## 1 Introduction  
The pattern of the laser beam profile is represented as a similar Gaussian intensity shape, followed by a dynamic spatial energy distribution according to the beam generation mechanism [1]. Nevertheless, several popular applications for a uniform intensity distribution would be desirable. For instance, a uniform intensity distribution in manufacturing materials means that the whole laser-lighted area is uniform. It is also useful in cases where laser light is mainly utilized for lighting. This is because consistent illumination gives identical features the same brightness regardless of where they are in the illumination field; thus, the image-processing task is simplified, and the contrast and resolution are improved. These same advantages extend to broad applications, not only in scientific studies but also in medicine. There are many strategies to convert a Gaussian beam into a uniform intensity distribution, such as spherical microlenses, freeform lenses, and aplanatic optics. [PERSON] proposed using micro-lenslet arrays to overcome the restriction in the size of optical systems [2]. [PERSON] proposed a novel circular dielectric internally reflecting optic, which can produce over 95% uniformity within an illuminated area [3]. [PERSON] presented a promising representative design for LED collimation [4]. Compared to free-form lenses, microlenses and CMA can overcome the restrictions in size to create extremely compact and lightweight optical systems. CMA not only has the function based on spherical microlens array but can also achieve a performance with a long focal depth and high lateral resolution. It can improve the output efficiency of OLEDs and the image quality at the same time. One of the most effective and flexible approaches is using a CMA. However, the fabrication of a CMA with complex features brings huge challenges to optical applications. Various techniques for manufacturing CMAs [5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18] are still being developed. The manufacturing techniques can be categorized into nonmechanical and mechanical methods based on the properties of material removal. The comparison of different manufacturing techniques for microlenses is summarized in Table 1.  
The most commonly nonmechanical methods contain reactive ion etching [8], photolithography [10], and femtosecond direct writing technology [11; 12]. However, these methods are restricted by manufacturing with expensive devices, particular materials, and time-consuming production procedures [13; 14]. Furthermore, available lens geometries are limited, and these current machining methods have difficulty achieving the shape accuracy in lens arrays [15; 16]. To realize the production of low-cost and high-precision lenses, ultra-precision machining methods are widely used in manufacturing moulds, including glass moulding and film rolling moulds [17]. However, the high rigidity and brittleness of glass make it difficult to machine by the roll-to-roll method. In modern industry, glass moulding has become an important replication-based technology for mass manufacturing these optical glass components [18]. Since the precision and quality of the machined surface will be directly reflected on the products, the structural mould still needs to be processed with ultra-precision machining technology to ensure that CMA has a high quality of the surface and precision. The ceramics (e.g., silicon carbide (SiC) and silicon nitride (SiN)) have excellent material properties, such as high wear resistance, great chemical stability, high thermal conductivity, high hardness, and high strength [5]. Increasingly, moulds are made of ceramics (such as SiC and SiN) rather than traditional metal materials. Furthermore, due to the high wear resistance and strength, it is extremely hard to machine micro-patterns on the ceramic surface.