Mode structure of active resonators

On the stability of modes in a laser resonator with an active medium

“…The pulsewidth reported here, 24 ns, is an order of magnitude wider than that reported by Liberman et al [ 4 ] . This width is consistent with the observation that laser operation was dependent on the existence of a cavity, whose roundtrip time was 7 ns.…”

“…These papers, dealing only with passive resonators, have value mainly because of the excellent fit shown between the experimentally observed intensity patterns of small cavities and the theoretical calculations. The stability of such modes and how such a mode builds up in time, however, are only fragmentarily studied, In a recent publication [4] we calculated the mode structure of active resonators for the case where diffraction losses are small, starting from the basic work of Kogelnik [ 51 . We found that for a stationary state an eigenmode with a Gaussian distribution satisfies the boundary conditions for any.…”

The effect of radial radiation transport on intensity characteristics and oscillation frequency of homogeneously broadened lasers

“…In [6], where the field distributions of Gaussian modes in a lenslike medium were calculated, we conveniently used the dimensionless parameters P(z), U(z), and Q(z), defined by = --.…”

“…beams [7]. In a previous publication [6] we calculated the influence of the radial index and gain parameters p and a on the beam parameters Q and U by applying the A B C D law to a complete round trip through a laser resonator consisting of two mirrors with radii of curvature R , and R2, respectively. In the present paper we shall be concerned with (6a) and we shall show how, for homogeneous broadening, competition between different Gaussian modes can force the laser to operate at a frequency different from the central frequency of the line.…”

“…Apart from the dispersion of the medium we also have to account for possible thermal effects to the index profile [6]. So we get function of frequency.…”