Abstract: A monolithic vertical optical cavity device built up along a vertical direction. The device has a bottom Distributed Bragg Reflector (DBR), a Quantum Well (QW) region consisting of least one active layer grown on top of the bottom DBR by using a Selective Area Epitaxy (SAE) mask such that the active layer or layers exhibit a variation in at least one physical parameter in a horizontal plane perpendicular to the vertical direction and a top DBR deposited on top of the QW region. A spacer is deposited with or without SAE adjacent the QW region. The device has a variable Fabry-Perot distance defined along the vertical direction between the bottom DBR and the top DBR and a variable physical parameter of the active layer. The varying physical parameter of the active layers is either their surface curvature and/or the band gap and both of these parameters are regulated by SAE. The monolithic vertical cavity device can be used as a Vertical Cavity Surface Emitting Laser (VCSEL) or a Vertical Cavity Detector (VCDET).