Page 198 - Tunable Lasers Handbook

176 F. J. Duarte

a
n ?mission beam

1
Pump beam

b

Emission beam

C

FIGURE 3 Excitation geometries utilized in pulsed dye lasers. (a) Transverse excitation. (b)
Collinear mo-sided transverse excitation. (c) Semilongimdinal excitation. (Reproduced with permis-
sion from Duane [371.)

At the amplification stages the dimensions of the pump beam are deter-
mined by the need to match the propagation geometry of the oscillator beam.
Dye laser cells are of trapezoidal, parallelogrammatic. and rectangular
geometries [37] (Fig. 4). Trapezoidal and parallelogrammatic geometries are
used to reduce parasitic broadband emission. For high-prf laser oscillators the
cross-sectional area of the dye passage is usually about 10 mm in length and a
fraction of a millimeter in width to help achieve dye flow speeds of a few m-s-l.
The length quoted here is along the optical axis of the cavity. Trapezoidal
geometries are also used in solid-state dye laser matrices for either transverse
and/or semilongitudii~al excitation [45,46].

2.2 Oscillators

Single-transverse-mode narrow-linewidth dispersive oscillators used in dye
laser systems are discussed in Chapter 2. The performances of representative