Peng C.-YTsao KCheng H.-TFeng MCHAO-HSIN WU2021-09-022021-09-02202010944087https://www.scopus.com/inward/record.uri?eid=2-s2.0-85093960530&doi=10.1364%2fOE.397878&partnerID=40&md5=411875cb93ec6d9fce20f58c71d89802https://scholars.lib.ntu.edu.tw/handle/123456789/580572This experiment presents dynamic behaviors between the operating current and the optical beam images of vertical-cavity surface-emitting lasers (VCSELs) with two different aperture diameters of 3 ?m (single-mode) and 5 ?m (multi-mode). These VCSELs exhibit complex optical phenomena under current injection such as thermal effects, modal competition, carrier distribution, and laser coherence which make the light field distribution difficult to predict. In this report, the DC properties, optical spectrum, and optical images were measured together at different operating currents to accurately evaluate the characteristics of the lasers. Unlike previous works, the variations of the far-field angle were precisely evaluated by the side-mode-suppression ratio (SMSR) of the optical spectrum. In addition to commonly used transform functions such as the Gaussian beam formula, the SMSR provides another tool for the judgment of far-field divergence which could prevent inaccurate analysis. Moreover, the impact of thermal lensing was calculated by the DC measurement and demonstrated by the far-field measurement at high injection current. Through this experiment, the interaction between the injection carrier, thermal lens effect, and current spreading was described as fully as possible. ? 2020 Optical Society of America under the terms of the OSA Open Access Publishing AgreementGaussian beams; Geometrical optics; Laser pulses; Optical properties; Transceivers; Carrier distributions; Current injections; Far field divergence; Far field measurement; Light field distribution; Operating currents; Side mode suppression ratios; Thermal lens effects; Surface emitting lasersjournal article10.1364/OE.397878331150692-s2.0-85093960530