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Original Article|68 Article(s)
Light-triggered interfacial charge transfer and enhanced photodetection in CdSe/ZnS quantum dots/MoS2 mixed-dimensional phototransistors
Ziwei Li, Wen Yang, Ming Huang, Xin Yang, Chenguang Zhu, Chenglin He, Lihui Li, Yajuan Wang, Yunfei Xie, Zhuoran Luo, Delang Liang, Jianhua Huang, Xiaoli Zhu, Xiujuan Zhuang, Dong Li, and Anlian Pan
Mix-dimensional van der Waals heterostructures (vdWHs) have inspired worldwide interests and efforts in the field of advanced electronics and optoelectronics. The fundamental understanding of interfacial charge transfer is of vital importance for guiding the design of functional optoelectronic applications. In this work, type-II 0D-2D CdSe/ZnS quantum dots/MoS2 vdWHs are designed to study the light-triggered interfacial charge behaviors and enhanced optoelectronic performances. From spectral measurements in both steady and transient states, the phenomena of suppressed photoluminescence (PL) emissions, shifted Raman signals and changed PL lifetimes provide strong evidences of efficient charge transfer at the 0D-2D interface. A series of spectral evolutions of heterostructures with various QDs overlapping concentrations at different laser powers are analyzed in details, which clarifies the dynamic competition between exciton and trion during an efficient doping of 3.9×1013 cm-2. The enhanced photoresponses (1.57×104 A·W–1) and detectivities (2.86×1011 Jones) in 0D/2D phototransistors further demonstrate that the light-induced charge transfer is still a feasible way to optimize the performance of optoelectronic devices. These results are expected to inspire the basic understanding of interfacial physics at 0D/2D interfaces, and shed the light on promoting the development of mixed-dimensional optoelectronic devices in the near future. Mix-dimensional van der Waals heterostructures (vdWHs) have inspired worldwide interests and efforts in the field of advanced electronics and optoelectronics. The fundamental understanding of interfacial charge transfer is of vital importance for guiding the design of functional optoelectronic applications. In this work, type-II 0D-2D CdSe/ZnS quantum dots/MoS2 vdWHs are designed to study the light-triggered interfacial charge behaviors and enhanced optoelectronic performances. From spectral measurements in both steady and transient states, the phenomena of suppressed photoluminescence (PL) emissions, shifted Raman signals and changed PL lifetimes provide strong evidences of efficient charge transfer at the 0D-2D interface. A series of spectral evolutions of heterostructures with various QDs overlapping concentrations at different laser powers are analyzed in details, which clarifies the dynamic competition between exciton and trion during an efficient doping of 3.9×1013 cm-2. The enhanced photoresponses (1.57×104 A·W–1) and detectivities (2.86×1011 Jones) in 0D/2D phototransistors further demonstrate that the light-induced charge transfer is still a feasible way to optimize the performance of optoelectronic devices. These results are expected to inspire the basic understanding of interfacial physics at 0D/2D interfaces, and shed the light on promoting the development of mixed-dimensional optoelectronic devices in the near future.
Opto-Electronic Advances
- Publication Date: Sep. 25, 2021
- Vol. 4, Issue 9, 210017-1 (2021)
Nano-buffer controlled electron tunneling to regulate heterojunctional interface emission
Wei Liu, Zhuxin Li, Zengliang Shi, Ru Wang, Yizhi Zhu, and Chunxiang Xu
Interface emission from heterojunction is a shortcoming for electroluminescent devices. A buffer layer introduced in the heterojunctional interfaces is a potential solution for the challenge. However, the dynamics for carrier tunneling to control the interface emission is still a mystery. Herein, the low-refractive HfO2 with a proper energy band configuration is employed as the buffer layer in achieving ZnO-microwire/HfO2/GaN heterojunctional light-emitting diodes (LEDs). The optically pumped lasing threshold and lifetime of the ZnO microwire are reduced with the introduced HfO2 layer. As a result, the interface emission is of blue-shift from visible wavelengths to 394 nm whereas the ultraviolet (UV) emission is enhanced. To regulate the interface recombination between electrons in the conduction band of ZnO and holes in the valence band of GaN, the tunneling electrons with higher conduction band are employed to produce a higher tunneling current through regulation of thin HfO2 film causing blue shift and interface emission enhancement. Our results provide a method to control the tunneling electrons in heterojunction for high-performance LEDs. Interface emission from heterojunction is a shortcoming for electroluminescent devices. A buffer layer introduced in the heterojunctional interfaces is a potential solution for the challenge. However, the dynamics for carrier tunneling to control the interface emission is still a mystery. Herein, the low-refractive HfO2 with a proper energy band configuration is employed as the buffer layer in achieving ZnO-microwire/HfO2/GaN heterojunctional light-emitting diodes (LEDs). The optically pumped lasing threshold and lifetime of the ZnO microwire are reduced with the introduced HfO2 layer. As a result, the interface emission is of blue-shift from visible wavelengths to 394 nm whereas the ultraviolet (UV) emission is enhanced. To regulate the interface recombination between electrons in the conduction band of ZnO and holes in the valence band of GaN, the tunneling electrons with higher conduction band are employed to produce a higher tunneling current through regulation of thin HfO2 film causing blue shift and interface emission enhancement. Our results provide a method to control the tunneling electrons in heterojunction for high-performance LEDs.
Opto-Electronic Advances
- Publication Date: Sep. 25, 2021
- Vol. 4, Issue 9, 200064-1 (2021)
Water-sensitive multicolor luminescence in lanthanide-organic framework for anti-counterfeiting
Tifeng Xia, Wenqian Cao, Yuanjing Cui, Yu Yang, and Guodong Qian
The development of high-level anti-counterfeiting techniques is of great significance in economics and security issues. However, intricate reading methods are required to obtain multi-level information stored in different colors, which greatly limits the application of anti-counterfeiting technology on solving real world problems. Herein, we realize multicolor information anti-counterfeiting under simply external stimulation by utilizing the functional groups and multiple emission centers of lanthanide metal organic framework (Ln-MOFs) to tune luminescence color. Water responsive multicolor luminescence represented by both the tunable color from red to blue within the visible region and high sensitive responsivity has been achieved, owing to the increased nonradiative decay pathways and enhanced Eu3+-to-ligand energy back transfer. Remarkably, information hidden in different colors needs to be read with a specific water content, which can be used as an encryption key to ensure the security of the information for high-level anti-counterfeiting. The development of high-level anti-counterfeiting techniques is of great significance in economics and security issues. However, intricate reading methods are required to obtain multi-level information stored in different colors, which greatly limits the application of anti-counterfeiting technology on solving real world problems. Herein, we realize multicolor information anti-counterfeiting under simply external stimulation by utilizing the functional groups and multiple emission centers of lanthanide metal organic framework (Ln-MOFs) to tune luminescence color. Water responsive multicolor luminescence represented by both the tunable color from red to blue within the visible region and high sensitive responsivity has been achieved, owing to the increased nonradiative decay pathways and enhanced Eu3+-to-ligand energy back transfer. Remarkably, information hidden in different colors needs to be read with a specific water content, which can be used as an encryption key to ensure the security of the information for high-level anti-counterfeiting.
Opto-Electronic Advances
- Publication Date: Aug. 25, 2021
- Vol. 4, Issue 8, 200063-1 (2021)
Tunable surface plasmon-polariton resonance in organic light-emitting devices based on corrugated alloy electrodes
Xue-Mei Wen, Yan-Gang Bi, Fang-Shun Yi, Xu-Lin Zhang, Yue-Feng Liu, Wen-Quan Wang, Jing Feng, and Hong-Bo Sun
We report a feasible method to realize tunable surface plasmon-polariton (SPP) resonance in organic light-emitting devices (OLEDs) by employing corrugated Ag-Al alloy electrodes. The excited SPP resonance induced by the periodic corrugations can be precisely tuned based on the composition ratios of the Ag-Al alloy electrodes. With an appropriate composition ratio of the corrugated alloy electrode, the photons trapped in SPP modes are recovered and extracted effectively. The 25% increasement in luminance and 21% enhancement in current efficiency have been achieved by using the corrugated Ag-Al alloy electrodes in OLEDs. We report a feasible method to realize tunable surface plasmon-polariton (SPP) resonance in organic light-emitting devices (OLEDs) by employing corrugated Ag-Al alloy electrodes. The excited SPP resonance induced by the periodic corrugations can be precisely tuned based on the composition ratios of the Ag-Al alloy electrodes. With an appropriate composition ratio of the corrugated alloy electrode, the photons trapped in SPP modes are recovered and extracted effectively. The 25% increasement in luminance and 21% enhancement in current efficiency have been achieved by using the corrugated Ag-Al alloy electrodes in OLEDs.
Opto-Electronic Advances
- Publication Date: Aug. 25, 2021
- Vol. 4, Issue 8, 200024-1 (2021)
High-Q resonances governed by the quasi-bound states in the continuum in all-dielectric metasurfaces
Cizhe Fang, Qiyu Yang, Qingchen Yuan, Xuetao Gan, Jianlin Zhao, Yao Shao, Yan Liu, Genquan Han, and Yue Hao
The realization of high-Q resonances in a silicon metasurface with various broken-symmetry blocks is reported. Theoretical analysis reveals that the sharp resonances in the metasurfaces originate from symmetry-protected bound in the continuum (BIC) and the magnetic dipole dominates these peculiar states. A smaller size of the defect in the broken-symmetry block gives rise to the resonance with a larger Q factor. Importantly, this relationship can be tuned by changing the structural parameter, resulting from the modulation of the topological configuration of BICs. Consequently, a Q factor of more than 3,000 can be easily achieved by optimizing dimensions of the nanostructure. At this sharp resonance, the intensity of the third harmonic generation signal in the patterned structure can be 368 times larger than that of the flat silicon film. The proposed strategy and underlying theory can open up new avenues to realize ultrasharp resonances, which may promote the development of the potential meta-devices for nonlinearity, lasing action, and sensing. The realization of high-Q resonances in a silicon metasurface with various broken-symmetry blocks is reported. Theoretical analysis reveals that the sharp resonances in the metasurfaces originate from symmetry-protected bound in the continuum (BIC) and the magnetic dipole dominates these peculiar states. A smaller size of the defect in the broken-symmetry block gives rise to the resonance with a larger Q factor. Importantly, this relationship can be tuned by changing the structural parameter, resulting from the modulation of the topological configuration of BICs. Consequently, a Q factor of more than 3,000 can be easily achieved by optimizing dimensions of the nanostructure. At this sharp resonance, the intensity of the third harmonic generation signal in the patterned structure can be 368 times larger than that of the flat silicon film. The proposed strategy and underlying theory can open up new avenues to realize ultrasharp resonances, which may promote the development of the potential meta-devices for nonlinearity, lasing action, and sensing.
Opto-Electronic Advances
- Publication Date: Jun. 20, 2021
- Vol. 4, Issue 6, 200030-1 (2021)
Customized anterior segment photoacoustic imaging for ophthalmic burn evaluation in vivo
Huangxuan Zhao, Ke Li, Fan Yang, Wenhui Zhou, Ningbo Chen, Liang Song, Chuansheng Zheng, Zhicheng Liu, and Chengbo Liu
Photoacoustic imaging has many advantages in ophthalmic application including high-resolution, requirement of no exogenous contrast agent, and noninvasive acquisition of both morphologic and functional information. However, due to the limited depth of focus of the imaging method and large curvature of the eye, it remains a challenge to obtain high quality vascular image of entire anterior segment. Here, we proposed a new method to achieve high quality imaging of anterior segment. The new method applied a curvature imaging strategy based on only one time scanning, and hence is time efficient and more suitable for ophthalmic imaging compared to previously reported methods using similar strategy. A custom-built photoacoustic imaging system was adapted for ophthalmic application and a customized image processing method was developed to quantitatively analyze both morphologic and functional information in vasculature of the anterior segment. The results showed that the new method improved the image quality of anterior segment significantly compared to that of conventional high resolution photoacoustic imaging. More importantly, we applied the new method to study ophthalmic disease in an in vivo mouse model for the first time. The results verified the suitability and advantages of the new method for imaging the entire anterior segment and the numerous potentials of applying it in ophthalmic imaging in future. Photoacoustic imaging has many advantages in ophthalmic application including high-resolution, requirement of no exogenous contrast agent, and noninvasive acquisition of both morphologic and functional information. However, due to the limited depth of focus of the imaging method and large curvature of the eye, it remains a challenge to obtain high quality vascular image of entire anterior segment. Here, we proposed a new method to achieve high quality imaging of anterior segment. The new method applied a curvature imaging strategy based on only one time scanning, and hence is time efficient and more suitable for ophthalmic imaging compared to previously reported methods using similar strategy. A custom-built photoacoustic imaging system was adapted for ophthalmic application and a customized image processing method was developed to quantitatively analyze both morphologic and functional information in vasculature of the anterior segment. The results showed that the new method improved the image quality of anterior segment significantly compared to that of conventional high resolution photoacoustic imaging. More importantly, we applied the new method to study ophthalmic disease in an in vivo mouse model for the first time. The results verified the suitability and advantages of the new method for imaging the entire anterior segment and the numerous potentials of applying it in ophthalmic imaging in future.
Opto-Electronic Advances
- Publication Date: Jun. 20, 2021
- Vol. 4, Issue 6, 200017-1 (2021)
Ultra-high resolution strain sensor network assisted with an LS-SVM based hysteresis model
Tao Liu, Hao Li, Tao He, Cunzheng Fan, Zhijun Yan, Deming Liu, and Qizhen Sun
Optical fiber sensor network has attracted considerable research interests for geoscience applications. However, the sensor capacity and ultra-low frequency noise limits the sensing performance for geoscience data acquisition. To achieve a high-resolution and lager sensing capacity, a strain sensor network is proposed based on phase-sensitive optical time domain reflectometer (φ-OTDR) technology and special packaged fiber with scatter enhanced points (SEPs) array. Specifically, an extra identical fiber with SEPs array which is free of strain is used as the reference fiber, for compensating the ultra-low frequency noise in the φ-OTDR system induced by laser source frequency shift and environment temperature change. Moreover, a hysteresis operator based least square support vector machine (LS-SVM) model is introduced to reduce the compensation residual error generated from the thermal hysteresis nonlinearity between the sensing fiber and reference fiber. In the experiment, the strain sensor network possesses a sensing capacity with 55 sensor elements. The phase bias drift with frequency below 0.1 Hz is effectively compensated by LS-SVM based hysteresis model, and the signal to noise ratio (SNR) of a strain vibration at 0.01 Hz greatly increases by 24 dB compared to that of the sensing fiber for direct compensation. The proposed strain sensor network proves a high dynamic resolution of 10.5 pε·Hz-1/2 above 10 Hz, and ultra-low frequency sensing resolution of 166 pε at 0.001 Hz. It is the first reported a large sensing capacity strain sensor network with sub-nε sensing resolution in mHz frequency range, to the best of our knowledge. Optical fiber sensor network has attracted considerable research interests for geoscience applications. However, the sensor capacity and ultra-low frequency noise limits the sensing performance for geoscience data acquisition. To achieve a high-resolution and lager sensing capacity, a strain sensor network is proposed based on phase-sensitive optical time domain reflectometer (φ-OTDR) technology and special packaged fiber with scatter enhanced points (SEPs) array. Specifically, an extra identical fiber with SEPs array which is free of strain is used as the reference fiber, for compensating the ultra-low frequency noise in the φ-OTDR system induced by laser source frequency shift and environment temperature change. Moreover, a hysteresis operator based least square support vector machine (LS-SVM) model is introduced to reduce the compensation residual error generated from the thermal hysteresis nonlinearity between the sensing fiber and reference fiber. In the experiment, the strain sensor network possesses a sensing capacity with 55 sensor elements. The phase bias drift with frequency below 0.1 Hz is effectively compensated by LS-SVM based hysteresis model, and the signal to noise ratio (SNR) of a strain vibration at 0.01 Hz greatly increases by 24 dB compared to that of the sensing fiber for direct compensation. The proposed strain sensor network proves a high dynamic resolution of 10.5 pε·Hz-1/2 above 10 Hz, and ultra-low frequency sensing resolution of 166 pε at 0.001 Hz. It is the first reported a large sensing capacity strain sensor network with sub-nε sensing resolution in mHz frequency range, to the best of our knowledge.
Opto-Electronic Advances
- Publication Date: May. 20, 2021
- Vol. 4, Issue 5, 200037-1 (2021)
Deep-learning-based ciphertext-only attack on optical double random phase encryption
Meihua Liao, Shanshan Zheng, Shuixin Pan, Dajiang Lu, Wenqi He, Guohai Situ, and Xiang Peng
Optical cryptanalysis is essential to the further investigation of more secure optical cryptosystems. Learning-based attack of optical encryption eliminates the need for the retrieval of random phase keys of optical encryption systems but it is limited for practical applications since it requires a large set of plaintext-ciphertext pairs for the cryptosystem to be attacked. Here, we propose a two-step deep learning strategy for ciphertext-only attack (COA) on the classical double random phase encryption (DRPE). Specifically, we construct a virtual DRPE system to gather the training data. Besides, we divide the inverse problem in COA into two more specific inverse problems and employ two deep neural networks (DNNs) to respectively learn the removal of speckle noise in the autocorrelation domain and the de-correlation operation to retrieve the plaintext image. With these two trained DNNs at hand, we show that the plaintext can be predicted in real-time from an unknown ciphertext alone. The proposed learning-based COA method dispenses with not only the retrieval of random phase keys but also the invasive data acquisition of plaintext-ciphertext pairs in the DPRE system. Numerical simulations and optical experiments demonstrate the feasibility and effectiveness of the proposed learning-based COA method. Optical cryptanalysis is essential to the further investigation of more secure optical cryptosystems. Learning-based attack of optical encryption eliminates the need for the retrieval of random phase keys of optical encryption systems but it is limited for practical applications since it requires a large set of plaintext-ciphertext pairs for the cryptosystem to be attacked. Here, we propose a two-step deep learning strategy for ciphertext-only attack (COA) on the classical double random phase encryption (DRPE). Specifically, we construct a virtual DRPE system to gather the training data. Besides, we divide the inverse problem in COA into two more specific inverse problems and employ two deep neural networks (DNNs) to respectively learn the removal of speckle noise in the autocorrelation domain and the de-correlation operation to retrieve the plaintext image. With these two trained DNNs at hand, we show that the plaintext can be predicted in real-time from an unknown ciphertext alone. The proposed learning-based COA method dispenses with not only the retrieval of random phase keys but also the invasive data acquisition of plaintext-ciphertext pairs in the DPRE system. Numerical simulations and optical experiments demonstrate the feasibility and effectiveness of the proposed learning-based COA method.
Opto-Electronic Advances
- Publication Date: May. 20, 2021
- Vol. 4, Issue 5, 200016-1 (2021)
Switchable diurnal radiative cooling by doped VO2
Minkyung Kim, Dasol Lee, Younghwan Yang, and Junsuk Rho
This paper presents design and simulation of a switchable radiative cooler that exploits phase transition in vanadium dioxide to turn on and off in response to temperature. The cooler consists of an emitter and a solar reflector separated by a spacer. The emitter and the reflector play a role of emitting energy in mid-infrared and blocking incoming solar energy in ultraviolet to near-infrared regime, respectively. Because of the phase transition of doped vanadium dioxide at room temperature, the emitter radiates its thermal energy only when the temperature is above the phase transition temperature. The feasibility of cooling is simulated using real outdoor conditions. We confirme that the switchable cooler can keep a desired temperature, despite change in environmental conditions. This paper presents design and simulation of a switchable radiative cooler that exploits phase transition in vanadium dioxide to turn on and off in response to temperature. The cooler consists of an emitter and a solar reflector separated by a spacer. The emitter and the reflector play a role of emitting energy in mid-infrared and blocking incoming solar energy in ultraviolet to near-infrared regime, respectively. Because of the phase transition of doped vanadium dioxide at room temperature, the emitter radiates its thermal energy only when the temperature is above the phase transition temperature. The feasibility of cooling is simulated using real outdoor conditions. We confirme that the switchable cooler can keep a desired temperature, despite change in environmental conditions.
Opto-Electronic Advances
- Publication Date: May. 20, 2021
- Vol. 4, Issue 5, 200006-1 (2021)
Directional sliding of water: biomimetic snake scale surfaces
Yizhe Zhao, Yilin Su, Xuyan Hou, and Minghui Hong
Bioinspired superhydrophobic surfaces have attracted many industrial and academic interests in recent years. Inspired by unique superhydrophobicity and anisotropic friction properties of snake scale surfaces, this study explores the feasibility to produce a bionic superhydrophobic stainless steel surface via laser precision engineering, which allows the realization of directional superhydrophobicity and dynamic control of its water transportation. Dynamic mechanism of water sliding on hierarchical snake scale structures is studied, which is the key to reproduce artificially bioinspired multifunctional materials with great potentials to be used for water harvesting, droplet manipulation, pipeline transportation, and vehicle acceleration. Bioinspired superhydrophobic surfaces have attracted many industrial and academic interests in recent years. Inspired by unique superhydrophobicity and anisotropic friction properties of snake scale surfaces, this study explores the feasibility to produce a bionic superhydrophobic stainless steel surface via laser precision engineering, which allows the realization of directional superhydrophobicity and dynamic control of its water transportation. Dynamic mechanism of water sliding on hierarchical snake scale structures is studied, which is the key to reproduce artificially bioinspired multifunctional materials with great potentials to be used for water harvesting, droplet manipulation, pipeline transportation, and vehicle acceleration.
Opto-Electronic Advances
- Publication Date: Apr. 06, 2021
- Vol. 4, Issue 4, 210008-1 (2021)
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