Ren

High-Speed polarimeter for solar magnetic field measurements: Supported by the National Science Foundation (NSF) under the grant AST-1906166, we are developing a high-speed and high-accuracy polarimeter that will be able to freeze the atmospheric turbulence perturbation and thus will be able to provide a true polarization measurement of the sun's atmosphere. This system will be used to investigate the solar magnetic fields, which is an important ingredient for the current space weather research and forecast.
Solar Adaptive Optics: Supported by the National Science Foundation (NSF) Early Career program under the grant ATM-0841440, we have developed the first portable solar Adaptive Optics (AO) system. Compared with other AO systems, our system will be extremely compact in physical size and will be able to be brought to any solar telescope for scientific observations. Our system also features low cost and high performance. We are using LabVIEW to develop the wave-front sensing and control software. We are also developing Multi-Conjugate AO (MCAO) system, which uses several deformable mirrors to correct the atmosphere turbulence in different altitudes so that a large and uniform corrected field of view is available. The following movies show our AO test (2013-07-11 day;Sunspot 1787) with the NSO 1.5-m McMP with the AO Off and AO On, at the visible 0.65 um with our 69-actuator AO system, and the same AO system with NSO Sunspot Dunn solar telescope in our recnt observation run (2014-08-16 morning;Sunspot region 2139) of a movie of AO on and AO off.

Stellar Adaptive Optics: Supported by the a grant from the U.S. Mt. Cuba Astronomical Foundation, we developed a poartable stellar Adaptive Optics (AO) system for nighttime astronomical high-contrast exoplanet imaging. Here are two movies of AO Off and AO On (2013-07-11 night; star Arcturus), showing the performance of our stellar AO system. Please note that the movies and correction are taken at the visible (0.45 - 0.8 um), with our 69-actuator AO system. This prototype will be replaced by our 277-actuator extreme AO currently developmed for high-contrast exoplanet imaging. Recently, our adaptive Optics, acted as the first visiting AO instrument in the world, was test with the ESO 3.6-metet NTT: see the movie with AO on and off.

Seeing Testing: Supported by the National Science Foundation (NSF) under the grant AST-1607921, we developed the first portable seeing profile measurement system. We have built a wave-front sensor called Differential Image Motion Monitor (DIMM) for solar seeing test of an astronomical site. The DIMM has a number of advantages over other approaches. Although the DIMM technique is widely used for stellar night-time testing where the target for wave-front sensing is a pint source, it is rarely used for solar seeing test where the target is a 2-dimensional structure and therefore cross-correlation technique is needed to track the solar structure. A movie of recent test at SFO using our recently developed wave-front sensor is available. The testing was performed at Feb. 27, 2008 by using sunspot 983, which indicates that excellent seeing conditions (r0 up to 100 mm) is available at the SFO!

3-D Image Spectroscopy: Supported by the National Science Foundation (NSF) under the grant AST 05-01743, we developed the 3-dimentional (3-D) image spectroscopy technique. Compared with other conversional spectrometer, the 3-D image spectroscopy technique allows the 3-D data tube (x, y spatial and spectrum information) to be collected in a single exposure. This is critical for the astronomical spectroscopy over a 2-dimentional field of view, such as the Sun.

Direct Detection of Earth-Like Planets: We are also developing high-contrast imaging techniques that will allow us eventually directly imaging of Earth-like planets that have life at an extra-solar system. This will answer the most fundamental scientific questions such as "are we alone in the universe?". The direct imaging of Earth-like planets will be one of the most important scientific advances in the next decade. We invented a technique called Stepped-Transmission Filter based coronagraph. Currently a prototype is being developed and progresses are being made.

Current Research Group Members

Dr.Mohanakrishna Ranganathan (Postdoctoral Researcher)
Jonathan Fernandez (Graduate Student)
Zijian Han (Graduate Student)
Zhiyao Wang(Graduate Student)
Yili Chen (Graduate Student)
Tianyu Zhang(Graduate Student)
Xiyang Kong(Graduate Student)
Kai Yan (Graduate Student)

Former Research Group Members/Visitors

Dr. Chang, Jun (Professor, Beijing Institute of Technology)
Dr. Dong, Bing (Associate Professor, Beijing Institute of Technology)
Dr. Zhang, Xiaofang (Associste Professor, Beijing Institute of Technology)
Dr. Dr. Wang, Xin (Research Associate professor, Beijing, China)
Dr. Dou, Jingpei (Research Professor,NIAOT/CAS)
Dr. Zhang, Xi (Research Associate Prefessor,NIAOT/CAS)
Dr. Zhao, Gong (Research Associate Prefessor,NIAOT/CAS)
Dr. Guo, Jing (Research Associate Prefessor,NIAOT/CAS)
Dr. Liu, Chengchao (Research Assistant Prefessor,NIAOT/CAS)

Graduated Students

Wang, Gong (Graduated)
Dr. Yang,Feng (Graduated)
Mr. Vincent Tagliamonti (Graduate Student, graduated)
Mr. Nathan Brown (Graduate Student, graduated)
Mr. Andrew Denio (Graduate Student, graduated)
Mr. Julius Chapman (Graduate Student, graduted)
Mr. Robert Broadfoot (Graduate Student, graduated)
Mr. Yang,Chao (Graduate Student)
Ms. Snow Wang (Graduate Student,graduated)
Ms. Li,Rong (Graduate Student, graduated)
Ms. Sizhen Liu (Graduate Student, garduated)

Publications

Biographical Sketches