Optically Pumped GaN-based Vertical Cavity Surface Emitting Lasers: Technology and Characteristics

Abstract

We review the fabrication technology and performance characteristics of optically pumped GaN-based vertical cavity surface emitting lasers (VCSELs). Two types of VCSELs with different microcavity structures are described. First type of VCSEL has a hybrid microcavity structure that consists of an epitaxially grown AlN/GaN distributed Bragg reflector (DBR), a GaN active layer with InGaN/GaN multiple quantum wells (MQWs), and a Ta 2 O 5 /SiO 2 dielectric DBR. Second type of VCSEL has a dielectric DBR microcavity structure that has a similar InGaN/GaN MQWs active layer sandwiched in two dielectric DBRs formed by Ta 2 O 5 /SiO 2 and TiO 2 /SiO 2. Both types of VCSELs achieved laser action under optical pumping at room temperature with emission wavelength of 448 and 414 nm for hybrid DBR VCSEL and dielectric DBR VCSEL, respectively. Both lasers showed narrow emission linewidth with high degree of polarization and large spontaneous emission coupling factors of about 10 À2. In addition, a high characteristic temperature of over 240 K was measured, and a distinct spatially inhomogeneous emission pattern was observed.

High Q microcavity light emitting diodes with buried AlN current apertures

“…However, to form VCSELs with double dielectric DBRs required complex fabrication process, such as laser lift-off or elaborated polishing and bonding process. 11 Despite of demonstration of room temperature current injected GaN-based VCSELs, the lateral optical confinement was still a lack in these VCSEL structures, resulting in higher optical loss and difficulty in controlling the quality of output beams. 12 In order to improve the optical confinement of these devices, we investigated a microcavity light emitting diode (MCLED) with a buried AlN current aperture, which can also be used as a lateral optical confinement layer.…”

Angular-Resolved Optical Characteristics and Threshold Gain Analysis of GaN-Based 2-D Photonics Crystal Surface Emitting Lasers

“…9. It's interesting to note that the threshold power density of GaN-based 2-D PCSEL is in the same or even better order than the threshold of the GaN-based VCSEL we have demonstrated recently 8 . Unlike the small emission spots observed in the GaN-based VCSELs, the large-area emission in 2-D PCSEL has great potential in applications and requires high power output operation.…”

GaN-based microcavity polariton light emitting diodes

“…Figure 3a shows numerical simulation result of the cavity photon mode and bared exciton mode versus temperature. The red-shift of the cavity photon energy with increasing temperature is estimated to be ∼0.054 meV/K [25] due to the temperature dependent refractive index. On the other hand, the QW excitons energy depicts a steeper decreasing tendency which follows the modified Varshni formula including the localization effect:…”