Sub-micrometre distance measurements with a broadly tunable short-external-cavity InGaAsP/InP diode laser

Measurement of distance using a custom-designed, broadly tunable InGaAsP/lnP short-external-cavity diode laser is described. A tuning range of over 100 nm was achieved with the custom-designed laser in a diffractive optical element short external cavity. This tuning range made it possible to achieve a sub-micrometre resolution in measurement of distance with a single laser source for an interferometer. A non-linear, least squares fitting method was used to extract the displacement from the raw data. This fitting method showed a potential for extraction of accurate displacement in the presence of noise.