With support from the Division of Materials Research, a collaboration between the Wide-Bandgaps group at North Carolina State University (NCSU) and the Quantum Optics group at the University of Ljubljana, Slovenia, has been established to explore the feasibility of using non-centrosymmetric wide bandgap semiconductors as nonlinear optical materials. In this work, AlGaN (aluminum gallium nitride) will serve as a model material for the investigation of the applicability of this semiconductor class as the high-quality quasi phase-matched structures for second harmonic generation (SHG). As a wide bandgap semiconductor, this will allow for SHG to shift the wavelength of available semiconductor lasers to the range of shorter wavelengths, where injection lasers are not available. In principle, it should allow for the frequency doubling of the output of a semiconductor laser with the shortest wavelength in the violet-blue region and produce a compact, coherent deep ultraviolet light source with wavelengths approaching 200 nm. This international collaboration seeks to demonstrate quasi-phase matched structures for SHG based on wide bandgap nitrides and to develop fundamental nonlinear optical concepts for efficient SHG in the UV spectrum that cannot be achieved in other systems. In order to realize this, two main challenges need to be met: (1) the demonstration of periodic lateral polarity control in AlGaN alloys, and (2) the development of the basic understanding of nonlinear optical characteristics of these structures. The group at NCSU addresses the first challenge, where their expertise in growth and control of polarity in III-nitrides has been demonstrated. The Quantum Optics group at the University of Ljubljana addresses the second challenge with their unique capabilities and expertise in harnessing non-linear optical properties of different materials. The periodic AlGaN structures are grown and fabricated using metalorganic chemical vapor deposition, with the choice of alloy composition and structure geometry based on the optical research by the group at Ljubljana.
NON-TECHNICAL SUMMARY: Nonlinear optical devices based on the aluminum gallium nitride semiconductors can provide a broad-based vehicle for laser light generation in the deep ultraviolet region of the electromagnetic spectrum, which is not accessible by any other solid-state technology. This can find uses in health care, bio-defense and other commercial and defense applications. The use of light sources in the deep UV will lead to detection systems of different chemical and biological aerosols, providing for detection of a variety of pollutant agents among other effluents. In general, this research will lead to materials that will be used for applications that deal with the preservation and extension of natural resources by: (1) allowing for the efficient use and transmission of electrical energy, (2) availability of clean potable water through disinfection by the use of UV light emitting diodes, and (3) emissions and other effluents detection. In addition, this challenging project will provide the opportunity to establish a research collaboration and student exchange between North Carolina State University and the University of Ljubljana. This opportunity will also help expose the students and researchers to state of the art facilities within NCSU and the University of Ljubljana for realizing this research, while at the same time building an international network for establishing future careers.
