1.  In the field of Nono-optoelectronics

(1) Real-time ultra-spectral imaging

(Optica 9, 461,2022 and Laser & Photonics Reviews, 2100663, 2022，
US Patent: 16/978,122, 16/978,137, 16/978,086, 17/423,423, 17/377,217, 17/377,147, 17/423.414, and Chinese Patent : ZL201921222710.3, ZL201921223201.2, )
Invented and demonstrated real-time ultra-spectral imaging by fitting thousands of micro-spectrometers as spectral pixels on a single chip with reconfigurable metasurfaces.
Real-time spectral imaging that can obtain spectral information of thousands of different locations in space at one time is eagerly expected for both fundamental scientific research and various practical applications. However, this has always been an elusive dream because it is impossible to integrate thousands of current optical spectrometers which consists of discrete devices with complex structures and large volumes. Huang invented a novel reconfigurable metasurface supercell and a unique algorithm grafting from compressive sensing, which enables 6336 image-adaptive micro-spectrometers operate simultaneously and reconstructs ultra-spectral imaging (Dl/l~0.001) covering a 300-nm-wide visible spectrum with an ultra-high center- wavelength accuracy of 0.04-nm standard deviation and spectral resolution of 0.8 nm. The resolution for the single micro-spectrometer is one order of magnitude higher than the best reported so far, while integration of 6336 micro-spectrometers for spectral imagining ushers in a new era in the field of spectroscopy. In this January, Science published a review paper listing this work as one of the leading research results in the field (Science 371 (6528), eabe0722.DOI: 10.1126/science.abe0722).
More importantly, this scheme is based on CMOS-compatible processing technology completely and can be extended to almost any commercial camera with different spectral bands to seamlessly switch between image and spectral image. It is promising to open up a new space for the application of spectral analysis combining with image recognition and intellisense.
Based on this invention, a startup company, Seetrum (Registration No: 9111 0108 MA01 W1PP 93, www.seetrum.com), was founded in 2020. Now Seetrum has more than 50 employees and completed the A+ round financing with company valuations of RMB 520 million. Two products, Hyperspectral Sensor and Water Quality Monitor, have been launched.

(2) Free electron light source with threshold-less Cherenkov radiation and coherent SPR amplified by stimulation

(Nature Photonics, 11, 289, 2017,
US Patent: 17/304,582, Chinese Patent : ZL201610952634.6)
Discovered and verified that Cherenkov radiation (CR) could be excited in multilayer hyperbolic metamaterial (HMM) no matter how slow the electrons moves (namely threshold-less CR), and demonstrated an on-chip free electron light source.
CR is the electromagnetic radiation emitted by a moving charge passing through a dielectric medium with a uniform velocity higher than the phase velocity of light in the medium. Therefore, high-energy electrons (tens of thousands of eV) are required to generate CR. CR is one of the approaches to realizing free-electron light source, which is rather important in a lot of fields due to its flexible wavelength selection. Similar to other methods for free electron light source, the electrons should be accelerated to an ultra-high velocity, which requires large volume (several to thousands of meters) equipment.
Huang discoved threshold-less CR in hyperbolic metamaterial and demonstrated an on-chip free electron light source by extracting the free electrons from a Mo tip with nano scale and having the electrons flied a distance of 200 micron above and parallel to the surface of HMM with the height of only 40nm. The wavelength of CR covers 500~900nm and the electron energy is only 250~1400eV, which is two to three orders of magnitude lower than previous reports. The measured output light power reaches 200nW which is two orders of magnitude higher than free electron light source by using other nanostructures. Nature Photonics published this work with a commentary, applauding this achievment is to “open exciting new avenues in nanotechnologies, and it is easy to imagine that it will find applications in the context of particle detection, nanoscale light sources, or biomedicine”.(Nature Photonics, 11, news & views, 2017)
This achievement was selected as one of the “Ten major developments in China's optics in 2017”.
Based on this important discovery, a compact THz radiator was invented (US Patent: 17/304,582) and ultra-narrow linewidth of 5kHz was demonstrated.
*Note：SPR is the short for “Smith-Purcell radiation”.
(3) Surface Plasmon Polariton
Developped a long range SPP waveguide with very low transmission loss of 0.67dB/mm. Proposed and realized a novel hybrid coupler, which consists of a dielectric waveguide and a SPP waveguide. The coupling efficiency is as high as 99%.
(Appl. Phys. Lett. 90, 141101, 2007 and Appl. Phys. Lett. 95, 091104, 2009,
US Patent : US 8358880 B2, Chinese Patent : ZL200910132692.4, ZL201210009165.6).
Proposed and verified two-surface-plasmon-absorption (TSPA) effect by carefully designing the experiment to exclude the possibility of two-photon-absorption. The subwavelength nanolithography beyond the diffraction limit based on TSPA has been demonstrated where the resist strips with resolution of ~1/11 of the exposure wavelength was achieved.
(Appl. Phys. Lett. 102, 063113, 2013, Patent : ZL201610064552.8)
Based on this hybrid coupler, a TM/TE polarization splitter with pure TM mode output and on-chip real-time substances identification for single molecule layer were invented.
(Appl. Phys. Lett. 100, 111108, 2012, and Appl. Phys. Lett. 102(6), 061109, 2013, Patent : ZL200810186418.0).
Carried out an investigation on improving the efficiency of dye-sensitized solar cells by introducing core-shell Au@PVP nanoparticles based on the localized surface plasmon effect. It was observed that the PCE has been enhanced by 32% from 5.94% to 7.85%.
(Scientific Reports, 3, 2112, 2013,
Patent : ZL201210365915.3, ZL201110286555.3)
(4) Photonic Crystal and Optomechanical Crystal
Invented and demonstrated an optical switch based on photonic crystal slow light waveguide and realized broadband (24 nm) operation with an ultra-compact (8 mm×17 mm) footprint. The extinction ratio of as high as 15 dB was obtained over the entire bandwidth, which is the widest bandwidth and smallest footprint for an optical switch reported up to now. Such small-foot print optical switches operating at a record bandwidth can potentially dramatically reduce the sizes and improve the overall performance of the future information systems such as supercomputers and interconnects at data centers.
(Appl. Phys. Lett. 101, 151110, 2012, Patent : ZL201310603561.6)
Developed the technology for high-aspect-ratio dry etching with high-quality for ultra-small feature patterns in InGaAsP substrate to realize photonic crystal structure with III-V active material. The etch depth up to 3.5 mm and 1.8 mm was achieved for the holes with diameter of 200 nm and slots with width of 40 nm, respectively. The latter corresponds to an aspect-ratio as high as 45. This result surpasses the previous highest aspect-ratio of 38, which has been reported by British research group in “J. Vac. Sci. Technol. B 2004,22: 1788” and maintained for nearly 10 years.
 (AIP Advances 3, 022122, 2013. )
Invented a kind of hetero optomechanical crystals with nanobeam cavities. In this structure, with optical and mechanical modes separately confined by two types of periodic structures, the optical field and the strain field are concentrated in the optomechanical cavity and resemble each other with an enhanced overlap. As a result, phonon lasing was realized with norrow linewidth of 5.4kHz and highest frequency of 6.22GHz reported up to now, which provides a new way for the high precision measurement and other related applications. 
(Scientific Reports, 5, 15964, 2015, Oral paper in IMCO’2009, arXiv:1907.06475 and 1906.12057 , Patent : ZL201310743586.6)
(5) Quantum entangled light source and optical vortices emitter with silicon micro-ring resonator
Invented and demonstrated a telecom band quantum entangled light sources (QLSs)with hybrid entangled biphoton state generation based on a silicon micro-ring resonator. Polarization entanglement and energy-time entanglement were realized by superpositing two biphoton states generated bi-directionally. It was demonstrated that the fringe visibilities of 93.8±2.1%/91.3±3.5% and 91.6±2.2%/92.0±1.3% by two photon interference under two non-orthogonal polarization bases and Franson-type interference under phase base at 4.61rad/5.72 rad, respectively. This work opens the door to the implementation of silicon photonic devices in generating complicated quantum entangled states. So far, we have realized various integrated QLSs based on silicon photonics, and applying them on applications of quantum communications.
(Photonics Research, 8(3), 235, 2020, Optics Express, 23(4), 3985, 2015,
Optics Letters, 39(8), 2526, 2014)
Invented and demonstrated an integrated photonic emitter with a wide switching range of orbital angular momentum (OAM) modes. Due to the nature of infinite dimensionality, the OAM has been considered as a new degree of freedom of light and widely expanded the scopes of substantial optical applications. Huang invented an integrated photonic emitter with a wide switching range of OAM modes. The independence of the micro-ring cavity and the scattering unit provides the flexibility to design the device and optimize the performance. Specifically, the dynamic switching of nine OAM modes (l = −4 ~ 4) with azimuthal polarization has been demonstrated by electrically controlled thermo-optic effect.
(Scientific Reports 6: 22512, 2016)
2. Research on Optical Devices for Optical Fiber Communication
(1) Proposed and developed a new type 1.55um lambda/8 phase-shifted DFB-LDs for 2.5-Gb/s directly modulated isolator-free uncooled optical transponders. Demonstrated their low chirp and strong feedback resistance characteristics. Isolator-free 2.5-Gb/s direct modulation transmission over 140-km NDSF with -20 dB external optical feedback was realized. The power penalty was as low as 1.7 dB at the bit error rate (BER) of 10E-10. Further potential for low chirp characteristics was also demonstrated by error-free 200-km transmission without optical feedback. (IEEE J. Quantum Electron. vol. 35, pp.1479-1484, 2002)
(2) Developed and implemented a novel design method for external optical feedback resistant DFB-LDs based on a dynamic transient analysis. Optimized the grating structure in partially-corrugated-waveguide laser diodes (PC-LDs), fabricated and measured these devices. With the external optical feedback of -20dB, the relative intensity noise (RIN) in 70% PC-LDs was suppressed to lower than -120dB/Hz, and the minimum RIN was as low as -126dB/Hz. (Electron. Lett., vol. 32, pp.1008-1009, 1996).
(3) Developed an improved the theory on the gain characteristics in strained QWs and discovered the advantages of tensile-strained QWs for semiconductor laser diodes. Based on this theory, designed and fabricated laser diodes with low threshold current density (217A/cm2 for a device cavity of 2mm), as well as optical amplifier with high output power (20.4dBm) with tapered-waveguide and tensile-strained QW structure. (IEEE J. Quantum Electron., vol. 29, no. 12, pp. 2950-2956, 1993, IEEE Photo. Tech. Lett., vol.5, no.2, pp.142-145, 1993, and IEEE J. Quantum Electron., vol. 30, no. 9, pp. 2034-2039, 1994)