Significance A series of new physical mechanisms and unique optoelectronic properties in nanostructures provide the possibility to explore and study new optoelectronic chips.
Progress Photons and phonons are important information carriers. Precise measurement of photons and phonons in micro-/nano- periodic structures allows the detection of multi-dimensional physical information and various physical quantities. Here, by manipulation of photons with metasurface units, a one-shot miniaturized ultraspectral camera with thousands of micro-spectrometers on a CMOS image sensor chip is proposed and applied to realize real-time on-chip spectral imaging. Micro-spectrometers with high center-wavelength accuracy of 0.1 nm and spectral resolution of 0.8 nm are realized and the ultraspectral imaging results for a plate of fruits just under the lighting of a fluorescent lamp are obtained. For phonons, opto-mechanical crystals are studied by dealing with the interaction between photons (light) and phonons (mechanical motion). A hetero opto-mechanical crystal is proposed and demonstrated by integrating two types of periodic structures into the system, and the optical and mechanical modes can be confined separately. This separate confinement gives rise to phonon lasing with a high mechanical frequency of 6.22 GHz. Moreover, radiation-pressure-antidamping enhanced opto-mechanical spring sensing based on a silicon nano-beam opto-mechanical structure is proposed and demonstrated, which allows for sensing resolution of ~10 -7.
Some interesting phenomena and novel devices are arising by free electrons interacting with various nano?structures. We demonstrate the first on?chip integrated free electron light source by greatly reducing electron energy to 0.25??1.4 keV for generating Cherenkov radiation (CR). In hexagonal boron nitride (hBN) with hyperbolic phonon polaritons, the theoretical and simulated results reveal that CR can be generated using free electrons with an extremely low kinetic energy of 1 eV, which is about two?orders of magnitude lower than that in multilayer plasmonic hyperbolic metamaterial. For generating Smith?Purcell radiation (SPR) in the deep UV region, we let an electron beam pass through a grating with 30 nm?wide slots and observe the SPR with the shortest wavelength of ~230 nm and the broadband SPR with wavelengths covering 230??1100 nm. We numerically investigate the SPASER excited by free electrons, and the tunable, deep?ultraviolet laser with output power density reaching about 30 W/μm2 and wavelength widely tuned by varying the electron energy. Our work opens up the possibility of exploring high performance on?chip integrated free electron light sources and optoelectronic devices, and provides a way for realizing an integrated free electron laser.
Introduced by Allen in 1992, orbital angular momentum (OAM) was characterized as a new freedom of lightwave. Since then, it has been attracted much research interest and shown the potential for various applications. Compared with the bulk optics, photonic integrated devices are much more compact and, the most importantly, compatible with the matured CMOS fabrication process. Since 2012, we has proposed and demonstrated integrated OAM emitters, plasmonic vortex arrays, angular momentum beam splitters and sorters, as well as the methods to identify the topological charges carried by OAM beams, etc. Here, three representative works are shown. Firstly, beams carrying OAM generated on chips are proposed for wireless optical interconnects and an integrated OAM emitter with a wide switching range of OAM modes is demonstrated. The independence of the micro-ring cavity and the gratings unit provides the flexibility to design the device and optimize the performances. Second, we propose an integrable method for generating vortex Smith-Purcell radiation by letting free electrons pass on holographic gratings and the numerical results indicate that the OAM wave with different topological charges can be obtained. Third, an angular momentum (AM) beam splitter has been demonstrated so that both spin and orbital components carried by lightwave can be distinguished simultaneously.
Photons are ideal flying qubits. Photonics provides an important way to develop quantum information technologies. A quantum information system based on photonics includes functional units for quantum state generation, manipulation, and detection. How to integrate these functions on a photonic chip is a crucial technology for future quantum information applications. We have taken part in the research of integrated quantum photonic circuits since 2010. In these ten years, we have developed comprehensive solutions on integrated quantum light sources for various quantum entangled state generation at telecom bands, based on spontaneous four-wave-mixing in silicon waveguides and micro-ring resonators. We have also developed technologies for quantum state manipulation and detection on a silicon photonic chip. Utilizing high-performance energy-time entangled photon pairs generated in silicon waveguides, we have proposed and demonstrated a scheme of temporal ghost imaging based on the frequency correlation in the photon pairs, and have developed a quantum secure ghost imaging scheme based on it. Recently, we have realized a fully connected quantum key distribution (QKD) network with 40 users and 780 QKD links based on a silicon photonic quantum light source. It is the entanglement-based QKD network with the largest user number to the knowledge of authors.
Conclusion and Prospect In summary, the research achievements of our research group in the field of nanostructured optoelectronic chips are reviewed. Various nanostructures have been successfully developed to control the mechanism of photons, electrons, phonons, surface plasmon polariton and their interactions, and a series of new functional optoelectronic chips have been realized, such as free electron radiation, real-time spectral imaging, phonon sensing, optical orbital angular momentum radiation, and quantum state generation and control. At present, some of the chips are being industrialized and expected to become practical in the near future.
