Research Article Integrated Duo Wavelength VCSEL Using an Electrically Pumped GaInAs/AlGaAs 980 nm Cavity at the Bottom and an Optically Pumped GaInAs/AlGaInAs 1550 nm Cavity on the Top Samiha Ishrat Islam, 1 Arnob Islam, 2 and Saiful Islam 3 1 Electrical and Electronic Engineering Department, American International University-Bangladesh, Dhaka 1213, Bangladesh 2 Electrical and Electronic Engineering Department, Northern University Bangladesh, Dhaka 1213, Bangladesh 3 Electrical and Electronic Engineering Department, Bangladesh University of Engineering and Technology, Dhaka 1000, Bangladesh Correspondence should be addressed to Saiful Islam; sislamk@yahoo.com Received 10 April 2014; Revised 17 August 2014; Accepted 20 August 2014; Published 29 October 2014 Academic Editor: Zhihao Chen Copyright © 2014 Samiha Ishrat Islam et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In this work, an integrated single chip dual cavity VCSEL has been designed which comprises an electrically pumped 980nm bottom VCSEL section fabricated using GaInAs/AlGaAs MQW active region and a 1550 nm top VCSEL section constructed using GaInAs/AlGaInAs MQW active region but optically pumped using half of the produced 980nm light entering into it from the electrically pumped bottom cavity. In this design, the active region of the intracavity structure 980 nm VCSEL consists of 3 quantum wells (QWs) using Ga 0.847 In 0.153 As, 2 barriers using Al 0.03 Ga 0.97 As, and 2 separate confnement heterostructures (SCH) using the same material as the barrier. Te active region of the top emitting 1550 nm VCSEL consists of 3 QWs using Ga 0.47 In 0.52 As, 2 barriers using Al 0.3 Ga 0.17 In 0.53 As, and 2 SCHs using the same material as the barrier. Te top DBR and the bottom DBR mirror systems of the 1550 nm VCSEL section plus the top and bottom DBR mirror systems of the 980 nm VCSEL section have been formed using GaAs/Al 0.8 Ga 0.2 As. Computations show that the VCSEL is capable of producing 8.5 mW of power at 980 nm from the bottom side and 2 mW of power at the 1550 nm from top side. 1. Introduction It is well known that 850 nm–980 nm (short wavelength) and 1300 nm–1550 nm (long wavelength) MQW edge emitting diode lasers are widely used in optical communication systems [1, 2]. For these wavelengths, VCSELs are much better because of the many well-known advantages of VCSELs [3]. Conventional VCSELs are electrically pumped by injection current. In such a device, undesirable heating happens due to the fow of injection current through the layers of materials of the top and bottom DBR mirror systems. To eliminate this unwanted heating, intracavity structure has been used by the designers although this may introduce slight complexity in fabricating the VCSELs. VCSEL with good beam quality (single transverse mode) greatly reduces the complexity of beam-shaping optics (com- pared to edge emitters) and increases the coupling efciency to the fber or pumped medium [4]. Unfortunately, poor beam quality is obtained from conventional electrically pumped VCSELs due to lasing of higher order transverse modes with even relatively small active diameters [4]. A transverse single-mode operation from large-area devices (large beam diameter) is always advantageous since such devices can provide low thermal resistance and high output power at small divergence angles [4]. In an electrically pumped VCSEL, it is not possible to inject carriers uniformly across a wide area for a large beam diameter in the laser cavity by traditional diode current injection [4]. As a result, other transverse modes are gen- erated beside fundamental transverse mode which in turn degrades beam quality of the laser [4]. In order to mitigate this problem, a thick doped semiconductor current spreading layer can be used. But such a doped layer has strong free Hindawi Publishing Corporation International Scholarly Research Notices Volume 2014, Article ID 627165, 10 pages http://dx.doi.org/10.1155/2014/627165