Superluminal Raman laser with enhanced cavity length sensitivity

We demonstrate experimentally a superluminal ring laser based on optically pumped Raman gain, and a self-pumped Raman depletion for producing anomalous dispersion, employing two isotopes of rubidium. By fitting the experiment data with the theoretical model, we infer that the spectral sensitivity of the superluminal Raman laser to cavity length change is enhanced by a factor of more than a thousand, compared to a conventional laser.