Spatial coherence produced in laser radiation on passing through the generation threshold

Sergei M. Arakelyan, Sergei A. Akhmanov, Vladimir G. Tunkin +1 more

Vladimir P Bykov

The quantum-mechanical state of laser radiation near the generation threshold is studied. It is shown that there is a second threshold in laser generation which lies above the first one. At the second threshold coherence appears in laser radiation. In a small region between the two thresholds the laser radiation is in an essentially quantum state, in which the average field strength is close to zero, but the average energy keeps a macroscopic value. Active atoms in superposition states are the sources of coherence in lasers. The laser active medium sufficiently enlarges the characteristic time of coherence.

A. M. Akulshin, Nafia Rahaman, Sergey A. Suslov +1 more

Population inversion on the 5D5/2−6P3/2 transition in rubidium atoms produced by cw laser excitation at different wavelengths has been analyzed by comparing the generated mid-infrared radiation at 5.23 μm originating from amplified spontaneous emission (ASE) and isotropic blue fluorescence at 420 nm. Using a novel method for detection of two-photon excitation via ASE, we have observed directional co- and counter-propagating emission at 5.23 μm. Evidence of a threshold-like characteristic is found in the ASE dependences on laser detuning and Rb number density. The power dependences of the backward- and forward-directed emission can be very similar; however, their spectral dependences are not identical. A new type of temporally and spatially coherent radiation is suggested.

А. Н. Ораевский

BERNARD SHORE

А.В. Андреев, Владимир Алексеевич Бушуев, Oleg Tikhomirov

Boundary-value problesm are solved for the spatial-temporal development of radiation in a mirrorless, single-pass ..gamma..-ray laser. The semiclassical approximation is used along with a quantum mechanical approach. (AIP)