Double microlens arrays (MLAs) in series can be used to divide and superpose laser beam so as to achieve a homogenized spot. However, for laser beam homogenization with high coherence, the periodic lattice distribution in the homogenized spot will be generated due to the periodicity of the traditional MLA, which greatly reduces the uniformity of the homogenized spot. To solve this problem, a monolithic and highly integrated double-sided random microlens array (D-rMLA) is proposed for the purpose of achieving laser beam homogenization. The periodicity of the MLA is disturbed by the closely arranged microlens structures with random apertures. And the random speckle field is achieved to improve the uniformity of the homogenized spot by the superposition of the divided sub-beams. In addition, the double-sided exposure technique is proposed to prepare the rMLA on both sides of the same substrate with high precision alignment to form an integrated D-rMLA structure, which avoids the strict alignment problem in the installation process of traditional discrete MLAs. Then the laser beam homogenization experiments have been carried out by using the prepared D-rMLA structure. The laser beam homogenized spots of different wavelengths have been tested, including the wavelengths of 650 nm (R), 532 nm (G), and 405 nm (B). The experimental results show that the uniformity of the RGB homogenized spots is about 91%, 89%, and 90%. And the energy utilization rate is about 89%, 87%, 86%, respectively. Hence, the prepared structure has high laser beam homogenization ability and energy utilization rate, which is suitable for wide wavelength regime.

The miniaturized and integrated microlens array (MLA) can effectively achieve the beam homogenization, compactness and miniaturization of laser systems. When the high-coherence laser beam is homogenized by means of using the MLA, interference fringes will occur in the homogenized light spot due to the periodicity of the MLA, which seriously affects the uniformity of the homogenized light spot. To solve this problem, a novel random microlens array (rMLA) structure was proposed for the purpose of achieving beam homogenization. The coherence in the homogenization process is suppressed by means of breaking the periodicity of the MLA. The homogenized light spot with a high energy utilization is then obtained accordingly. In the fabrication process, a clever method of combining chemical etching with lithography technology is performed to fabricate a honeycomb rMLA and a rectangular rMLA. The experimental results show that the energy utilization rate of the two types of the rMLAs is about 90%, and the uniformity of the homogenized light spots generated by the honeycomb rMLA and the rectangular rMLA are more than 80% and 85%, respectively. Meanwhile, fully cost-effective fabrication is possible to be realized.

When the high coherence laser beam is homogenized by microlens array (MLA), interference fringes will be generated reducing the uniformity of homogenized spot. A novel close packed random rectangular microlens array (rRMLA) is proposed to solve this problem. By designing the MLA with random apertures and random focal lengths of sub-lenses, the phase regulation can be realized, so as to disturb the coherent superposition fringes for improving the uniformity. To realize the dense arrangement of a MLA with random rectangular aperture, an iterative segmentation method is proposed to design the structure of rRMLA with controllable divergence angle and high filling factor. Theoretical simulations and experimental results both demonstrate the improvement of uniformity of the homogenized spot based on the proposed rRMLA.

Miniaturized bionic compound eyes featured with multi-aperture imaging have potential applications in the areas of micro opto-electro-mechanical-system. In this manuscript, we present a novel structure of the bionic compound eye with multiple focal lengths consists of an array of individual lenses with 1000 µm diameter. The simulation results of the designed multifocal bionic compound eye (MBCE) with two focal lengths of 190 mm and 44.4 mm demonstrate excellent two-order focusing abilities. Moving mask exposure technology was used to fabricate the designed MBCE with the corresponding imaging experiments conducted to validate the two-order imaging ability of the fabricated MBCE. Experimental results revealed that the developed structure has potential applications in diverse optical imaging systems such as three-dimensional imaging and real-time detection of unconfined or fluctuating targets.

We have recently shown that spiral phase plates (SPPs) with continuous surface can be fabricated with one time exposing process only [35]. Four categories of SPPs with different topological charges at wavelength of 532 nm were prepared, and the corresponding vortex beams were obtained. In this paper, in order to verify the optical effects' quality of the SPPs, the optical characteristics, including the diffractive and interferential characteristics, were systematically analyzed in the Fresnel diffraction region. In addition, the optical characteristics have been used to describe the surface profile of the SPPs. The results show that the SPPs have good surface quality and excellent optical effects. Compared with the other generation methods for vortex beam, this method is particularly suitable for obtaining a vortex beam with high efficiency and continuous phase and is extremely promoting R&D of the corresponding applications.

The artificial compound eye (ACE) structure is a new type of miniaturized, lightweight and intelligent imaging system. This paper has proposed to design a multi-spectral ACE structure to enable the structure to achieve multi-spectral information on the basis of imaging. The sub-eyes in the compound eye structure have been designed as diffractive beam splitting lenses with the same focal length of 20 mm, but with the different designed center wavelengths of 650 nm, 532 nm, and 445 nm, respectively. The proximity exposure lithography and reactive ion etching process were used to prepare the designed multi-spectral ACE structure, and the spectral splitting and multi-spectral imaging experiments were carried out to verify the multi-spectral imaging function of the structure without axial movement. Furthermore, the structure can be designed according to actual requirements, which can be applied to covert reconnaissance, camouflage identification, gas leakage or other fields.