Parametric study of multi-outputs T-junction spatial mode demultiplexers design with an objective-first algorithm

We design two different compact and low-loss 2D T-junction optical mode demultiplexing by using objective-first inverse design algorithm. These devices are designed for transverse-electric (TE) and transverse magnetic (TM), separately. High device performances were achieved for the specific designs of 1x2, 1x3 mode demultiplexers with fractional footprints at the orders of a few microns. The presented T-junction 1x2, 1x3 devices operate at the C-band; the device has a footprint of 2.8 mu m x 2.8 mu m and 4.44 mu m x 4.44 mu m, respectively and splits TE/TM0,1,2 modes efficiently. The modal efficiencies at the corresponding target wavelength of each vertically or horizontally aligned channels were obtained mostly to be near-unity together with minimal crosstalk ranges of around <-30 dB. The electromagnetic inverse design allowing the implementation of more than three output channels along with the novel functionalities will pave the way for compact and manufacturable 1xN couplers, which is of ultimate significance for integrated photonics.