  We experimentally demonstrate the difference between a ridge polariton laser,
and a conventional edge-emitting ridge laser operating under electron-hole
population inversion. The horizontal laser cavities are 20 -- 60 $\mu$m long
GaN etched ridge structures with vertical Bragg reflectors. We investigate the
laser threshold under optical pumping and assess quantitatively the effect of a
varying optically-pumped length. The laser effect is achieved for an exciton
reservoir length of just 15% of the cavity length, which would not be possible
in a conventional ridge laser, with an inversion-less polaritonic gain about 10
times larger than in equivalent GaN lasers. The modelling of the cavity free
spectral range demonstrates the polaritonic nature of the modes.
