The monolithic integration of four 1.55-μm range InGaAsP/InP distributed feedback lasers with a 4× 1 multimode-interference （MMI） optical combiner using the varied width ridge method is proposed and demonstrated. The average output power is 1.5 mW when the current of LD is 100 mA and the threshold current is 30-35 mA at 25 ℃. The lasing wavelength is 1.55-μm range and 40 dB sidemode suppression ratio is obtained. The four channels can operate separately or simultaneously.
A 13-channel, InP-based arrayed waveguide grating （AWG） is designed and fabricated in which the on-chip loss of the central channel is about -5 dB and the crosstalk is less than -23 dB in the center of the spectrum response. However, the central wavelength and channel spacing are deviated from the design values. To improve their accuracy, an optimized design is adopted to compensate the process error. As a result, the central wavelength 1549.9 nm and channel spacing 1.59 nm are obtained in the experiment, while their design values are 1549.32 nm and 1.6 nm, respectively. The route capability and thermo-optic characteristic of the AWG are also discussed in detail.
A 1.65μm three-section distributed Bragg reflector （DBR） laser for CH4 gas sensors is reported. The DBR laser has a wide tunable range covering the R3 and R4 methane absorption line manifolds. The wavelength tunability properties, temperature stability and laser linewidth are characterized and analyzed. Several advantages were demonstrated compared with traditional DFB lasers in harmonic detection.
