Semiconductor lasers with fiber delay lines generate 60 ps pulses
| Robert Huber and Christian Jirauschek with their lab equipment. (Image: Heddergott and Benz, copyright TUM) |
Munich, Germany--Researchers at the Technische Universität Muenchen (TUM) and LMU Munich have created cheap, robust semiconductor lasers that can produce high-energy light pulses as short as 60 ps without the drawbacks of previous approaches in terms of power consumption and device size.1
The device is a Fourier domain mode-locked (FDML) laser, which means it sweeps through a range of optical frequencies at a 390 kHz repetition rate; its laser cavity includes a kilometer-long energy-storage fiber. Outside the cavity is another fiber, this one with a dispersion that causes the light from each continuous-wave frequency sweep to "pile up" (temporally compress) into a single 60 to 70 ps pulse.
The storage of the laser energy in the long fiber, rather than the small piece of semiconductor, means that a low-power oscillator can produce high-energy pulses.
And the devices could soon be producing femtosecond pulses. "Our models and simulations actually let us identify changes in the experimental setup that could yield a further thousandfold improvement in performance," says Christian Jirauschek of TUM, "potentially producing pulses shorter than 30 fs."
REFERENCE:
1. Christoph M. Eigenwillig et al., Nature Communications 4, No. 1848, 14 May 2013. DOI: 10.1038/ncomms2870