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Targeting high-speed, low-cost, short-reach intra-datacenter connections, we designed and tested an integrated silicon photonic circuit as a transmitter engine. This engine can be packaged into an optical transceiver module which meets the QSFP-DD Form Factor, together with other electrical/optical components. We first present the design and performance of a high-speed silicon modulator, which had a 3-dB EO bandwidth of &gt, 40 GHz and an ER of &gt, 5 dB. We then incorporated the engine onto a test board and injected a 53.125 Gbaud PAM4 signal. Clear eye patterns were observed at the receiver with TDECQ ~3 dB for all four lanes.

An RF-Photonic phased array antenna beamformer was previously demonstrated using cascaded fiber Bragg gratings with 1 x 2 couplers for true-time-delay beamforming. This work's focus is to design, build, and test an integrated Si-photonic beamforming circuit to replace the fiber-optics system, allowing for chip-scale beamformers with low size, weight, power, and cost. Several metastructure waveguides were designed to provide a strong slowlight effect near their transmission band edge. By tuning the wavelength near the band edge, tunable optical truetime delay is achieved. We report the design, simulation, fabrication and test of these high-contrast metastructure waveguides to provide group velocity variation against wavelength near the band-edge. Wavelength-tunable delay was verified using both an interferometric approach using an integrated Mach-Zehnder interferometer, and using a direct measurement of the true-time delay of an RF signal modulated onto a C-band optical carrier. We have also designed an integrated photonic beamforming circuit for a small array, including photodetectors, fabricated by AIM Photonics. Experimental test results for those integrated photonic circuits will be discussed. We will continue to improve our integrated photonic circuit to pursue larger array implementation. The goal is to further integrate this photonic circuit with an RF phase array antenna and demonstrate the scan of an RF beam by optical control.

Dense integration of electro-optic (EO) devices in photonic integrated circuits (PICs) is critical to achieve high-capacity, compact and low-cost transceiver modules, and fulfill the increasing bandwidth and/or bandwidth density demands for future computers, servers, data centers, and transport optical network systems. However, the EO crosstalk due to high integration density may degrade the signal transmission performance and eventually limit the possible density of integration. In this content, the study of the EO crosstalk of a PIC and its impact is crucial. In this paper, we systematically investigate and characterize the EO crosstalk between parallel silicon Mach–Zehnder modulators (MZMs). The performance penalty due to crosstalk is measured for different integration densities and data rates. For the MZM pair with a separation of 200 μm, there is a ∼−20 dB RF crosstalk in the frequency range >10 GHz, and up to 1.1 dB power penalty and 2.2 dB optical signal-to-noise ratio penalty are observed for 36-Gb/s on-off-keying signals. Our study can serve as a reference for integration density of large-scale silicon PICs for various applications.

Injection-type silicon electro-optic modulators are widely used in onchip optical interconnections due to its high modulation efficiency. However, as the modulator dimension approaches the wavelength limit, it becomes hard to improve the modulator speed by shrinking the device. A new approach to further scale down the dimension of an intrinsic device in injection-type electro-optic modulators without suffering from subwavelength confinement problem is proposed. The device consists of stacked PN or PiN cells connected by tunneling structures to enable current conduction. The diffusion capacitance is reduced due to the reduction of quasi-neutral region width in each device. In this paper, a detail study is given to the case of a two-cell modulator. A twofold of capacitance reduction and speed improvement are observed. Further speed improvement is expected by splitting the modulator into more cells, and the simulation approach for the tunneling structures in such an optical device is also discussed in details.

The electro-optic crosstalk between two parallel silicon Mach-Zehnder modulators is characterized. Up to 1.6 dB power penalty is observed for 36-Gb/s on-off-keying signals with a ∼-20 dB crosstalk, posing challenge to dense photonic integration.

In this work, we have designed a novel Si based 1-dimensional high contrast meta-structure waveguide that has slow light effect as well as phase tunability using p-n junction. The goal is to use such waveguide to design active optical devices such as high frequency modulators and tunable filters for analog RF-photonics or data communication applications. The Si ridge waveguide has a pair of high contrast grating wings adhered to the waveguide core in the center. Grating bars at two sides of the waveguide are doped P and N-type respectively, while a p-n junction region is formed in the middle of the waveguide core. By applying a voltage to bias the p-n junction, one can sweep the free carriers to change the effective index of the waveguide as well as the dispersion property of the grating. This metastructure Si waveguide is ideal in the design of high frequency optical modulators since the slow light effect can reduce the modulator waveguide length, increase the modulation efficiency as well as compensate other nonlinearity factors of the modulator for analog applications.

We investigate a linearization technique in silicon electro-optic (EO) modulator for spur-free dynamic range (SFDR) improvement. Using 3rd-order derivative of the transfer function, an optimal DC bias is applied to get a maximum SFDR.

The spontaneous emission (SE) of Er3+ embedded in a double slot dielectric structure was studied by a quantum-electrodynamical formalism. The study shows that the slot width and the position of Er3+ in slot structure have a significant effect on the SE. The double slot waveguides were fabricated by embedding two low-index Er/Yb silicate material layers into high-index silicon. The radiative efficiency of Er3+ in the double slot waveguides is found to be higher than that of the single slot waveguide, which is consistent with the theory simulation. The 0.67 dB signal enhancement at 1.53 µm in a 4.6-mm-long slot waveguide was observed pumped by 1476 nm laser. These results show the relevance of our model to study the SE processes in multilayer structures and are important for future realization of silicon-compatible active optical devices.