Narrow-linewidth swept laser phase reconstruction and noise measurement technology and its applications.

A dynamic noise characterization technique for measuring narrow-linewidth frequency-sweep lasers based on phase reconstruction method is proposed. The phase and the frequency fluctuation power spectral density (PSD) of the swept optical field within a specific time window are recovered mainly by demodulating the differential phase information of the 120-degree phase difference interferometer. Then the details of the laser noise characteristics and the performance evolution law of the frequency sweep process can be observed by investigating the calculated frequency fluctuation PSD. Moreover, the integration time linewidth and Lorentzian linewidth of the swept frequency field can be obtained by introducing the integral algorithm even beyond the limit of PSD physical resolution. Meanwhile, the power of this method is verified by applying it to a kHz-linewidth frequency swept laser source based on high-order modulation-sideband injection-locking. The results show many features of the laser such as specific noise peaks and the laser characteristic evolution rules which could not be measured by other traditional methods.