Abstract A three-level $\Lambda$-type atomic system is pumped by an incoherent radiation field. The system lases without population inversion in the steady state. We analyze the inversionless gain and origin of the gain.
Received: 08 April 1996
Accepted manuscript online:
Altmetric calculates a score based on the online attention an article receives. Each coloured thread in the circle represents a different type of online attention. The number in the centre is the Altmetric score. Social media and mainstream news media are the main sources that calculate the score. Reference managers such as Mendeley are also tracked but do not contribute to the score. Older articles often score higher because they have had more time to get noticed. To account for this, Altmetric has included the context data for other articles of a similar age.
