High-Power Single-Mode Fiber Coupling of a Laterally Tapered Single-Frequency Diode Laser

In this letter, we investigate experimentally single-mode fiber (SMF) coupling of a nondiffraction limited, astigmatic beam generated by a near-infrared distributed Bragg reflector tapered diode laser at high output powers. In particular, a systematic study of the coupling efficiency as well as spectral and spatial laser beam characteristics behind the SMF is carried out in dependence on the properties of the collimated beams in front of the SMF, which are generated at given operating points of the diode laser. A stigmatic, nearly Gaussian laser beam is obtained behind the SMF independent on the diode laser operating point and the input optical power. A maximum power of 3.5 W ex fiber at a power coupling efficiency of 65% is reached.