Michael J. Ludowise

In/sub 1-x/Ga/sub x/P/sub 1-z/As/sub z double-heterojunction-laser operation (77/sup 0/ K, yellow) in an external grating cavity

In1−xGaxP1−zAsz double‐heterojunction lasers fabricated by liquid‐phase epitaxy are operated at λ ≲6000 A (77 °K) in an external grating cavity to provide wavelength‐selective optical feedback. Diodes with and without antireflecting coatings and with heterobarrier heights of ∼20, ∼65, and ∼90 meV are examined. With external grating feedback, laser operation occurs at reduced threshold current densities and narrower linewidths and, depending upon heterobarrier height, can be tuned over an appreciable wavelength range. Within certain tuning limits on either side of line center, the carrier recombination is drawn to the grating wavelength and, as in earlier work, laser operation on a homogeneously broadened line is observed. Beyond these limits, particularly for excitation just above the threshold of stimulated emission, laser operation on an inhomogeneously broadened line can be distinguished. These observations showing that homogeneous and inhomogeneous line broadening occur in a semiconductor laser are ac...

Optical cavity effects in InGaN/GaN quantum-well-heterostructure flip-chip light-emitting diodes

Optical cavity effects have a significant influence on the extraction efficiency of InGaN/GaN quantum-well-heterostructure flip-chip light-emitting diodes (FCLEDs). Light emitted from the quantum well (QW) self-interferes due to reflection from a closely placed reflective metallic mirror. These interference patterns couple into the escape cone and cause significant changes in the extraction efficiency as the distance between the QW and the metallic mirror varies. In addition, the radiative lifetime of the QW also changes as a function of the distance between the QW and the mirror surface. Experimental results from packaged FCLEDs, supported by optical modeling, show that a QW placed at a neighboring position corresponding to a minimum in overall light extraction. Furthermore, the optical model and experimental data are used to estimate the absolute internal quantum efficiency.