| 摘要 |
A material which is capable of absorbing and storing the energy of illuminating pulses is illuminated by a first high-intensity light pulse, and is subsequently illuminated by a second high-intensity pulse. When the homogeneous relaxation process of the material is sufficiently long as compared to the time separation of the pulse, a photon echo pulse is emitted from the material at a time following the second pulse substantially equal to the time separation of the first and second pulses. In a modification of the invention, the first and second pulses are angularly displaced, and the photon echo pulse is thereby emitted at an angle of twice the displacement from the first pulse.
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