3D-printed facet-attached microlenses for advanced photonic system assembly

Abstract

Wafer-level mass production of photonic integrated circuits (PIC) has become a technological mainstay in the field of optics and photonics, enabling many novel and disrupting a wide range of existing applications. However, scalable photonic packaging and system assembly still represents a major challenge that often hinders commercial adoption of PIC-based solutions. Specifically, chip-to-chip and fiber-to-chip connections often rely on so-called active alignment techniques, where the coupling efficiency is continuously measured and optimized during the assembly process. This unavoidably leads to technically complex assembly processes and high cost, thereby eliminating most of the inherent scalability advantages of PIC-based solutions. In this paper, we demonstrate that 3D-printed facet-attached microlenses (FaML) can overcome this problem by opening an attractive path towards highly scalable photonic system assembly, relying entirely on passive assembly techniques based on industry-standard machine vision and/or simple mechanical stops. FaML can be printed with high precision to the facets of optical componen ts using multi-photon lithography, thereby offering the possibility to shape the emitted beams by freely designed refractive or reflective surfaces. Specifically, the emitted beams can be collimated to a comparatively large diameter that is independent of the device-specific mode fields, thereby relaxing both axial and lateral alignment tolerances. Moreover, the FaML concept allows to insert discrete optical elements such as optical isolators into the free-space beam paths between PIC facets. We show the viability and the versatility of the scheme in a series of selected experiments of high technical relevance, comprising pluggable fiber-chip interfaces, the combination of PIC with discrete micro-optical elements such as polarization beam splitters, as well as coupling with ultra-low back-reflection based on non-planar beam paths that only comprise tilted optical surfaces. Based on our results, we believe that the FaML concept opens an attractive path towards novel PIC-based system architectures that combine the distinct advantages of different photonic integration platforms.

Coupling Nanowire Quantum Dots to Optical Waveguides by Microsphere-Induced Photonic Nanojet

“…New advances in the development of 3D printing of microlenses by multiphoton laser lithography [45] could provide useful tools for the monolithic integration of microspheres and a facilitation of nanowire coupling. Furthermore, new photonic assembly techniques based on 3D-printed facet-attached microlenses [46] in optical circuits could be also investigated in terms of their adaptability to host nanowires in a controllable way as quantum emitters. However, it is anticipated that the requirement of high-refractive index (>1.75) microspheres would be very challenging to be met by the 3D printing of mainly polymer materials.…”

Imaging/nonimaging microoptical elements and stereoscopic systems based on femtosecond laser direct writing

“…Asa et al proposed an efficient optical trapping technique based on a reverse transmission fiber that uses a converged fiber with a 3D-printed diffractive Fresnel lens on its surface 247 . Based on the basic principle of conventional optical trapping, increasing the NA of the focused beam changes the distribution of optical forces, leading to optical trapping in both the lateral and axial directions, as shown in Fig.…”

Packaging of micro-lens arrays to photonic integrated circuits using beam shape evaluation

“…However, the methods of attachment of the MLs to the PIC are still time-consuming and expensive, therefore the benefit of PIC pluggability cannot be utilized on a commercial high-volume scale. There are methods of 3D-printing of MLs directly on the PIC facet [19], although they bear severe limitations. The main issue is that it is much more difficult to expand the beam to sufficiently large mode-field diameters (MFDs upwards of 50 µm-a minimal requirement for pluggability) because the lenses would have to be very long.…”