(3+1)D-printed adiabatic 1-to-N couplers

Abstract

Low-loss single-mode optical coupling is a fundamental tool for most photonic networks, in both, classical and quantum settings. Adiabatic coupling can achieve highly efficient and broadband single-mode coupling using tapered waveguides and it is a widespread design in current 2D photonic integrated circuits technology. Optical power transfer between a tapered input and the inversely tapered output waveguides is achieved through evanescent coupling, and the optical mode leaks adiabatically from the input core through the cladding into the output waveguides cores. We have recently shown that for advantageous scaling of photonic networks, unlocking the third dimension for integration is essential. Two-photon polymerization (TPP) is a promising tool allowing dynamic and precise 3D-printing of submicrometric optical components. Here, we leverage rapid fabrication by constructing the entire 3D photonic chip combining one (OPP) and TPP with the (3+1)D flash-TPP lithography configuration, saving up to ≈ 90 % of the printing time compared to full TPP-fabrication. This additional photo-polymerization step provides auxiliary matrix stability for complex structures and sufficient refractive index contrast ∆n ≈ 5 × 10 −3 between core-cladding waveguides and propagation losses of 1.3 dB/mm for single-mode propagation. Overall, we confront different tapering strategies and reduce total losses below ∼ 0.2 dB by tailoring coupling and waveguides geometry. Furthermore, we demonstrate adiabatic broadband functionality from 520 nm to 980 nm and adiabatic couplers with one input and up to 4 outputs. The scalability of output ports here addressed can only be achieved by using the three-spatial dimensions, being such adiabatic implementation impossible in 2D.

(3+1)D printing towards the scalable and efficient integration of high-performance hybrid platforms

“…We developed flash-TPP [2], a simple lithographic configuration that combines DLW-TPP and OPP for the ultra-fast fabrication of polymer-cladded single-mode photonic waveguides and adiabatic splitters. We obtained low 1.3 dB/mm (0.26 dB) propagation (injection) losses and record optical coupling losses of 0.06 dB with very symmetric (3.4 %) splitting ratios for adiabatic couplers [3].…”

“…1 (b-c). Via flash-TPP, we fabricated single-mode * e-mail: adria.grabulosa@femto-st.fr optical splitters leveraging adiabatic transfer from one input to up to 4 outputs in a single component [3]. We showed a general tapering strategy that can be applied to higher-order 1 to M couplers, see the output intensity profiles of 1 to 2, 1 to 3 and 1 to 4 adiabatic couplers in Fig.…”

Two‐Photon Polymerization Lithography for Optics and Photonics: Fundamentals, Materials, Technologies, and Applications

“…[587,588] With the bundle of photonic waveguides, deep neural network based optical image reconstruction has been demonstrated. [587] Combined with the optical interconnects, [589,590] and couplers, [591] along with the rapid development of photonic circuits and chips, all-optical devices capable of in-plane and out-of-plane coupling, signal collection and processing, are possible to be achieved in one 3D printing step. Reproduced with permission.…”

“…With the ~ 25-years development, the application of TPL has been involved in almost all the aspects of optics and photonics, along with the innovation of materials and techniques. From discrete elements to integrated systems, [772,773] from chip-scale to wafer-scale, the pursuit of structural precision, surface smoothness, bulk uniformity, optical transparency, etc. of optical elements never ceased.…”

Additive 3D photonic integration that is CMOS compatible

“…In 3D, 1 to M optical couplers can simply be realized by arranging numerous output waveguides around the input waveguide, something impossible to realize in a purely 2D integration setting. We demonstrated broadband 1 to M splitters leveraging adiabatic coupling [6,63]. Adiabatic coupling achieves low-loss singlemode optical transfer from 1 to M waveguides through evanescent waves, where the optical mode adiabatically leaks from a tapered core of an input waveguide towards the cladding into inversely-tapered cores of the output waveguides [64,65].…”