RESUMO
We demonstrate the lateral optical confinement of GaN-based vertical-cavity surface-emitting lasers (GaN-VCSELs) with a cavity containing a curved mirror that is formed monolithically on a GaN wafer. The output wavelength of the devices is 441-455 nm. The threshold current is 40 mA (Jth = 141 kA/cm2) under pulsed current injection (Wp = 100 ns; duty = 0.2%) at room temperature. We confirm the lateral optical confinement by recording near-field images and investigating the dependence of threshold current on aperture size. The beam profile can be fitted with a Gaussian having a theoretical standard deviation of σ = 0.723 µm, which is significantly smaller than previously reported values for GaN-VCSELs with plane mirrors. Lateral optical confinement with this structure theoretically allows aperture miniaturization to the diffraction limit, resulting in threshold currents far lower than sub-milliamperes. The proposed structure enabled GaN-based VCSELs to be constructed with cavities as long as 28.3 µm, which greatly simplifies the fabrication process owing to longitudinal mode spacings of less than a few nanometers and should help the implementation of these devices in practice.
RESUMO
Blue-violet optical pulses of 9-kW peak power and 150-fs duration were obtained from a GaInN master oscillator power amplifier system using a nonlinear dispersion compensator. Seed pulses from a dispersion-compensated GaInN mode-locked semiconductor laser diode were stretched to 3-ps duration using a nonlinear dispersion compensator with a spatial light modulator that added second-order phase dispersion to an optimized nonlinear phase dispersion compensating the higher-order dispersion of the optical pulses. The stretched phase-optimized pulses were efficiently amplified to 3.0 nJ by a GaInN semiconductor optical amplifier. The amplified pulses were subsequently compressed using a linear pulse compressor, yielding 1.4-nJ femtosecond pulses. The obtained results show the highest peak-power ever reported for an electrically-pumped semiconductor gain medium.
RESUMO
Blue-violet optical pulses of 140-fs duration and 60-W peak power were obtained from a dispersion-compensated GaInN mode-locked semiconductor laser diode using a nonlinear pulse compression technique. Wavelength-dependent group velocity dispersion expressed by third-order phase dispersion was applied to the optical pulses using a pulse compressor with a spatial light modulator. The obtained optical pulses had the shortest duration ever obtained for a mode-locked semiconductor laser diode using edge-emitting type devices.
