Colorless grating couplers realized by interleaving dispersion engineered subwavelength structures

Abstract

We investigate the waveguide dispersion of subwavelength structures, and propose that the waveguide dispersion can be reduced by reducing the period of subwavelength structures. A 3 dB bandwidth increment of 20% has been observed by introducing this concept into previously demonstrated grating couplers. To fully exploit the bandwidth merits of the structures, gratings with interleaved subwavelength structures were designed and fabricated. Two typical types of interleaving geometries have been investigated. Both demonstrated a 1 dB bandwidth ∼70 nm, a 3 dB bandwidth ∼117 nm, and a peak efficiency ∼-5.1 dB at 1570 nm for transverse-electric polarized light. The simulation confirms that the dispersion engineering adds an extra 12 nm to the 1 dB bandwidth.

High‐Speed Modulator Based on Electro‐Optic Polymer Infiltrated Subwavelength Grating Waveguide Ring Resonator

“…A polarization maintaining fiber (PMF, OZ Optics PMF‐1550‐8/125‐0.25‐L) is used to couple the light into the modulator. The light from the output grating coupler is collected by a standard single mode fiber (SMF, Corning SMF‐28) . The RF signal, which is output from the port #1 of the vector network analyzer (VNA, Agilent N5230A), is applied to the sample via a GSG probe (Cascade ACP40‐GSG‐250).…”

“…The light from the output grating coupler is collected by a standard single mode fiber (SMF, Corning SMF-28). [50,51] The RF signal, which is output from the port #1 of the vector network analyzer (VNA, Agilent N5230A), is applied to the sample via a GSG probe (Cascade ACP40-GSG-250). The aligned grating couplers and the applied GSG probe is shown in Figure 3f.…”

“…The proposed SWG ring resonator based modulator is shown in Figure a. Subwavelength grating couplers are exploited for interfacing single mode fibers . The rounded rectangular shape is adopted instead of the most common circular shape to gain more flexibility in tuning the coupling strength between the bus waveguide and the ring resonator.…”

“…Subwavelength grating couplers are exploited for interfacing single mode fibers. [50,51] The rounded rectangular shape is adopted instead of the most common circular shape to gain more flexibility in tuning the coupling strength between the bus waveguide and the ring resonator. The zoomed-in schematic of the SWG ring resonator is shown in Figure 2b.…”

Integrated dispersive structures for bandwidth-enhancement of silicon grating couplers

“…However, the spectral distribution of the efficiency of grating couplers is not uniform, but has a maximum at a distinct wavelength and then decays on both sides, resulting in a limited optical bandwidth of about 40 nm (Hoppe et al 2020;Zaoui et al 2014). There are other designs with enhanced bandwidth (Chen et al 2011Xu et al 2013), but reduced efficiency. Obviously, there is a trade-off between maximal coupling efficiency and bandwidth.…”