Scientists use wide bandgap semiconductor materials to advance nonlinear optical technology

The field of ultrafast nonlinear photonics has now become a focus of numerous studies, as it can achieve a large number of applications in cutting-edge chip based spectroscopy and information processing. The latter particularly requires a strong intensity dependent optical refractive index, which can modulate optical pulses at a time scale even exceeding picoseconds and a sub millimeter scale suitable for integrated photonics.

Despite significant progress in this field, there is currently no platform to provide this functionality for the ultraviolet (UV) spectral range. Now, an international team of scientists, including EPFL, has achieved significant nonlinearity of ultraviolet light matter mixed states (excitons polarons) in a waveguide made of aluminum indium gallium nitride. The waveguide is a broadband semiconductor material behind solid-state lighting technologies such as white LEDs and blue laser diodes.

This study was published in Nature Communications and originated from a collaboration between the University of Sheffield, ITMO St. Petersburg, Chalmers Institute of Technology, University of Iceland, and LASPE of the Institute of Physics at the EPFL School of Basic Sciences.

Scientists used a compact 100 micrometer long device to measure the ultrafast nonlinear spectral broadening of ultraviolet pulses, which is 1000 times larger than that observed in ordinary ultraviolet nonlinear materials, comparable to non ultraviolet polarizer devices. The use of aluminum nitride indium gallium is an important step towards a new generation of integrated ultraviolet nonlinear light sources for cutting-edge spectroscopy and measurement.

Rapha ë l Butt é of EPFL, who participated in this study, said, "The system is a highly robust and mature semiconductor platform that exhibits strong exciton optical conversion in the ultraviolet spectral range and exhibits the same performance at room temperature.". The nonlinear exciton interactions in the system can be comparable to those in other polaron material systems, such as gallium arsenide and peroxides, but they cannot work simultaneously under ultraviolet and room temperature conditions. “

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