Universal Near-Infrared and Mid-Infrared Optical Modulation for Ultrafast Pulse Generation Enabled by Colloidal Plasmonic Semiconductor Nanocrystals.
Field effect relies on the nonlinear current-voltage relation in semiconductors; analogously, materials that respond nonlinearly to an optical field can be utilized for optical modulation. For instance, nonlinear optical (NLO) materials bearing a saturable absorption (SA) feature an on-off switching behavior at the critical pumping power, thus enabling ultrafast laser pulse generation with high peak power. SA has been observed in diverse materials preferably in its nanoscale form, including both gaped semiconductor nanostructures and gapless materials like graphene; while the presence of optical bandgap and small carrier density have limited the active spectral range and intensity. We show here that solution-processed plasmonic semiconductor nanocrystals exhibit superbroadband (over 400 THz) SA, meanwhile with large modulation depth (∼7 dB) and ultrafast recovery (∼315 fs). Optical modulators fabricated using these plasmonic nanocrystals enable mode-locking and Q-switching operation across the near-infrared and mid-infrared spectral region, as exemplified here by the pulsed lasers realized at 1.0, 1.5, and 2.8 μm bands with minimal pulse duration down to a few hundreds of femtoseconds. The facile accessibility and superbroadband optical nonlinearity offered by these nonconventional plasmonic nanocrystals may stimulate a growing interest in the exploiting of relevant NLO and photonic applications.
Qiangbing
Q
Guo
State Key Laboratory of Precision Spectroscopy, East China Normal University , Shanghai 200062, China.
Yunhua
Y
Yao
Guangdong Provincial Key Laboratory of Nanophotonic Functional Materials and Devices, School of Information and Optoelectronic Science and Engineering, South China Normal University , Guangzhou, Guangdong 510006, China.
Zhi-Chao
ZC
Luo
Key Laboratory for Laser Plasmas (Ministry of Education), IFSA Collaborative Innovation Center, Department of Physics and Astronomy, Shanghai Jiao Tong University , Shanghai 200240, China.
Zhipeng
Z
Qin
Key Laboratory for Laser Plasmas (Ministry of Education), IFSA Collaborative Innovation Center, Department of Physics and Astronomy, Shanghai Jiao Tong University , Shanghai 200240, China.
Guoqiang
G
Xie
Guangdong Provincial Key Laboratory of Nanophotonic Functional Materials and Devices, School of Information and Optoelectronic Science and Engineering, South China Normal University , Guangzhou, Guangdong 510006, China.
Meng
M
Liu
School of Information and Electrical Engineering, Zhejiang University , City College, Hangzhou 310015, China.
Jia
J
Kang
State Key Laboratory of Precision Spectroscopy, East China Normal University , Shanghai 200062, China.
Shian
S
Zhang
School of Information and Electrical Engineering, Zhejiang University , City College, Hangzhou 310015, China.
Gang
G
Bi
Xiaofeng
X
Liu
Jianrong
J
Qiu
localized surface plasmon resonance; nonlinear optics; optical modulation; semiconductor nanocrystals; superbroadband; ultrafast photonics