Tunable narrow band add-drop filter design based on apodized long period waveguide grating assisted co-directional...

Area of Science:

• Photonics
• Optical Communications
• Materials Science

Background:

• Add/drop filters are crucial for optical interconnects in data centers and communications.
• Existing filters based on ring resonators and waveguide Bragg gratings are well-established.
• Long period waveguide grating (LPWG) based filters remain underexplored.

Purpose of the Study:

• To propose and analyze an apodized LPWG-assisted co-directional coupler for narrow band add/drop filtering.
• To combine silicon (Si) and titanium dioxide (TiO2) waveguides for enhanced filter performance.
• To investigate the thermal tunability and potential for dense wavelength division multiplexing (DWDM).

Main Methods:

• Utilized a combination of the finite element method (FEM) and transfer matrix method (TMM) for analysis.
• Designed an apodized LPWG structure integrated with Si and TiO2 waveguides.
• Employed a titanium nitride (TiN) metallic heater for thermal tuning.

Main Results:

• Achieved a narrow bandwidth of 1.4 nm due to the high group index difference between Si and TiO2.
• Demonstrated a high side lobe suppression ratio (SLSR) of 25.7 dB and low insertion loss of 0.6 dB.
• Obtained a thermal tuning efficiency of 0.07 nm/mW and cascaded two LPWGs for a tunable dual-channel filter with 185 GHz spacing and <20 dB crosstalk.

Conclusions:

• The proposed apodized LPWG co-directional coupler offers efficient narrow band add/drop filtering.
• The hybrid Si/TiO2 structure provides excellent thermal tunability and potential for DWDM applications.
• This filter design shows promise for advanced optical communication systems.