More Like this

1. Epitaxial mid-IR nanophotonic optoelectronics

   https://doi.org/10.1063/5.0086774  

   Nordin, L.; Wasserman, D. (May 2022, Applied Physics Letters)

   There are a range of fundamental challenges associated with scaling optoelectronic devices down to the nano-scale, and the past decades have seen significant research dedicated to the development of sub-diffraction-limit optical devices, often relying on the plasmonic response of metal structures. At the longer wavelengths associated with the mid-infrared, dramatic changes in the optical response of traditional nanophotonic materials, reduced efficiency optoelectronic active regions, and a host of deleterious and/or parasitic effects makes nano-scale optoelectronics at micro-scale wavelengths particularly challenging. In this Perspective, we describe recent work leveraging a class of infrared plasmonic materials, highly doped semiconductors, which not only support sub-diffraction-limit plasmonic modes at long wavelengths, but which can also be integrated into a range of optoelectronic device architectures. We discuss how the wavelength-dependent optical response of these materials can serve a number of different photonic device designs, including dielectric waveguides, epsilon-near-zero dynamic optical devices, cavity-based optoelectronics, and plasmonic device architectures. We present recent results demonstrating that the highly doped semiconductor class of materials offers the opportunity for monolithic, all-epitaxial, device architectures out-performing current state of the art commercial devices, and discuss the perspectives and promise of these materials for infrared nanophotonic optoelectronics. 

   more » « less
2. Effect of disorder and plasmonic confinement on mode localization in disordered arrays of hybrid waveguides

   https://doi.org/10.1364/OE.550319  

   Hashemizad, Amir; Man, Weining; Xu, Huizhong (February 2025, Optics Express)

   We study mode localization in a quasi-one-dimensional disordered array of titanium dioxide waveguides above a silver film embedded inside a fused silica matrix. Disorder is introduced by randomly offsetting waveguides from their periodic positions by up to 20% of the array period. Using a perturbative coupled mode theory with nearest-neighbor coupling, we study how mode localization changes with increasing disorder and array size. Our results show mode localization, as measured by both the average effective mode area and variance for all modes, intensifies with increasing disorder, especially for the fundamental modes with tighter plasmonic confinement. Remarkably, we find the average variance scales with the array size, resulting in a universal dependence of normalized variance on disorder for arrays of any size. These findings may have implications for designing photonic devices and developing efficient photodetectors. 

   more » « less
3. Finite-difference time-domain methods

   https://doi.org/10.1038/s43586-023-00257-4  

   Teixeira, F. L.; Sarris, C.; Zhang, Y.; Na, D.-Y.; Berenger, J.-P.; Su, Y.; Okoniewski, M.; Chew, W. C.; Backman, V.; Simpson, J. J. (December 2023, Nature Reviews Methods Primers)

   The finite-difference time-domain (FDTD) method is a widespread numerical tool for full-wave analysis of electromagnetic fields in complex media and for detailed geometries. Applications of the FDTD method cover a range of time and spatial scales, extending from subatomic to galactic lengths and from classical to quantum physics. Technology areas that benefit from the FDTD method include biomedicine — bioimaging, biophotonics, bioelectronics and biosensors; geophysics — remote sensing, communications, space weather hazards and geolocation; metamaterials — sub-wavelength focusing lenses, electromagnetic cloaks and continuously scanning leaky-wave antennas; optics — diffractive optical elements, photonic bandgap structures, photonic crystal waveguides and ring-resonator devices; plasmonics — plasmonic waveguides and antennas; and quantum applications — quantum devices and quantum radar. This Primer summarizes the main features of the FDTD method, along with key extensions that enable accurate solutions to be obtained for different research questions. Additionally, hardware considerations are discussed, plus examples of how to extract magnitude and phase data, Brillouin diagrams and scattering parameters from the output of an FDTD model. The Primer ends with a discussion of ongoing challenges and opportunities to further enhance the FDTD method for current and future applications. 

   more » « less
4. Epsilon-near-zero plasmonic waveguides to enhance nonlinear coherent light-matter interactions

   https://doi.org/10.1117/12.2320011  

   Argyropoulos, Christos; Li, Ying; Subramania, Ganapathi S.; Foteinopoulou, Stavroula (September 2018, Active Photonic Platforms X)

   We demonstrate a way to coherently control light at the nanoscale and achieve coherent perfect absorption (CPA) by using epsilon-near-zero (ENZ) plasmonic waveguides. The presented waveguides support an effective ENZ response at their cut-off frequency, combined with strong and homogeneous field enhancement along their nanochannels. The CPA conditions are perfectly satisfied at the ENZ frequency, surprisingly by a subwavelength plasmonic structure, resulting in strong CPA under the illumination of two counter-propagating plane waves with appropriate amplitudes and phases. In addition, we investigate the nonlinear response of the proposed ENZ plasmonic configuration as we increase the input intensity of the incident waves. We demonstrate that the CPA phenomenon can become both intensity- and phasedependent in this case leading to new tunable all-optical switching and absorption devices. 

   more » « less
5. Ultrathin-shell epitaxial Ag@Au core-shell nanowires for high-performance and chemically-stable electronic, optical, and mechanical devices

   https://doi.org/10.1007/s12274-021-3718-z  

   Zhu, Yangzhi; Kim, Sanggon; Ma, Xuezhi; Byrley, Peter; Yu, Ning; Liu, Qiushi; Sun, Xiaoming; Xu, Da; Peng, Sangshan; Hartel, Martin C.; et al (November 2021, Nano Research)

   Abstract Silver nanowires (AgNWs) hold great promise for applications in wearable electronics, flexible solar cells, chemical and biological sensors, photonic/plasmonic circuits, and scanning probe microscopy (SPM) due to their unique plasmonic, mechanical, and electronic properties. However, the lifetime, reliability, and operating conditions of AgNW-based devices are significantly restricted by their poor chemical stability, limiting their commercial potentials. Therefore, it is crucial to create a reliable oxidation barrier on AgNWs that provides long-term chemical stability to various optical, electrical, and mechanical devices while maintaining their high performance. Here we report a room-temperature solution-phase approach to grow an ultra-thin, epitaxial gold coating on AgNWs to effectively shield the Ag surface from environmental oxidation. The Ag@Au core-shell nanowires (Ag@Au NWs) remain stable in air for over six months, under elevated temperature and humidity (80 °C and 100% humidity) for twelve weeks, in physiological buffer solutions for three weeks, and can survive overnight treatment of an oxidative solution (2% H 2 O 2 ). The Ag@Au core-shell NWs demonstrated comparable performance as pristine AgNWs in various electronic, optical, and mechanical devices, such as transparent mesh electrodes, surface-enhanced Raman spectroscopy (SERS) substrates, plasmonic waveguides, plasmonic nanofocusing probes, and high-aspect-ratio, high-resolution atomic force microscopy (AFM) probes. These Au@Ag core-shell NWs offer a universal solution towards chemically-stable AgNW-based devices without compromising material property or device performance. 

   more » « less