Research On Dual Wavelength DFB Laser Based On Sampled Moire Grating

Dual-wavelength semiconductor lasers are widely used in terahertz/millimeter wave communication,dual-frequency laser radar,microwave photonics and other fields.Traditional dualwavelength semiconductor lasers are based on discrete devices,which are difficult to be applied due to their large volume,complex system and poor stability.How to realize monolithic dual-wavelength semiconductor laser is of great research value.Integrated semiconductor lasers have been commonly employed to produce dual-wavelength lasing in various ways such as multi-section DFB laser,dualwavelength laser source integrated with Y-branch section,and laterally coupled DFB laser.However,the single-chip integrated dual-wavelength laser has complex structure,difficult manufacturing process and high production cost.The key of the research is to reduce the difficulty and cost of singlechip integrated dual-wavelength semiconductor laser chip and improve the performance of dualwavelength semiconductor laser.In this paper,a dual-wavelength semiconductor laser based on sampled Moire gratings is designed and fabricated using reconstruction-equivalent-chirp technique.Using REC technology,the machining accuracy of nanometer level can be achieved by using micron level processing technology,and REC technology is compatible with common DFB laser manufacturing technology platform,so the manufacturing cost is lower.On this basis,the sampled moire grating dual-wavelength laser chip with integrated absorption modulator was developed,which realized the power adjustment between the two modes of the laser and improved the stability of the dual-wavelength laser chip.The main research contents of this paper are as follows:(1)The reconstruction-equivalent-chirp technique is applied to the design of sampled moire gratings,and the length and initial phase of sampled moire gratings are determined,which results in two π phase shifts in the resonator cavity,and the dual-wavelength maser is generated in the ±1 order channel.The cosine toe-cutting effect of sampled moire grating can reduce the F-P effect and improve the side mode rejection ratio.The effects of different grating lengths and refractive index modulation depths on the bimodal properties,the effects of the ridged waveguide on the bimodal lasing at different positions of the interface of the grating and the sectional modes of the ridged waveguide are calculated by simulation.A moire grating semiconductor laser chip based on REC technology was designed and fabricated,and its performance was tested.The experimental results show that the laser chip exhibits good dual-wavelength lasing in the current of 290 m A,and the dual-wavelength interval decreases with the increase of injection current.In the temperature range from 19 ℃ to 34 ℃,the wavelength difference,side mode rejection ratio and main mode power difference of the laser tend to be stable.(2)A dual wavelength laser based on sampled moire grating with integrated electrical absorption modulator(EAM)was developed.Four wave mixing(FWM)occurs because the gain distribution in the laser cavity is affected by the electric absorption modulator,which makes the two modes reach a good and stable phase relationship at a certain EAM voltage.By using the characteristics of FWM,the phase difference of longitudinal mode is adjusted to lock the phase of optical signal,and the coupling between the two longitudinal modes in EAM is enhanced to improve the beat performance.The flow wafer work of a single-chip integrated sampled moire grating dual-wavelength semiconductor laser with an electrical absorption modulator is completed and its performance is tested.The experimental results show that by injecting the reverse bias voltage into the EAM,the power difference between the two modes can be adjusted,and the dual-wavelength lasing characteristics can be achieved in the current range of 230 m A to 320 m A,which improves the stability of the dual-wavelength laser chip.In the temperature range from 19 ℃ to 34 ℃,the wavelength difference,side mode rejection ratio and main mode power difference of the laser do not change significantly.