## 1 Introduction  
High-aspect-ratio, sub-wavelength structures have a wide range of applications in major projects such as metasurfaces, X-ray diffraction spectroscopy devices, space particle capture, and deep-grain film imaging devices for space-to-ground observation [1; 2]. Laser processing technologies, which are universal tools for manufacturing, have become one of the main methods of nano-processing due to their high precision [3]. To manufacture a high-aspect-ratio, sub-wavelength structure, the resolution and depth of focus (DOF) in laser processing technologies need to be improved simultaneously. Generally, in traditional laser processing technologies such as nanoimprint lithography, electron beam direct-writing lithography, multi-photon direct writing, etc. [4; 5; 6], resolution can be improved by increasing the numerical aperture (NA) of the lens, but this will cause rapid divergence along the focal point in the direction of beam propagation. Therefore, laser processing cannot be realized within a certain depth range. Breaking through the physical limitations of long DOF and high resolution has always been a major scientific problem in super-diffraction laser processing. However, an optical needle with high purity longitudinal polarization and homogeneous intensity along the optical axis can increase resolution while increasing the DOF. This has potential applications in optical manipulation and acceleration [7], optical trapping [7, 8], material processing [9], super-resolution focus [10, 11], and optical data storage [12], which has attracted great attention from scientists in this field. The traditional method of creating an optical needle is to use a high NA objective lens to tightly focus a cylindrical vector beam incident parallel to the optical axis [13]. In addition, to improve the DOF and resolution of the optical needle, many scientists have designed filters with different structures to modulate the incident beam. For instance, [PERSON] et al. designed a phase filter composed of a 0, \(\pi\) ring phase structure. The phase filter was introduced to control the light field in the focal region by polarization and phase modulation [14]. According to the principle of multi-focus superposition, an amplitude filter based on Euler transformation, which was applied to modulate the amplitude and phase of the incident radial polarized Bessel-Gaussian beam, was proposed to generate the longitudinally polarized long focal depth structure [15]. Moreover, a high-purity longitudinal polarization field with extremely long depth of focus can be obtained by focusing the polarized beam using a simplified discrete complex pupil filter and a high NA lens [16]. All of the above methods improve the resolution or the DOF of the optical needle. However, the created optical needle is immovable, which is called a static optical needle. Traditional laser processing technologies usually use both mechanical scanning and vector scanning to increase processing speed [17], while the laser processing method based on a static optical needle can only use mechanical scanning. In addition, it has been found that the oblique incidence angle of the incident beam will reduce the DOF of the optical needle, so it is necessary to accurately control the angle of the incident beam, which is difficult for laser processing. In this paper, we propose a modulation and control technology for generating movable super-diffraction optical needles by oblique incidence. The confocal scanning system consists of a two-dimensional (2D) galvanometer system, a scan lens, and a tube lens, which is used to achieve oblique incidence control instead of normal incidence. According to vector diffraction theory, we establish a mathematical and physical model for modulating and controlling the movable super-diffraction optical needle (MSON). We then simulate and analyze the effect of oblique incidence on the resolution, DOF, uniformity, and side lobes of the MSON.