The polarization control of silicon photonic integrated devices is an urgent problem caused by the birefringence effect due to the structural asymmetry of the silicon (Si) waveguide (450 nm × 220 nm), which results in polarization loss, polarization mode dispersion, and wavelength polarization related issues. This work presents a proposal for a compact silicon hybrid plasmonic waveguide (HPW) polarization controller. The proposed design includes two sets of Bragg gratings, placed within different material layers of the polarization controller. By changing the relative positions of the two sets of Bragg gratings, the absorption problem generated by the hybridized modes can be reduced or even eliminated, thus the reflection spectrums of the TE and TM polarization mode are optimized. Besides, one polarization mode of TE mode and TM mode has a high reflectivity, while the other polarization mode has a high transmission by designing different grating periods and other parameters. Based on the simulations and design, the silicon HPW polarization controller has an optimal length of 23.247 microns when used as a TM-mode polarization reflector, and the corresponding optimal length is 19.694 microns when used as a TE-mode polarization reflector. At the working wavelength, the polarization extinction ratio (ER) and insertion loss (IL) of the TM-mode polarization reflector are greater than 28.1 dB and less than 0.087 dB, respectively, and the ER and IL of the TE-mode polarization reflector are greater than 18.9 dB and less than 0.085 dB, respectively. Compared with conventional silicon waveguide polarization controllers, TE mode and TM mode separation, selection, transmission, and reflection of the proposed silicon HPW polarization controller can be achieved with a compact size. In the future, will be potential for widespread applications for this technology in both silicon photonic devices and silicon photonic integrated circuits.
The beam quality of the semiconductor laser is influenced by the structure of the laser's own waveguide as well as the beam shaping system. The cylindrical lens is used to compress the laser beam in the fast-axis direction in optically pumped source applications. Significant spectral deterioration occurs during the shaping of the laser beam. The spectrum of the laser split into some small peaks and misaligned with the absorption peaks of the crystal, resulting in a decrease in the overall absorption efficiency. In this paper, the reasons of spectral deterioration are investigated, and the spectral characteristics are optimized by varying the the output facet coating film’s reflectivity of the semiconductor laser chip. An improvement scheme for spectral deterioration of high power semiconductor lasers after beam shaping is proposed. The experiment results shows that the deterioration of the spectrum is significantly eliminated when the coating film’s reflectivity is adjusted from 0.88% to nearly 15%. A 976nm high power semiconductor laser chip with 7.16% reflectivity coating film has the highest slope efficiency. Due to a trade-off between spectral quality and the slope efficiency, it is necessary to choose an appropriate coating film’s reflectivity on the output facet surface to achieve both high output power and good spectra. This has important application prospects in future solid-state laser pump source applications.
32-channel hybrid III-V/silicon laser arrays operating at C-band with 100GHz wavelength spacing are designed and simulated. Each channel of the hybrid III-V/silicon laser arrays includes III-V/silicon waveguide gain region with lateral sampled Bragg grating (LSBG) on silicon waveguide for selecting a single longitudinal mode, tapered III-V/silicon waveguide coupling region and silicon waveguide light output region. Light generated by III-V active region evanescently couples to the silicon waveguide, and outputs from the silicon waveguide. The seed grating’s period of LSBG is fixed and varing the sampled grating period of LSBG for selecting wavelength. The transfer matrix method is used to simulate LSBG’s parameters of hybrid III-V/silicon laser arrays. The simulation results show that 32- wavelengths are selected successfully by LSBG when the sampling grating periods are between 4.6 μm and 6.9 μm while the seed grating is fixed at 251 nm. Besides, the tapered III-V/silicon waveguide coupling region is designed and simulated by eigenmode expansion method of commercial software to convert the light spot size and increase the coupling efficiency from III-V to silicon waveguide. By optimizing the parameters, the coupling efficiency is up to 90% while hybrid III-V/silicon tapered waveguide length is fixed at 400μm
We designed and analyzed the ring resonators used as external optical cavities for hybrid tunable lasers based on silicon waveguides. The designed double-ring resonators (DRRs) for tunable lasers on silicon can provide a tuning range over 40 nm by micro-heaters, which cover the entire C-band with a high tuning accuracy.
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