For Scientific Research & Industry Modernisation.
Fig. 1. The microlens array designed by Innofocus. As shown in the figure, the microlens array are all in the same plane, while forming a dense structure with no gaps in between.
One important branch of computational imaging is light field imaging. The core optical element in optical field imaging is the microlens array, which is made of transparent glass with many tiny lenses engraved on its surface to form an array structure for imaging. The relatively established process for making quartz microlenses is photoresist patterning with engraving, but there are various problems with this method.
The commonly used photoresist method of producing graphics with engraving is not freely adjustable as the design of the lens needs to be determined by the mask plate graphics, and is costly, requiring processing of the mask plate for each new design of the lens array. In addition, each new design involves the fabrication of a new mask plate, resulting in a complicated and time-consuming process.
Based on Innofocus’ understanding of fabricating micro-optical components, we use laser 3D nano-printing to fabricate micro-lens arrays in a way that overcomes the problems faced by traditional processes. There are two main methods:
1. Polymer mask etching
This mainly includes two steps:
1) Fabrication of microlens array structures in polymers using laser nano 3D printing
2) The polymeric microlens array is then used as a mask to transfer the pattern onto the quartz substrate by means of etching
2. Laser direct writing in quartz glass coupled with selective acid etching
This mainly includes two steps:
1) A high power laser is used to introduce a phase transition directly inside the quartz glass by means of a femtosecond laser to write the anti-structure of the microlens array
2) Using selective acid etching to remove the area that need to be etched.
Fig. 2. The surface morphology of a single microlens
Fig. 3. The surface morphology of 2X2 microlens
The cost of laser processing is extremely low as no mask production is required, and each new lens array design only requires the generation of a new processing file, allowing for rapid design optimisation comparisons
Widely used in virtual reality, automotive lighting, optical imaging, radar ranging, infrared imaging
Femtosecond laser processing with the NanoPrint 3D Intelligent Nano-fabrication system allows direct writing of micro-, sub-micron and even nano-scale 3D micro and nano structures in transparent media, with the advantages of maskless, flexible structure, simple design and fast processing speed. By combining with different optical materials, it can achieve a wide range of applications in the field of all-optical communication, especially in the fabrication of diffractive optics, integrated optics, on-chip optics, silicon photonics, nano-optics, and quantum optics, which stand out among the many micro and nano fabrication technologies and become increasingly important in enabling technology.
Three-dimensional micro-nano structures can be designed to enhance the interaction between the local optical field and matter, thus giving rise to a variety of linear and non-linear optical phenomena and shortening the scale of action, thus effectively achieving miniaturization, integration and low energy consumption of devices. For example, Nanoprint 3D Intelligent Laser Nano-Fabrication system can realize various miniature diffractive optical elements including micro-lens, integrated grating, and waveband sheet, which can play a great role in imaging, wavelength selection and dispersion compensation.
In addition, the NanoPrint system’s unique high-power femtosecond laser enables interaction with different materials such as glass, silicon, sulfur-based glass, and lithium niobate crystals. These materials can effectively introduce nonlinear optical interactions for wavelength conversion, optical switching, nonlinear tuning, etc. Nonlinear interactions in nanoscale waveguides can be exploited to generate effective sources of entangled photons for quantum optics. Femtosecond lasers can introduce ultra-high refractive index changes in optical fibers, bulk glass, and two-dimensional materials to form high-quality optical waveguides, ultra-thin devices, and complex three-dimensional integrated optical systems such as optical connectors and on-chip integration, which are essential enabling components for ultrafast, ultra-high-capacity, and quantum communications
Micro-optical components are key components in the manufacture of small optoelectronic systems, which have the advantages of small size, light weight, low cost, and can achieve novel functions such as tiny, array, integration, imaging and wavefront conversion that are difficult to achieve with ordinary optical components. At present, miniaturization and integration of optical systems have become a major trend in various applications. Micro-optics are playing an increasing role in optical imaging and display systems, optoelectronic systems, laser devices, thermal imaging devices, night vision devices, infrared scanning devices, display systems, camera systems, zoom lenses, medical diagnostic fundoscopes, endoscopes, progressive lenses, cell phones, PDAs, CDs and DVDs, etc.
Driven by the application demand, the research on micro-optical component fabrication technology is also in progress. In addition to the traditional ultra-precision mechanical fabrication technology, a variety of modern fabrication technologies have also emerged, such as electron beam writing technology, photolithography, etching technology, replication technology and coating technology. These technologies are developed from microelectronic component microfabrication technology, but unlike the original electronic components, three-dimensional molding accuracy and assembly accuracy is critical for optical components, will directly affect their performance, so each of these methods has its own defects and limitations of use. Generally speaking, machining accuracy and machining speed and output are conflicting goals that are difficult to balance.
The fabrication of NanoPrint 3D Intelligent Laser Nano-fabrication system, based on the non-linear action of laser and matter, can realize three-dimensional high-precision micro-nano structures in a variety of materials, providing a new idea for micro-optical component fabrication. It also utilizes the technology of multi-focus parallel processing, which can increase the fabrication efficiency and productivity hundreds of times, pushing the laser direct writing technology from the laboratory to the production manufacturing environment.
The laser 3D nano-fabrication technology represented by NanoPrint system has realized the fabrication of aspheric lenses, microlens arrays, pyramidal microstructure surfaces, reflection-reducing gratings, free-form optical elements and other structures with advantages that traditional fabrication equipment does not have, such as flexible structure design, high precision and high speed. It is mainly characterized by the ability to fabricate true three-dimensional structures with nanometer-level precision.