Analysis of Dynamic Properties of Dispersion-Tuned Swept Lasers

Dispersion-tuned swept lasers (DTSLs) can sweep the lasing wavelength widely at high speed without need for any filter and have good potential for sensing applications, such as swept-source optical coherence tomography (SS-OCT). Properties of DTSLs, tuning range, tuning speed, and spectral linewidth, etc., are determined by several parameters, amount of dispersion, cavity length, modulation frequency and depth, and nonlinearity. Two models have been suggested to analyze and design the DTSLs, which are both only valid for steady states without wavelength sweep. For interferometric sensing applications, coherence (∝ instantaneous linewidth) of the DTSL under fast sweep is of great importance. In this paper, we propose two models for analysis of dynamic properties of DTSLs, expanding the two steady-state models, and present the results of numerical calculations. We confirmed that the two dynamic-state models give similar results for the typical DTSLs used for the SS-OCT. We found that the sweep can be fast without spread of the instantaneous linewidth when the sweep is toward the longer wavelength with anomalous dispersion and high modulation frequency.