The field of ultrafast nonlinear photonics has now become the focus of numerous studies, as it enables a host of applications in advanced on-chip spectro­scopy and information processing. The latter in particular requires a strongly intensity-dependent optical refrac­tive index that can modulate optical pulses faster than even picosecond timescales and on sub-millimeter scales suitable for inte­grated photonics.

Despite the tremendous progress made in this field, there is currently no platform providing such features for the ultraviolet spectral range, which is where broadband spectra generated by nonlinear modulation can be used for new on-chip ultrafast chemical and biochemical spectro­scopy devices. Now, an inter­national team of scientists including EPFL have achieved giant nonlinearity of UV hybrid light-matter states up to room temperature in a waveguide made of AlInGaN, a wide bandgap semi­conductor material behind the solid-state lighting technology and blue laser diodes. 

The scientists used a compact 100 µm-long device, to measure an ultrafast nonlinear spectral broadening of UV pulses with a non­linearity 1000 times larger than that observed in common UV nonlinear materials, which is comparable to non-UV polariton devices. Using AlInGaN is a signi­ficant step toward a new generation of integrated UV nonlinear light sources for advanced spectro­scopy and measurement. “The AlInGaN system is a highly robust and mature semi­conductor platform that shows strong excitonic optical transitions up to room temperature in the UV spectral range,” says EPFL's Raphaël Butté. (Source: EPFL)

Reference: D. M. Di Paola et al.: Ultrafast-nonlinear ultraviolet pulse modulation in an AlInGaN polariton waveguide operating up to room temperature, Nat. Commun. 12, 3504 (2021); DOI: 10.1038/s41467-021-23635-6

Link: Advanced Semiconductors for Photonics and Electronics, École Polytechnique Fédérale de Lausanne EPFL, Lausanne, Switzerland