Deep-ultraviolet integrated photonic and optoelectronic devices:A prospect of the hybridization of group Ⅲ–nitrides, Ⅲ–oxides,and two-dimensional materials

Progress in the design and fabrication of ultraviolet and deep-ultraviolet groupⅢ–nitride optoelectronic devices,based on aluminum gallium nitride and boron nitride and their alloys,and the heterogeneous integration with two-dimensional and oxide-based materials is reviewed.We emphasize wide-bandgap nitride compound semiconductors(i.e.,(B,Al,Ga)N)as the deep-ultraviolet materials of interest,and two-dimensional materials,namely graphene,two-dimensional boron nitride,and two-dimensional transition metal dichalcogenides,along with gallium oxide,as the hybrid integrated materials.We examine their crystallographic properties and elaborate on the challenges that hinder the realization of efficient and reliable ultraviolet and deep-ultraviolet devices.In this article we provide an overview of aluminum nitride,sapphire,and gallium oxide as platforms for deep-ultraviolet optoelectronic devices,in which we criticize the status of sapphire as a platform for efficient deep-ultraviolet devices and detail advancements in device growth and fabrication on aluminum nitride and gallium oxide substrates.A critical review of the current status of deep-ultraviolet light emission and detection materials and devices is provided.

The effect of turbulence on NLOS underwater wireless optical communication channels [Invited]

Conventional line-of-sight underwater wireless optical communication(UWOC)links suffer from huge signal fading in the presence of oceanic turbulence due to misalignment,which is caused by variations in the refractive index in the water.Non-line-of-sight(NLOS)communication,a novel underwater communication configuration,which has eased the requirements on the alignment,is supposed to enhance the robustness of the UWOC links in the presence of such turbulence.This Letter experimentally and statistically studies the impact of turbulence that arises from temperature gradient variations and the presence of different air bubble populations on NLOS optical channels.The results suggest that temperature gradient-induced turbulence causes negligible signal fading to the NLOS link.Furthermore,the presence of air bubbles with different populations and sizes can enhance the received signal power by seizing the scattering phenomena from an ultraviolet 377 nm laser diode.

Facile integration of electro-optic SiO_(2)/ITO heterointerfaces in MIS structures for CMOS-compatible plasmonic waveguide modulation

By taking advantage of the absence of diffraction limit restrictions in plasmonic structures,strong modal confinement is made possible,paving the way for improved optical processes and miniaturized photonic circuit integration.Indium tin oxide(ITO)has emerged as a promising plasmonic material that serves as a relatively low-carrier density Drude metal by its electro-optic tunability and versatility as an integrative oxide.We herein demonstrate the facile integration of SiO_(2)/ITO heterointerfaces into metal-insulator-semiconductor(MIS)electro-optic structures.The first MIS device employs a SiO_(2)/ITO heterostructure grown on thin polycrystalline titanium nitride(poly-TiN)and capped at the ITO side with thin aluminum(Al)film contact electrode.The TiN interlayer acts as a bottom electrode,forming a metal-insulator-semiconductor-metal(MISM)heterojunction device,and grows directly on(100)-oriented silicon(Si).This MISM device enables one to examine the electrical properties of semiconductive ITO layers.The second MIS device incorporates a semiconductive ITO layer with a SiO_(2)dielectric spacer implemented on a silicon-on-insulator(SOI)platform,forming a graded-index coupled hybrid plasmonic waveguide(CHPW)modulator.This device architecture represents a crucial step towards realizing plasmonic modulation using oxide materials.The CHPW device performance presented herein provides a proof-of-concept that demonstrates the advantages offered by such device topology to perform optical modulation via charge carrier dispersion.The graded-index CHPW can be dynamically reconfigured for amplitude,phase,or 4-quadrature amplitude modulation utilizing a triode-like biasing strategy.It exhibited extinction ratio(ER)and insertion loss(IL)levels of around 1 dB/μm and 0.128 dB/μm,respectively,for a 10μm waveguide length.