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.
The continuous wave operation of a gallium-nitride-based vertical-cavity surface-emitting laser (GaN-based VCSEL) that uses boron ion implantation for lateral current confinement and a curved mirror for lateral optical confinement was investigated. The threshold current was 0.25 mA (Jth = 3.5 kA cm−2) for a 3 μm diameter current aperture at room temperature and the lasing wavelength was 445.3 nm. This is the lowest threshold current recorded for a GaN-based VCSEL. This result is considered to be a milestone for the further miniaturization of GaN-based VCSELs by the implementation of lateral optical confinement due to the incorporation of a curved mirror.
We report single transverse mode operation of a blue GaN-based vertical-cavity surface-emitting laser (GaN-VCSEL) with a monolithically incorporated curved mirror. For a device with a 4 μm current aperture diameter and a curved mirror with a radius of curvature (ROC) of 51 μm, single transverse mode operation was confirmed up to an output power of 3.2 mW under continuous wave operation at 20 °C. For a device with a smaller ROC of 31 μm, multi transverse mode operation was confirmed, indicating that the transverse mode can be controlled by the cavity design of such GaN-VCSELs.
We have generated single-transverse-mode optical pulses with 100 W peak power and 3 ps duration at 1 GHz repetition from a blue-violet GaInN mode-locked laser diode (MLLD) and a semiconductor optical amplifier (SOA) without the use of any pulse compression. The generation of clean optical pulses without subpulse components from the MLLD and the reduction in amplified spontaneous emission in the SOA by incorporating a flare waveguide structure resulted in effective amplification of optical pulses to produce over 100 W peak power.
We demonstrate a room-temperature continuous-wave operation of green vertical-cavity surface-emitting laser (VCSEL) with a 20 μm long cavity possessing a dielectric curved mirror formed over a {20−21} semi-polar gallium nitride substrate. The emission wavelength and the threshold current were 515 nm and 1.8 mA, respectively. We also confirmed that white light is generated by overlaying three prime colors of light, i.e. red, blue and green, emitted only from VCSEL.
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