Ultrafast Wavenumber Linear-Step-Swept Source Based on Synchronous Lightwave Synthesized Frequency Sweeper

An ultrafast wavenumber linear-step-swept source based on a synchronous light-wave synthesized frequency sweeper (SLSFS) is demonstrated. A multi-wavelength source is used as a seed source. In SLSFS, the swept range of different wavelength components is precisely controlled by a stable programmable radio frequency signal applied on a dual-parallel Mach-Zehnder modulator instead of a conventional wavelength filter. The identical frequency shifting step of all the wavelength components promises high linear sweeping in the frequency domain. The key significance of this technique is that the swept rate and the swept range increases as the number of the seed wavelengths increases. Experimentally, a 120 kHz swept rate over the 4.75 nm range with a 8.6 GHz swept step is achieved when using two coupled DFB-LDs as the seed source. The K-linearity of Pearson's correlation coefficients is 0.99999. We also acquired the swept rates of 400 kHz, 800 kHz, and 1.23 MHz over the 7.86 nm range with a 8.6 GHz swept step using an F-P LD as a seed source.