skip to main content

This content will become publicly available on January 29, 2025

Title: Inverse-designed broadband low-loss grating coupler on thick lithium-niobate-on-insulator platform

A grating coupler on 700-nm-thick Z-cut lithium-niobate-on-insulator platform with high coupling efficiency, large bandwidth, and high fabrication tolerance is designed and optimized by inverse design method. The optimized grating coupler is fabricated with a single set of e-beam lithography and etching process, and it is experimentally characterized to possess peak coupling efficiency of −3.8 dB at 1574.93 nm, 1 dB bandwidth of 71.7 nm, and 3 dB bandwidth of over 120 nm, respectively.

more » « less
Award ID(s):
2048202 2016244
Author(s) / Creator(s):
; ;
Publisher / Repository:
AIP Publishing
Date Published:
Journal Name:
Applied Physics Letters
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Grating coupler devices provide efficient, foundry-compatible vertical fiber-to-chip coupling solutions in integrated photonic platforms. However, standard grating coupler designs are highly polarization sensitive, which hinders their adoption. We present a new, to the best of our knowledge, type of 1D polarization-insensitive grating coupler (PIGC) that is based on a zero-birefringence subwavelength “corelet” waveguide. We demonstrate a PIGC for coupling in the telecommunications O-band in a 45-nm-node monolithic silicon-on-insulator (SOI) CMOS electronic-photonic platform, with measured insertion losses of 6.7 and 6.1 dB to transverse electric and transverse magnetic polarizations, respectively, and a ±1-dB polarization dependent loss bandwidth of 73 nm.

    more » « less
  2. In this paper, we present the design, optimization, and implementation of a sub-wavelength grating (SWG) multi-mode interference coupler (MMI) on the silicon nitride photonic integrated circuit (PIC) platform with a significantly enhanced bandwidth compared to the conventional MMI. We extend the SWG MMI theory, previously presented for the silicon-on-insulator platform, to the Si3N4/SiO2platform. Our approach involves an initial parameter optimization for a non-paired design, followed by a shift to a paired design that offers a smaller footprint and a broader bandwidth. The optimized SWG MMI exhibits a 1 dB bandwidth of 300 nm for both the insertion loss and power imbalance, making it a significant addition to silicon nitride photonics.

    more » « less
  3. We demonstrate robust mode conversion up to the 12th higher order mode in silicon waveguides by using an optimized adiabatic directional coupler and using subwavelength waveguides. The conversion efficiency is better than -1.5 dB over a 75 nm bandwidth and tolerating ±30 nm fabrication variations. 
    more » « less
  4. As silicon photonics transitions from research to commercial deployment, packaging solutions that efficiently couple light into highly compact and functional sub-micrometer silicon waveguides are imperative but remain challenging. The 220 nm silicon-on-insulator (SOI) platform, poised to enable large-scale integration, is the most widely adopted by foundries, resulting in established fabrication processes and extensive photonic component libraries. The development of a highly efficient, scalable, and broadband coupling scheme for this platform is therefore of paramount importance. Leveraging two-photon polymerization (TPP) and a deterministic free-form micro-optics design methodology based on the Fermat’s principle, this work demonstrates an ultra-efficient and broadband 3-D coupler interface between standard SMF-28 single-mode fibers and silicon waveguides on the 220 nm SOI platform. The coupler achieves a low coupling loss of 0.8 dB for the fundamental TE mode, along with 1 dB bandwidth exceeding 180 nm. The broadband operation enables diverse bandwidth-driven applications ranging from communications to spectroscopy. Furthermore, the 3-D free-form coupler also enables large tolerance to fiber misalignments and manufacturing variability, thereby relaxing packaging requirements toward cost reduction capitalizing on standard electronic packaging process flows.

    more » « less
  5. Bragg-grating based cavities and coupler designs present opportunities for flexible allocation of bandwidth and spectrum in silicon photonic devices. Integrated silicon photonic devices are moving toward mainstream, mass adoption, leading to the need for compact Bragg grating based designs. In this work we present a design and experimental validation of a cascaded contra-directional Bragg-grating coupler with a measured main lobe to side-lobe contrast of 12.93 dB. This level of performance is achieved in a more compact size as compared to conventional apodized gratings, and a similar design philosophy can be used to improve side-lobe reduction in grating-based mirror design for on-chip lasers and other cavity-based designs as well. 
    more » « less