Broadband Optoelectronic Devices Research Articles

A facile approach towards fabrication and ultrabroad band emission properties of nickel ion-doped ZnAl2O4 transparent ceramics

We report the preparation method and broadband emission characteristics of nickel ion-doped ZnAl2O4 transparent ceramics. The transparent ceramics were prepared with melting-vaporing procedure, for the first time, to the best of our knowledge, and possesses the ultrabroad band emission spectra ranging from 1050 to 1550 nm under the excitation of a 980 nm laser. The analysis of crystal structure of this ceramics shows that the diffraction peaks of the crystal-phase match perfectly with ZnAl2O4 crystal. This material shows high luminance efficiency and has great potential for broad band optoelectronic materials and devices including optical coherence tomography imaging system and optical communication measurement instruments.

Broadband Passive Photonic Diodes With the Saturable Absorption in Antimony Thin Film

The low-dimensional nonlinear optical materials can provide a cost-effective and feasible way to realize the broadband optoelectronic devices. Here, we investigated the broadband nonlinear optical absorption of antimony thin film, and fabricated a broadband passive photonic diode with antimony thin film to achieve the all-optical nonreciprocal function with optical nonreciprocity factor about 5 dB at 780 nm and 2 dB at 1560 nm, respectively. The experimental results show the potential applications of antimony-based materials in broadband passive photonic diodes, and may make inroads for the cost-effective and reliable broadband optoelectronic devices.

Fast and Broadband Photoresponse of a Few-Layer GeSe Field-Effect Transistor with Direct Band Gaps.

Few-to-monolayer germanium selenide, a new IV-VI group layered material recently fabricated by mechanical exfoliation and subsequent laser thinning, is promising in very fast and broadband optoelectronic applications for its excellent stability, complicated band structures, inert surface properties, and being a natural p-type semiconductor. However, large-scale production of such few-layer GeSe devices with superior performance is still in early stages. In this study, field-effect transistors made of few-layer GeSe with direct band gaps are fabricated. Transistor performance with Schottky contact characteristics is measured at room temperature. A field-effect mobility of 4 cm2/(V s) and drain currents modulated both by holes and electrons are measured. Photoresponses as a function of illumination wavelength, power, and frequency are characterized. The few-layer GeSe transistor shows photoresponse to the illumination wavelengths from visible up to 1400 nm and a photoresponse rise (fall) time of 13 μs (19 μs), demonstrating very broadband and fast detection. The ambipolar behavior and the photoresponse characteristics demonstrate great potential of few-layer GeSe for applications in highly stable, very fast, and very broadband optoelectronic devices.

Broadband mid-infrared nonlinear optical modulator enabled by gold nanorods: towards the mid-infrared regime

Mid-infrared pulsed lasers operating around the 3 μm wavelength regime are important for a wide range of applications including sensing, spectroscopy, imaging, etc. Despite the recent advances in technology, the lack of a nonlinear optical modulator operating in the mid-infrared regime remains a significant challenge. Here, we report the third-order nonlinear optical response of gold nanorods (GNRs) ranging from 800 nm to the mid-infrared regime (2810 nm) enabled by their size and overlapping behavior-dependent longitudinal surface plasmon resonance. In addition, we demonstrate a wavelength-tunable Er3+-doped fluoride fiber laser modulated by GNRs, which can deliver pulsed laser output, with the pulse duration down to 533 ns, tunable wavelength ranging from 2760.2 to 2810.0 nm, and spectral 3 dB bandwidth of about 1 nm. The experimental results not only validate the GNRs’ robust mid-infrared nonlinear optical response, but also manifest their application potential in high-performance broadband optoelectronic devices.

PbS Quantum Dots/2D Nonlayered CdSxSe1–x Nanosheet Hybrid Nanostructure for High-Performance Broadband Photodetectors

Two-dimensional (2D) nonlayered nanomaterials have attracted extensive attention for electronic and optoelectronic applications recently because of their distinct properties. In this work, we first employed a facile one-step method to synthesize 2D nonlayered cadmium sulfide selenide (CdS xSe1- x, x = 0.33) nanosheets with a highly crystalline structure and then we introduced a generic spin-coating approach to fabricate hybrid nanomaterials composed of PbS quantum dots (QDs) and 2D CdS xSe1- x nanosheets and demonstrated their potential for high-performance broadband photodetectors. Compared with pure 2D CdS xSe1- x nanosheet photodetectors, the photoelectric performance of the PbS/CdS xSe1- x hybrid nanostructure is enhanced by 3 orders of magnitude under near-infrared (NIR) light illumination and maintains its performance in the visible (Vis) range. The photodetector exhibits a broadband response range from Vis to NIR with an ultrahigh light-to-dark current ratio (3.45 × 106), a high spectral responsivity (1.45 × 103 A/W), and high detectivity (1.05 × 1015 Jones). The proposed QDs/2D nonlayered hybrid nanostructure-based photodetector paves a promising way for next-generation high-performance broadband optoelectronic devices.

Broadband optoelectronic synaptic devices based on silicon nanocrystals for neuromorphic computing

Optically stimulated synaptic devices are critical to the development of neuromorphic computing with broad bandwidth and efficient interconnect. Although a few interesting materials have been employed to fabricate optically stimulated synaptic devices, the use of silicon (Si) that is the material of choice for very large-scale integration circuits in the conventional von Neumann computing has not been explored for optically stimulated synaptic devices. Here we take advantage of one of the most important nanostructures of Si — Si nanocrystals (NCs) to make synaptic devices, which can be effectively stimulated by light in the unprecedented broad spectral region from the ultraviolet to near-infrared, approaching the wavelength of ∼ 2 µm. These optically stimulated Si-NC-based synaptic devices demonstrate a series of important synaptic functionalities, well mimicking biological synapses. The plasticity of Si-NC-based synaptic devices originates from the dynamic trapping and release of photogenerated carriers at defects such as dangling bonds at the NC surface. The current facile use of Si NCs in broadband optoelectronic synaptic devices with low energy consumption has important implication for the large-scale deployment of Si in the emerging neuromorphic computing.

High-performance flexible and broadband photodetectors based on PbS quantum dots/ZnO nanoparticles heterostructure

Flexible and broadband photodetectors have drawn extensive attention due to their potential application in foldable displays, optical communications, environmental monitoring, etc. In this work, a flexible photodetector based on the crystalline PbS quantum dots (QDs)/ZnO nanoparticles (NPs) heterostructure was proposed. The photodetector exhibits a broadband response from ultraviolet-visible (UV-Vis) to near infrared detector (NIR) range with a remarkable current on/off ratio of 7.08×103 under 375 nm light illumination. Compared with pure ZnO NPs, the heterostructure photodetector shows the three orders of magnitude higher responsivity in Vis and NIR range, and maintains its performance in the UV range simultaneously. The photodetector demonstrates a high responsivity and detectivity of 4.54 A W−1 and 3.98×1012 Jones. In addition, the flexible photodetectors exhibit excellent durability and stability even after hundreds of times bending. This work paves a promising way for constructing next-generation high-performance flexible and broadband optoelectronic devices.

Wideband absorption in Thue–Morse quasiperiodic graphene-based hyperbolic metamaterials

A broadband absorber which was proposed by Thue–Morse structures containing graphene-based hyperbolic metamaterials (GHMM) is theoretically investigated. The Thue–Morse layer is composed of a lossy dielectric, conventional material layer, and GHMM. It is shown to absorb roughly 80% of all available electromagnetic waves at an 11 terahertz absorption bandwidth at normal angle incidence. The absorption bandwidth and absorptance is affected by incident angle, Fermi energy, and the thickness of dielectric. These findings can lead to the development of midinfrared photonic devices and have potential applications for designing broadband optoelectronic devices.

Wideband absorption in one dimensional photonic crystal with graphene-based hyperbolic metamaterials

A broadband absorber which was proposed by one dimensional photonic crystal (1DPC) containing graphene-based hyperbolic metamaterials (GHMM) is theoretically investigated. For TM mode, it was demonstrated to absorb roughly 90% of all available electromagnetic waves at a 14 THz absorption bandwidth at normal incidence. The absorption bandwidth was affected by Fermi energy and thickness of dielectric layer. When the incident angle was increased, the absorption value decreased, and the absorption band had a gradual blue shift. These findings have potential applications for designing broadband optoelectronic devices at mid-infrared and THz frequency range.

Stable High-Performance Flexible Photodetector Based on Upconversion Nanoparticles/Perovskite Microarrays Composite.

Methylammonium lead halide perovskite has emerged as a new class of low-temperature-processed high-performance semiconductors for optoelectronics, but with photoresponse limited to the UV-visible region and low environmental stability. Herein, we report a flexible planar photodetector based on MAPbI3 microarrays integrated with NaYF4:Yb/Er upconversion nanoparticles (UCns) that offers promise for future high performance and long-term environmental stability. The promise derives from the confluence of several factors, including significantly enhanced photons absorption in the visible spectrum, efficient energy transition in the near-infrared (NIR) region, and inhibition of water attack by the hydrophobic UCns capping layer. The UCns layer aided in remarkably enhanced photodetection capability in the visible spectrum with detectivity (D*) reaching 5.9 × 1012 Jones, among the highest reported values, due to the increased photocarrier lifetime and decreased reflectivity. Excellent NIR photoresponse with spectral responsivity (R) and D* as high as 0.27 A W-1 and 0.76 × 1012 Jones were obtained at 980 nm, respectively, superior to the reported values of state-of-the-art organic-perovskite NIR photodetectors. Moreover, the hydrophobic UCns capping layer serving as a moisture inhibitor allowed significantly enhanced long-term environmental stability, e.g., 70% vs 27% performance retained after 1000 h exposure in 30-40% RH humidity air without encapsulation for the bilayer and the neat MAPbI3 devices, respectively. These results suggest that the composite based on perovskite and UCns is promising for constructing high-performance broadband optoelectronic devices with long-term stability.

Investigate the effects of EG doping PEDOT/PSS on transmission and anti-reflection properties using terahertz pulsed spectroscopy

The conductivity of poly(3,4-ethylene dioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS) is significantly enhanced on adding some organic solvent such as ethylene glycol (EG). In this paper, the optoelectronic properties of EG doped PEDOT/PSS on transmission and anti-reflection effects are investigated in detail by terahertz time domain spectroscopy (THz-TDS). The transmission line circuit theory gives us an insight into the THz transmission mechanisms of the main and second pulses. In particular, we show that the conductivities of 10% EG doped PEDOT/PSS are nearly frequency independent from 0.3 to 1.5 THz. To demonstrate applications of this property, we design and fabricate broadband terahertz neutral density filters and anti-reflection coatings based on 10% EG doped PEDOT/PSS thin films with varying thickness. Our measurements highlight the capability of THz-TDS to characterize the conductivity of EG doped PEDOT/PSS, which is essential for broadband optoelectronic devices in THz region.

Ultrafast photocurrents at the surface of the three-dimensional topological insulator Bi2Se3.

Three-dimensional topological insulators are fascinating materials with insulating bulk yet metallic surfaces that host highly mobile charge carriers with locked spin and momentum. Remarkably, surface currents with tunable direction and magnitude can be launched with tailored light beams. To better understand the underlying mechanisms, the current dynamics need to be resolved on the timescale of elementary scattering events (∼10 fs). Here, we excite and measure photocurrents in the model topological insulator Bi2Se3 with a time resolution of 20 fs by sampling the concomitantly emitted broadband terahertz (THz) electromagnetic field from 0.3 to 40 THz. Strikingly, the surface current response is dominated by an ultrafast charge transfer along the Se–Bi bonds. In contrast, photon-helicity-dependent photocurrents are found to be orders of magnitude smaller than expected from generation scenarios based on asymmetric depopulation of the Dirac cone. Our findings are of direct relevance for broadband optoelectronic devices based on topological-insulator surface currents.

Wideband absorption in fibonacci quasi-periodic graphene-based hyperbolic metamaterials

A heterostructure containing a Fibonacci quasi-periodic layer and a resonant metal back reflector is proposed, which can realize wideband absorption. The Fibonacci layer is composed of graphene-based hyperbolic metamaterials and isotropic media to obtain wideband absorption. To enhance absorption, an impedance-matching layer is put on top of the Fibonacci layer. It is shown to absorb roughly 90% of all available electromagnetic waves in an 11 terahertz absorption bandwidth for a transverse magnetic mode at normal angle incidence. The absorption bandwidth is affected by the reflection band gap. Compared with some previous designs, our proposed structure has a larger absorption bandwidth and higher absorption in the mid-infrared range. The results should be valuable in the design of infrared stealth and broadband optoelectronic devices.

All-optical control of ultrafast photocurrents in unbiased graphene.

Graphene has recently become a unique playground for studying light-matter interaction effects in low-dimensional electronic systems. Being of strong fundamental importance, these effects also open a wide range of opportunities in photonics and optoelectronics. In particular, strong and broadband light absorption in graphene allows one to achieve high carrier densities essential for observation of nonlinear optical phenomena. Here, we make use of strong photon-drag effect to generate and optically manipulate ultrafast photocurrents in graphene at room temperature. In contrast to the recent reports on injection of photocurrents in graphene due to external or built-in electric field effects and by quantum interference, we force the massless charge carriers to move via direct transfer of linear momentum from photons of incident laser beam to excited electrons in unbiased sample. Direction and amplitude of the drag-current induced in graphene are determined by polarization, incidence angle and intensity of the obliquely incident laser beam. We also demonstrate that the irradiation of graphene with two laser beams of the same wavelength offers an opportunity to manipulate the photocurrents in time domain. The obtained all-optical control of the photocurrents opens new routes towards graphene based high-speed and broadband optoelectronic devices.

A New Method for Measuring the Frequency Response of Broadband Optoelectronic Devices

A new and simple method based on the frequency-sweep method for measuring the frequency response of broadband optoelectronic devices is demonstrated. The electro-absorption modulator (EAM) can function as both modulator and receiver with the same frequency response. With this property, the frequency responses of a distributed feedback (DFB) laser at different bias currents were measured from dc to 20 GHz by the method. The results were quite identical with the results measured by the frequency-sweep method with broadband photodetector. Besides, the measurement bandwidth is not limited by the bandwidths of the devices, and the results are not influenced by the bandwidths of the EAM or other devices.

Graphene Photonics, Plasmonics, and Broadband Optoelectronic Devices

Graphene has been hailed as a wonderful material in electronics, and recently, it is the rising star in photonics, as well. The wonderful optical properties of graphene afford multiple functions of signal emitting, transmitting, modulating, and detection to be realized in one material. In this paper, the latest progress in graphene photonics, plasmonics, and broadband optoelectronic devices is reviewed. Particular emphasis is placed on the ability to integrate graphene photonics onto the silicon platform to afford broadband operation in light routing and amplification, which involves components like polarizer, modulator, and photodetector. Other functions like saturable absorber and optical limiter are also reviewed.