Focused-Ion Micromachined Unstable Resonator Semiconductor Lasers.
This dissertation presents geometrical analysis and experimental investigation of edge emitting unstable resonator semiconductor lasers (URSLs) with emphasis on the understanding of their lasing mechanisms and operating characteristics. On the theoretical side, a geometrical URSL model is established to describe general device operating characteristics, such as the dependence of lasing threshold and efficiency on laser cavity length and resonator magnification. From the experimental side, investigations have centered on URSLs with circularly cylindrical end mirrors. For device fabrication, mirror processing technology based on focused -ion-beam micromachining (FIBM) has achieved nanometer levels of surface roughness. High performance URSLs have been fabricated from several types of III-V quantum well materials emitting at different wavelengths. For example, a 200 μm times 500 μm GaAs/AlGaAs single quantum well triplet URSL can provide a total output power up to 2.0 Watts, and a nominal virtual source brightness as high as 430 MW/cm^2-Sr. Comprehensive characterization procedures have been carried out for many of the FIBM URSLs. The experimental results obtained have enriched the understanding of fundamentals of URSLs. Curved subthreshold spatio-spectral patterns were observed for the first time to the author's knowledge. The virtual source width (FWHM) of an URSL usually reaches roughly diffraction-limited value around threshold, and then broadens with increasing injection levels. Streak camera results show that the delay between the formation of unstable resonator modes and the turn-on time of light emission is less than a few cavity round-trips. Further analyses of URSL temporal dynamics suggest that the broadening of the virtual source profiles can be correlated, at least in some cases, to the erratic dynamics of multiple lateral modes. Different lateral mode characteristics were observed for URSLs with different resonator magnifications. URSLs with other types of resonator structures, such as self-collimated, refractive-aberration-corrected (RAC) mirror, hybrid, coreless, and dual curvature mirror, have also been studied. Although the devices do not perform as well as cylindrical half-symmetric URSLs, experimental observations have helped understanding lasing characteristics of unstable resonator semiconductor lasers.
- Pub Date:
- January 1995
- Engineering: Electronics and Electrical; Physics: Optics