Silicon lateral-apodized add–drop filter for on-chip optical interconnection

Abstract

A lateral-apodized add-drop filter is demonstrated in a multimode asymmetric waveguide Bragg grating. This design utilizes two individual superposed gratings with the same sidewall corrugation depth. The strong side lobes of the grating filter are efficiently suppressed by mapping the target apodization profile into lateral shifts between the periods of the two gratings. Compared with other apodized technology, this device is easier to be realized. Experimental results show that the side-lobes suppression ratio can reach 18.5 dB, and a bandwidth of 9.5 nm is achieved by a large corrugation width of 150 nm. The insertion loss at the drop port is only 0.8 dB, and the extinction ratio is up to 24 dB at the through port.

Polarization Splitter-Rotator Based on Multimode Waveguide Grating

“…For the uniform MWG considered above, the parameters extracted from the dispersion diagram of Figure 2a are Ng TE1 = 5.05, Ng TM0 = 4.11, and ∆λ/λ 2 c = 0.463 × 10 3 m −1 , leading to κ = 6.66 × 10 3 m −1 . This value is lower than the one of common waveguide Bragg gratings without polarization conversion, typically > 50 × 10 3 m −1 [40]. Additionally, we can effectively tune κ by using lateral phase delay modulation [41], for the purpose of apodization design.…”

Silicon photonic filters

“…Therefore, circulators are usually needed for separating the reflected light from the input port, which makes the system very complicated. In order to solve this problem, a promising approach is developing add‐drop photonic filters with four ports (ie, input, through, drop and add) by introducing some other waveguide structures, including the combination of an MMI and two waveguide Bragg gratings, 35,36 grating‐assisted contra‐directional couplers 37,38 and multimode waveguide gratings (MWGs) 39,40 . One should be noticed that the MWG filters have been attractive because of their large fabrication tolerance and simple fabrication.…”

“…Currently, silicon photonic filters have been used widely as a key role in not only the wavelength‐division‐multiplexing (WDM) systems but also spectroscopy sensing. Here, we mainly focus on silicon‐based on‐chip WDM filters with different structures, such Mach‐Zehnder interferometers (MZIs), 12‐19 micro‐ring resonators (MRRs), 20‐34 waveguide Bragg gratings, 35‐46 arrayed‐waveguide gratings (AWGs), 47‐64 and echelle diffraction gratings (EDGs) 62,65‐67 . Figure 1 gives a summary of the reported on‐chip photonic filters based on silicon‐on‐insulator (SOI) nanophotonic waveguides.…”

A Four-Channel DWDM Tunable Add/Drop Demultiplexer Based on Silicon Waveguide Bragg Gratings

“…Conventional apodization methods which modulate recessing amplitude or duty cycle of the corrugation could only suppress sidelobes on the long-wavelength side of the center wavelength [21]. To address this issue, we have developed a phase apodization technique which is able to suppress sidelobes on both sides of the center wavelength in [16]. As shown in Fig.…”

“…A repeated filtering at the same central wavelength enables a rapid roll-off of the spectrum and thus reduces the 3 dB bandwidth furthermore. Thirdly, the phase apodization technique we proposed in [16] is utilized to suppress sidelobes on both sides of the central wavelength. With these special measures, the pass band of the filter exhibits 3 dB and 20 dB bandwidths of 0.4 nm and 0.8 nm, respectively, while the SLSR is 26 dB.…”