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The Study of Photonic Crystal Vertical-Cavity Surface-Emitting Lasers

Author: LiXinTao
Tutor: SunXiaoHong
School: Zhengzhou University
Course: Optics
Keywords: photonic crystal band-gap defect mode vertical cavity surfaceemitting lasers single transverse mode laser threshold
CLC: TN248
Type: Master's thesis
Year: 2012
Downloads: 96
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Abstract

Vertical cavity surface emitting lasers (VCSEL) were proposed in1977and their performance has been greatly improved during the30years of research. The devices which have lots of advantages should be given as much as possible study and development, so the applications of VCSEL are still expanding ceaselessly. Naturally, the requirements in performance are also getting higher and higher. However, it’s difficult to resolve the problems which appear in the process of developing the devices for new applications by traditional methods, so we need to find a new way.In1987, the concept of photonic crystal is presented.Photonic crystals are artificial microstructures with materials of different dielectric constant (or tensor) arraying periodically (or quasi-periodically) in the space, and they have strong ability to control the propagation of light. Photonic crystal has lots of optical properties, and its most basic characteristics is that it has the photonic band-gap. Photonic band gap is a frequency band, and if the frequency of the photon is in the band-gap, it can not propagate in the photonic crystal. The more practical application is that we introduce defects in photonic crystals, so defect mode will be in the band gap. The exact design of photonic crystal and its defect structures make us get effective control of the photon. We will have more choice in the design of vertical cavity surface emitting lasers, if photonic crystals which have defects are made into the lasers.Firstly, we calculated and analyzed the band-gap of the two-dimensional triangular structure of air holes in photonic crystal by the finite difference time domain method. This provides the subsequent chapters direction for the design of the laser resonator. In the study of photonic crystal vertical cavity surface emitting lasers,we work in two aspects:the control of photonic crystal in the laser mode and the reducing of the laser threshold. Using the photonic crystal fiber single transverse mode theory, we analyze the require of the crystal structure parameters with which photonic crystal vertical cavity surface emitting lasers can excite single transverse mode.And then, according to the result of the calculating of the complete band gap,we optimize the photonic crystal structure parameters. In order to reduce the laser threshold, we the make the analysis of the various factors that influence the laser threshold. We introduce the photonic crystals in the traditional vertical cavity surface emitting lasers, use the rate equations of the carrier surface density and photon number surface density, and analysis the affect of the different parameters of the photonic crystal structure in each factor.The results show that the introduction of photonic crystal in vertical-cavity surface-emitting lasers can help the devices to achieve single-transverse mode lasing, and the introduction of the photonic crystal can also reduce the laser threshold. From the perspective of producing technology, photonic crystal vertical-cavity surface-emitting lasers are easier to achieve the two-dimensional parallel integration than the conventional vertical-cavity surface-emitting laser.

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