We have demonstrated a 60 nm-tunable, 160 psec-width, optical pulses from a 980 nm Grating Coupled Surface Emitting Laser (GCSEL) in an external cavity under nanosecond pump pulses. GCSEL is in-plane laser monolithically integrated with grating outcoupler. The grating was detuned from second order Bragg condition and it served as an efficient interface between planar waveguide and free space. Wavelength tuning was simply achieved by tilting an external flat mirror provided wavelength selective feedback to the GCSEL chip. Gain switched pulses with wavelength linewidth less than 0.1 nm and peak power of 200 mW have been obtained. In our experiments we measured a shortest optical pulses by reducing a distance between external mirror and laser diode chip. This corresponded with decreasing the effective laser cavity length and the cavity round-trip time as well.