Int. J. Nanoelectronics and Materials 4 (2011) 65-72 The effect of reflectivity on vcsel output performance Farah Z. Jasim * , Khalid Omar, Z. Hassan Nano-Optoelectronics Research and Technolgy Laboratory, School of Physics, University Sains Malaysia, 11800 Penang, Malaysia. Received 10 October 2009; received in revised form 2 May 2010; accepted 30 September 2010 Abstract The effect of the reflectivity of the output mirror on the single-mode multi-quantum wells (MQWs) vertical cavity surface emitting lasers (VCSEL) performances is investigated. Relevant VCSEL design with numerous (DBR) pairs has been designed and characterized using laser technology-integrated simulation program ISETCAD. The number of quarter-wave DBR that remaining in the upper mirror could be used to achieve the optimum performance of VCSEL in a top surface emitting geometry, such as maximum output power, threshold current, slope output efficiency, differential quantum efficiency and mode gain. Keywords: Al GaAs; DBRs; MQWs; VCSEL. PACS: 81.07.-b; 81.07.St; 03.67.Ac; 78.67.De. 1. Introduction In the preceding analysis of the threshold conditions of vertical cavity surface emitting laser (VCSEL), the power reflectivity of mirrors is required to be greater than 0.9 [1-5]. High reflectivity can be obtained by coating an almost perfect conductor (i.e., with large but finite conductivity) on the surface of the confinement layer. However, semiconductor multilayered mirrors with high reflectivity and low absorption loss which is called Distributed Bragg reflectors (DBRs) are utilized in VCSELs. DBRs consist of epitaxially grown of repeating pairs of quarter-wavelength-thick high and low-refractive index semiconductor layers. Therefore, combining the multiple quarter-wavelengths thick of high-to-low refractive index layers will result in a maximum reflectance greater than 99% [6-9]. A simple equation can be used to calculate the reflectivity of single DBR at normal incidence as in Eq. (1). 2 2 2 1 2 2 1 1 1                                  m m n n n n R (1) * ) For correspondence; Email: frlaser@yahoo.com .