A new GaInAsP/InP injection laser was fabricated on semi-insulating substrates. The structure utilises a single LPE growth process on a grooved substrate to form an index guided device. Current confinement was obtained by the semi-insulating InP surrounding the GaInAsP active layer. Threshold current as low as 28 mA with 250 μm cavity length was obtained. The light/current characteristic was linear up to five times Ith. A single longitudinal mode at 1.20 μm up to 1.3 Ith was observed.