Optical Axis Determination of Semiconductor Laser Systems

An optical axis determination method for semiconductor laser systems of invisible wave length, e. g. 1.3, 1.5 μm, has been proposed. A semiconductor laser module with a microlens shaped by the surface tension of melted glass is discussed. The optical axis of the system is determined as follows. At first, the axis of the lens is searched from interference fringes made by reflecting He-Ne laser visible light. This axis is then used as the reference axis. Next, the electromotive current in the semiconductor laser is measured by illuminating the semiconductor laser with a He-Ne laser light from the opposite direction against the laser emission. At the same time, the angle of the illuminating laser light is continuously changed by means of an f·θ lens. The illuminating laser light axis which corresponds to the desired optical axis is found when the maximum electromotive current is obtained. The spacial orientated axis is determined by independently measuring the maximum currents along two directions orthogonal to each other.