Abstract

Short-reach, low-cost, and large-capacity optical transport systems can be realized by using the T-band (1000-1260 nm) because it has five times wider bandwidth than that of the C- and L-bands combined [1]. In this study, we developed a wavelength-selective external cavity laser using an InAs quantum dot (QD) gain chip and a planar lightwave circuit (PLC) for T-band communications [2]. Fig. 1 shows the configuration of the proposed external cavity laser. It consists of an InAs QD gain chip, two aspheric lenses, and a PLC. The 1×16 optical switch, the arrayed-waveguide grating (AWG), and the directional coupler are integrated on a silica PLC chip. The facets of the gain chip and the PLC chip with high-reflection coatings, as shown in Fig. 1, configure the laser cavity. The light emitted from the gain chip is focused onto the PLC chip through the lenses and then enters one of the input waveguides of the AWG. The 1×16 switch is composed of 15 1×2 Mach-Zehnder interferometer switches, and the lasing wavelength can be selected by switching the input waveguide of the AWG. In the QD gain chip, multi-stacked InAs QD layers are sandwiched between AlGaAs cladding layers grown on a GaAs substrate [3]. The 3-dB amplified spontaneous emission spectrum ranges from 1033 nm to 1067 nm at an injection current of 200 mA. The AWG is designed with a center wavelength of 1060 nm, FSR of 10.3 THz, and channel spacing of 400 GHz, and it has 16 input waveguides.

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