Investigation of spectral characteristics of solitary diode lasers with integrated grating resonator

This report examines the properties of high-power DFB diode
lasers emitting at 780 nm which shall be used for high-precision
spectroscopy of ultra-cold Rubidium atoms. Consequently,
research efforts were aiming to provide both, high
output power and high spectral short-term stability (low shortterm
line width).
For this purpose, the short-term line width of a DFB laser has
been analyzed with heterodyne and self-delayed heterodyne
methods. By optimizing the laser parameters (chip length,
coupling coeffi cient and coating of the coupling facet) these
lasers achieved excellent performance in terms of stable
single-mode operation at high output power and small line
width. The best results were delivered by 3 mm long DFB
lasers with a 95% refl ectivity coating of the rear facet and a
5% refl ectivity coating of the front facet and a coupling coeffi
cient of approximately 2 cm-1. These lasers show an output
power of 270 mW and an intrinsic line width of 20 kHz (10 μs)
in stable single-mode operation. This is a world-wide unique
combination of output power and intrinsic line width for DFB
diode lasers at this wavelength.