Rearch On The Characteristics Of The Grating Feedback External-cavity Diode Lasers

The performance characteristics of grating-feedback external-cavity diode lasers(ECDL), narrow line-width, large continuous tuning range and excellent output stability, are of critical importance for their applications in experiments and engineering. Studying these characteristics will help design and optimize the structures of ECDL. The mode structure, line-width, dynamic mode stability and tuning character of the Littrow-type-based ECDL are extensively studied in this thesis. The main contents of this thesis are as follows.(1) A mathematic model of mode structure of the grating-feedback ECDL is established and this mathematic model differs form the existing research which uses the Airy function to describe the mode structure. Based on this model, the effect of these different structure parameters on the mode structure is discussed.(2) The effect of the front facet reflectivity of the FP LD on the mode structure of ECDL output beam and the threshold current of ECDL is analyzed. It is shown that decreasing the front facet reflectivity can reduce the influence of internal cavity on the mode structure so that to improve the spectrum purity and stability of the mode structure, and has on significant effect on the threshold current of the ECDL.(3) The character of the ECDL dynamic mode stability is studied. The general Littrow-type ECDL are simplified to assume the grating and the pivot arm are on the same plane. It is proposed that a more general scheme that the grating and the pivot arm don't lie on the same plane. It can readily achieve a 9.37 nm mode hop free tuning range at 780 nm. In addition, decreasing the distance between the grating surface and pivot arm and increasing the distance between the pivot point and grating can be simultaneously used to obtain a large mode-hop free tuning range and narrow line-with. It also develops a novel Littrow-type external-cavity diode laser with a plane mirror fixed relative to the grating. It is estimated that when the initial distance between the grating and the mirror is 2.7 mm, no mode-hop occurs within the tuning range of 4.3nm, and the lateral shift of the output beam is only 9.7?m(4) The analysis of linewidth in external-cavity diode laser(arrays) is made in details. It focus on the effect of feedback coupling efficiency on the ECDL linewidth. It uses coupling theory to calculate the feedback coupling efficiency. The result shows that the coupling efficiency is closely related to the location of the collimating lens. The lens is deposited over a distance of 4.51 mm from the LD with a positioning accuracy of 0.0317 mm and a tilt error of 13.5?. Based on the theory of the geometrical optics transformation matrix, the numerical analysis of the external cavity diode laser arrays(ECDLA) output linewidth is performed. A method which uses a cylindrical lens set at an angle to the beam is proposed for correcting the “Smile” effect. For the proposed method, the “Smile” effect which shows a parabola type can be reduced availably. The result of simulation analysis by Zemax is agreeable to the existing research.