5 research outputs found
Heterogeneously Integrated Silicon Photonics for the Mid-Infrared and Spectroscopic Sensing
Besides being the foundational material for microelectronics, crystalline silicon has long been used for the production of infrared lenses and mirrors. More recently, silicon has become the key material to achieve large-scale integration of photonic devices for on-chip optical interconnect and signal processing. For optics, silicon has significant advantages: it offers a very high refractive index and is highly transparent in the spectral range from 1.2 to 8 μm. To fully exploit silicon’s superior performance in a remarkably broad range and to enable new optoelectronic functionalities, here we describe a general method to integrate silicon photonic devices on arbitrary foreign substrates. In particular, we apply the technique to integrate silicon microring resonators on mid-infrared compatible substrates for operation in the mid-infrared. These high-performance mid-infrared optical resonators are utilized to demonstrate, for the first time, on-chip cavity-enhanced mid-infrared spectroscopic analysis of organic chemicals with a limit of detection of less than 0.1 ng
Engineering of Interfacial Electron Transfer from Donor–Acceptor Type Organic Semiconductor to ZnO Nanorod for Visible-Light Detection
Interfacial electron transfer (IET) plays a key role
in photoactive
organic/inorganic hybrid nanomaterials and remains elusive with regard
to interfacial energy level alignment. In this study, we prepared
hybrid ZnO nanorods by grafting n-type perylene bisimide (PBI) derivatives
bearing carboxylic acid groups at nitrogen positions. No evidence
in terms of direct electron transfer from PBI to ZnO can be observed
in PBI/ZnO hybrids. In sharp contrast, incorporation of electron-rich
oligothiophene (<i>n</i>T, <i>n</i> = 1, 2) moieties
into PBI core at bay positions resulted in a highly efficient cascade
IET in <i>n</i>T-PBI/ZnO (<i>n</i> = 1, 2) hybrid
nanorods, which was initiated by photoinduced electron transfer (PET)
from <i>n</i>T (<i>n</i> = 1, 2) to PBI and then
followed by charge shifting from PBI anion to ZnO across the interface.
High performance UV–vis photodetectors based on <i>n</i>T-PBI/ZnO (<i>n</i> = 1, 2) hybrids have been fabricated
and show responsivity of 21.2 and 12.4 A/W and an on/off ratio as
high as 537 and 403, whereas that based on PBI/ZnO shows little visible-light
response. Our results suggest that donor–acceptor type compounds
can be used for constructing photoactive hybrid nanomaterials, in
which efficient cascade IET modifies interfacial electronic structure
and helps extend the spectral response range
High-Speed Carbon Nanotube Photodetectors for 2 μm Communications
In the era of big data, the growing
demand for data transmission
capacity requires the communication band to expand from the traditional
optical communication windows (∼1.3–1.6 μm) to
the 2 μm band (1.8–2.1 μm). However, the largest
bandwidth (∼30 GHz) of the current high-speed photodetectors
for the 2 μm window is considerably less than the developed
1.55 μm band photodetectors based on III–V materials
or germanium (>100 GHz). Here, we demonstrate a high-performance
carbon
nanotube (CNT) photodetector that can operate in both the 2 and 1.55
μm wavelength bands based on high-density CNT arrays on a quartz
substrate. The CNT photodetector exhibits a high responsivity of 0.62
A/W and a large 3 dB bandwidth of 40 GHz (setup-limited) at 2 μm.
The bandwidth is larger than that of existing photodetectors working
in this wavelength range. Moreover, the CNT photodetector operating
at 1.55 μm exhibits a setup-limited 3 dB bandwidth over 67 GHz
at zero bias. Our work indicates that CNT photodetectors with high
performance and low cost have great potential for future high-speed
optical communication at both the 2 and 1.55 μm bands
High-Speed Compact Plasmonic-PdSe<sub>2</sub> Waveguide-Integrated Photodetector
Waveguide-integrated
photodetectors are essential components in
integrated photonic circuits since they facilitate light conversion
into electrical signals. Nonetheless, optical absorption and carrier
collection can significantly affect the device performance. As a solution
to this issue, plasmonic slot waveguides confine optical energy within
a subwavelength scale in a photoconductive detector, enhancing optical
absorption and providing extremely short channels to collect carriers.
Two-dimensional van der Waals layered palladium selenide (PdSe2) exhibits the merits of a narrow bandgap and high carrier
mobility, thus positioning it as a favorable candidate material for
photodetectors operating at the telecommunication band. In this study,
we propose and experimentally verify a high-speed PdSe2-plasmonic waveguide-integrated photodetector with a dark current
of 4.5 μA and an intrinsic responsivity of 560.1 mA·W−1 at 3 V. Additionally, it has an internal quantum
efficiency of 32.3%, and the measured 3 dB bandwidth is 17.5 GHz.
This integrated photodetector fulfills the requirements of various
critical applications in optical communication, microwave photonics,
sensing, and imaging