Study And Design Of Inter Cavity Sub Wavelength Tunable Vertical-cavity Surfaceemitting Lasers

With the rapid development of science and technology in the information age,high performance vertical cavity surface emitting laser(VCSEL)has become a core component of high speed and high density integration. With its unique circular symmetric spot, small volume, low power consumption and high degree of coherence array integration features, and compared with conventional edge emitting lasers,VCSEL can be analyzed directly on the test chip, greatly reducing the manufacturing cost. Therefore, it is mass produced because of great commercial and military value and has been widely used in the fields of optical switch, optical interconnection,optical computing and biological medicine. Therefore, in recent years, tunable VCSEL has been gradually realized in LAN / multimode optical fiber transmission digital communication(access network, backbone network) and dense wavelength division multiplexing(DWDM) system, such as all optical network applications. On the other hand, the light source performance are required higher and higher, for example, in the super fast broadband optical information network and high performance super computer(HPC), they all need to achieve more than 1 x 106 of the optical channel, while the traditional VCSEL laser can obtain 25 gbps above the modulation rate, but due to the quantum well electronic response speed limit, to further improve the modulation rate becomes very difficult. In the electronic product research and development(laser mouse, laser TV, laser radar), medical imaging scans and so on, in order to obtain higher reliability and product quality, the laser light output must single-mode polarization. Comprehensive view, the traditional VCSEL in the domain of new and high technology have to face two difficulties: how to achieve a wide range of light single polarization, in order to achieve lower dispersion noise and more channel space; how to keep high integration, to achieve lower cost and smaller volume. Therefore, a wide range of VCSEL polarization control technology has become a research hotspot and difficulty in tuning the semiconductor light source in the field of high performance. In order to solve these problems, we based on micro nano grating structure and development tunable VCSEL multiple optical cavity coupling theory, propose the grating coupled micro cavity laser structure; and on the basis come true single polarization control of tunable VCSEL technology. In the process of controlling the polarization of the light wave,the orthogonal polarization state is modulated by the grating strong diffraction effect.The main contents of this paper are as follows:1. According to the equivalent medium theory, the variation characteristics of the equivalent refractive index of the polarized light under different sub-wavelength grating parameters are obtained. On this basis, using rigorous coupled wave analysis method get the relationship between the design of sub wavelength grating with the transmission of different polarized light, and the realization of TE and TM two kinds of equivalent refractive index anisotropy of polarization difference reached 2. Study found that the influence of sub-wavelength grating design cycle on TE and TM polarized light equivalent refraction rate is very small,for TM polarization changes in refraction rates for 0.0035 and for TE is 0.0014.When the incident wavelength is 850 nm, for both TE and TM polarization and subwavelength grating for duty ratio is 0.23 and 0.8, TE and TM polarized light transmittance can reach 99%. In addition, subwavelength grating thickness on TE and TM polarized light transmittance has periodic impact, in the each cycle has the optimal grating thickness to make their transmittance reached largest, for TE polarized cycle is 150 nm, the TM polarized light cycle is 300 nm.2. A wavelength tunable VCSEL physical model was built, then study the influence of different grating structure design in polarization control and wavelength tuning. The wavelength tuning range and polarization stability of three kinds structures are compared. These structures contain the sub wavelength grating on the inner cavity and top DBR under surface and the top DBR surface. When the air gap changes 300 nm, the cavity sub wavelength grating VCSEL wavelength tuning range of 54 nm, while the other two kinds of structure design and distribution of 20 nm and 12 nm. Finally get the optimal structure design of the wide range polarization stable cavity sub wavelength grating VCSEL.3. Design and optimization of the inner cavity sub wavelength grating wavelength tunable VCSEL. Theoretical analysis the influence of sub wavelength grating parameters on the TE/TM polarization wavelength tuning range, and obtain the maximum TE/TM polarization tuning range grating parameters: TE polarization duty cycle is 0.6, thickness is 100 nm, period is 200nm; for TM polarization duty cycle should 0.07, thickness is 150 nm, period is 200 nm. At last study the inner cavity sub wavelength grating tunable VCSEL threshold gain, so we can draw a conclusion that the TM mode single polarization maximum wavelength tuningrange, under TE polarization stable 18 nm wavelength tuning range, and for the TM polarization can realize wavelength tuning range of 21 nm.