Ring Dye Lasers

In order to observe such high-resolution fluorescence excifafion spectra, the laser must have a very small line width. To achieve this a ring dye laser, a modification of the dye laser described in Section 9.2.10, is used a line width as small as 0.5 MFIz (1.5 x 10 cm ) can be obtained. 

A remarkable feature of these spectra is the resolution of individual rotational lines in such large molecules. [Note that the expanded specttum in, for example. Figure 9.47(a) covers only 5000 MFIz (0.17 cm )]. This is due partly to the very low rotational temperature (3.0 K for aniline and 2.2 K for aniline Ar), partly to the reduction of the Doppler broadening and partly to the very high resolution of the ring dye laser used. 

One variation in dye laser constmction is the ring dye laser. The laser cavity is a reentrant system, so that the laser light can circulate in a closed loop. The ring stmcture provides a high degree of stabiUty and a narrow spectral width. The spectral width of a conventional dye laser on the order of 40 GH2 is narrowed to a value as small as a few MH2. Such systems offer very high resolution in spectroscopic appHcations. 

ESO VLT/Max Planck CW Dye Laser. The MPI is developing a CW dye laser for deployment on one ESO 8-m VLT telescope in 2004 (Eig. 13). The oscillator is a Coherent 899 ring dye laser, with a 2-5 W output, pumped by a 10 W, Coherent Verdi frequency-doubled Nd YAG laser. The beam is amphfied in a four-pass amphfier with 4 high velocity dye jets pumped with 4 10 W Verdi lasers. The system utihzes Rhodamine 6G in ethylene glycol however, because of the high pump power, the dye degrades quickly, and must... 

The advent of ultrafast pump-probe laser techniques62 and their marriage with the TOF method also enables study of internal ion-molecule reactions in clus-ters.21,63-69 The apparatus used in our experiments is a reflectron TOF mass spectrometer coupled with a femtosecond laser system. An overview of the laser system is shown in Figure 4. Femtosecond laser pulses are generated by a colliding pulse mode-locked (CPM) ring dye laser. The cavity consists of a gain jet, a... 

Some of the earlier experiments were carried out using our home-built colliding pulse modelocked (CPM) ring dye laser. Equipped with two excimer... 

The rms linewidth of the dye laser has so far been reduced to 300 Hz relative to a reference cavity with the help of an intracavity ADP phase modulator and a fast servo system which compensates for small rapid optical path fluctuations in the liquid dye jet [24]. A perhaps even more elegant alternative is the external laser frequency stabilizer [25] which compensates for phase and frequency noise after the light has left the laser cavity. J. Hall and coworkers [26] have recently reduced the linewidth of a commercial ring dye laser to sub-Hz levels with such a device. 

Wise FW, Walmsley lA, Tang CL (1988) Simultaneous formation of solitons and dispersive waves in a femtosecond ring dye-laser. Opt Lett 13 129-131... 

The excitation beam is provided by a home-made c.w. ring dye Laser 57. At 7780 and 7600 A (approximate wavelengths of the 2S-8D... 

In a later experiment the laser was replaced by a cw ring dye laser, the output of which was amplified in four stages, using a XeCl excimer laser as pump. In this way the cw output (30 60 mW) at 486 nm was amplified into 25 mJ, 10 ns pulses with a repetition rate of 50 s . In addition in this later experiment the frequency of the transition was determined with respect to the saturated spectrum of Tc2, a line of which lies within 50 MHz of half the 1 S- 2 S energy interval. Furthermore, an acousto-optic modulator was used to create a laser sideband at 50 MHz higher than the fundamental frequency so that each Tea absorption line consisted of 3 peaks, at vo, vo + 50 MHz and Vo + 25 MHz, the cross-over resonance. 

Colliding pulse mode locking CPM Passive mode locking and eventual synchronous pumping Ring dye laser <100 fs 1 nJ... 

At a proper choice of the amplifying gain and the absorption losses, this situation will automatically be realized in the passively mode-locked ring dye laser. It leads to an energetically favorable stable operation, which is called colliding-pulse mode (CPM) locking, and the whole system is termed a CPM laser. This mode of operation results in particularly short pulses down to 50 fs. There are several reasons for this pulse shortening ... 

Pulse widths below 100 fs can be reached with this CPM technique [675, 676]. If the CPM ring dye laser is synchronously pumped by a mode-locked argon laser stable operation over many hours can be realized [677]. Using a novel combination of saturable absorber dyes and a frequency-doubled mode-locked Nd YAG laser as a pump, pulse widths down to 39 ps at A = 815 nm have been reported [678]. 

Johnston, T. E, Jr., Brady, R. H., and Proffitt, W. (1982). Powerful single-frequency ring dye laser spanning the visible spectrum, Appl. Opt. 21,2307-2316. 

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