Additive manufacturing of precision optics at micro and nanoscale

TL;DR: This review is mainly focused on discussions about optical fabrication at micro and nanoscale since the additive manufacturing processes available today are not easily scalable to large size optics.

Abstract: In optical manufacturing, as an alternative, additive manufacturing processes have been gaining a lot of interest because of their unique capabilities in the fabrication of extremely complex shapes that was quite difficult or impossible in the past using traditional fabrication methods, such as precision machining, compression or injection molding processes. Additive manufacturing also provides extreme flexibility to the design and manufacturing of optical components compared to more traditional processes. Additive manufacturing can be utilized to fabricate single optical elementss or systems at both microscale or nanoscale level. Other advantages over conventional methods are less material waste and less time between design and manufacturing. Moreover, its capability in the manufacturing of multiple parts without assembly, although has not yet been completely developed, can be considered another advantage.  Additive manufacturing of precision optics offers a solution to extremely high level of customization. At present stage, additive manufacturing of precision optical components excels at both microscale (microlens or micromirror) and nanoscale optical fabrication with most work conducted on the processes for microoptical components. Thus this review is mainly focused on discussions about optical fabrication at micro and nanoscale since the additive manufacturing processes available today are not easily scalable to large size optics. The limitations and achievements of these additive manufacturing methods for micro and nanoscale optical fabrication are discussed in details in the review as well. For applications of additive manufacturing of optics with nanoscale features, the processes reviewed include dip pen nanolithography, electrohydrodynamic jet printing, and direct laser writing.  Additive manufacturing of precision optical devices has shown promising results in fabricating high performance optical components. The devices and systems consisting of these components have also demonstrated unique features and performance. Although the exact capability of this exciting technology is difficult to determine based on the existing information, the information available today clearly described a promising group of processes that could potentially revolutionize optical fabrication in the near future. However, before additive manufacturing can be further implemented, there are many unanswered questions and issues need to be resolved. These issues include, but are certainly not limited to, things such as index distribution, geometry, and volume shrinkage of the optical elements. The aim of this review is to provide a platform for researchers and industrial communities to engage and eventually implement this cutting edge manufacturing process and its associated products.