Study On The Gain Characteristics Of Vertical-Cavity Semiconductor Optical Amplifiers In Small Signal Based On The Transfer Matrix Method

With the development of VCSEL technologies, vertical-cavity semiconductor optical amplifiers (VCSOAs) have become to attract people's increasing interest. There have been some research results which indicate that VCSOAs have the inlierent advantages of high-fiber coupling efficiency, polarization insensitivity, and low noise figure, etc. Furthermore, they can be a low-cost alternative to in-plane SOAs. So they have potential applied prospects in the domain of optical modulations, optical switches as well as optical detections.This paper studies the gain characteristics of the VCSOA in small signal using the transfer matrix method which mainly bases on the structure of the VCSOA comprised of different material layers. Firstly, according to the similar method dealing with the DBR, the characteristic matrices of the layers in the active region are built up. Then after multiplying the characteristic matrices of all the layers in the DBR and the active region orderly, the transfer matrix of the whole equipment are obtained. Finally combining with the substrate refractive index, we achieve the gain and bandwidth characteristics of the VCSOA in small signal.The paper considers the fact that the real part of the quantum wells complex refractive index will vary with the pumping carrier concentrations. The gain characteristics are respectively simulated and calculated along with variable carrier concentrations and layers of the DBR. At the same time, the gain characteristics versus the position of the quantum well stacks are predicted. The results produced by the transfer matrix method are in agreement with that of conventional F-P method, further more, the causes of some discrepancies are analyzed, proving the correctness of the transfer matrix method.The virtues of the transfer matrix are mainly that it analyses the VCSOA as a whole, never introducing the effective optical cavity length and gain enhancement. When the material or structure parameters change, the equipment can be analyzed strictly according to its structure. After straightly putting the parameters into the characteristic matrices, we can obtain the gain characteristics of VCSOAs.