Lens-less semiconductor optical amplifier (SOA) modules using laser welding techniques

We report the high performance SOA modules made using laser welding technique. The SOA chip is DH structure and its stripe of active layer is tilted by 7/spl deg/ and facet is AR coated for low reflection of 10/sup -5/ order. We used a cylindrical type laser welding (it is 3-point welding) for fiber fixing the fiber for direct coupling. We used specially designed the components of ferrule, sleeve, and submodule. The lap welding is used in the ferrule-sleeve fixing and lap-fillet welding in sleeve-submodule the fixing is used. The welding loss is usually less than 0.5 dB after a readjustment. This method is proven to be a very simple and stable technique for direct coupling. The chip gain and far field angle are 30 dB and 160/spl times/160 respectively, and the fiber is taper lensed fiber. With the coupling loss and the welding loss of -2.2 dB/facet, we can obtain the module gain of 25 dB.