Optical output power fluctuation due to reflected lightwaves in laser diode modules

The optical output power fluctuation caused by axial displacement of optical components in an actual laser diode module subject to the influence of reflected light waves has been theoretically investigated. Results are based on the comparison of data from two analytical methods. One takes the emission spectrum shift of a laser diode into consideration while the other ignores wavelength shift. It has been clarified that the differences between these two results are relatively small, as long as it can be assumed that the laser diode oscillates in the initial longitudinal mode. Suppression methods for the reflected lightwaves are also discussed. Practical and efficient antire-flection techniques for the laser diode modules are presented.