Photonic Devices Based On Waveguide Mode Manipulation

Optical communication systems can benefit from the use of multidimensional orthogonal multiplexing,which utilizes different physical dimensions of light to improve capacity.Effective manipulation of the mode field,including amplitude,wavelength,and lateral spatial structure and so on.In this thesis,the new InP semiconductor lasers and silicon reconfigurable photonic devices for the application of silicon based heterogeneous integrated optoelectronic chips are proposed,and the mode field manipulation is demonstrated on the InP active platform and the silicon passive platform respectively.In the InP-based active platform,the longitudinal mode and transverse mode of the laser can be manipulated efficiently by switching the parity time symmetry state of the system through electric pumping.In the silicon-based passive platform,an inverse-designed photonic-crystal-like subwavelength structure combined with non-volatile and high refractive index contrast optical phase change materials is proposed,and the refractive index distribution can be reconfigurable on the nearsubwavelength scale,thus multifunctional reconfigurable manipulation of optical field power,wavelength and mode can be achieved with the same hardware construction.The main research contents are as follows:(1)An electrically pumped single longitudinal-mode parity-time symmetric FP laser is proposed.The longitudinal mode manipulation of laser is studied with the parity time symmetry theory model under the electric pumped frequency detuning.A single longitudinal mode,high power,directly-modulated and low-cost FP laser is demonstrated with coupled straight waveguides.The dynamic modulation characteristics of the PT symmetric laser are experimentally demonstrated for the first time to our best knowledge.This work is valuable in both theory and applications.The SMSR of the PT symmetric FP laser reaches 24 d B,and the optical power coupled into the fiber is 1.7 d Bm.Under single longitudinal mode operation,the modulation bandwidth of the laser is 7.9 GHz,and the transmission of 5 Gbps NRZ signal in 10 km single mode fiber is demonstrated.(2)An electrically pumped single transverse-mode laser arrays based on parity-time symmetry is proposed.A structure of parity-time symmetric ridge waveguide array is adopted,and a single transverse mode,fabrication error and frequency detuning insensitive and easy to expand laser array is demonstrated.It is valuable in high power and high beam quality light source.Single transverse-mode PT-symmetric laser arrays composed of four,six and ten-ridge gain lattice have been experimentally demonstrated.The emission power of PT-symmetric laser arrays composed of four ridges is about five times higher than that of the single-ridge laser with the same pump density.Our experimental results indicate that the PT-symmetric laser array is insensitive to fabrication.Single transverse-mode operations are still obtained with the ±170 nm gap variation.(3)Silicon-based subwavelength reconfigurable devices are proposed.By utilizing a photonic-crystal-like membrane structure and a low-loss phase-change material,multifunctional reconfigurable manipulation of power,wavelength and mode is demonstrated.First,a multifunctional reconfigurable mid infrared silicon-based mid-infrared photonic platform is achieved,and four power splitters with different split ratio and one wavelength division multiplexer base on the same platform are designed and theoretically demonstrated.Then,the multifunctional reconfigurable silicon-based photonic platform is demonstrated in the near-infrared communication band.The platform is tuned block by block to solve the contradiction between the diffraction limitation of a focused beam and inverse design subwavelength scale.Four power splitters with different split ratios and one mode division multiplexer base on the same platform are designed and theoretically demonstrated.