Abstract
A variety of potential applications such as visible light communications require laser sources with a narrow linewidth and a single wavelength emission in the blue light region. The gallium nitride (GaN)-based distributed feedback laser diode (DFB-LD) is a promising light source that meets these requirements. Here, we present GaN DFB-LDs that share growth and fabrication processes and have surface gratings and sidewall gratings on the same epitaxial substrate, which makes LDs with different structures comparable. By electrical pulse pumping, single-peak emissions at 398.5 and 399.95 nm with a full width at half maximum (FWHM) of 0.32 and 0.23 nm were achieved, respectively. The surface and sidewall gratings were fabricated alongside the p-contact metal stripe by electrical beam lithography and inductively coupled plasma etching. DFB LDs with 2.5 μm ridge width exhibit a smaller FWHM than those with 5 and 10 μm ridge widths, indicating that the narrow ridge width is favorable for the narrowing of the line width of the DFB LD. The slope efficiency of the DFB LD with sidewall gratings is higher than that of surface grating DFB LDs with the same ridge width and period of gratings. Our experiment may provide a reliable and simple approach for optimizing gratings and GaN DFB-LDs.
Highlights
Gallium nitride (GaN) laser diodes (LDs) are potentially used in displays, medical application, visible light communications (VLC), etc [1,2,3,4]
LDs with ridge widths of 2.5 and 10 μm, respectively, that are compared with the fabricated distributed feedback laser diode (DFB-LD)
The surface and sidewall gratings alongside the p-contact were investigated by the FDTD method
Summary
Gallium nitride (GaN) laser diodes (LDs) are potentially used in displays, medical application, visible light communications (VLC), etc [1,2,3,4]. It is inevitable that there that are distinct differences in the optical and electrical surface gratings andLDs sidewall the same epitaxial substrate. Is inevitable that properties of DFB with gratings different on kinds of grating structures It isTherefore, difficult toit systematically there are distinct differences in the optical and electrical properties of DFB. LDs with different compare and analyze the performance of DFB LDs with surface and sidewall gratings, because kinds they of grating structures. DFB LDs with different structures, the same the epitaxial substrate, which canofprovide some experimental evidencesit is necessary to fabricate. The ridge finite-difference-time-domain was used to analyze the influence designed structure of LDs, DFB-LDs with surface and sidewall gratings of different periods and the width of the ridge and the types of gratings on the properties of DFB LDs. Based on the designed ridge widths were fabricated onsurface the same. Of the DFB LDs, including the linewidth, slope efficiency, and threshold current, were measured and analyzed. and Fabrication
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