25.8Gbps Direct Modulation AlGaInAs DFB lasers with Ru-doped InP Buried Heterostructure for 70°C operation
25.8Gbps Direct Modulation AlGaInAs DFB lasers with Ru-doped InP Buried Heterostructure were fabricated for the first time. The lasers achieved high output power and clear eye opening at 70°C and are promising for uncooled operation.
Design and Fabrication of Wide Wavelength Range 25.8-Gb/S, 1.3-μM, Push-Pull-Driven DMLs
We design and fabricate wide wavelength range directly modulated lasers (DMLs) on the same InP wafer to realize a large-capacity monolithically integrated light source array up to 1 Tb/s. We demonstrate a 25.8-Gb/s push-pull operation over a 30-nm wavelength range, which is conventionally about 14 nm for 100 GbE applications. To extend the operating wavelength range, we design the wavelength dependence of the differential gain (∂G/∂n) for an InGaAlAs multiple quantum well structure, and realize high frequency relaxation oscillation resulting from the high differential gain over a wide range. Next, we also design the wavelength detuning (Δλ) under an operating injection current condition by taking account of the thermal effect of the chip, because Δλ determines ∂G/∂n, and the threshold current of the laser diode (LD). In addition, to achieve a 25.8-Gb/s push-pull operation, we fabricate a ridge waveguide structure buried in benzocyclobutene (BCB) with a low parasitic capacitance, and electrically isolate the DML from the neighboring chip by etching off n-InP. By using this design and structure, we achieve a 3-dB-down frequency bandwidth of over 20 GHz from 1290 to 1320 nm. We also achieve a mean output power of 8.0 dBm, and a dynamic extinction ratio of 5 dB. We measure the 25.8-Gb/s transmission characteristics, and obtain clear eye openings for a back-to-back configuration. We also measure the bit-error-rate performance, and obtain error-free operation for a 30-nm operating wavelength range.
Finite Difference Modeling on the Temperature Field of Substrate in Friction Surfacing
Friction surfacing is an advanced process of great potential, especially in the field of repair and reclamation of worn and damaged components. As a kind of thermal processing technology, the temperature profile and changes of the substrate in friction surfacing are important factors to get coatings of high quality. In this paper, the temperature field of the substrate during the process is simulated by finite difference method. The results are consistent with experiments, reappearing the temperature change of the substrate during friction surfacing, allowing further study on figuration and quality of coatings.