4.6-W Single Frequency Semiconductor Disk Laser With ${<}{\rm 75}\hbox{-}{\rm kHz}$ Linewidth

We report on a single frequency semiconductor disk laser producing 4.6 W of output power with the free-running linewidth of <;75 kHz derived from delayed self-heterodyne measurements. The implementation of the flip-chip gain design allows for considerable power scaling with good beam quality and high spectral purity.