Fig. 1. Schematic diagram of the cascaded narrow linewidth diamond Raman laser system. λ/2, half-wave plate; IC, input coupler; OC, output coupler; PZT, piezoelectric-actuated translation stage; LPF, long-pass filter; BS, beam splitter; FPI, Fabry–Pérot interferometer.

Fig. 2. Plots showing (a) variation of the first Stokes field and residual fundamental powers with respect to incident fundamental (pump) power and (b) wavelength stability of the first Stokes field at an output power of 10 W and monitored over a period of 10 minutes.

Fig. 3. First Stokes output spectrum and longitudinal-mode structure for different Raman cavity lengths obtained by controlling the voltage applied to the PZT. Black represents the output spectrum and red represents the corresponding FPI transmission signal. From (a) to (c), the cavity length decreases incrementally by 690 nm.

Fig. 4. Schematic diagram showing the change in longitudinal-mode structure of the cavity in relation to the SRS gain for different cavity lengths. Gray and red represent the resonant cavity’s intrinsic longitudinal modes, while blue represents the diamond Raman gain spectrum. To facilitate clearer comparison, the FSR has been appropriately magnified. (The Raman linewidth of diamond is ~40 GHz and the resonant cavity FSR is ~1.33 GHz. As a result, there are about 30 longitudinal modes within the Raman gain bandwidth.)

Fig. 5. Plots showing (a) the coherence envelope function of the fundamental field and (b) a collection of coherence envelope functions of the first Stokes field at maximum pump power.

Fig. 6. Plots showing (a) the power-transfer characteristics of the first and second Stokes outputs as a function of pump/fundamental power and (b) the wavelength stability of the second Stokes output at a power of 8 W.

Fig. 7. Plots showing (a) the coherence envelope functions of the second Stokes output at maximum pump power and (b) the noise characteristics of the fundamental and second Stokes outputs.