Continuous wavelength sweep of external cavity 630 nm laser diode without antireflection coating on output facet

We developed a simple method of continuous wavelength sweep using a commerc ial laser diode (LD) without antireflection (AR) coating. A 630 nm AlGaInP LD was installed in a Littrow-type external cavity. In this cavity, the LD has the same effect as an etalon, and its free spectral range can be contro lled easily by the LD drive current. By scanning the grating angle of the e xternal cavity and LD drive current simultaneously, we obtained single-mode oscillation and continuous wavelength sweep of over 22 GHz without mode ho pping. This technique is simple and inexpensive because it does not need AK coating on its output facet, and does not use a servo system which require s apparatuses such as a lock-in amplifier and local oscillator.