Laser terahertz emission microscopy of nanostructured spintronic emitters

Abstract

Laser terahertz (THz) emission spectroscopy has broken the diffraction limit of THz frequencies and offers multifaceted spectroscopic and imaging capabilities for understanding the light–matter interaction in various quantum and energy materials. However, this advanced technique has not yet been applied in the recently extensively studied spintronic THz emission process, in which the material surface morphology may play an important role. Here, we conduct THz emission microscopy on 5.4-nm thick Pt/CoFeB/W heterostructures and obtain twice enhanced THz by tightly focusing the pumping laser, delicately choosing the radiation location on nanofilms and coating gold nanorods. Through THz emission mapping, the material surface morphology and its modification have a strong correlation with THz emission performance from spintronic emitters. Our proposed femtosecond fiber laser driven spintronic THz emission microscopy can provide exciting possibilities for studying surface morphology sensitive THz emission materials and microdomain ultrafast dynamics for low-dimensional small samples via further coupling optical microscopy.