Reconfigurable Silicon Photonic Processor Based on SCOW Resonant Structures

Abstract

Reconfigurable photonic processors, which can be programmed to perform multiple photonic processing tasks by using the same hardware platform, own the advantages of higher flexibility and more cost-effectiveness compared with application-specific photonic integration circuits (ASPICs). In this paper, we present a novel programmable photonic processor based on two-dimensional meshes of self-coupled optical waveguide (SCOW) resonant structures. The proposed processor can be configured for realizing various basic optical components, as well as cascaded and coupled components. As a proof-of-principle, we experimentally demonstrate the concept with a 3 × 1 SCOW-based processor on the silicon platform, including tunable couplers, variable optical attenuators, and phase shifters. We implement eight different configurations using the chip, including ring resonators, Mach-Zehnder interferometers, Fabry-Perot resonators, and composite structures built of these basic components. These results demonstrate that the proposed processor can be a promising candidate for multi-functional photonic processors.

Optical Implementation of 2 × 2 Universal Unitary Matrix Transformations

“…In the next sections, we will restrict the analysis of the unitary universality to SU(2), a Lie subgroup of U(2) exclusively including the unitary matrices with determinant equal to 1. [ 2,3 ] Remarkably, this will allow us to: i) simplify the discussion of the optical processors reported in previous works to demonstrate that the unitary universality is not hold, [ 16,19–23,25–34 ] and ii) uncover compact architectures of universal U(2) processors in Section 4. Specifically, the restriction to SU(2) can be done by excluding the term in T 2 .…”

“…where 𝛿 ∈ [0, 2𝜋) is the global phase shifting and R n(𝛼) is a matrix that allows us to move between two arbitrary points of the Bloch sphere (from e A to e B ) by performing a rotation of an angle 𝛼 ∈ [0, 2𝜋] around an arbitrary unit vector n = n x x + n y ŷ + n z ẑ, with n x,y,z ∈ [−1, 1]. In line with the dimension of U(2) (dim U (2) = 4), [3] T 2 is a parametric unitary matrix encompassing [26][27][28][29][30][31] and corresponding SU(2) processor. [30] b) BB architecture reported in refs.…”

“…Basically, two popular optical architectures of the BB have been proposed in the state of the art, sketched in Figure 2. [16,[19][20][21][22][23][25][26][27][28][29][30][31][32][33][34] Both structures are composed by fixed couplers (MMIs or symmetric DCs) and PSs. Each coupler implements a perfect 50:50 beamsplitter and each PS encodes a tunable real parameter of the BB transfer function.…”

“…In this work, it is shown that the existing architectures of the BB [16,[19][20][21][22][23][25][26][27][28][29][30][31][32][33][34] lead to optical processors which do not satisfy the unitary universality (at least) for the case n = 2. To overcome this 2) (the yellow lines represent the matrix nature of the transformation).…”

Programmable Wavelength Filter with Double Ring Loaded MZI

“…This design has been theoretically demonstrated its capability to realize high-quality bandpass filters, and can theoretically fit certain exact bandpass profiles. Even though other types of structures have also been proposed to realize filters, such as nested ring Mach-Zehnder interferometers 6 , re-configurable silicon processors based on resonant self-coupled optical waveguides (SCOW) 7 , response shaping with a silicon ring resonator via double injection 8 , and the cross-ring resonator MZI interleavers 9 , none of them has demonstrated their structure to be able to exactly fit to the proposed bandpass filters.…”