Inverse Design of SiN based Wavelength Demultiplexer

We have designed an ultra compact silicon nitride based $1 \times 4$ wavelength demultiplexer using inverse method in near infrared region. The device exhibits high transmission charactrestics for the four-channels(1490 nm, 1520nm, 1550nm and 1580nm) with 30 nm channel spacing and with the footprint of $6 \times 6 \mu m^{2}$. Peak transmission achieved is -0.5 dB for the 1490 nm channel and -0.1 dB for the 1520nm, 1550nm and 1580 nm channel. The maximum crosstalk is -15 dB for 1490nm, -13.5 dB for 1520nm, -13 dB for 1550 nm and -12 dB for 1580 nm.