Analysis On Beam Parameters Of Restricted Diffraction From Single Mode Optical Waveguide

All-optical network is the current and future development of one of the main direction of the industry has become a consensus, optical signal processing, integrated optoelectronic, fiber optic sensors and sensor systems, and other technology have been developing rapidly, a wide range of applications in many areas, dielectric waveguides is base for that these devices and systems of designs. Therefore, this article has studied the characteristics and the light beam parameters of multi-quantum wells waveguide and the single mode fiber end surface diffraction beam, it is provides the theory support and the instruction for the application of the dielectric waveguides in integrated optical devices.In paraxial condition, the refractive index symmetric multi-quantum wells waveguide is studied, the far-field diffraction field distribution of the waveguide in multiple quantum wells output end with slit restricted is analyzed. The curves of diffraction beam full angle at half maximum, the amplitude drop to Me the far-field divergence angle, the beam propagation factor, the near field mode field half-width, far-field divergence angle each one of them along with the slit half-width are obtained, respectively. To facilitate analysis and calculation, the curve fitting method is employ, the curves of full angle at half maximum, the far-field divergence angle of amplitude drop to 1/e, the near field mode field half-width along with the slit half-width change is fitted, respectively, and the relative error which the fitting caused is calculated for appraisal fitting precision. The full angle at half maximum and the amplitude drop to Me the far-field divergence angle is analyzed that the second moment, differential operator, the equivalent matching efficiency of three method Gaussian approximation of waveguide mode field is reasonable and accurate. Based on the factor M~2 of beam is close to unit, to the far-field diffraction amplitude can be approximate by Gaussian function, and the far field divergence angle of its Gaussian approximation is calculated by maximum efficiency matched method.The far-field amplitude distribution expression of the single-mode optical fiber which output end surface restricted is derived. Based on the amplitude distribution expression and the curves of the full angle at half maximum, the far-field divergence angle of amplitude drop to Me, the beam propagation factor, near-field mode field half-width, far-field divergence angle with the normalized circular aperture radius are studied. And their relationships curves are fitted out by functions. The relative error caused by fitting is calculated, appraisal fitting precision. Used the full angle at half maximum and the amplitude drops to the Me far-field divergence angle had analyzed the second moment method, the differential operator method, the equivalent matching efficiency method of the three Gaussian approximation are reasonable and accurate, respectively.Based on the far-field diffraction distribution analytic function expression of single-mode optical fiber, the curves of their far-field divergence angle of the beam power of 50% and 86.5% with the fiber normalized frequency are studied, and the curves function expression are fitted out, respectively. The relative error which caused by fitting are calculated to evaluating the accuracy and reasonable of the fitting. The result of second moment algorithm and differential operator algorithm to determine the far-field divergence angle radius have some differences, so the equivalent matching efficiency method is employed for far-field divergence angle, and the curve of far-field divergence angle along with the radius of the fiber normalized frequency is obtained, and its function expression is fitted, the precision of fitting is analyzed by the relative error.