CMOS-compatible intra-chip photonics brings new class of sensors
Optical IO program director at imec and responsible for the silicon photonics technology platform, Philippe Absil came with extra solutions for high-speed intra-package interconnects. To support the Terabit-scale Ethernet of the future, transceivers capable of 50Gbit/s+ data rates will be required with operating power scaling down an order of magnitude from 20pJ/bit with today’s embedded optical modules to only a few pJ/bit with integrated optical modules (IOMs).
This calls for photonics integrated circuits with absolute nanometer-scale fabrication control to achieve high index contrast waveguides (capable of low-loss µm-scale bending radii) and smart routing elements (directional couplers and sub-wavelength gratings).
As imec’s answer, Absil unveiled a fully integrated silicon photonics platform to support high-performance optical transceivers (25Gbit/s and beyond), enabling chip-level large-scale integration using standard high-yield 130nm CMOS processes. The researcher presented his results on a photonics demonstrator featuring low loss (2.5dB/cm) strip waveguides with 2.5nm of thickness control and highly efficient grating couplers (2.5dB insertion loss) made of doped glass, with 50GHz-capable Ge-on-Si waveguide photodiodes for the optical-to-electrical (O-to-E) signal conversion, 25Gb/s Mach-Zhender interferometer and micro-ring modulators (28Gb/s at 1V, 40Gb/s at 3.3V) for the electrical-to-optical (E-to-O) signal conversion.
In a prototyping example, Absil showcased the 3D heterogenous integration of a 40nm CMOS driver chip on top of a photonics chip, assembled through a 150µm-pitch flip-chip process. Running at 10Gb/s, the drivers and the photonics elements (modulators, passive filters for multiplexing/de-multiplexing, thermo-optic tuners and single fiber I/Os) dissipated 0.38pJ/bit from a 1V power supply.
Absil also disclosed a Ge photodiode integrated with a Si ring modulator capable of 20Gb/s operation. Such combinations have already lead to proprietary silicon photonics bio sensors aimed at the analysis of clinical samples.
Capable of sensing molecular bindings directly, offering real-time results for multiple arrays of tests on a single-chip, the photonics sensors could accelerate diagnostics and drug developments. The prototypes are produced via the ePIXfab and Europractice IC service.
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