Highly efficient broadband silicon nitride polarization beam splitter incorporating serially cascaded asymmetric directional couplers

Abstract

The implementation of a polarization beam splitter (PBS) on a silicon nitride platform remains challenging owing to its relatively low index. We therefore propose a silicon nitride PBS that exploits serially cascaded asymmetric directional couplers (ADCs), leading to a high polarization extinction ratio (PER) over a broad bandwidth. The ADC spatially routes incident light through polarization-selective mode coupling under a small footprint of 112 µm. The proposed PBS does not require an active phase control. It is thus effectively realized via a single-step lithography process. The measured transverse-electric and transverse-magnetic PERs were determined to be above 23 dB and 10 dB over an 80-nm bandwidth, respectively, spanning λ = 1520 − 1600 n m . The proposed device is thus anticipated to play a key role in providing polarization diversity in photonic-integrated circuits.

Dispersive silicon–nitride optical phased array incorporating arrayed waveguide delay lines for passive line beam scanning

“…2 a. To achieve single-mode operation, SiN waveguides were designed by resorting to a width (W wg ) and thickness of 1 µm and 500 nm, respectively 16 , 20 . The tapers acting as the LBE elements adjust the effective aperture at the end facet, facilitating a flexible full width at half maximum beamwidth (Δθ FWHM ) along the vertical direction.…”

“…Arrays of tapered waveguides have been used to implement a line beam emitter, with the intention of adjusting the beamwidth along the vertical direction. Because line beam scanning with AWDLs increases propagation loss due to the increased waveguide length, we adopted silicon nitride as the material of choice because of its low propagation loss and high-power handling capacity 16 – 19 . To the best of our knowledge, there has been no report on a dispersive OPA that enables passive line-beam scanning.…”

Reconfigurable fiber-to-waveguide coupling module enabled by phase-change material incorporated switchable directional couplers

“…The optimal parameters of the widths and gap of the SDC were determined by meticulously analyzing the effective refractive indices of its eigenmodes. To ensure single-mode operation for a 500-nm thick SiN waveguide 5 , the w 1 and w 3 values were identically set at 750 nm. Figure 3 a portrays the TE field distribution of the supermodes pertaining to the SDC at λ = 1550 nm for both the aGSST and cGSST states.…”

Polarization/wavelength multiplexing devices realized by silicon nitride subwavelength grating structures

“…As another choice on CMOS platform of silicon photonics, SiN could offer extra benefits such as large visible range, low propagation loss, large bandwidth, etc [11][12][13][14][15]. But according to our knowledge, there are still very few studies on SWGbased devices made of SiN, probably due to its relatively low refractive index.…”