Abstract

Photon-pumped far infrared or sub-millimeter stimulated emission can usually be obtained at a length of longer than 1 meter. Though Everitt el al. have proved that a cavity of 5cm could result in stimulated emission, the cavity composed of two mirrors along the propagation direction has to use a pinhole for the coupling in and coupling out the cavity. It has been realized that even if there is no mirror along the propagation direction to form a cavity, one can still have stimulated emission at a length of 1.5cm to 5cm.^[1] The chamber used in the experiment is shown in Fig. l. A tube of internal diameter 3 cm was sealed at one end with teflon and the other with NaCl crystal. Two mirrors interfaced arranged the inner tube with surfaces parallel to the axis and one of the two mirrors can be adjusted along the direction perpendicular to the axis of the tube. The amplification of spontaneous emission can be detected when the distance between the mirrors is adjusted to the resonance condition. The intensity of the stimulated emission varies periodically with the change of the mirror separation half wavelength.

© 1992 IQEC