Homogeneously broadened line , laser

To achieve the instability of homogeneous broadened line lasers, a satisfaction of much more difficult conditions is required large gain and the so-called bad-cavity properties. This special regime for damping constants and mode intensity is fulfilled in the far-infrared lasers [36]. In 1985 Weiss et al. [37,38] experimentally found a period doubling route to chaos in the NH3 laser. Further experimental investigation of chaotic dynamics in such lasers was reported later [39]. 

We have discussed gain saturation in detail for a homogeneously-broadened line since simple explicit expressions can be obtained for the gain coefficient and the intensity of laser radiation. Unfortunately this is not possible in the case of inhomogeneous broadening which we examine in the following section. 

Fig.13.7. Laser amplifier gain as a function of input signal intensity. , experimental results obtained on the 3-51 pm line of Xe. Solid plot is of the theoretical prediction, equation (13.35), for a homogeneously-broadened line. (After Bridges (1963).)...

A laser with a homogeneously-broadened line is operated in a cavity in which one mirror is perfectly reflecting while the other has an output transmission of t. The total round trip loss of the cavity is therefore given by 6 = t + 6 where 6 represents the unavoidable fractional cavity losses. Plot the laser output power for several different values of 6 as a function of the mirror transmission t and show that the mirror transmission for maximum output power is given by... 

The laser transition has to be homogeneously broadened, which is to say that a sufficient number of collisions has to occur during the time of the oscillator pulse. Only then is Am in (83) the full inversion under the entire line profile. 

In the case of inhomogeneous laser transitions, the whole line profile can be divided into homogeneously broadened subsections with the spectral width (for example, the natural linewidth or the pressure- or... 

Fig. 2.7 Excitation resonance broadening of a two-level system with increasing laser radiation intensity (w is the field frequency, ujo is the central transition frequency, F = jTi is the homogeneous spectral-line half-width, and G is the saturation parameter).

There is essential difference between homogeneous and inhomogeneous laser transitions. For homogeneously broadened transitions, the whole area under the gain profile of Fig.5.14 above the threshold line can be converted into induced emission at a single frequency w. The induced emission power is according to (2.67)... 

---