Short, broadband, and polarization-insensitive adiabatic Y-junction power splitters

Area of Science:

• Integrated photonics
• Waveguide devices
• Optical signal processing

Background:

• Adiabatic Y-junction power splitters offer excellent performance characteristics including low loss, broad bandwidth, and polarization insensitivity.
• A key limitation of adiabatic power splitters is their typically long device lengths, which can be challenging for compact integrated photonic circuits.
• Nonlinear taper profiles present a potential solution for reducing the physical footprint of these devices.

Purpose of the Study:

• To develop and demonstrate a method for significantly reducing the length of adiabatic Y-junction power splitters.
• To maintain or improve the low loss and balanced splitting performance of these devices after length reduction.
• To validate the optimized designs experimentally on a silicon-on-insulator (SOI) platform.

Main Methods:

• Development of a taper profile optimization algorithm utilizing polynomial functions.
• Fabrication of adiabatic power splitters with varying minimum feature sizes (80 nm, 120 nm, 160 nm) on a 220 nm SOI platform.
• Experimental characterization of device performance, including insertion loss, transmission, and spectral response for both transverse electric (TE) and transverse magnetic (TM) modes.

Main Results:

• The optimized nonlinear taper profile successfully reduced the required transition lengths of adiabatic power splitters.
• A device with a 120 nm minimum feature size achieved a compact length of 14 µm.
• Measured losses were as low as 0.25 dB (TE) and 0.23 dB (TM) in the 1500-1600 nm wavelength range.
• Average transmission of -3 ± 0.5 dB demonstrated highly balanced power splitting across a wide spectral range.

Conclusions:

• The polynomial-based taper profile optimization algorithm effectively shortens adiabatic Y-junction power splitters without compromising optical performance.
• The demonstrated devices show excellent low-loss and balanced splitting characteristics, suitable for various integrated photonic applications.
• This approach enables the creation of more compact and efficient power splitters on the SOI platform.