Absorption saturation resonances in a double-mode mode-locked He–Ne/CH4 laser

An investigation was made of the amplitude characteristics of a double-mode He–Ne/CH₄ laser with linearly and orthogonally polarised modes, when the cavity was frequency-modulated at a frequency close to the intermode spacing. Under these conditions the intensities of the individual modes had resonance structures near the centre of an absorption line. These structures were narrow: their widths were less than the homogeneous width of an absorption line.