High-performance and compact integrated photonic dichroic filters and triplexer realized by an efficient inverse design

Integrated optical filters are key components in various photonic integrated circuits for applications of communication, spectroscopy, etc. The dichroic filters can be flexibly cascaded to construct filters with various channel numbers and bandwidths. Therefore, the development of high-performance and compact dichroic filters is crucial. In this work, we develop the dichroic filters with 1.49/1.55-mu m channels by an inverse design. Benefiting from a search-space-dimension control strategy and advanced optimization algorithm, our efficient design method results in two high-performance dichroic filters without and with subwavelength gratings (SWGs). The comparison suggests that SWGs in filters can be useful for loss reduction and footprint compression by dispersion engineering. The developed dichroic filter with SWGs exhibits measured bandwidths of 26/29 nm, excess losses of < 0.5 dB, and crosstalks of <-10 dB with a compact footprint of 2.5 x 22.0 mu m(2). It has advantages in performance or compactness compared to the previously reported counterparts. A triplexer with a footprint of 10.5 x 117 mu m2 is developed based on the dichroic filters, also showing decent overall performance and compactness. (c) 2023 Optica Publishing Group

Automated summary

This work develops high-performance dichroic filters with 1.49/1.55-μm channels using an inverse design. The introduction of subwavelength gratings (SWGs) leads to loss reduction and footprint compression. The developed filters exhibit improved performance and compactness compared to previous counterparts. Additionally, a triplexer based on these filters shows decent overall performance and compact size.