Use of glass solder in fixing an optical fiber in a laser package

Abstract

In order to couple the light emitted from a semiconductor laser into the core of an optical fibre, where the core and laser emitting are not matched, it is necessary to use a lens system. This lens system then focuses the divergent light into the fibre core, often this lens is fabricated on the end of the fibre. When the lens is on the end of the fibre, it must be fixed in place in front of the emitting laser using a method that will hold the fibre in position relative to the laser during the lifetime of the laser. This reliability requirement is particularly critical in the case of lasers with a highly elliptical output beams. The tolerances for the displacement of the lensed fibre relative to the laser are extremely tight, a movement of less than 0.5 microns in the vertical direction can cause a drop in coupled power of greater than 10%. In this paper existing techniques of fixing the fibre relative to the laser are outlined and contrasted with an improved method using glass solder. The improved method is described with salient features such as the fixing of the fibre to a rigid support member and the laser welding process used to fix the rigid support member in front of the laser explained in detail. Other aspects of the laser design including thermal dissipation are also discussed in detail. Finite element analysis (FEA) has used extensively to demonstrate the capacity of the design. Device performance and reliability information is also presented demonstrating the capability of this technique in the fixing of an optical fibre relative to a laser device.

A Quantitative Postweld Shift Measurement and Compensation Technique in Butterfly Laser Module Packages

“…16) There are many other methods for fabricating the fiber ferrule, such as the use of glass solder. 17,18) Namely, glass solder has a low CTE, which matches very well with the glass fiber. It also eliminates the need for fiber metallization thus reducing the manufacturing cost.…”