Wavelength Demultiplexers Based on Self-Imaging in Optical Lattices with Length-Modulated Waveguides

We have proposed a wavelength demultiplexer based on wavelength-dependent self-imaging in linearly coupled optical lattices, implemented using a simple and compact photonic lattice configuration [1]. Straight waveguides ensure low propagation losses, while intuitive control of the coupling parameters allows precise tuning of both the output wavelength and the operational bandwidth. An experimental proof of concept is provided through fabrication of the demultiplexers in borosilicate glass using femtosecond laser writing techniques [2, 3]. The wavelength separation is achieved via self-imaging and perfect state transfer of the input optical field during propagation through a lattice with length-modulated waveguides. Specifically, longer wavelengths revive in the input waveguide, whereas shorter wavelengths are fully transferred to the opposite output port. However, this approach allows for dichroic separation only. To extend the splitting capability to multiple wavelengths, we introduce a modified structure with waveguide lengths as additional parameters. Only the input waveguide and its nearest neighbor are of equal lengths, while successive waveguides are gradually shortened. We will present the design principle, numerical simulations and performance evaluation of 3- and 4- wavelength demultiplexers.