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We propose two-photon absorption light-induced self-written (LISW) waveguide formation using short-wavelength infrared pulse laser light. It is suitable and efficient for single-mode optical interconnection, and also promising for small-core single-mode optical interconnection. The approach offers the possibility of not only decreasing the insertion loss, but also reducing the interconnection task time. We assessed this approach for single-mode optical interconnection. We obtained an LISW waveguide loss of about 0.06 dB for an LISW waveguide length of 100 μ m and a connection loss per facet of about 0.37 dB. We also presented the results on the interconnection between high-numerical-aperture small-core thermally-diffused expanded-core single-mode fibers having the mode field diameters of about 3 μm by using the same approach. The results showed the present approach to be a promising alternative route for efficient interconnection of small-core single-mode optical devices, such as silicon nanowires with appropriate configurations. [ABSTRACT FROM AUTHOR]

We have developed a novel phase modulator, based on fin-type electrodes placed at self-imaging positions of a silicon multimode interference (MMI) waveguide, which allows reduced scattering losses and relaxes the fabrication tolerance. The measured propagation losses and spectral bandwidth are 0.7 dB and 33 nm, respectively, on a 987 μm-long phase shifter. Owing to the self-imaging effect in the MMI waveguide, the wave-front expansion to the electrode was counteracted, and therefore, the scattering loss caused by electrode fins was successfully mitigated. As a proof-of-concept for the MMI-based phase modulator applications, we performed optical modulation based on Mach–Zehnder interferometers (MZIs). The π shift current of the modulator was 1.5 mA. [ABSTRACT FROM AUTHOR]