Temperature characterizations of silica asymmetric Mach–Zehnder interferometer chip for quantum key distribution

Quantum key distribution(QKD)system based on passive silica planar lightwave circuit(PLC)asymmetric Mach–Zehnder interferometers(AMZI)is characterized with thermal stability,low loss and sufficient integration scalability.However,waveguide stresses,both intrinsic and temperature-induced stresses,have significant impacts on the stable operation of the system.We have designed silica AMZI chips of 400 ps delay,with bend waveguides length equalized for both long and short arms to balance the stresses thereof.The temperature characteristics of the silica PLC AMZI chip are studied.The interference visibility at the single photon level is kept higher than 95%over a wide temperature range of 12℃.The delay time change is 0.321 ps within a temperature change of 40℃.The spectral shift is 0.0011 nm/0.1℃.Temperature-induced delay time and peak wavelength variations do not affect the interference visibility.The experiment results demonstrate the advantage of being tolerant to chip temperature fluctuations.

The 8×10 GHz Receiver Optical Subassembly Based on Silica Hybrid Integration Technology for Data Center Interconnection

An 8×10 GHz receiver optical sub-assembly （ROSA） consisting of an 8-channel arrayed waveguide grating （AWG） and an 8-channel PIN photodetector （PD） array is designed and fabricated based on silica hybrid integration technology. Multimode output waveguides in the silica AWG with 2% refractive index difference are used to obtain fiat-top spectra. The output waveguide facet is polished to 45° bevel to change the light propagation direction into the mesa-type PIN PD, which simplifies the packaging process. The experimentM results show that the single channel I dB bandwidth of AWG ranges from 2.12nm to 3.06nm, the ROSA responsivity ranges from 0.097 A/W to 0.158A/W, and the 3dB bandwidth is up to 11 GHz. It is promising to be applied in the eight-lane WDM transmission system in data center interconnection.

High efficiency,small size,and large bandwidth vertical interlayer waveguide coupler

Since the advent of three-dimensional photonic integrated circuits,the realization of efficient and compact optical interconnection between layers has become an important development direction.A vertical interlayer coupler between two silicon layers is presented in this paper.The coupling principle of the directional coupler is analyzed,and the traditional method of using a pair of vertically overlapping inverse taper structures is improved.For the coupling of two rectangular waveguide layers,a pair of nonlinear tapers with offset along the transmission direction is demonstrated.For the coupling of two ridge waveguide layers,a nonlinear taper in each layer is used to achieve high coupling efficiency.The simulation results show that the coupling efficiency of the two structures can reach more than 90%in a wavelength range from 1500 nm to 1650 nm.Moreover,the crosstalk is reduced to less than-50 d B by using multimode waveguides at intersections.The vertical interlayer coupler with a nonlinear taper is expected to realize the miniaturization and dense integration of photonic integrated chips.