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        Ultra-long-working-distance spectroscopy with 3-D-printed as

        time:2020-05-09 source:browse:182

        Ultra-long-working-distance spectroscopy with 3-D-printed aspherical microlenses

        Ultra-long-working-distance spectroscopy with 3D-printed aspherical microlenses
        Scanning electron microscope image of 3D-printed aspherical microlenses. Thanks to short printing time, it is possible to produce hundreds of such microlenses on one sample Credit: Aleksander Bogucki, et al

        Additive manufacturing is a technique in which a three-dimensional object is produced by successively adding new layers of building material to those that have already been deposited. Recently, commercially available 3-D printers have been experiencing rapid development and so have 3-D-printing materials, including transparent media of high optical quality. These advancements open up new possibilities in many fields of science and technology including biology, medicine, metamaterials studies, robotics and micro-optics.

        Researchers from the Faculty of Physics, University of Warsaw, Poland, have designed tiny lenses (with dimensions as small as a fraction of a human hair diameter) that can easily be manufactured using a laser 3-D printing technique on top of various materials, including fragile novel 2-D graphene-like materials. The lenses increase the extraction of light emitted from semiconductor samples and reshape its outgoing part into an ultra-narrow beam.

        Thanks to this property, there is no longer a need for including a bulky microscope objective in the experimental setup when performing optical measurements of single nanometre-sized light emitters (like quantum dots), which up to now could not be avoided. A typical microscope objective used in such a study has roughly a handbreadth size, weights up to one pound (half a kilogram) and must be placed at a distance of about one-tenth of an inch (few millimetres) from the analysis sample. These impose significant limitations on many types of modern experiments, like measurements in pulsed high magnetic fields, at , or in microwave cavities, which on the other hand can easily be lifted by the new lenses.

        The high speed of the 3-D-printing technique makes it very easy to produce hundreds of microlenses on one sample. Arranging them into regular arrays provides a convenient coordinate system, which accurately specifies the location of a chosen nanoobject and allows for multiple measurements in different laboratories all over the world. The invaluable opportunity of coming back to the same light emitter allows for much more time-efficient research and hypothesis testing. Specifically, one can entirely focus on designing and performing a new experiment on the nanoobject studied before, instead of carrying out a time-consuming investigation of thousands of other nanoobjects before eventually finding an analogue to the one in question.

        The shape of the proposed microlenses can easily be adapted to the so-called 2.5-D microfabrication technique. The objects satisfying its prerequisites can be produced over large-scale surfaces by pressing a patterned stamp against the layer of material they are supposed to be made of. The 2.5-D fabrication protocol is especially attractive from the viewpoint of potential applications of the microlenses, as can be readily up-scaled, which is an important factor in possible future industrial use.