Narrow Emission of Blue GaN-Based Vertical-Cavity Surface-Emitting Lasers With a Curved Mirror

Abstract

We report a narrow divergence angle in a blue gallium-nitride-based visible vertical-cavity surface-emitting laser (GaN-VCSEL) with a curved mirror. This device exhibited continuous-wave operation at a wavelength of 447.9 nm. The fullwidth at half-maximum divergence angle of the 8 µm-aperture VCSEL was 3.9°when the device was operated at a current of 1.2 × Ith, where Ith is the threshold current. In this type of cavity, the radius of curvature (ROC) of the curved mirror determines the near-field pattern (NPF) and far-field pattern (FFP). The authors fabricated devices having ROC up to 988 µm, which is more than 10 times greater than the ROC of the mirror used in the previously reported structures, allowing this narrow emission. The I-L characteristics showed that the Ith value increased with increasing ROC. The present study investigates the mechanism behind this tendency in detail.

Spontaneously implemented spatial coherence in vertical-cavity surface-emitting laser dot array

“…The operation of VCSELs with such cavities has been reported 15 . The radius of curvature (ROC) is correlated to the width of the FFP of the device 16 , 17 . In the present study, the FWHM of the FFP in the direction corresponding to the short axis of the lens is 5.2°, which indicates that the ROC should be approximately 150 µm.…”

Highly-efficient operation and mode control in GaN-based VCSELs with a curved mirror

“…The curved mirror provided lateral optical confinement to eliminate the diffraction loss, thereby improving the laser characteristics. After the report of operation under pulsed current injection in 2018 [9], blue VCSELs with similar structures, efficient current confinement by ion implantation [10], sub-milliampere operation [11], stabilized lateral modes [12], high efficiency operation up to 13.5% [13] (see Figure 1a), long life reaching 2000 h [14], generation of spatially coherent dot array of VCSEL modes [15], and narrow emission angle of 3.9° for circular aperture [16] and 0.5 degree for oblong aperture [17] have been reported. Recently, we reported CW-operation green VCSELs [18] with milliwatt class outputs and high-efficiency operation [19] (see Figure 1b).…”

Study on Bottom Distributed Bragg Reflector Radius and Electric Aperture Radius on Performance Characteristics of GaN-Based Vertical-Cavity Surface-Emitting Laser

“…This is one reason why, despite considerable theoretical and experimental work, nitride-based VCSELs have not yet been commercialized. Although there are laboratory-built VCSEL laser designs using nitride technology that achieve powers of several to several tens of milliwatts [5,[8][9][10][11][12], many prototypes of VCSEL lasers based on GaN remain in the research phase, mainly due to the difficulty involved in manufacturing monolithic versions.…”