Novel technique for measuring linewidth enhancement factor enabled by photonic integration

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Abstract

The linewidth enhancement factor (LEF) is a key parameter to describe the relation between gain and phase changes, which is essential in describing the various noise effects in semiconductor optical amplifiers, saturable absorbers, and semiconductor lasers. Different techniques for measuring the LEF of a material have been developed, but they are indirect and/or only work for forward bias. We propose a new, simple method to directly measure the LEF for both forward and reverse bias, using photonic integration. Our method uses an on-chip asymmetric Mach-Zehnder interferometer to measure gain and phase change as a function of bias in a short piece of semiconductor material. The LEF of the material is calculated from the ratio between the gain and phase change. By integrating the material and the interferometer on a photonic chip, we can achieve very short sections of the material (down to 12 μm) and have high phase stability in the interferometer, which are both necessary for this technique. Time domain traveling wave simulations show that we can measure a LEF set beforehand with the measurement method. We demonstrate the measurement method on saturable absorbers of lengths between of 12 μm and 42 μm, fabricated in indium phosphide.
Original languageEnglish
Title of host publicationESLW 2023 Workshop Booklet
PublisherUniversity of Glasgow
Number of pages23
Publication statusPublished - 30 Sept 2023
Event2023 European Semiconductor Laser workshop - University of Glasgow, Glasgow, United Kingdom
Duration: 29 Sept 202230 Sept 2023

Conference

Conference2023 European Semiconductor Laser workshop
Abbreviated titleESLW 2023
Country/TerritoryUnited Kingdom
CityGlasgow
Period29/09/2230/09/23

Keywords

  • Linewidth enhancement factor
  • alpha factor
  • Measurement technique
  • active-passive integration

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