Abstract
Micro-ring lasers can be regarded as photonic quantum wires and have attracted a lot of research interest because of their desired properties of high spontaneous emission factor (β) and low lasing threshold. In our lab we have succeeded in fabricating both micro-disk and micro-ring InGaAsP/InGaAs quantum well semiconductor lasers. An etching and bonding technique is developed to transfer the microcavities on top of the sapphire for optical pumping experiment at 77 K. Figure 1 shows the SEM picture of a micro-ring laser with an outer diameter of 4.4 μm and an inner diameter of 2.87 μm. The waveguide layer consists of three quantum wells and the total thickness is 0.2 μm. Figure 2 plots the lasing power as a function of the pump power. The emission spectra at different pumping levels are also shown. Single-mode emission lasing at the 1.5135 μm wavelength was observed and the threshold pumping density is about 3000 W/cm2. For large rings, multimode emission resulting from both transverse and longitudinal nature was observed. Figure 3 shows the emission spectrum for another micro-ring laser with an outer diameter of 22.38 μm and an inner diameter of 8.63 μm. Two main lasing modes are clearly observed. In our experiment, the 632.8 nm HeNe laser pump beam is normal incident to the wafer and the collection of output light is at an angle about 70-80° from the surface normal. This is because that the emission pattern is expected to have a small azimuthal angle.
© 1996 Optical Society of America
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