Progress made in the improvement of integration density of photonic chips

Waveguide array is one of the fundamental building blocks for integrated photonics, a branch of study that examines the ability of integrated devices on a single chip to achieve faster and more efficient transmission and processing of information. A dense waveguide array could enable a high-density integration of waveguide components and significantly reduce on-chip occupancy area and cost. This could also improve the performance of other devices, such as a wider field of view for an on-chip optical phased array and ultra-dense space-division multiplexing. However, due to the increasing quantum tunneling effect of the photons from one waveguide to its neighbors, direct reduction of the waveguide separations will result in a crosstalk boost that hinders the independent control of signal in a waveguide.

Recently, a research group led by Assistant Professor Zou Yi in SIST experimentally demonstrated the half-wavelength pitched dense waveguide arrays with low-crosstalk and broadband by introducing an artificial gauge field (AGF). Leveraging the AGF-induced additional phases, they significantly suppressed the crosstalk inside the half-wavelength pitched waveguide arrays to -30 dB, and achieved broadband and low insertion loss simultaneously. The experimental results showed a minimum crosstalk of <-35 dB at the wavelength of 1520 nm in the 750 nm pitched straight waveguide array with negligible insertion loss, of which the pitch is even smaller than half of the wavelength. The researchers also demonstrated the 90-degree bent half-wavelength-pitched waveguide arrays, which consist of 64 waveguides and possess -30 dB crosstalk suppression from 1480 nm to 1550 nm and >100 nm bandwidth for the crosstalk lower than -25 dB, respectively. Such bent waveguide arrays enable both broadband crosstalk suppression and on-chip flexible routing.

The results were published in the paper entitled “Artificial gauge field enabled low-crosstalk, broadband, half-wavelength pitched waveguide arrays” in Laser & Photonics Reviews. Research Assistant Professor Zhou Peiji and Ph.D. candidate Li Ting in SIST are the co-first authors of the paper. Prof. Zou Yi is the corresponding author. The devices are fabricated in ShanghaiTech University Quantum Device Lab (SQDL).

An AGF-enabled ultra-dense low crosstalk waveguide array

Measurement results of the proposed bent half-wavelength-pitched waveguide arrays

**This article is provided by Prof. Zou Yi