Michael Pfeffer

Disruptive: making lenses in a foundry

So far, people have thought of optics as mainly consisting of bulky lenses. A team from Harvard University has started to change that. Federico Capasso, the leader of this team, aspires to nothing less than a new kind of optics [1]. His flat lenses, known as metalenses, perform wavefront shaping with nanometer-tall and -wide structures. In a breakthrough reported this year [2], he and his team demonstrated a metalens that focuses all the colors of visible light in the same focal spot of size limited by the diffraction of light. No existing single lens can do that: to make such achromatic lens, a stack of multiple lenses is required, with precisely controlled curvature and optical alignment, which leads to greatly increased weight, thickness, and cost. While applications such as super-thin cellphone lenses are appealing, it is the manufacturing process that excites Federico Capasso: metalenses can be made by conventional lithography used in the fabrication of electronic chips, as his group recently showed [3]. No more molding and polishing: optics and electronics can be made in the same fab. AOT Editor-in-Chief Michael Pfeffer talked to Federico Capasso on his invention and its applications. Andreas Thoss edited and shortened the 40 min conversation.

Reviewer recognition and editor’s note

After several incredibly good years it is surprising to write again: What a year! Once again it was an excellent one for optics and photonics. Sales from fiber laser pioneer IPG topped even the optimistic expectations, Trumpf and Coherent also posted record revenues. Many of these results were driven by investments in semiconductor and consumer electronics industries. And so, lithography giant ASML announced recently, that their EUV sales crossed the 1 billion Euro mark. The same message came from Carl Zeiss, their semiconductor manufacturing business went from 972 million Euro in 2015/2016 to 1.2 billion in 2016/2017. For our journal Advanced Optical Technologies (AOT) it was an exciting year, too. There were lots of excellent papers published, some are already collecting citations. Two examples of those are: – ‘Light sources for high-volume manufacturing EUV lithography: technology, performance, and power scaling’ by Igor Fomenkov et al., and – ‘Characterization and mitigation of 3D mask effects in extreme ultraviolet lithography’ by Andreas Erdmann et al. These two papers stand for a number of excellent publications in advanced lithography, a core topic of AOT. However, AOT covered much more throughout last year: – Photonics in Security Systems/Guest Editors: Hans-Dieter Tholl, Heinz-Wilhelm Hübers – Optical Nanostructuring/Guest Editors: Jan van Schoot, Helmut Schift – Optical Surfaces/Guest Editor: Angela Duparré – Ptychography/Guest Editors: Andreas Erdmann, Guohai Situ

Introduction to the special issue on ‘Standards in Optics and Optical Measurement’

From a purely scientific point of view standards do not appear interesting for a scientific journal. However, as standards are legally considered as ‘generally recognized codes of practice’, scientific evidence has to be provided. Moreover, the method to verify a certain standardized parameter or process has to be taken into account too. This is why we dedicated this issue of Advanced Optical Technologies to ‘Standards in Optics and Optical Measurement’. Especially when it comes to international standards, the aspect of ‘generally recognized codes of practice’ has to face an internationally accepted definition or procedure, beyond all national traditions and customs. This became clearly visible to our editorial board when dealing with Schröder et al.’s contribution on ‘Standardization of light scattering measurements’. Sometimes readers of optical ISO standards may wonder about ‘somehow strange indications’. Often these are the result of long discussions and acceptance processes by the national committees; especially, because mostly the national language of the majority of ISO members is not English. Often there is no direct linguistic correspondence for certain technical expressions, thus traditional national expressions and definitions have to be brought into question and premised on a clear scientific base. As we are all interested in protecting our health, especially our eyes, against harmful optical radiation, the article of Gappenach et al. addresses all those being interested in the scientific base when selecting laser eye protectors. The challenge for the members of the corresponding technical committee TC 94 was not only to manage the physical technical issues but also to respect biomedical and health-protection criteria. Again, scientific evidence has to be proven. Materials with new properties will certainly play a major role in future optical systems, devices and elements. Along with the increased importance of materials, the challenge of how to verify and characterize certain material parameters emerges. Standards could play a prominent role here. That is why we decided to invite Peter Hartmann to do a review article on optical glass standards. Most people will hardly distinguish between the characteristics of standards, e.g. published as MIL-standards and those published as ISO-standards. However, with respect to the origination process these two standard types differ greatly. Whereas the first are merely driven by governmental, political or societal aspects, the latter are driven by economical and industrial parameters. Subsequently, the origination process is typically a topdown-process in the case of MIL-standards, whereas ISO-standards are created by multinational teams in a democratic bottom-up process. However, this requires much more balancing and therefore a clear scientific base. Within ISO the field of optics and photonics is mainly covered by the Technical Committee TC 172, dealing with standardization of terminology, requirements, interfaces and test methods in the field of optics and photonics. This includes complete systems, devices, instruments, ophthalmic optics, optical and photonic components, auxiliary devices and accessories, as well as materials. Optics and photonics are used in the meaning of generation, handling and detection of optical radiation including signal processing. For specific items there are further technical committees such as in the field of cinematography (ISO/ TC 36), photography (ISO/TC 42), eye protectors (ISO/TC 94), micrographics (ISO/TC 171), fiber optics for telecommunication (IEC/TC 86) and electrical safety of optical elements, and general lighting. Standards are a crucial requirement in the global development processes of complex products such as optical systems. In this issue we intend to cover some of the new and challenging aspects in the development of such standards. I hope that you find it as exciting to read as we did to prepare.

Optics for laser material processing

No abstract available.