Oxide isolation suffices for independently addressable, single-mode VCSEL array

Researchers at the University of California (Berkeley, CA) have developed an oxide-confinement fabrication method for a single-mode vertical-cavity surface-emitting laser (VCSEL) array that avoids the difficult planarization ste¥usually required prior to connecting lasers with their

Oxide isolation suffices for independently addressable, single-mode VCSEL array

Researchers at the University of California (Berkeley, CA) have developed an oxide-confinement fabrication method for a single-mode vertical-cavity surface-emitting laser (VCSEL) array that avoids the difficult planarization ste¥usually required prior to connecting lasers with their

contact pads at the perimeter of the die. Two-dimensional VCSEL arrays are ideal sources for applications such as optical scanners and displays, and such applications require uniform

characteristics across the array and high yields.

The Berkeley grou¥grew a 4 8 VCSEL array on an n+ gallium arsenide (GaAs) substrate using molecular-beam epitaxy (MBE) in a two-ste¥process. A single oxidation layer on the array defines the laser apertures and isolates the electrical connections between each VCSEL and its contact pad. The device has a lithographically defined pitch of 250 250 ?m in which each VCSEL emits at 870 nm, is oxide-isolated, and is independently addressable. Each VCSEL

structure in the array consists of a GaAs quantum-well active region between two distributed Bragg reflectors. Oxide confinement, as well as isolation of the p-n junction in the contact pad and its connection to the VCSEL, is provided by an aluminum arsenide (AlAs) layer between the to¥mirror and the active region. An important design consideration in the process is to make the diameter of each VCSEL post larger than the width or length of its contact pad. This configuration shifts the limiting variable on array density from thermal crosstalk to minimum array size.

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