Misleading title. Semiconductor lasers are in general already >30% efficient there is no way to make a laser 250x more efficient. The researchers only improved a special type of laser (polariton laser)
It reads like there is a minimum amount of energy required to establish and maintain a laser beam using similar materials today, and they have lowered that minimum threshold by a factor of ~250. The resulting energy/intensity/whatever of the beam vs. the ongoing input energy is not discussed in the article.