https://absimage.aps.org/image/MAR14/MWS_MAR14-2014-020819.pdf

Van der Waals heterostructures

Science and technologies based on terahertz frequency electromagnetic radiation (100 GHz–30 THz) have developed rapidly over the last 30 years. For most of the 20th Century, terahertz radiation, then referred to as sub-millimeter wave or far-infrared radiation, was mainly utilized by astronomers and some spectroscopists. Following the development of laser based terahertz time-domain spectroscopy in the 1980s and 1990s the field of THz science and technology expanded rapidly, to the extent that it now touches many areas from fundamental science to 'real world' applications. For example THz radiation is being used to optimize materials for new solar cells, and may also be a key technology for the next generation of airport security scanners. While the field was emerging it was possible to keep track of all new developments, however now the field has grown so much that it is increasingly difficult to follow the diverse range of new discoveries and applications that are appearing. At this point in time, when the field of THz science and technology is moving from an emerging to a more established and interdisciplinary field, it is apt to present a roadmap to help identify the breadth and future directions of the field. The aim of this roadmap is to present a snapshot of the present state of THz science and technology in 2017, and provide an opinion on the challenges and opportunities that the future holds. To be able to achieve this aim, we have invited a group of international experts to write 18 sections that cover most of the key areas of THz science and technology. We hope that The 2017 Roadmap on THz science and technology will prove to be a useful resource by providing a wide ranging introduction to the capabilities of THz radiation for those outside or just entering the field as well as providing perspective and breadth for those who are well established. We also feel that this review should serve as a useful guide for government and funding agencies.

The 2016 terahertz science and technology roadmap

Solar-energy conversion usually takes one of two forms: the 'quantum' approach, which uses the large per-photon energy of solar radiation to excite electrons, as in photovoltaic cells, or the 'thermal' approach, which uses concentrated sunlight as a thermal-energy source to indirectly produce electricity using a heat engine. Here we present a new concept for solar electricity generation, photon-enhanced thermionic emission, which combines quantum and thermal mechanisms into a single physical process. The device is based on thermionic emission of photoexcited electrons from a semiconductor cathode at high temperature. Temperature-dependent photoemission-yield measurements from GaN show strong evidence for photon-enhanced thermionic emission, and calculated efficiencies for idealized devices can exceed the theoretical limits of single-junction photovoltaic cells. The proposed solar converter would operate at temperatures exceeding 200 degrees C, enabling its waste heat to be used to power a secondary thermal engine, boosting theoretical combined conversion efficiencies above 50%.

http://absimage.aps.org/image/MAR10/MWS_MAR10-2009-006451.pdf

Photon Enhanced Thermionic Emission for Solar Concentrator Systems

The year 2019 marks the 10th anniversary of the first report of ultrafast fiber laser mode-locked by graphene. This result has had an important impact on ultrafast laser optics and continues to offer new horizons. Herein, we mainly review the linear and nonlinear photonic properties of two-dimensional (2D) materials, as well as their nonlinear applications in efficient passive mode-locking devices and ultrafast fiber lasers. Initial works and significant progress in this field, as well as new insights and challenges of 2D materials for ultrafast fiber lasers, are reviewed and analyzed.

/pdf/ultrafast-fiber-lasers-mode-locked-by-two-dimensional-1q60eopf48.pdf

Ultrafast fiber lasers mode-locked by two-dimensional materials: review and prospect

The data-science revolution is poised to transform the way photonic systems are simulated and designed. Photonic systems are, in many ways, an ideal substrate for machine learning: the objective of much of computational electromagnetics is the capture of nonlinear relationships in high-dimensional spaces, which is the core strength of neural networks. Additionally, the mainstream availability of Maxwell solvers makes the training and evaluation of neural networks broadly accessible and tailorable to specific problems. In this Review, we show how deep neural networks, configured as discriminative networks, can learn from training sets and operate as high-speed surrogate electromagnetic solvers. We also examine how deep generative networks can learn geometric features in device distributions and even be configured to serve as robust global optimizers. Fundamental data-science concepts framed within the context of photonics are also discussed, including the network-training process, delineation of different network classes and architectures, and dimensionality reduction. Neural networks can capture nonlinear relationships in high-dimensional spaces and are powerful tools for photonic-system modelling. This Review discusses how deep neural networks can serve as surrogate electromagnetic solvers, inverse modelling tools and global device optimizers.

Deep neural networks for the evaluation and design of photonic devices

Anisotropic Nonlinear Optical Properties of a SnSe Flake and a Novel Perspective for the Application of All-Optical Switching

Ultrafast terahertz transmission/group delay switching in photoactive WSe2-functionalized metaphotonic devices

Silicon (Si) photonics have established as leading technologies in addressing the rapidly increasing demands of huge data transfer in optical communication systems with compact footprints, small power consumption, and ultradense bandwidth, which are driven by the next generation supercomputers and big data era. Particularly, Si photonics will penetrate into optical communication links at an ever‐small scale, namely chip‐to‐chip and on‐chip. However, the nanostructures made of Si with an indirect bandgap are not ideal candidates for on‐chip light sources, modulators, and photodetectors, which most‐frequently require optical materials with direct bandgap. Thanks to the advent of graphene, transition metal dichalcogenides and other two‐dimensional (2D) materials, which can facilitate extraordinary progresses in improving device performance at the ultrathin scale, their integration with Si photonics furnishes a heterogeneous platform to construct fully functional and highly integrated photonic communication systems. In this work, the current advancements in the on‐chip applications of Si photonics‐2D materials heterostructures, inclusive of all essential chip‐scale modules and integrated circuits, as well as the future prospective and challenges are reviewed and discussed. The present study sets out to objectively measure the feasibility of the hybrid integration between Si photonics and 2D materials in on‐chip optical communications and the advanced applications beyond.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/lpor.202000239

Jie You

Papers

Ultrafast fiber lasers mode-locked by two-dimensional materials: review and prospect

Anisotropic Nonlinear Optical Properties of a SnSe Flake and a Novel Perspective for the Application of All-Optical Switching

Ultrafast terahertz transmission/group delay switching in photoactive WSe2-functionalized metaphotonic devices

Hybrid/Integrated Silicon Photonics Based on 2D Materials in Optical Communication Nanosystems

Ultrafast Carrier Transfer Promoted by Interlayer Coulomb Coupling in 2D/3D Perovskite Heterostructures