Optical Transistor Research Articles

Optical Transistor for Amplification of Radiation in a Broadband Terahertz Domain.

We propose a new type of optical transistor for a broadband amplification of terahertz radiation. It is made of a graphene-superconductor hybrid, where electrons and Cooper pairs couple by Coulomb forces. The transistor operates via the propagation of surface plasmons in both layers, and the origin of amplification is the quantum capacitance of graphene. It leads to terahertz waves amplification, the negative power absorption, and as a result, the system yields positive gain, and the hybrid acts like an optical transistor, operating with the terahertz light. It can, in principle, amplify even a whole spectrum of chaotic signals (or noise), which is required for numerous biological applications.

Dual-gate transistor amplifier in a multimode optomechanical system.

We present a dual-gate optical transistor based on a multimode optomechanical system, composed of three indirectly coupled cavities and an intermediate mechanical resonator pumped by a frequency-matched field. In this system, two cavities driven on the red mechanical sidebands are regarded as input/ouput gates/poles and the third one on the blue sideband as a basic/control gate/pole, while the resonator as the other basic/control gate/pole. As a nonreciprocal scheme, the significant unidirectional amplification can be resulted by controlling the two control gates/poles. In particular, the nonreciprocal direction of the optical amplification/rectification can be controlled by adjusting the phase differences between two red-sideband driving fields (the pumping and probe fields). Meanwhile, the narrow window that can be analyzed by the effective mechanical damping rate, arises from the extra blue-sideband cavity. Moreover, the tunable slow/fast light effect can be observed, i.e, the group velocity of the unidirectional transmission can be controlled, and thus the switching scheme of slow/fast light effect can also utilized to realize both slow and fast lights through opposite propagation directions, respectively. Such an amplification transistor scheme of controllable amplitude, direction and velocity may imply exciting opportunities for potential applications in photon networks and quantum information processing.

Artificial Synapses: Near‐Infrared‐Irradiation‐Mediated Synaptic Behavior from Tunable Charge‐Trapping Dynamics (Adv. Electron. Mater. 2/2020)

In article number 1900765, Vellaisamy A. L. Roy, Ye Zhou, Su-Ting Han, and co-workers demonstrate a photonic synaptic transistor based on a tunable charge-trapping medium. The device senses and responds to near-infrared light signals, and can mimic memorization and dynamic forgetting processes, enabling device-level synaptic evolution from short-term to long-term neuroplasticity.

Temperature- and thickness-dependence of robust out-of-plane ferroelectricity in CVD grown ultrathin van der Waals α-In2Se3 layers

Two-dimensional (2D) ferroelectric materials with unique structure and extraordinary optoelectrical properties have attracted intensive research in the field of nanoelectronic and optoelectronic devices, such as optical sensors, transistors, photovoltaics and non-volatile memory devices. However, the transition temperature of the reported ferroelectrics in 2D limit is generally low or slightly above room temperature, hampering their applications in high-temperature electronic devices. Here, we report the robust high-temperature ferroelectricity in 2D α-In2Se3, grown by chemical vapor deposition (CVD), exhibiting an out-of-plane spontaneous polarization reaching above 200 °C. The polarization switching and ferroelectric domains are observed in In2Se3 nanoflakes in a wide temperature range. The coercive field of the CVD grown ferroelectric layers illustrates a room-temperature thickness dependency and increases drastically when the film thickness decreases; whereas there is no large variance in the coercive field at different temperature from the samples with identical thickness. The results show the stable ferroelectricity of In2Se3 nanoflakes maintained at high temperature and open up the opportunities of 2D materials for novel applications in high-temperature nanoelectronic devices.

Proposed GaAs and Si OPFET Photodetectors for Solar Cell Applications

The potential of the GaAs and Si-based Optical Field Effect Transistor (OPFET) photodetectors for use in solar cell applications has been examined. The solar power spectrum with the air mass (AM0) suitable for satellite and space vehicle applications is provided as an input. The detectors closely reproduce the input spectrum while delivering sufficient output current with high responsivity, External Quantum Efficiency (EQE), and low switching times. These parameters along with the photovoltage generated as a function of wavelength are plotted and deeply analyzed. The comparative study of the Si and the GaAs OPFET detectors is presented. The analysis is based on the structural, material parameters, and the external factors applied. The gate materials utilized are Indium-Tin-Oxide (ITO) for Si and gold (Au) for GaAs. Two distinct illumination models: Buried-gate front-illuminated OPFET and the generalized model of OPFET are being considered for the study. The proposed devices show great potential for solar cell applications.

A multilevel vertical photonic memory transistor based on organic semiconductor/inorganic perovskite quantum dot blends

A vertical photonic memory transistor based on organic semiconductor/inorganic perovskite quantum dots blends was fabricated, which presents new routes for low operational conditions for high-performance photonic memory with high storage density.

Long-range Graphene Surface Plasmon Polariton induced Tunable Optical Bistability in Terahertz Range

An idea towards the low threshold optical bistability and tunability of bistable thresholds at THz frequency under realistic situation is analyzed through a proposed multilayered configuration. The proposed configuration comprises a coupling prism of silicon, and monolayer graphene sheets spatially separated through 35 nm thick polymer which is sandwiched between an air gap of thickness 4.6 μm and a kerr polymer (GaAs) at 300 K temperature and at an incident light frequency of 2 THz. Utilizing the large nonlinear effect of the configuration obtained by the nonlinearity of the kerr polymer and the high local field effect due to long-range graphene surface plasmon resonance, the switching-down and switching-up threshold values for optical bistability have been markedly reduced upto 1.21×105 V/m and 1.24×105 V/m respectively thereby rendering a minimum threshold intensity of 7.2 kW/cm2 than the articles reported till date. Tunability of the switching-down and switching-up threshold values have also been realized from 1.21×105 V/m to 5.18×105 V/m and 1.24×105 V/m to 1.424×106 V/m respectively through electrical or chemical modification of the charge carrier density and hence fermi energy of the graphene from 0.23 eV to 0.41 eV and from 1.21×105 V/m to 1.56×105 V/m and 1.24×105 V/m to 2.12×105 V/m respectively for the variation in incident angle from 70° to 88°. The effect of damping rate of graphene on optical bistability behavior has also been observed. Therefore the proposed optical bistable configuration finds potential applications in the field of all-optical switching, optical transistor, optical logic, nano-illumination and optical memory with low input threshold at THz frequency and can also be used to realize tunable optical bistable device for future THz optical communication technology.

Optical transistor and router application of Autler–Townes-splitting in various solid atomic-like media

We compare the Autler–Townes (AT)-splitting in E u 3 + : Y P O 4 , P r 3 + : Y P O 4 , and P r 3 + : Y 2 S i O 5 crystals. The AT-splitting in P r 3 + : Y 2 S i O 5 is stronger than other two-doped crystals, while the P r 3 + ion has a stronger dressing than the E u 3 + ion in a host material of YPO. The stronger dressing in YSO is attributed to the C 2 h symmetry of the YSO crystal and its nondegeneracy, making the dressing sensitive to doped material. By investigating the relationship between spectral AT-splitting (SAT-splitting) and temporal AT-splitting (TAT-splitting), we observed that TAT-splitting depends upon the dressing effect and phonon-assisted nonradiative transition whereas SAT-splitting results only from the dressing effect. Based on our results, we proposed a model for an optical router and transistor (amplifier and switch). The router action results from the SAT- and TAT-splitting while the transistor was realized by a switch from bright to dark dressed states.

Fast, Infrared-Active Optical Transistors Based on Dye-Sensitized CdSe Nanocrystals.

We report an optically gated transistor composed of CdSe nanocrystals (NCs), sensitized with the dye zinc β-tetraaminophthalocyanine for operation in the first telecom window. This device shows a high ON/OFF ratio of 6 orders of magnitude in the red spectral region and an unprecedented 4.5 orders of magnitude at 847 nm. By transient absorption spectroscopy, we reveal that this unexpected infrared sensitivity is due to electron transfer from the dye to the CdSe NCs within 5 ps. We show by time-resolved photocurrent measurements that this enables fast rise times during near-infrared optical gating of 47 ± 11 ns. Electronic coupling and accelerated nonradiative recombination of charge carriers at the interface between the dye and the CdSe NCs are further corroborated by steady-state and time-resolved photoluminescence measurements. Field-effect transistor measurements indicate that the increase in photocurrent upon laser illumination is mainly due to the increase in the carrier concentration while the mobility remains unchanged. Our results illustrate that organic dyes as ligands for NCs invoke new optoelectronic functionalities, such as fast optical gating at sub-bandgap optical excitation energies.

Highly Efficient Ionic Photocurrent Generation through WS2 -Based 2D Nanofluidic Channels.

The unique feature of nacre-like 2D layered materials provides a facile, yet highly efficient way to modulate the transmembrane ion transport from two orthogonal transport directions, either vertical or horizontal. Recently, light-driven active transport of ionic species in synthetic nanofluidic systems attracts broad research interest. Herein, taking advantage of the photoelectric semiconducting properties of 2D transition metal dichalcogenides, the generation of a directional and greatly enhanced cationic flow through WS2 -based 2D nanofluidic membranes upon asymmetric visible light illumination is reported. Compared with graphene-based materials, the magnitude of the ionic photocurrent can be enhanced by tens of times, and its photo-responsiveness can be 2-3.5 times faster. This enhancement is explained by the coexistence of semiconducting and metallic WS2 nanosheets in the hybrid membrane that facilitates the asymmetric diffusion of photoexcited charge carriers on the channel wall, and the high ionic conductance due to the neat membrane structure. To further demonstrate its application, photonic ion switches, photonic ion diodes, and photonic ion transistors as the fundamental elements for light-controlled nanofluidic circuits are further developed. Exploring new possibilities in the family of liquid processable colloidal 2D materials provides a way toward high-performance light-harvesting nanofluidic systems for artificial photosynthesis and sunlight-driven desalination.

Photoinduced Directional Proton Transport through Printed Asymmetric Graphene Oxide Superstructures: A New Driving Mechanism under Full‐Area Light Illumination

Abstract2D‐material‐based membranes with densely packed sub‐nanometer‐height fluidic channels show exceptional transport properties, and have attracted broad research interest for energy‐, environment‐, and healthcare‐related applications. Recently, light‐controlled active transport of ionic species in abiotic materials have received renewed attention. However, its dependence on inhomogeneous or site‐specific illumination is a challenge for scalable application. Here, directional proton transport through printed asymmetric graphene oxide superstructures (GOSs) is demonstrated under full‐area illumination. The GOSs are composed of partially stacked graphene oxide multilayers formed by a two‐step direct ink writing process. The direction of the photoinduced proton current is determined by the position of top graphene oxide multilayers, which functions as a photogate to modulate the horizontal ion transport through the beneath lamellar nanochannels. This transport phenomenon unveils a new driving mechanism that, in asymmetric nanofluidic structures, the decay of local light intensity in depth direction breaks the balance of electric potential distribution in horizontal direction, and thus generates a photoelectric driving force for ion transport. Following this mechanism, the GOSs are developed into photonic ion transistors with three different gating modes. The asymmetrically printed photonic‐ionic devices provide fundamental elements for light‐harvesting nanofluidic circuits, and may find applications for artificial photosynthesis and artificial electric organs.

All-optical switch and transistor based on coherent light-controlled single two-level atom coupling with two nanowires**Project supported by the National Natural Science Foundation of China (Grant Nos. 11864018 and 11574229), the Scientific Research Foundation of Education Department of Jiangxi Province, China (Grant No. GJJ170645), and the Doctor Startup Fund of the Natural Science of Jinggangshan University, China (Grant No. JZB16003).

Atom–nanowire coupling system is a promising platform for optical quantum information processing. Unlike the previous designing of optical switch and transistor requiring a dedicated multi-level emitter and high fineness microcavity, a new proposal is put forward which contains a single two-level atom asymmetrically coupled with two nanowires. Single-emitter manipulation of photonic signals for bilateral coherent incident is clear now, since we specify atomic saturation nonlinearity into three contributions which brings us a new approach to realizing light-controlled-light at weak light and single-atom levels. An efficient optically controllable switch based on self-matching-induced-block and a concise optical transistor are proposed. Our findings show potential applications in full-optical devices.

12 GHz spontaneous optical bandwidth tunnel junction light-emitting transistor

In this report, a quantum-well based light-emitting transistor with an Al0.1Ga0.9As/In0.05Ga0.95As tunnel junction collector in a common-emitter configuration with a double-digit gigahertz optical −3 dB bandwidth (f−3 dB) is demonstrated. Both the electrical and optical characteristics and the corresponding carrier dynamics are investigated. From microwave measurements, a −3 dB bandwidth up to 12.6 GHz via direct voltage (field) modulation is exhibited when the device is operated in a negative differential resistance state. The voltage-modulated optical characteristics are sensitive to the operation of the base-collector tunnel junction. The “enhanced single-pole optical response” can be attributed to the modulation amplitude decay at low frequencies due to the high impedance at the base-collector junction.

Multilevel Photonic Transistor Memory Devices Using Conjugated/Insulated Polymer Blend Electrets.

Photonic data storage has diverse optoelectronic applications such as optical sensing and recording, integrated image circuits, and multibit-storage flash memory. In this study, we employ conjugated/insulated polymer blends as the charge storage electret for photonic field-effect transistor memory devices by exploring the blend composition, energy level alignment, and morphology on the memory characteristics. The studied conjugated polymers included poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PF), poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), poly[{2,5-di(3',7'-dimethyloctyloxy)-1,4-phenylene-vinylene}-co-{3-(4'-(3″,7″-dimethyloctyloxy)phenyl)-1,4-phenylenevinylene}-co-{3-(3'-(3',7'-dimethyloctyloxy)phenyl)-1,4-phenylenevinylene}] (SY-PPV), and poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,8-diyl)] (F8BT), and the insulated polymers were polystyrene (PS) and poly(methyl methacrylate) (PMMA). The photonic memory device using the PF/PS blend electret exhibited a dynamic switching behavior with light-writing and voltage-erasing processes both within only 1 s, along with a high contrast on the current on/off ratio between "Photo-On" and "Electrical-OFF" over 106 and the decent retention time for more than 3 months. In addition, the multilevel memory behavior could be observed using different light sources of 405, 450, and 520 nm or energy intensity, which was supported by surface potential analysis. The characteristics were superior to those of the devices using PF/PMMA blend due to the higher charge storage behavior of PS supported by fluorescence analysis. The PF/PS blend film prepared from the chlorobenzene solvent exhibited mesh-like and aggregated PF domains in the PS matrix and enhanced the contact surface area between the semiconductor and blend electret, leading to a higher memory window. The photonic memory behavior was also observed in the blend electrets of PS with the low band gap polymer, MEH-PPV, SY-PPV, or F8BT, by changing the photoresponsive light sources. Our study demonstrated a new electret system to apply on the multilevel photonic memory devices.

Off-Resonance Control and All-Optical Switching: Expanded Dimensions in Nonlinear Optics

The theory of non-resonant optical processes with intrinsic optical nonlinearity, such as harmonic generation, has been widely understood since the advent of the laser. In general, such effects involve multiphoton interactions that change the population of each input optical mode or modes. However, nonlinear effects can also arise through the input of an off-resonant laser beam that itself emerges unchanged. Many such effects have been largely overlooked. Using a quantum electrodynamical framework, this review provides detail on such optically nonlinear mechanisms that allow for a controlled increase or decrease in the intensity of linear absorption and fluorescence and in the efficiency of resonance energy transfer. The rate modifications responsible for these effects were achieved by the simultaneous application of an off-resonant beam with a moderate intensity, acting in a sense as an optical catalyst, conferring a new dimension of optical nonlinearity upon photoactive materials. It is shown that, in certain configurations, these mechanisms provide the basis for all-optical switching, i.e., the control of light-by-light, including an optical transistor scheme. The conclusion outlines other recently proposed all-optical switching systems.

Multi-spectral gate-triggered heterogeneous photonic neuro-transistors for power-efficient brain-inspired neuromorphic computing

For the realization of low-power consumption brain-inspired neuromorphic computing devices which mimic the biological neuronal information processing methodology, the development of photonic transistors capable of synaptic behaviors and neuronal computation have attracted lots of interests. Here, metal-chalcogenide (MC)/metal-oxide (MO) heterogeneous photonic neuro-transistors capable of multi-spectrum triggered synaptic responses and corresponding neuronal computation were developed for an intelligent and energy efficient neuromorphic device. The photonic transistor architecture including a solution-processed broadband photo-active heterogeneous channel and electronic modulatory terminal enable to establish power-saved multi-level writing/reading processing. The multi-spectral gate-triggerings and their synaptic responses were emulated via the broadband absorbing MC/MO heterogeneous semiconducting structure and its defective hetero-interface, which can be fine-tuned by varying photo-spectrum of applied spikes and controlling of interfacial traps in-between, respectively. More importantly, the multi-spectrum triggered heterogeneous photonic neuro-transistors can facilitate wider dynamic and more intelligent neuronal computation such as multi-level dendritic summation and fire behaviors, logic-computation, and associated learning beyond conventional simple synaptic-level photonic devices. The results reported here argue that the multi-spectral activated heterogeneous photonic neuro-transistor outperforms current state-of-neuro-devices, provide a facile and generic route to achieve high-density and energy efficient neuromorphic system.

Optomechanically induced transparency and nonlinear responses based on graphene optomechanics system

Due to its unique properties of low mass density, high frequency, high quality-factor and intrinsically small size, graphene has received significant attention and is considered as an ideal material for fabricating nanomechanical systems. In this work, we demonstrate theoretically the coherent optical propagation under different detuning regimes in the graphene resonator-microwave cavity system. In the red detuning, optomechanically induced transparency induced the slow light effect is investigated and the maximum group delay can reach 0.4 ms. In the blue detuning, advancing microwave signal can reach 0.12 ms, and the parametric amplification process can behave as an optical transistor to amplify a weak microwave field via manipulating the pump field. Further, we research the nonlinear effects of four-wave mixing (FWM), and the FWM intensity can be efficiently controlled and modulated by the pump power, such as FWM spectrum can present the phenomenon of normal mode splitting with controlling the pump power. A straightforward optical means for determining the frequency of the resonator by the FWM spectrum is also presented. The graphene optomechanics may indicate applications in quantum information processing.

Hyperparallel transistor, router and dynamic random access memory with unity fidelities.

We theoretically implement some hyperparallel optical elements, including quantum single photon transistor, router, and dynamic random access memory (DRAM). The inevitable side leakage and the imperfect birefringence of the quantum dot (QD)-cavity mediates are taken into account, and unity fidelities of our optical elements can be achieved. The hyperparallel constructions are based on polarization and spatial degrees of freedom (DOFs) of the photon to increase the parallel efficiency, improve the capacity of channel, save the quantum resources, reduce the operation time, and decrease the environment noises. Moreover, the practical schemes are robust against the side leakage and the coupling strength limitation in the microcavities.

Scalable in operando strain tuning in nanophotonic waveguides enabling three-quantum-dot superradiance.

The quest for an integrated quantum optics platform has motivated the field of semiconductor quantum dot research for two decades. Demonstrations of quantum light sources, single photon switches, transistors and spin-photon interfaces have become very advanced. Yet the fundamental problem that every quantum dot is different prevents integration and scaling beyond a few quantum dots. Here, we address this challenge by patterning strain via local phase transitions to selectively tune individual quantum dots that are embedded in a photonic architecture. The patterning is implemented with in operando laser crystallization of a thin HfO2 film 'sheath' on the surface of a GaAs waveguide. Using this approach, we tune InAs quantum dot emission energies over the full inhomogeneous distribution with a step size down to the homogeneous linewidth and a spatial resolution better than 1 µm. Using these capabilities, we tune multiple quantum dots into resonance within the same waveguide and demonstrate a quantum interaction via superradiant emission from three quantum dots.

Manipulating visible signal with plasmonic-based optical transistor: A new application to amplification

In this work, a visible signal of 380 nm to 740 nm is manipulated with plasmonic-based transistor structure to realize an amplifying application. The outcomes of the three-layer structure show excellent properties pertaining to the immense intensity or colossal amplification of the signal at the plasmonic layer. The simulation output, which is carried out using finite difference time domain method shows that a feeble intensity is fetched with respect to violet, blue, green, yellow, orange, regime, however, a massive intensity is going and get to the same layer pertaining to red spectrum. Further,a thorough investigation is made for the signal of 625 nm–740 nm (red signal regime) and a linear variation is developed between intensity and wavelength for the red regime. Finally, a linear variation is developed between amplifying intensity with respect to the wavelength of the red signal.