High Power Density Beam from Narrow Diode-Laser Arrays in Axial Symmetry (original) (raw)

We present the intracavity generation of beams with radial polarization at an average output power of 750 W and an optical efficiency of 43% from a continuous wave thin-disk laser. Circular grating waveguide output couplers (GWOC) were used to select the radial polarization. The sensitivity of the polarizing function of the GWOC with regards to the fabrication tolerances is also analysed in details with a particular emphasis on the effect of the duty cycle and the geometrical profile of the gratings. Furthermore, we present the conversion of femtosecond laser pulses from linear to azimuthal polarization using a nanograting-based polarization converter. Azimuthally polarized beams with an average power of up to 850 W, a pulse duration of 400 fs and a pulse repetition rate of 1 MHz were generated in this way with a conversion efficiency of >90%.

Low confinement laser diode structure permits lower modal gain, longer devices and wider stripes. The optimum value of the confinement factor is correlated with the modal attenuation coefficient. For an 1 cm-1 modal attenuation coefficient, the optimum operation is obtained in 12 micrometers stripe and 0.007 confinement factor. In such structures, fundamental lateral mode is preserved at power higher than 1 W.