|
Two-photon lithography based 3D Direct Laser Writing (DLW) has shown its unique potential as a method to fabricate and integrate miniaturized optical elements which can parallel the function of bulk optical elements used in large scale systems [1]. Up to now, this fabrication method has been mainly used to obtain reflective, refractive and diffractive optical elements. The difficulty on using and controlling printable materials with intrinsic birefringence in 3D DLW has so far prevented the scaling down of polarization retarders elements. Here we present the DLW fabrication of a miniaturized Fresnel Rhomb, which is a prism in which the light gets reflected two times with a precise incidence angle to have a 90 degrees phase shift between the p and s polarization components, thus acting as a quarter-waveplate. Being not based on an intrinsically birefringent material, this optical element features a very broadband behavior covering a band exceeding 300 nm. To demonstrate the direct integration and flexibility provided by this method we have printed a miniaturized optical assembly consisting of the Fresnel Rhomb and a collimating micro lens on a polarization maintaining optical fiber so as to obtain a miniaturized on-fiber broadband source of pure circularly polarized light. This structure could find application to create a remote ultra compact probe in circular dichroism and Raman Optical Activity spectroscopies but could also be used as a phase retarder for other integrated applications, where control of the polarization on small scales is needed.
[1] Dietrich, P. I., Blaicher, M., Reuter, I., Billah, M., Hoose, T., Hofmann, A., et al. (2018). In situ 3D nanoprinting of free-form coupling elements for hybrid photonic integration. Nature Photonics, 1–9. http://doi.org/10.1038/s41566-018-0133-4
|
