SAFELOC: self-aligned fiber entry low-loss optical coupler

Published/Posted: August 24, 2026

Authors: R. Kudalippalliyalil; T. Chakraborty; S. T. Lipkowitz; C. Munley; T. E. Murphy; K. E. Grutter

Abstract: We present self-aligned fiber entry low-loss optical couplers (SAFELOCs), three-dimensionally tapered polymer waveguides that efficiently couple tapered optical fibers to on-chip waveguides across multiple material platforms with low insertion loss (≲1 dB) over the C and L -bands. SAFELOCs incorporate 3D fiber receptacles for passive, mechanical alignment, enabling broadband coupling without precision stages or active feedback. Experimental measurements confirm low insertion loss consistent with simulations, and the design can achieve minimal polarization dependence. The tapered fiber receptacle also allows permanent fiber attachment while expanding alignment tolerance, facilitating simultaneous coupling of fiber arrays for multi-port photonic circuits. While demonstrated in the C and L bands on Si3N4, Si, and SU-8, the two-photon lithography fabrication process can be applied to other materials, and the polymer’s broad transparency window suggests compatibility down to 400 nm, highlighting the versatility and scalability of SAFELOCs.

Citation:
R. Kudalippalliyalil, T. Chakraborty, S. T. Lipkowitz, C. Munley, T. E. Murphy and K. E. Grutter, "SAFELOC: self-aligned fiber entry low-loss optical coupler", Opt. Express 34(17) 32424 (2026)
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Manuscript: Kudalippalliyalil_OE_17_32424_2026.pdf

Supplemental Files:

Kudalippalliyalil_OE_17_32424_2026-Supplemental.pdf -