Discrete mode laser diodes emitting single wavelength mode at λ∼657 and 689 nm for optical atomic clock applications

Compact monolithic single-mode red emitting diode lasers are still not readily available for many wavelengths in the visible spectrum. Strontium lattice and Calcium clocks are some of the most widely investigated optical clocks worldwide and the pertinent transitions wavelengths required are in the red and blue wavelength spectral region. The current state of the art in laser technology employs external cavity laser diodes and frequency doubling crystals in order to hit the desired wavelength with external amplifiers used to meet the power requirements. Compact rugged monolithic narrow linewidth laser sources operating in the red and blue wavelengths have been identified by the European Space Agency as a key technology that could be used to replace all of these costly, energy inefficient and vibration sensitive components and to one day facilitate the optical clock leaving the laboratory and to eventually end up on a satellite in space.