Large-scale integrated silicon photonic circuits suffer from two inevitable issues that boost the overall power consumption. First, fabrication imperfections even on sub-nm scale result in spectral device non-uniformity that require fine-tuning during device operation. Second, the photonic devices need to be actively corrected to compensate thermal drifts. As a result significant amount of power is wasted if no athermal and wavelength-trimmable solutions are utilized. Consequently, in order to minimize the total power requirement of photonic circuits in a passive way, trimming methods are required to correct the device inhomogeneities from manufacturing and athermal solutions are essential to oppose temperature fluctuations of the passive/active components during run-time. We present an approach to fabricate CMOS backend-compatible and athermal passive photonic filters that can be corrected for fabrication inhomogeneities by UV-trimming based on low-loss amorphous-SOI waveguides with TiO2 cladding. The trimming of highly confined 10 μm ring resonators is proven over a free spectral range retaining athermal operation. The athermal functionality of 2nd-order 5 μm add/drop microrings is demonstrated over 40°C covering a broad wavelength interval of 60 nm.

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The large-scale and low-cost fabrication of high sensitivity sensors for the real-time detection of biochemicals and molecular substances opens up new opportunities in the areas of bioanalytic screening and medical diagnostics. Planar integrated photonic resonators that can be fabricated with a low footprint, in spatial and wavelength multiplexed arrangements, and that enable integration with microfluidics on the wafer scale have emerged as a promising sensing platform for these application fields. We realized an optofluidic and label-free biosensor that is based on hydrogenated amorphous silicon microring resonators embedded in silicon/glass microfluidic channels for analyte injection and biomolecule immobilization. The optofluidic sensor merits for refractive index and biomolecule sensing are evaluated by sensitivity and detection limit simulations, whereas a proof of concept is demonstrated by real-time protein immobilization experiments of functionalized resonators.

Optical multiplexers are key components of modern data transmission systems that have evolved from long-haul fiber communication applications down to the photonic interconnect level on-chip, which demand high bandwidths and low-power photonic links with small footprint. We present compact, energy-efficient, and high-bandwidth optical add/drop multiplexers that are based on complementary metal-oxide-semiconductor (CMOS) backendcompatible hydrogenated amorphous silicon microring resonators. We study the manufacturing nonuniformity of the as-fabricated devices and analyze the static power consumption that is required to actively align the multiplexers to a 100-GHz grid by using state-of-the-art microheaters. The microring filter banks are in excellent agreement with the design and satisfy a good tradeoff between concurrent properties of high-data-rate capability, low filter loss, high channel isolation, and manufacturing uniformity, which facilitates the operation with low static power consumption. In addition, we demonstrate that it is possible to permanently correct the unavoidable fabrication imperfections and to arrange the individual wavelength channels by a postfabrication trimming method so that the static power is reduced by more than an order of magnitude and allows minimization of these parts of the overall power requirements of such photonic integrated circuits down to record low metrics of a few femtojoules per bit.

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