  We present hybrid-integrated extended cavity diode lasers tunable around 637
nm, with a gain-wide spectral coverage of 8 nm. This tuning range allows
addressing the zero-phonon line of nitrogen vacancy centers and includes the
wavelength of HeNe lasers (633 nm). The lasers provide wide mode-hop free
tuning up to 97 GHz and a narrow intrinsic linewidth down to 10 kHz. The
maximum output power is 2.5 mW in a single-mode fiber, corresponding to an
on-chip power of 4.0 mW. Full integration and packaging in a standard housing
with fiber pigtails provide high intrinsic stability and will enable
integration into complex optical systems.
