Figure 2 | Scientific Reports

Figure 2

From: Application of a self-injection locked cyan laser for Barium ion cooling and spectroscopy

Figure 2

Output power and cavity ringdown of a high power WGM laser near 493 nm. (a) Dependence of the output laser power on the detuning from resonance at low laser power. The laser current controls detuning from the laser cavity resonance. The laser light near \(f_\text {laser} = 607\) THz does not enter the WGM cavity if the fabry perot mode is detuned from the WGM with bandwidth \(f_\text {laser} / Q_{int} =\) 607 THz/10\(^9\)\(\approx \) 607 kHz. The optical power then exits the laser assembly (see Fig. 1) with large linewidth. As the detuning becomes smaller at low optical power, up to 90% of the non-resonant light enters WGM cavity and is absorbed or reflected back to the laser, reducing the output power of the laser. Self-injection locking is sustained here, and the figure shows a dynamic locking range of approximately 20 GHz. The output laser power has linewidth much less than the bandwidth of the WGM cavity. (b) Ring-down signal from the WGM cavity while coupling to a higher order mode at high power. The ring-down time of 0.17 \(\upmu \)s corresponds to a loaded Q-factor of \(2 \times 10^6\). The internal Q-factor \(Q_{int}\) of the resonator, inferred from the measured contrast from an optical spectrum analyzer with low-power laser operation, exceeds \(10^9\).

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