Synchronously-pumped mode-locked dye lasers

The time-resolved Raman spectra were measured with a picosecond time-resolved Raman spectrometer which employs a standard pump-probe technique. The details of the spectrometer have been publish elsewhere. The followings are concise description of the apparatus The output from a synchronously pumped mode-locked dye laser is amplified with the output from a cw Nd YAG regenerative amplifier. The second harmonic (294 nm, 2 kHz, 1-2 mW) of the amplified light (588 nm, 3.2 ps, 2 kHz, 15 mW) was used as a... 

In order to overcome this obstacle, we used a synchronously pumped, mode-locked dye laser, cavity-dumped at 4 MHz and time-correlated single-photon counting detection (18). Because of the higher sensitivity of this experimental system we were able to work at low e, using aqueous rhodamine B solutions with concentrations down to 10" M. To examine the dependence of the fluorescence decays on we chose to work with surface-solution interfaces, so as to minimize the problems associated with inhomogeneous surface coverage, which arise with dry surfaces... 

A three-pulse technique using a synchronously pumped mode-locked dye laser together with a modified Michelson interferometer has been described. By this technique, ps fluorescence decay times may be evaluated without the disadvantages of up-conversion or Kerr cell methods. The suitability of the system for the analysis of low. optical quality samples was suggested. An injection mode-locked Nd-YAG ring laser was used as an excitation source for a zero-background fluorescence study of the time evolution of the emission from large hydrocarbons with 12 ps resolution. ... 

G.W. Fehrenbach, K.J. Gruntz, R.G. Ulbrich, Subpicosecond light pulses from synchronously pumped mode-locked dye lasers with composite gain and absorber medium. Appl. Phys. Lett. 33, 159 (1978)... 

P.K. Benicewicz, J.P. Roberts, A.J. Taylor, Generation of 39 fs pulses and 815 nm with a synchronously pumped mode-locked dye laser. Opt. Lett. 16, 925 (1991)... 

For excitation and detection of fine structure beats with a frequency of 517 GHz subpicosecond light pulses are necessary. For this purpose we used a synchronously pumped mode-locked dye laser with saturable absorber in the dye solution. The dye laser generates light pulses of about ItOO fs duration at a pulse rate of 8U MHz. It is pumped by a frequency doubled actively mode-locked Nd YAG laser and tuned to a wavelength of 589.3 nm for resonant excitation of the Na atoms into the 3p fine structure states. 

Synchronously Pumped Mode-Locked Dye Laser. Organic dyes have proven to possess excellent properties for the generation of ultrashort laser pulses. Numerous approaches have been taken to the mode-locking of a dye laser, including both active and passive techniques. As a result, tunable continuous wave (cw) dye lasers have been successfully mode-locked over the past 25 years [183, 184], and pulse widths on picosecond and femtosecond timescales have been reported by many groups. 

Laser II A femtosecond mode-locked dye laser (Coherent, Satori) synchronously pumped using a cw mode-locked and frequency-doubled Nd YAB laser (Coherent, Antares), generating pulses in 76 MHz repetition rate and 250-fs fwhm. 

These features are exploited in an experiment which is taking place in our laboratory. A schematic diagram of this experiment is shown in figure 4. The system consists of an all-lines violet mode-locked Kr+ ion laser operating at a repetition rate of about 250 MHz Which synchronously pumps a C102 dye laser. The dye laser typically produces about 300 mW of average power and pulse durations of about 3 psec. This is frequency doubled to 243 nm in a crystal of p-barium borate to produce in excess of 2 mW average power. The output from the second harmonic crystal is then mode-matched into an ultra-violet enhancement cavity. The free... 

Picosecond pulses can be produced in a number of different types of laser systems. As an example, a brief description is first given of a synchronously pumped c.w. dye laser such as can be readily assembled from commercially available units. Generation of repetitive subnanosecond pulses in a c.w. laser by mode-locked synchronous pumping was first described by Harris et al. [12]. The essential features of such a system are shown in Fig. 3. In this system, an acousto-optically mode-locked ion laser is used to pump the dye laser. In order to achieve synchronous pumping, the length of the dye cavity must be adjusted so that the dye laser intermode spacing is an integral multiple of the pump mode-locker frequency. 

Time resolved hole burning spectra were measured by means of a femtosecond transient absorption spectrometer system. A second harmonics of a mode locked cw Nd + YAG laser (Quantronix, 82MHz) was used for a pumping source. A synchronously pumped rhodamine 6G dye laser with a saturable absorber dye jet (DODCl/DQOCI) and dispersion compensating prisms in the cavity was used. The output of the dye laser (lOOfs fwhm, 600pJ/pulse) was... 

Ultrafast fluorescence quenching dynamics were studied by the fluorescence-up-conversion method with femtosecond mode-locked laser systems. For the studies of oxazine dyes, a synchronously pumped hybrid mode-locked dye laser with group velocity... 

A broader application range is opened by a system of two independently tunable mode-locked dye lasers, which have to be pumped by the same pump laser in order to synchronize the pump and probe pulses [808]. For studies of vibrational levels in the electronic ground states of molecules the difference frequency generation of these two dye lasers can be used as a tunable infrared source for direct excitation of selected levels on infrared-active transitions. Raman-active vibrations can be excited by spontaneous or stimulated Raman transitions (Chap. 3). Another useful short-pulse source for these experiments is a three-wavelength Ti sapphire laser, where two of the wavelengths can be indepently tuned [811]. 

J. Kiihl, H. Klingenberg, D. von der Linde, Picosecond and subpicosecond pulse generation in synchroneously pumped mode-locked CW dye lasers. Appl. Phys. 18,279 (1979)... 

Nanosecond absorbance transients were measured with a single beam instrument (11). Excitation was provided by a 6-8 ns, 1 mJ 610 nm pulse from a NdrYAG pumped rhodamine dye laser. Absorption transients were either detected with a Hamamatsu R928 (A<900 nm) or R406 (A>900 nm) photomultiplier operating with a 2.5 ns response time. Picosecond absorbance transients were measured with a double beam apparatus (11). 1.5 ps, 1 mJ, 610 nm excitation pulses were generated by using the output of a mode-locked Ar" laser to synchronously pump a rhodamine dye laser. 

Scavennec, A. (1976). Mismatch effects in synchronous pumping ofthe continuously operated mode-locked dye laser, Optics Commun. 17, 14-17. 

The experimental set-up we used is shown in Fig. 2, A synchronously pumped mode-locked and cavity-dvunped dye laser, which can be timed to the D or Dj line of Cs, generates pulses of about 20 ps duration at a pulse rate of U MHz and peak powers of several hundred watt. They are split into linearly polarized pump pulses and stronger circularly polarized probe pulses, which pass an optical delay line. Both beams are focussed into a common interaction region where they act on the Cs vapor, which is contained in a cell at room temperature. The radiated wave propagating in pump pulse direction is detected by a photomultiplier, which measures the transmitted average intensity behind a crossed polarizer as a function of the delay time. 

Fig.9.20. (a) Active mode locking by acousto-optic modulation, (b) Synchronous pumping of a dye laser equipped with a cavity dumper, (c) Passive mode-locking using a saturable absorber... 

The experimental arrangement which is similar to that of time-resolved polarization spectroscopy (Fig. 12.11) is depicted in Fig. 12.16. The pulse train is provided by a synchroneously pumped, mode-locked CW dye laser. A fraction of each pulse is split by the beam splitter BS and passes... 

For many applications the time interval AT = 2nd/c between two successive pulses should not be too short. This implies that the cavity length d has to be sufficiently long. In order to avoid inconveniently large geometrical extensions of the arrangement, an optical delay line can be used. Figure 11.9 illustrates a synchronously pumped mode-locked cw dye laser system with such an optical delay line. 

Figure 11.11 shows such a combination of cavity dumping and mode locking. The time interval aT between successive pulses can be controlled between Is and 0.3 ys. The cavity dumping technique can be also applied to synchronously pumped mode-locked cw dye lasers. 

The earliest subpicosecond systems incorporated dye laser technology. Shank, Ippen, and their colleagues at the Bell Laboratories [34] were the first to develop mode-locked subpicosecond lasers and to show how to compress pulses to very short values. With the colliding-pulse mode-locked (CPM) laser they achieved reduced pulse widths well into a subpicosecond range. Two approaches based on synchronously pumped dye lasers and colliding pulse dye lasers are commonly employed to produce subpicosecond pulses. These are briefly discussed below. 

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