100 Gb/s Silicon Photonic WDM Transmitter with Misalignment-Tolerant Surface-Normal Optical Interfaces

Abstract

A 4 × 25 Gb/s ultrawide misalignment tolerance wavelength-division-multiplex (WDM) transmitter based on novel bidirectional vertical grating coupler has been demonstrated on complementary metal-oxide-semiconductor (CMOS)-compatible silicon-on-insulator (SOI) platform. Simulations indicate the bidirectional grating coupler (BGC) is widely misalignment tolerant, with an excess coupling loss of only 0.55 dB within ±3 μm fiber misalignment range. Measurement shows the excess coupling loss of the BGC is only 0.7 dB within a ±2 μm fiber misalignment range. The bidirectional grating structure not only functions as an optical coupler, but also acts as a beam splitter. By using the bidirectional grating coupler, the silicon optical modulator shows low insertion loss and large misalignment tolerance. The eye diagrams of the modulator at 25 Gb/s don’t show any obvious deterioration within the waveguide-direction fiber misalignment ranger of ±2 μm, and still open clearly when the misalignment offset is as large as ±4 μm.

Broadband High-Efficiency Grating Couplers for Perfectly Vertical Fiber-to-Chip Coupling Enhanced by Fabry-Perot-like Cavity

“…where n is the index of refraction of the cavity medium, D is the cavity spacing, and ρ 1 and ρ 2 are the phase shifts of the two reflecting surface, respectively. Apparently, R cavity is a periodic function of the cavity spacing D. Note that, zero reflection is possible, only when R 1 = R 2 and ϕ = mπ (m is an integer), according to Equations (1) and (2). In other words, the closer R 1 is to R 2 , the less reflection there will be for the Fabry-Perot cavity around the resonance wavelength.…”

“…Benefitting from mature complementary metal-oxide-semiconductor (CMOS) technology, various photonic devices have been demonstrated based on low loss silicon-on-insulator (SOI) waveguides, showing great promise for electronic-photonic integrated circuits, high-density photonic integrated circuits (PICs), and three-dimensional (3D) photonic integration [ 1 , 2 , 3 , 4 , 5 ]. Grating couplers (GCs) enable optical coupling between standard single-mode optical fiber and high index contrast SOI waveguides, and have gained widespread usage as fiber-to-chip couplers for SOI PICs [ 6 , 7 , 8 ].…”

Efficiency Enhanced Grating Coupler for Perfectly Vertical Fiber-to-Chip Coupling

“…In order to avoid complicated design or extra fabrication steps, a grating coupler that enables vertical to in-plane bidirectional transmission with bi-layer anti-reflection cladding was proposed in our previous work [23]. The bidirectional grating coupler functions as both a fiber coupler and optical power splitter, so that it cannot only act as a highly efficient vertical coupler but also work in Mach-Zehnder type optical modulators [24][25][26]. However, directly depositing Si 3 N 4 on SOI grating introduces extra deposition and etching steps into CMOS technology.…”

Editorial for the Special Issue on Silicon Photonics Bloom

“…This Special Issue of Micromachines , entitled “Silicon Photonics Bloom”, has 10 research papers and 2 review articles, covering the scale from material preparation [ 1 , 2 ], to single device design [ 3 , 4 , 5 , 6 , 7 ], to photonic integration [ 8 , 9 , 10 , 11 ], to system architecture [ 12 ]. The demonstrated devices and components include source generation [ 1 , 5 , 6 , 11 ], modulators [ 7 ], switches [ 4 , 8 ], gratings [ 3 , 10 ], and couplers [ 9 , 12 ] and are applied to applications such as dispersion control [ 3 ], photonic memory [ 4 ], optic communication [ 8 , 10 ], polarization management [ 9 ], and photonic computing [ 12 ]. The spectrum of the contributed research spans a wide range, from visible [ 1 , 2 , 6 ], to telecom wavelength [ 3 , 4 , 7 , 8 , 9 , 10 ], to mid-IR [ 11 ], to terahertz frequencies [ 5 ].…”

“…Geometrical analysis based on phasors and a Poincare sphere shows that the component can be configured as either a polarization compensator or a polarization controller. Active MZIs and micro-ring filters are also used in the work [ 10 ]. Huang et al experimentally presented a 100 Gb/s silicon photonic WDM transmitter which consists of a passive bidirectional grating coupler and active Si components.…”