Abstract
We report on a practical method for developing InGaN-based edge emitting laser diodes of cavity length down to 45 μm. Samples consisting of one uncoated cleaved facet and one etched facet coated with a high-reflectivity (HR) dielectric distributed Bragg reflector (DBR) exhibit lasing in the continuous wave (cw) regime for cavity lengths down to 250 μm and lasing under pulsed injection for lengths as short as 100 μm. For samples having a second HR dielectric DBR, we could demonstrate cw lasing for a cavity length as short as 45 μm with a threshold current below 10 mA being reported for a 75 μm long device. Through a systematic study of the threshold current (Ith) and the slope efficiency (ηs) as a function of cavity length, it is proposed that the parameters underpinning the evolution of Ith and ηs with decreasing cavity length and their overall degradation in the short cavity regime are free carrier absorption, Auger processes and the decrease in the recombination losses due to nonuniform carrier distribution across the multiple quantum well active region.
Highlights
Over the last twenty-five years, III-nitride (III-N) optoelectronics has benefited from tremendous progress, which led to the solid-state lighting revolution [1,2,3]
Samples consisting of one uncoated cleaved facet and one etched facet coated with a high-reflectivity (HR) dielectric distributed Bragg reflector (DBR) exhibit lasing in the continuous wave regime for cavity lengths down to 250 μm and lasing under pulsed injection for lengths as short as 100 μm
For samples having a second HR dielectric DBR, we could demonstrate cw lasing for a cavity length as short as 45 μm with a threshold current below 10 mA being reported for a 75 μm long device
Summary
Over the last twenty-five years, III-nitride (III-N) optoelectronics has benefited from tremendous progress, which led to the solid-state lighting revolution [1,2,3]. Taking into account the value of internal losses, αi ∼ 30 ± 2 cm−1, extracted from HP modal gain measurements performed on standard 600 μm long LDs (see SM section 2), mirror losses (αm) are estimated to 32 ± 2 cm−1 for this sample, from which a peak reflectivity (RHR) of 90 ± 7% is deduced for the coated HR mirror using R = 0.18 for the uncoated facet This mirror reflectivity is close to the targeted value of 98% predicted by transfer matrix simulations, which indicates the high quality of the etched mirror and the limited impact of undesired thickness fluctuations and/or short scale layer waviness.
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