Abstract
Abstract Adiabatic waveguide taper and on-chip wavelength demultiplexer are the key components of photonic integrated circuits. However, these two kinds of devices which were designed by the traditional semi-analytic methods or the brute-force search methods usually have large size. Here, based on the regularized digital metamaterials, a two-channel focused wavelength demultiplexer with a footprint of 2.4 × 10 μm2 has been proposed. The designed demultiplexer can directly connect to a grating coupler under the absence of a long adiabatic waveguide taper. The objective first method and the modified steepest descent method are used to design the demultiplexer which splits 1520 nm and 1580 nm light. Experimental results show that the insertion loss of the upper (lower) channel of the demultiplexer is −1.77 dB (−2.10 dB) and the crosstalk is −25.17 dB (−12.14 dB). Besides, the simulation results indicate that the fabrication tolerance of the device can reach ±20 nm in etching depth and ±10 nm in plane size changing. Benefitted from the extensibility of the design method, other types of ultra-compact “focused” devices, like mode splitters, mode converters, and power splitters can also be designed. Most importantly, this design method can be used to design devices with more complicated functionalities, such as multi-channel focused wavelength demultiplexers.
Highlights
For photonic integrated circuits (PIC), high density means low power consumption and high performance
Driven by the demand of highly integrated photonic circuits, various computational optimization methods have been proposed to decrease the footprints of single device, including the objective first method [4, 5], direct-binary-search (DBS) method [6,7,8], topology optimization [9], adjoint shape optimization [10,11,12], genetic algorithm (GA) [13, 14], particle swarm method [15], and deep learning [16,17,18,19]
We have experimentally demonstrated a two-channel focused wavelength demultiplexer with a footprint of 2.4 × 10 μm2 by using the objective first method [4, 33, 34] and modified steepest descent method
Summary
For photonic integrated circuits (PIC), high density means low power consumption and high performance. Driven by the demand of highly integrated photonic circuits, various computational optimization methods have been proposed to decrease the footprints of single device, including the objective first method [4, 5], direct-binary-search (DBS) method [6,7,8], topology optimization [9], adjoint shape optimization [10,11,12], genetic algorithm (GA) [13, 14], particle swarm method [15], and deep learning [16,17,18,19] Through applying these design methods, numerous digital-metamaterials-based devices have been proposed [20], ranging from quantum applications [21] to metalens [22, 23]. The proposed WDM grating can separate vertically incident light into two separate waveguides with high splitting ratio, but due to the high selectivity of the grating to working wavelengths, it will be difficult to design other complicated WDM gratings, for example, the multi-channel WDM gratings and broadband WDM gratings
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