1 Abstract-A new scheme of oriented-hyperboloid -microlens (OHM) with passive alignment to achieve high polarized extinction ratio (PER) is proposed and demonstrated high efficiency coupling of high-power 980 nm pump lasers to polarization maintaining fibers (PMFs). Using an automatic grinding machine and a charge-coupled-device to precisely control and attain the required minor radius of curvature 4 -4.8 m, offset within 0.7 m, and axis orientation accuracy 1º, the OHM exhibited a high-average PER of 31.7 dB and a high-average coupling efficiency of 83.4%. For a 30 dB PER, the angular misalignment tolerance of the OHM was measured to be 2º. The unique advantage of the proposed OHM is passive alignment to achieve high PER by only aligning the OHM endface of the fast axis parallel to the axis of laser polarization. This newly developed OHM with unique passive alignment to achieve high polarization is beneficial for the applications of laser/PMF modules where mode polarization and high coupling efficiency are required for use in high precision fiber optic gyroscopes as well as many low-cost and high-performance lightwave interconnection applications.Index Terms-Passive alignment polarization-maintaining fiber, oriented hyperboloid microlens, fiber optic gyroscope.
Characteristics of hole formation in laser welding technique for optoelectronic packaging have been investigated by metallographic microscopes. The results show that the dimension of hole depends on the power density of laser beam and the hole disappears as the power density below 3 x 1 O5 W/cm2. The hole generation between welded sections can cause spatial nonuniformity of solidificationshrinkage during laser welding process, resulting in generating micromovement. Micromovement due to failure mechanism of the hole formation during laser welding process may affect the alignment for optoelectronic packages, particularly for single-mode fiber applications. Based on our understanding of laser welding process characteristics, a reliability study of receptacle laser packages is currently under investigation.
A new scheme of hyperboloid microlens (HM) employing automatic grinding and precise fusing techniques to achieve high-average and high-yield coupling efficiency from high-power 980-nm lasers into single mode fibers is proposed and demonstrated. The fiber endface of the HM exhibited a double-variable curvature in the major and minor axes that was characterized as a hyperboloid. By selecting half transverse length of the hyperbola and using fusing process to precise and quantitative controlling the required minor radius of curvature within 2.4-2.8 m and offset within 0.8 m, the HMs exhibited a high-average coupling efficiency of 83%. For fabricated high-coupling HMs, the result was also found that the tolerance of minor radius of curvature decreased as the offset increased. This study demonstrates that the proposed HMs through both automatic grinding and precise fusing techniques can achieve high-average and high-yield coupling efficiency better than any other grinding techniques to form asymmetric microlenses for utilizing in many low-cost lightwave interconnection applications.
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