LASING WITHOUT INVERSION - THE ROAD TO NEW SHORT-WAVELENGTH LOSERS

Lasing Without Inversion (LWI) is a novel technique in laser physics w hich holds the promise of a solution to one of the most fundamental pr oblems in short-wavelength laser research. Making use of quantum coher ence and interference effects, this technique allows lasing even if on ly a small fraction of population is in the excited state, i.e., even if the population of the active medium is not inverted. The intense th eoretical work on the subject has been verified by several experiments which confirmed that LWI is indeed possible. The efforts of researche rs are presently directed to demonstrate LWI in the UV and X-ray spect ral regions.