Fig. 1. Experimental scheme and methods of the proposed device. (a) Principle of Raman laser switching in a two-mode-family Raman laser; (b) experimental photograph of the fabricated WGM microrod cavity with a diameter of ∼1.96 mm; (c) experimental setup and device for generation and switching of Raman lasers in a silica rod microcavity. CW laser, continuous-wave tunable laser diode; EDFA, erbium-doped fiber amplifier; PC, polarization controller; PD, photodetector; OSA, optical spectrum analyzer; OSC, digital storage oscilloscope; AFG, arbitrary function generator. A microfiber is exploited as an evanescent coupler to couple light in and out of the silica rod microcavity.

Fig. 2. Switching of multimode Raman lasing, calculated by using Eqs. (3)–(5). (a) Intracavity powers of pumped mode, Mode 1, and Mode 2 with the increase of injection power P_in; (b) calculated mode profiles for TE₀₀, TE₀₂, and TE₁₀ modes in a silica rod microcavity using finite-element method; (c), (d) gain of two Raman modes from the pump and the other mode; The black (purple) dotted line represents the cavity loss of Mode 1 (Mode 2). We adopt TE₀₂ (TE₁₀) for pumped mode and Raman Mode 1, and TE₀₀ (TE₀₀) for Raman Mode 2 in panel (c) [panel (d)].

Fig. 3. (a), (b) Raman switching process between two modes while decreasing the detuning between the resonance and pump with a silica rod microcavity of (a) ∼1.96 mm and (b) ∼1.1 mm in diameter; inset, microscopic image of the silica microrod cavity; (c) output powers of Mode 1 (crosses) and Mode 2 (squares) for the nine states in (a); (d) extinction ratio of the two lasing modes in (a).

Fig. 4. Experimental switching of single-mode Raman lasing with different axial mode families; the Raman offset transits from 1659.52 to 1692.19 nm. The pump wavelength and launched pump power are 1551 nm and 300 mW.

Fig. 5. Intensity stability of the Raman laser emission over 47 min for Stokes frequency excited at 1672 nm; the colored area indicates the standard deviation from the mean value.