The focus of Dr. Ren’s studies is to create new ideas for generating a robust prototype fabrication process for low-cost, non-vacuum based CIGS solar cells in terms of reliability, uniformity, and conversion efficiency. Dr. Ren develops CIGS thin films from nanocrystals created using a solution-based-chemistry approach.
He applies the newest techniques in ultrafast pump-probe laser spectroscopy to study the energy conversion and transfer processes in the absorbing layer to aid the design, synthesis, and optimization of thin film solar cells. The time-resolved spectroscopic measurements will allow him to investigate local phenomena such as those occurring at grain boundaries that determine the overall conversion efficiency of solar cells.
Dr. Ren has also created ultrafast spectroscopic optical techniques to answer questions regarding the complex magnetization reversal, the mechanism of ultrafast demagnetization, and the spin relaxation processes in magnetic nanostructures. He developed a nanometer-resolution, ultrafast spectroscopic near-field technique to investigate the spin and magnetization dynamics in the individual magnetic element and to realize the coherent control of laser-induced processes.
Most recently, Dr. Ren actively collaborates with research groups from Weill-Cornell Medical College to develop a novel therapeutic approach towards cellular energy maintenance. He applies state-of-art optical technologies to study a biological process that is fundamental to life.
1. “Quasiparticle relaxation across the multiple superconducting gaps in the electron-doped BaFe1.85Co0.15As2”, Y. H. Ren, Y. Gong, T. Nosach, J. Li, J. J. Tu, L. J. Li, G. H. Cao, and Z. A. Xu, J. Appl. Phys. 111, 07E134 (2012).
2. “Solution-based synthesis of CsSnI3 and the demonstration of its thin-film formation by ultrasonic spray method” , Zhuo Chen, Bo Gao, Chonglong Yu, Yuhang Ren, and Kai Shum, (submitted 2012).
3. “Non-thermal excitation and control of magnetization in Fe/GaAs films by ultrafast laser pulses”, Y. Gong, X. H. Zhang, J. H. Zhao, R. Kutayiah, Z. Cevher, and Y. H. Ren, J. Appl. Phys. 111, 07D505 (2012).
4. “Coherent spin precession via photoinduced antiferromagnetic interactions in La0.67Ca0.33MnO3”，H. B. Zhao, D. Talbayev, X. Ma, Y. H. Ren, A. Venimadhav, Q. Li, G. Luepke, Phys. Rev. Lett., 107, 207205 (2011).
5. “Electric field modulation of surface anisotropy and magneto-dynamics in multiferroic heterostructures”, J. Lou, M. Liu, D. Reed, Y. H. Ren, N. X. Sun, J. Appl. Phys. 109, 07D731 (2011).
6. “Distinct quasiparticle relaxation dynamics in an electron-doped superconductor, BaFe1.9Ni0.1As2”, Y. Gong, W. Lai, T. Nosach, L. J. Li, G. H. Chao, Z. A. Xu, Y. H. Ren, New J. Phys. 12, 123003 (2010).
7. “Universal entangler with photon pairs in arbitrary states”, Bing He, Janos Bergou, and Yuhang Ren, J. Phys. B: At. Mil. Opt. Phys. 43, 025502 (2010).
8. “Optical properties of the iron arsenic superconductor BaFe1.85Co0.15As2”, J. J. Tu, J. Li, W. Liu, A. Punnoose, Y. Gong, Y. H. Ren, L. J. Li, G. H. Cao, Z. A. Xu, C. C. Homes, Phys. Rev. B 82, 174509 (2010).
9. “Giant electric field tuning of magnetism in novel multiferroic FeGaB/Lead Zinc Niobate-Lead Titanate (PZN-PT) heterostructures”, J. Lou, M. Liu, D. Reed, Y. H. Ren, N. X. Sun, Adv. Mat. 21, 4711 (2009).
10. “Ultrafast quasi-particle dynamics of charge/orbital ordered and ferromagnetic clusters in La(0.7)Ca(0.3)MnO(3)”, Y. H. Ren, M. Ebrahim, Z. A. Xu, G. Luepke, NEW J. Phys. 11, 113013 (2009).
11. “Magnetic anisotropy and spin wave relaxation in CoFe/PtMn/CoFe trilayer films”, Y. H. Ren, C. Wu, G. Yu, C. Pettiford, and N. X. Sun, J. App. Phys. 105, 073910 (2009).
12. “Ultrafast optical study of spin wave resonance and relaxation in CoFe/PtMn/CoFe trilayer films”, Y. H. Ren, C. Wu, Y. Gong, C. Pettiford, and Nian X. Sun, J. Appl. Phys. 105, 07D304 (2009).
13. “Time-resolved optical studies of spin and quasiparticle dynamics in in colossal magnetoresistance materials: La0.67Ca0.33 MnO3, La0.67Sr0.33MnO3, and Sr2FeMoO6”, Y. H. Ren, M. Ebrahim, H.B. Zhao, G. Luepke, Z. A. Xu, V. Adyam, and Qi Li, Phys. Rev. B 78, 014408 (2008).
14. “Ferromagnetic resonance studies of surface and bulk spin-wave modes in CoFe/PtMn/CoFe multilayer films”, Cheng Wu, Steven Greenbaum, Carl Pettiford, Nian X Sun, Yuhang Ren, J. Appl. Phys. 103. 07B525 (2008).
15. “Angular dependence of spin-wave resonance and relaxation in half-metallic Sr2FeMoO6 thin films”, Tetiana Nosach, Gabriella Mullady, Steven Greenbaum, Adyam Venimadhav, Qi Li, Yuhang Ren, J. Appl. Phys. 103. 07E311 (2008).
16. “Universal discriminator for completely unknown optical qubits”, Bing He, Janos Bergou, Yuhang Ren, Phys. Rev. A 76, 032301 (2007).
17. “Generation and detection of coherent longitudinal acoustic phonons in the La0.67Sr0.33MnO3 thin films by femtosecond light pulses”, Y. H. Ren, M. Trigo, R. Merlin, Venimadhav Adyam, and Qi Li, Appl. Phys. Lett. 90, 251918 (2007).
18. “Light-induced magnetic precession in (Ga,Mn)As slabs: Hybrid standing-wave Damon-Eshbach modes”, D. M. Wang, Y. H. Ren, X. Liu, J. K. Furdyna, M. Grimsditch, and R. Merlin, Phys. Rev. B 75, 233308 (2007).
19. “Ultrafast magneto-optical Kerr study of standing spin waves in ferromagnetic GaMnAs films”, D. M. Wang, Y. H. Ren, X. Liu, Y. J. Cho, J. K. Furdyna, M. Grimsditch, and R. Merlin, Superlattices and Microstructures 41, 372 (2007).
20. “Anomalous first-to-zero sound crossover in La1-xCaxMnO3: hard solid shows soft side”, Yuhang Ren, G. Lüpke, Yufeng Hu, Qi Li, C. S. Hong, N. H. Hur, and R. Merlin, Phys. Rev. B 74, 012405 (2006).