Blue and green edge-emitting laser diodes and vertical-cavity surface emitting lasers on C-plane GaN substrates

Abstract

This paper reports the latest device performance of high-power blue and green edge-emitting laser diodes (LDs). The epitaxial layers of LDs were grown by metal organic chemical vapor deposition (MOCVD) on C-plane free-standing GaN substrates. And a ridge type structure was formed at the top of p-type layers. Fabricated every LD chip was mounted on a heat sink using a junction down method in a TO-Φ9 mm package. We optimized the epitaxial and the device structures for high efficiency and high optical output power. A new developed 455 nm blue LD showed the optical output power and the voltage of 5.90 W and 3.81 V at the forward current of 3 A under Continuous Wave (CW) operation. The wall-plug efficiency (WPE) of the 455 nm blue LD was 51.6 % at 3 A. This is the highest WPE reported so far. The peak WPE of the 455 nm LD was 52.4 % at the forward current of 2.2 A. And a new developed 525 nm green LD showed the optical output power and the voltage of 1.86 W and 4.12 V at the forward current of 1.9 A under CW operation. The wall-plug efficiency (WPE) of the 525 nm green LD was 23.8 % at 1.9 A. This is the highest WPE reported so far. The peak WPE of the 525 nm LD was 25.9 % at the forward current of 1.1 A.

Influence of sidewall grating etching depth on GaN-based distributed feedback laser diodes

“…GaN-based laser diodes (LDs), can feature highly efficient luminescence and a wide emission range, from deep ultraviolet to infrared, and are widely utilized in laser displays, laser lighting, laser machining and visible light communications, etc [1][2][3][4][5]. However, these LDs all come with a Fabry-Pérot (FP) cavity and operate in multiple longitudinal modes * Author to whom any correspondence should be addressed.…”

Green-wavelength GaN-based photonic-crystal surface-emitting lasers

“…In contrast, GaNbased visible-wavelength semiconductor lasers have the advantage of low power consumption due to their high WPE, and compact size. Since GaN-based edge-emitting laser diodes (EELDs) were first confirmed to oscillate in 1995, 1) their characteristics have improved over the years, 2,3) including the expansion of their lasing wavelengths to ranges from green 4,5) to ultra-violet. [6][7][8][9] Recently, the output power of the EELDs with a center wavelength of 532 nm has reached 1.64 W. 3) However, the EELDs have several problems, such as multimode oscillation in both longitudinal and transverse directions, as well as wide divergence of radiation beams and catastrophic optical damage (COD) derived from the small cross section of the ridge.…”

“…Since GaN-based edge-emitting laser diodes (EELDs) were first confirmed to oscillate in 1995, 1) their characteristics have improved over the years, 2,3) including the expansion of their lasing wavelengths to ranges from green 4,5) to ultra-violet. [6][7][8][9] Recently, the output power of the EELDs with a center wavelength of 532 nm has reached 1.64 W. 3) However, the EELDs have several problems, such as multimode oscillation in both longitudinal and transverse directions, as well as wide divergence of radiation beams and catastrophic optical damage (COD) derived from the small cross section of the ridge. GaN-based verticalcavity surface-emitting lasers (VCSELs) have also been developed because of their attractive features, such as low threshold oscillation due to their small resonator volume, the possibility of integration, and vertical single-mode operation with a distributed Bragg reflector (DBR).…”

“…As the lattice constant increased, As demonstrated in the above current injection test and the photonic band analysis, we have successfully developed the PCSELs with single-mode Γ-point operation at green wavelengths. On the other hand, the operating characteristics as a laser diode (LD) are still at a primitive level compared with those of PCSELs at blue wavelengths 22) as well as those of existing EELDs 3) and VCSELs at green wavelengths. 14) The WPE can be improved by optimizing both the PC and the epitaxial crystal layers.…”

“…However, the operating characteristics as a LD, such as WPE, current threshold, and slope efficiency, are still behind those of existing LDs. 3,14,22) CW operation is one of the main objectives for future research. The WPE is expected to be improved by optimizing both the PC and the epitaxial crystal layers.…”