Non-orthogonality of the longitudinal eigenmodes of a distributed feedback laser

<title>Influence of excess quantum noise and full saturation effect on light coherence in Fabry-Perot and distributed feedback lasers</title>

“…Here, re'R is the complex reflection coefficient, YN is the complex propagation constant, which is the solution of the eigenvalue equation [3], and N describing the number of longitudinal modes denotes the sequence of solutions of the eigenvalue equation [3]. The two-mirror laser with unsaturable gain coefficient g0 and a constant loss coefficients within the gain medium a0 (region II) and distributed losses a11 and a12 in regions I and II (i.e., in extra cavity devices) is shown in Fig.…”

“…Here, P is the noise strength for orthogonal laser modes and K is the longitudinal excess noise factor which is defmed in terms ofthe spatial distribution ofthe laser modes [1][2][3][4][5][6][7][8].…”

“…These properties are described by the amplitude correlation function and the correlation function of the intensity fluctuation of the laser mode. In the case of more realistic laser systems, the non-orthogonal nature of the laser modes leads to the excess quantum noise dependent on the spatial distribution of the laser modes and simultaneously determined by the geometry of the laser resonator [1][2][3][4][5][6][7]. This effect especially modifies the statistical properties of laser radiation including the mean laser intensity, intensity fluctuations, and laser linewidth [9][10].…”