Advancements in VCSEL technology: transverse mode control and matrix-addressable 2-D arrays

Abstract

We contribute with a theoretical analysis, fabrication, and characterization of a novel vertical-cavity surface-emitting laser (VCSEL) type, namely multi-spot surface-etched single-higher-order transverse mode VCSEL. This device exhibits high power in a single mode and a low differential resistance. There are two main differences between this VCSEL and a standard one. Firstly, concerning the layer structure, a quarter-wavelength antiphase layer is added. This layer is then selectively removed in a single processing step by means of wet-chemical etching such that the threshold gain of a desired mode, which is of higher order, is very low compared with that of all other transverse modes. Secondly, concerning the shape of the mesa. It is of rectangular shape, where one side of the aperture is much larger than the other. With this asymmetric transverse cavity, single polarization can be achieved. The manufacturing of this VCSEL needs only one additional lithography and etching step, which makes it attractive for commercial fabrication. The continuous-wave maximum output power of the single-higher-order transverse mode and the differential resistance of this device are 12 mW and 18 ohms ­, respectively. The corresponding single-mode, single-polarization output power is 12 mW. As an attractive application of this VCSEL that we have investigated is optical manipulation of micro-particles such as deflection and trapping. In addition, VCSELs are ideally suited to form two-dimensional (2-D) arrays of compact optical sources owing to their low threshold currents and high packing density. In this field, we introduce the manufacturing and characterization of top-emitting 16£16 elements wire-bonded 2-D matrix-addressable VCSEL arrays emitting in the 850 nm wavelength range, which may find future applications such as non-mechanical particle movement with optical multi-tweezers, confocal microscopy or free-space communications with beam steering capability.