Fig. 2: Measured linewidth enhancement of SBLs near the exceptional point.
From: Petermann-factor sensitivity limit near an exceptional point in a Brillouin ring laser gyroscope
a Measured SBL beating frequency is plotted versus pump detuning for three distinct locking zones, corresponding SBL amplitude ratios \(q\): 1.15 (blue), 1 (orange), 0.85 (red). Solid curves are theoretical fittings. Inset is a typical Allan deviation measurement of frequency (\({\sigma }_{\nu }(\tau )\)) versus gate time \(\tau\). Error bars give the standard error of the mean. The short-term part is fitted with \(\sqrt{{S}_{\nu }/(2\tau )}\) where \({S}_{\nu }\) is the one-sided power spectral density of the white frequency noise plotted in b. b Measured white frequency noise of the beating signal is determined using the Allan deviation measurement. Data point color corresponds to the amplitude ratios used in a. The Petermann factor PF (solid lines) and NEF (dashed lines) theoretical predictions use parameters obtained by fitting from a.
