University of Göttingen, Göttingen, Germany

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