Control of optical mode distribution through etched microstructures for improved broad area laser performance

Abstract

Etching microstructures into broad area diode lasers is found to lead to more uniform near field and increased power conversion efficiency, arising from increased slope. Self-consistent device simulation indicates that this improvement is due to an increase in the effective internal injection efficiency above threshold-the nonuniform near field leads to regions of inefficient clamping of the carrier density in the laser stripe. Measurements of spontaneous emission through the substrate confirm the predicted carrier profile. Both experiment and theory show that improved overlap between carrier and power distributions correlates with improved slope.

Control of lateral divergence in high-power, broad-area photonic crystal lasers

“…Hence, the distribution of the NF profile for devices with trenches becomes more concentrated at the central region, and is better matched with the current profile of BA lasers. 18) The obtained lateral beam waist of w 95%,WT and w 95%,W=O were 94.4 and 96.7 µm, respectively. The corresponding FF angles at the same injection level were 9.34 and 10.85°, respectively.…”

Low lateral divergence 2 μm InGaSb/ AlGaAsSb broad-area quantum well lasers

“…3. The increased output power might be due to the suppressing of high order lateral modes [16,22], which reduce the mode competition and lead to a more uniform near field and better matching between the mode profile and injected current profile [16]. Although the enhanced heat dissipation from the deeply etched trenches seems like also one of the reasons, the influence is small because the area of trenches is just 0.8% of the whole contact area.…”

“…Hence the controlling of lateral modes in BALs is crucial for the realization of high power and high brightness. Some approaches to control the lateral modes and suppress filamentation in mid-infrared and near-infrared lasers have been proposed, for instance, selective wet etching [9], curved waveguide [10], anti-guiding layer [11], the use of external cavities [12,13], leaky ridge-waveguide [14], tapered gain regions [15], etched microstructures [16] and Bragg gratings [17]. Although the tapered gain regions have achieved the diffraction limited beam quality [15,18], the long and narrow ridge section used as mode filtering limits the total cavity length, the volume of gain medium, thermal dissipation area and hence the possible highest power [18].…”

Beam control of high-power broad-area photonic crystal lasers using ladderlike groove structure

“…Accordingly, the slope efficiency of the LLGS laser is improved by 17.4% compared with the standard laser (∼0.76 W=A). The decreased threshold current might be due to the improved internal injection efficiency 23) attributed to the tailored current injection by the LLGS in BA PBC lasers. The inset shows the lasing spectra for these two devices at 1 W output power.…”