Because traffic toward and inside datacenters is increasing, the power consumption of electrical wiring in ethernet switches for datacenter should be addressed. Co-packaged optics (CPO) is a promising solution, where optical components are integrated into the same package substrate as electrical elements. We have proposed one of the CPO modules, where micro-mirror- based optical redistribution is adopted for low-loss and broadband optical coupling. CPO is required to operate at high temperatures; however, this redistribution uses materials with different coefficients of thermal expansion; thus, there is concern about its operation. In this study, the thermo-optical characteristics in the C-band were analyzed by the finite element method for thermal deformation and physical optical propagation analysis. The coupling efficiency of more than 85% was obtained at 1550 nm in the specified temperature range of 15–85 °C, and the difference in the average coupling loss between 20 °C and 85 °C was 0.49 dB in the calculation. The temperature-dependent transmittance was experimentally demonstrated using fabricated optical redistribution, and the average loss difference in C-band was 0.80 dB at 25 °C, 55 °C, and 85 °C.

We propose silicon (Si)-photonics-embedded interposers as a novel packaging platform to achieve co-packaged optics. An interposer is an organic substrate that has Si-photonics transceiver dies buried in it and polymer optical waveguides connecting the embedded Si chips and optical connectors. We also developed a Si-photonics-device-embedding process and investigated the properties and operations of embedded Si-photonics devices as a feasibility study. The embedded arrayed waveguide grating and reflective optical filter showed a wavelength shift on the order of 0.1 nm with our embedding process. The shifts seem to be due to the difference in ambient temperature during the measurements and induced strain. Though this embedding process is presumed to affect the spectrum for Si-photonics devices, the difference is small enough to be controlled. Embedded Si-photonics transmitter- and receiver-integrated circuits successfully demonstrated 25-Gb/s operations. The proposed Si-photonics-embedded interposer is a promising candidate for a co-packaged optics platform to eliminate the interconnect bandwidth bottleneck for high-performance computing systems.

The thermal tolerance of mirror-based optical redistribution is analyzed for co-packaged optics. In physical optics propagation analysis, considering thermal deformation, a coupling efficiency of over 0.9 is obtained in the range 0–100 °C.

We propose a novel high-density and low-profile multi-fiber passive assembly technology to polymer waveguides. We developed a small-sized ferrule with a footprint of only 5 × 5 mm and a thickness of 0.5 mm. An embedded 12 v-groove silicon chip was employed as a receptacle, and we formed the facet of waveguides on the v-groove chip. The optical properties for the proposed structure were experimentally demonstrated. The propagation loss of the single mode waveguides was as small as 0.5 dB/cm for the wavelength of 1310 nm and the average connecting loss of 3.06 dB was obtained.

We propose silicon (Si)-photonics-embedded interposers to minimize the Si photonics chip size and achieve highly precise optical fiber alignment. The interposers are organic interposer substrates that have Si photonics transceiver dies buried in the substrate and polymer optical waveguides connecting the Si chips and optical connectors. We investigated the effect of the embedding process on the operation of half-buried Si-photonics transceiver chips in an organic substrate and successfully observed 25-Gb/s operations. The Si-photonics-embedded interposer is expected to be a co-packaged optics platform to eliminate the interconnect bandwidth bottleneck for high-performance computing systems.