| Optical pulses custom-shaped by coherent CW laser combination are shown here with a 100-GHz repetition rate. (Credit: University of Southampton) |
By combining light generated at different wavelengths from different continuous-wave (CW) laser diodes, researchers at the University of Southampton (Southampton, England) can create trains of arbitrarily shaped optical pulses.1 The technique could be useful in telecommunications, metrology, sensing, and materials processing.
Five phase-locked laser diodes
In the technique, five laser diodes with wavelengths ranging from 1548.8 to 1552.6 nm are phase-locked to the same optical-frequency comb via injection locking, ensuring mutual coherence; the optical power and phase of each laser diodes is separately controlled to customize the waveform, which repeats at a 100 GHz rate.
"As our new technique is based on a different approach to that currently used, it has several distinct features that are relevant in many applications," says David Wu, lead author of the study and winner of the 2014 Engineering and Physical Sciences Research Council (EPSRC) ICT Pioneers award for this work. "First, it is easily scalable -- by combining a larger number of input lasers, shorter or more complicated-shape pulses and/or more power can be obtained. It can also generate pulses with a very low level of noise (down to the quantum limit) and very high (greater than 1 THz) repetition frequencies. Finally, it consists of miniature and low-cost semiconductor lasers that can be all integrated on the same chip, making our pulse generator potentially very compact, robust, energetically efficient, and low-cost."
"We believe that this work is likely to be of direct interest to scientists working in virtually any field of optics where pulsed laser sources are used," adds Radan Slavik, who leads the research group. "We also believe that the concept and phase-locking technology developed could be widely applicable with the broader optics/photonics community."
Source: http://www.southampton.ac.uk/mediacentre/news/2015/jan/15_07.shtml#.VL_ksN_HlTY
REFERENCE:
1. David S. Wu et al., Optica (2015); http://dx.doi.org/10.1364/OPTICA.2.000018