Directional couplers with integrated carbon nanotube incandescent light emitters

Infrared Light-Emitting Diodes Based on Chirality-Sorted Carbon Nanotube Films

An important goal in carbon nanotube optoelectronics is to achieve a high-performance near-infrared light source. But there are still many challenges such as the purity of single-walled carbon nanotube (SWCNT) chirality, nonradiative defects, thin-film quality, and device structure design. Here, we realize infrared light-emitting diodes (LEDs) based on chirality-sorted (10, 5) SWCNT network films, which operate at a low bias voltage and emit at a telecom O band of 1290 nm. Asymmetric palladium (Pd) and hafnium (Hf) contacts are used as electrodes for hole and electron injection, respectively. However, the large Schottky barrier at the interface of the SWCNTs and the Hf electrode, primarily resulting from the polymer wrapped on the nanotube surface during the sorting process, leads to inefficient electron injection and thus a low electroluminescence efficiency. We find that the efficiency of electron injection can be improved by the local doping of the nanotubes with dielectric layers of YOX-HfO2, which reduces the Schottky barrier at the SWCNT/Hf interface. Accordingly, the (10, 5) SWCNT film-based LED achieves an external quantum efficiency of larger than 0.05% without any optical coupling structure. With further improvement, we expect that such an infrared light source will have great application potential in the carbon nanotube monolithic optoelectronic integrated system and on-chip optical interconnection, especially in the field of short-distance optical fiber communications and data center.

Fluorescent incandescent light sources from individual quadrilateral ZnO microwire via Ga-incorporation

By means of nanophotonics principle, the thermal radiation can be tailored, thus, traditional tungsten lamp light source can glow the vitality and the vigor due to the low-efficiency approaching to commercial fluorescent or light-emitting diode bulbs. However, too far by demanding exacting terms, such as high-temperature thermal radiation (∼ 3000 K), high-vacuum encapsulation technology, restricted spectrally controllable source and so on, tungsten-based incandescent lamp filament has greatly limited the application in lighting, diagnosis and treatment, communication, imaging, etc. Herein, individual Ga-doped ZnO microwires (ZnO:Ga MWs) were successfully synthesized, which can be utilized to construct typical incandescent sources. By adjusting the Ga-incorporation, lighting colors are tuned in the visible spectral band. Especially, by incorporating Au quasiparticle nanofilms, the incandescent lighting features can further be modulated, such as the emission peaks, the modulation of lighting regions. Therefore, individual ZnO:Ga MWs based incandescent emitters can undertake a new function of the oldest, affordable and easily prepared light sources. While preliminary, individual ZnO:Ga MWs being treated as efficient incandescent light sources, can also open up intriguing scientific questions, and possible applications of linear, transparent, flexible displays and optical interconnects with electronic circuits.

Photocurrent spectroscopy of dye-sensitized carbon nanotubes

Monochiral (7,5) single walled carbon nanotubes (SWCNTs) are integrated into a field effect transistor device in which the built-in electric field at the nanotube/metal contact allows for exciton separation under illumination. Variable wavelength spectroscopy and 2D surface mapping of devices consisting of 10-20 nanotubes are performed in the visible region and a strong correlation between the nanotube's second optical transition (S₂₂) and the photocurrent is found. After integration, the SWCNTs are non-covalently modified with three different fluorescent dye molecules with off-resonant absorption maxima at 532 nm, 565 nm, and 610 nm. The dyes extend the absorption properties of the nanotube and contribute to the photocurrent. This approach holds promise for the development of photo-detectors and for applications in photovoltaics and biosensing.

Sub-nanosecond light-pulse generation with waveguide-coupled carbon nanotube transducers

Carbon nanotubes (CNTs) have recently been integrated into optical waveguides and operated as electrically-driven light emitters under constant electrical bias. Such devices are of interest for the conversion of fast electrical signals into optical ones within a nanophotonic circuit. Here, we demonstrate that waveguide-integrated single-walled CNTs are promising high-speed transducers for light-pulse generation in the gigahertz range. Using a scalable fabrication approach we realize hybrid CNT-based nanophotonic devices, which generate optical pulse trains in the range from 200 kHz to 2 GHz with decay times below 80 ps. Our results illustrate the potential of CNTs for hybrid optoelectronic systems and nanoscale on-chip light sources.