Title : Dynamic parameter measurement of Ultra-Narrow-Linewidth lasers
Abstract:
With excellent properties of the high purity spectrum and long coherent length, narrow-linewidth lasers can be applied in many fields, such as optical quantum information, low-noise microwave generation, high-resolution spectroscopy, precise sensing, high-speed optical coherent communication and so on. We propose the fundamental route to achieve the deep compression of the laser linewidth and demonstrate that the Rayleigh Backscattering (RBS) as weak feedback is an efficient linewidth-compression mechanism to realize the route. In theory, the dynamic characteristics of the spectrum evolution of Rayleigh scattering in a one-dimensional waveguide (ODW) is investigated based on the quantum theory and a spectrum evolution model of RBS source is established. In the experiment, to verify the linewidth compression mechanism, we construct dynamic laser parameter measurement method based on short delayed fiber self-heterodyne interferometer (SDSHI), and analyze the corresponding optical frequency evolution process from quantum theory. Based on the SDSHI method, we demonstrate and observe the Rayleigh-scattering-based linewidth compression process of fiber lasers and semiconductor lasers. The linewidths of fiber lasers are dynamically compressed to sub-100 Hz from the conventional value of >1 kHz. Meanwhile, the linewidths of DFB semiconductor lasers are compressed to 200 Hz from the conventional value of >1 MHz within 1 ms. We also explore the measurement of dynamic parameters of tunable lasers. With all-optical tunable narrow-band fiber Bragg gratings and RBS linewidth compression, we obtain tunable fiber lasers with a precise tuning step of less than 0.02 nm and linewidth of about 200 Hz. With all-fiber acousto-optical tunable filters, we obtain fast tunable narrow-linewidth fiber lasers with a tuning band of 20 nm and switching time of less than 1 ms.
