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Proceedings Paper

Characterization of VCSEL modal output using near-field scanning optical microscopy
Author(s): William C. Bradford; Joseph D. Beach; Reuben T. Collins; David Galt; David W. Kisker
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Paper Abstract

The Near-Field Scanning Optical Microscope (NSOM) is a tool that combines the spatial resolution of scanning probe microscopy with optical characterization techniques. Using this technique, we have generated high-resolution spatial intensity maps of the output from vertical-cavity surface-emitting lasers (VCSELs) in the near-field region of the facet as a function of operating current. The VCSELs studied were proton implanted, gain guided devices designed to operate at ~850nm. Optical signals that have been spatially imaged include total intensity, the spectrally resolved intensity of individual transverse modes, and the derivative of intensity with respect of operating current. Deviations from expected mode patterns in the devices have been qualitatively linked to unacceptable levels of noise in operating lasers. These deviations can be observed at operating currents below the actual onset of unacceptable noise. We have also found that derivative spectroscopy can be used to sensitively detect the cutoff points of transverse modes. Using the spatial intensity profile at the cutoff point of an allowed mode, a first approximation to the index of refraction profile can be made that is in good agreement with prior work. A series of index profile estimates from the cutoff points of a VCSEL can provide information on the evolution of the index profile and the thermal lens as the power is ramped up.

Paper Details

Date Published: 4 June 2002
PDF: 10 pages
Proc. SPIE 4649, Vertical-Cavity Surface-Emitting Lasers VI, (4 June 2002); doi: 10.1117/12.469220
Show Author Affiliations
William C. Bradford, Colorado School of Mines (United States)
Joseph D. Beach, Colorado School of Mines (United States)
Reuben T. Collins, Colorado School of Mines (United States)
David Galt, Cielo Communications, Inc. (United States)
David W. Kisker, Cielo Communications, Inc. (United States)

Published in SPIE Proceedings Vol. 4649:
Vertical-Cavity Surface-Emitting Lasers VI
Chun Lei; Sean P. Kilcoyne, Editor(s)

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