## 1 Introduction  
As a new type of one-dimensional nanomaterial, carbon nanotubes (CNTs) have been proved to have excellent performance in electrical, mechanical and thermal fields, and have broad application prospects in the manufacture of Micro-Nano devices [1; 2]. However, the excellent electrical properties of CNTs cannot be reflected very well due to the difficulty in forming a reliable Ohmic contact between the CNTs and the electrodes in the preparation of the Micro-Nano devices. Therefore, the development of Micro-Nano devices based on CNTs is restricted [3]. The main problem is that when the size of the connection and the accuracy of the interconnection become more than a certain scale range, the energy field law and connection principle of the connect process make a qualitative change due to the size effect, which will seriously restrict the reliability and stability of CNTs-based electronic device connects. In order to solve this problem, various physical or chemical methods have been explored to achieve a connection [4; 5; 6; 7; 8; 9]. For example, [PERSON] [10] obtained good results using rapid annealing to reduce the electrical resistance of the contact surface between the CNTs and electrodes. However, the method may damage the CNTs in a large area or cause damage to a circuit composed of low-melting-point material. [PERSON] [11] used electron beam-induced deposition (EBID) technology to deposit graphitized carbon, which achieved Ohmic contact between end-opening multi-walled carbon nanotubes (MWCNTs) and metal electrodes in the low temperature manufacturing process. However, because the deposition solder at a specific location is difficult to achieve and may affect certain circuits, it is hard to meet the needs of large-scale fabrication with this method.  
Laser beams have been used in the fabrication of Micro-Nano devices widely. They mainly depend upon the thermal effect of laser to realize the connection between CNTs and the metal electrodes. The connection effect obtained by laser irradiation has the advantages of smaller contact resistance [12], higher stability and better mechanical properties, compared with other physical or chemical methods [13; 14; 15; 16]. However, the reduction of the size of the electrodes and the thickness results in significant size effect [17]; therefore, the higher laser power radiates the thermal effect of the metal surface to destroy the metal surface, which is unacceptable. A lower laser power does not form enough heat accumulation on the surface to make a connection possible.  
In this paper, we used femtosecond laser illumination to connect single-walled carbon nanotubes (SWCNTs) and MWCNTs to the electrodes. The femtosecond laser pulse width is smaller than the electron cooling time, making it possible to add significant energy to the target material before mechanical or thermal responses can take place [18], and the damage of the surface morphology of the electrode by heat accumulation can be avoided. At the same time, femtosecond laser irradiation will cause Plasmon resonance on the metal surface, accelerating the atom diffusion inside the material, thereby realizing the connection between the CNTs and the electrodes [19]. The characterization and analysis of the experimental results show that under the irradiation of a femtosecond laser, both SWCNTs and MWCNTs have a good connection with the electrodes. The resistance of the SWCNTs in contact with the electrodes was tested, and the results showed that it was greatly reduced.