The objective of this project is to integrated emerging 2D materials in silicon-based, planar photonic circuits to achieve broadband optoelectronic devices operating in the near- to mid-infrared spectral range. The 2D materials that has been studied include graphene, black phosphorus (BP), and topological insulator bismuth selenide. These materials have many remarkable optoelectronic properties that can be optimally utilized in integrated photonic platforms. The research approach is to develop fabrication processes and conduct characterization and measurement of 2D materials integrated optoelectronic devices. The specific research goals include development of broadband and highly efficient photodetectors and modulators for the near- and mid-infrared, investigation and utilization of nonlinear optical phenomena in 2D materials, and demonstration of waveguide integrated and coupled 2D light emitters.

Intellectual Merit:  Previously, the optoelectronic properties of 2D materials have been investigated with various free-space optical characterization techniques but not yet been widely utilized for integrated optoelectronic devices. The proposed research will achieve integration of 2D materials in planar photonic circuits in order to demonstrate practical optoelectronic devices with unprecedented performances and to better exploit their novel optical properties. The integrated approach will also provide effective near-field means to investigate the optoelectronic properties of the 2D materials. The project developed the first waveguide integrated black phosphorus photodetector with a high responsivity and low dark current for near-infrared light. The research also investigated the fundamental carrier dynamics and third-order optical nonlinearity in black phosphorous. The project further demonstrated mid-infrared electro-absorptive modulation using the quantun-confined Franz-Keldysh effect in BP. The research furtuer integrate BP with mid-infrared silicon and plasmonic waveguides to improve modulation efficiency on an integrated photonic platform. The research also demonstrated spin-momentum locked interaction between the surface state of topological insulator bismuth selenide and the transverse spin angular momentum of the evanescent field of a waveguide mode. 

Broader Impact: The project was highly interdisciplinary and fostered collaboration in areas of photonics, material science, and condensed matter physics. The project made an impact on the photonics industry by providing a new class of optoelectronic materials and devices that can be integrated with current integrated photonic systems. The education and outreach activities of the project encouraged high-schools students to pursue a career in science and engineering and disseminate the research through undergraduate participation in research and curriculum development. The PI and the graduate students presented  a series of experimental demonstrations of optical science (named "The Light Fantastic") to K-12 students annually during STEM summer camps and visits to local schools.

Publications:

1. Youngblood, Nathan, Che Chen, Steven J. Koester, and Mo Li. "Waveguide-integrated black phosphorus photodetector with high responsivity and low dark current." Nature Photonics 9, no. 4 , 247-252 (2015). DOI: 10.1038/nphoton.2015.23
2. Youngblood, Nathan, and Mo Li. "Ultrafast photocurrent measurements of a black phosphorus photodetector." Applied Physics Letters 110, no. 5 , 051102 (2017). DOI: 10.1063/1.4975360
   
3. Chen, Che, Nathan Youngblood, Ruoming Peng, Daehan Yoo, Daniel A. Mohr, Timothy W. Johnson, Sang-Hyun Oh, and Mo Li. "Three-dimensional integration of black phosphorus photodetector with silicon photonics and nanoplasmonics." Nano letters 17, no. 2 , 985-991 (2017). DOI: 10.1021/acs.nanolett.6b04332
   
4. Luo, Siyuan, Li He, and Mo Li. "Spin-momentum locked interaction between guided photons and surface electrons in topological insulators." Nature communications 8, no. 1 , 1-7 (2017). DOI: 10.1038/s41467-017-02264-y
   
5. Peng, Ruoming, Kaveh Khaliji, Nathan Youngblood, Roberto Grassi, Tony Low, and Mo Li. "Midinfrared electro-optic modulation in few-layer black phosphorus." Nano letters 17, no. 10, 6315-6320 (2017). DOI: 10.1021/acs.nanolett.7b03050
   
6. Youngblood, Nathan, Ruoming Peng, Andrei Nemilentsau, Tony Low, and Mo Li. "Layer-tunable third-harmonic generation in multilayer black phosphorus." Acs Photonics 4, no. 1 , 8-14 (2017). DOI: 10.1021/acsphotonics.6b00639
   
7. Li, Mo, Li He, and Seokhyeong Lee. "Chiral interaction between photon angular momentum and surface electrons in topological insulators (Conference Presentation)." In 2D Photonic Materials and Devices III, vol. 11282, p. 112820O. International Society for Optics and Photonics, 2020. DOI: 10.1117/12.2552970
   
8. Peng, Ruoming, Che Chen, and Mo Li. "Broadband waveguide integrated black phosphorus modulator for mid infrared application." In CLEO: Science and Innovations, pp. SM2B-3. Optical Society of America, 2018. DOI: 10.1364/CLEO_SI.2018.SM2B.3
   
9. He, Li, Junyang Chen, and Mo Li. "Coupling photon spin with electron spin in integrated photonic chips." In Optical Fiber Communication Conference, pp. M3G-3. Optical Society of America, 2018. DOI:10.1364/OFC.2018.M3G.3
   

Last Modified: 07/27/2020
Modified by: Mo Li