The mode characteristics (dispersion relation and $Q$ factor) of metal-coated microcylinders are achieved from the analytical resonance eigenequation. Among the resonance modes, two surface plasmon polariton (SPP) modes have completely different characteristics compared to the hybrid plasmonic whispering gallery modes (WGMs). In the metal-coated microcylinder, the $Q$ factor of the asymmetrical SPP mode can be greater than the symmetric mode, and the hybrid plasmonic WGMs have a greater mode index range, extending down to zero. Also, the mode indexes and $Q$ factors of the resonance modes are measured by the attenuated total reflection and resonance linewidth method, respectively. The experimental results agree well with the theoretical.

In this study, nanosecond-pulse lasing was achieved using a vertical-external-cavity surface-emitting laser (VECSEL) with only a single gain chip. A simple linear-cavity setup was used for the VECSEL, and pulsed lasing with a pulse width of ∼9 ns and a repetition frequency of ∼54 MHz was achieved. Dual-wavelength lasing at 974 and 978 nm was observed. The average output power during pulsed operation exceeded 100 mW. As the pumping power was increased, the laser output power could be switched off. However, stable dual-wavelength emission was maintained. The maximum output power under dual-wavelength operation could reach 455 mW.

Dual-wavelength output devices have a wide range of applications in mid-infrared band difference frequency generation, anti-interference lidar, dual-wavelength holographic interferometry, and other applications. Vertical external cavity surface-emitting lasers (VECSELs) are a type of semiconductor laser that can achieve single-chip dual-wavelength output by designing the chip structure. In this paper, we present a single-chip VECSEL that can switch between dual-wavelength and single-wavelength output modes. The VECSEL can simultaneously emit coaxial laser beams at 967 nm and 1013 nm, with a wavelength spacing of about 45 nm. The degree of mismatch between the gain peaks of the two quantum wells in the gain chip and the corresponding cavity modes is different. By adjusting the pump power, the temperature of the active region can be changed, which alters the matching relationship between the gain peaks and the cavity modes and controls the output mode of the VECSEL. The dual-wavelength output mode maintains a stable wavelength spacing at different operating temperatures. The laser output mode can be switched between single-wavelength and dual-wavelength, and the beam divergence angle is less than 8°. The dual-wavelength output power can exceed 400 mW, and the long-wavelength output power can reach up to 700 mW.

Blue lasers are integral to a variety of applications, including marine communication, underwater resource exploration, cold laser processing, laser medicine, and beyond. Vertical external cavity surface-emitting lasers (VECSELs) have the advantages of high output power and tunable wavelength, and can output blue laser via frequency doubling. In this article, a new type of intracavity beam control external-cavity structure is introduced. The laser beam waist is effectively adjusted by intracavity beam control, and the frequency conversion efficiency is improved. A laser cavity stability analysis model was developed to investigate the impact of laser cavity lens parameters and relative positions on stability. The external resonant cavity of VECSELs utilizes two optical lenses to position the beam waist near the laser output coupling mirror and locates the frequency doubling crystal at a high optical power density position to optimize frequency conversion efficiency. The VECSEL straight external-cavity structure achieves a frequency conversion efficiency of up to 60.2% at 488 nm, yielding a blue laser output exceeding 1.3 W. The full width at half maximum of the 488 nm spectrum measures approximately 0.23 nm. This intracavity beam-controlled direct external-cavity structure effectively mitigates laser mode leakage and shows potential for the development of an efficient and compact blue laser source.