Breaking of tiny light pulses observed in a nanophotonic chip for the first time

(Nanowerk News) An international team of scientists has observed the splitting of optical pulses in a nanoscale photonic chip for the first time. The pulse splitting phenomenon, called soliton fission, could lead to novel rainbow light sources used in compact optical communications systems and lab-on-a-chip spectroscopic tools for portable medical diagnostics.
CUDOS’ Dr Chad Husko and Dr Matthias Wulf of the FOM Institute-AMOLF in the Netherlands led the study, which also included partner institute Thales Research, and Technology (France) who developed the photonic chip. The results appeared today in Nature Communications ("Free-carrier-induced soliton fission unveiled by in situ measurements in nanophotonic waveguides").
Using a special near-field scanning optical microscope, the team was able to directly map the pulse evolution directly inside the photonic chip by bringing the microscope tip mere nanometers from the material surface.
“Measuring spatio-temporal dynamics of nanoscopic objects is a challenging task,” said Professor Kobus Kuipers AMOLF NanoOptics group leader and co-author.
“Fortunately, our unique microscope allows us to track the pulse evolution not only in space, but also in time. To our knowledge, these measurements are the first of their kind.”
Beyond the experimental observation, the study highlights a new mechanism for breaking the pulses apart. The team additionally derived a theoretical description of the phenomenon.
“It was exciting to realise that we were measuring physics unique to intense light interacting with free carriers (electron-hole pairs)”, said Dr. Wulf.
“Observing solitons at the nanoscale has been a long-standing goal of the field. To have realized this challenging experiment is a really exciting result," said Professor Benjamin Eggleton, CUDOS Director and co-author.
And the rainbow light sources?
“When the pulses split apart, they also spread out in colour. Cases with extremely energetic pulses lead to a bright rainbow spectrum known as ‘supercontinuum,’ ” said Dr. Husko.
Amongst their many uses, supercontinuum sources are excellent spectroscopic tools as evidenced by their role in the breakthrough experiment cited in the 2005 Nobel Prize in Physics.
“Now that we have a new technique to induce pulse breaking, we’re excited to see where the field will take it. On-chip spectroscopy and mid-infrared light sources in integrated photonic chips are just a few ideas,” said Dr. Husko.
Source: Cudos