Regenerative amplifier

Bade P, Bourvier M and Coe J S 1987 Nd YLF mode-locked oscillator and regenerative amplifier Opt. Lett. 12 319-21... 

Vaillancourt G, Norris T B, Coe J S, Bade P and Mourou G 1990 Operation of a 1 kHz pulse-pumped Tfsapphire regenerative amplifier Opf. Lett. 15 317-19... 

Rudd J V, Korn G, Kane S, Squier J, Mourou G and Bade P 1993 Chirped-pulse amplification of 55 fs pulses at a 1 kHz repetition rate in a TIAI203 regenerative amplifier Opt. Lett. 18 2044-6... 

Norris T B 1992 Femtosecond pulse amplification at 250 kHz with a Ti sapphire regenerative amplifier and application to continuum generation Opt. Lett. 17 1009-11... 

Joo T, Jia Y and Fleming G R 1995 Ti sapphire regenerative amplifier for ultrashort high-power multikilohertz pulses without an external stretcher Opt. Lett. 20 389-91... 

This particular bifurcation exists in the example from electronics mentioned above the regenerative amplifier has as its phase portrait SUS and after the bifurcation it becomes simply US, that is, an ordinary oscillator. 

Figure 6.2 A fourth-order coherent Raman spectrometer constructed with a Ti sapphire regenerative amplifier (Ti sapphire) and noncollinear optical parametric amplifier (NOPA).

Very recently, white light continuum pulses of duration ca. 200 fsec, pulse energy ca. 1 / J, and peak wavelength of ca. 780 nm have been generated at repetition rates up to 250 kHz by commercially available Ti sapphire regenerative amplified laser systems. Such systems are very expensive, but the expected easier use, as compared with homemade systems, should open up new research applications for time-resolved fluorescence and absorption techniques in the near-IR. 

A schematic diagram of the non-scanning picosecond fluorescence Kerr gate microscope is depicted in Figure 3.9a. A femtosecond Ti sapphire laser with regenerative amplifier provided femtosecond pulses (800 nm, 1 mJ, 110 fs) at a... 

The femtosecond (fs) laser system consists of a TiiSapphire laser and a regenerative amplifier pumping two independent optical parametric amplifiers that provide laser pulses of around 100 fs duration over a very broad range of wavelengths (250-2000 nm). The signal is detected in the transmitted phase-matching direction lc = k3 + k2 — ki and recorded by a spectrometer with spectral resolution = 2 nm. The spectra are measured by scanning over the... 

The experimental setup for time-resolved Raman spectroscopy was based on a 1 kHz Ti sapphire regenerative amplifier system. We used the third harmonic of the output as the pump pulse to generate solvated electrons. The fundamental pulse or the output of a H2 Raman shifter was used to probe Raman scattering. The Raman scattering was analyzed by... 

The laser system consisted of a home-built Ti sapphire fs laser oscillator and regenerative amplifier (RGA). The pulse duration was 50 fs at 800 nm and 1 kHz repetition rate. The output of the RGA was split into two parts. One part was used as pump pulse. The other part served as a source for the generation of probe pulses with the help of a non-collinear optical parametric amplifier (NOPA, Clark). The sample preparation was explained elsewhere [7]. Briefly, sodium (Alfa Aesar) was used as received and sodium bromide (Alfa Aesar) was dried and re-crystallized under vacuum. The preparation of the samples was carried out in a glovebox under argon atmosphere. Localized electrons were generated by heating the metal-salt mixture to 800 °C, i.e. well above the melting point of the salt. 

Details of the laser systems for pump-probe experiments are described elsewhere [8,10], except for a femtosecond IR probe system. For probing IR wavelengths (5 10 pm), a regenerative amplifier system of a Ti sapphire laser (800 nm wavelength, 160 fs FWHM pulse... 

Immediately upon excitation of an IPCT band with a fs laser at 400 nm, transient absorption was observed for both salts in solutions with a peak at about 600 nm, characteristic of 4,4/-bipyridinium radical cations. Figure 20 shows the transient absorption spectra of PV2+(I )2 in methanol solution. A marked increase in the absorbance of the 4,4/-bipyridinium radical cations took place within 1 ps after excitation. 4,4/-Bipyridinium radical cations were thus formed in a fs time scale by the photoinduced electron transfer from a donor I- to an acceptor 4,4/-bipyridinium upon IPCT excitation [48], The time profiles of transient absorption at 600 nm are shown in Fig. 21 for (a) PV2+(I )2 in a film cast from DME and (b) PV2+(TFPB )2 in DME solutions. Both of them showed a very rapid rise in about 0.3 ps, which was almost the same as the time resolution of our fs Ti sapphire laser measurement system with a regenerative amplifier. Similar extremely rapid formation of 4,4/-bipyridinium radical cations was observed for PV2+(I )2 salts in methanol and dimethylsulfoxide solutions upon IPCT excitation, respectively. These results demonstrated that the charge separated 4,4/-bipyridinium radical cations were formed directly upon IPCT excitation because of the nature of IPCT absorption bands (that the electrons correlated with the IPCT band are transferred partially at the ground state and completely at the excited state). Such a situation is very different from usual photochromism which is caused by various changes of chemical bonds mainly via the excited singlet state. No transient absorption was observed for PV2+(I )2... 

Recent Experimental Approaches Our most recent attempt to investigate the problem of ground-state heterogeneity experimentally uses tunable pump laser pulses derived from a home-made optical parametric amplifier (Fig. 1.9). A white light continuum is used to seed a two-stage optical parametric amplifier pumped by the second harmonic of a regeneratively amplified Ti-sapphire laser... 

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