Fig. 1. Schematic of a square-FP coupled-cavity laser

Fig. 2. Reflection spectrum (dashed line) of a square microcavity with a=18 μm and w=2 μm and the corresponding mode intensity (solid line) of the coupled cavity with the FP cavity length L=550 μm

Fig. 3. Magnetic field distributions for modes with reflectance R>0.7 in 2-fold longitudinal microcavity mode intervals

Fig. 4. Magnetic field distributions in coupled mode ⑥

Fig. 5. SEM images of (a) the square cavity and (b) sidewalls after ICP etching; (c) microscopic image of the square FP coupled-cavity laser

Fig. 6. (a) Variations of laser single-mode fiber-coupled output power and voltage with FP cavity injection current I_FPfor fixed square cavity currents I_SQ of 18 mA and 35 mA, respectively; (b) lasing spectrum of the coupled-cavity laser when I_SQ is 35 mA and I_FP is 165 mA

Fig. 7. (a) Spectrum of laser; (b) side-mode suppression ratio and main-mode wavelength of the laser varying with FP cavity injection current I_FP at fixed square cavity current I_SQ=18 mA

Fig. 8. Detailed spectra at fixed square cavity current I_SQ=18 mA and FP cavity injection currents of 20 mA, 70 mA, 155 mA, and 160 mA, respectively

Fig. 9. (a) Frequency noise power spectral densities of a square FP coupled-cavity laser for injection currents I_FP of 165 mA and I_SQ of 35 mA, respectively; (b) variation of the Lorentzian linewidth of the laser with the FP cavity injection current for injection currents I_SQ of 35 mA and 40 mA