Probe delay line

The properties of the piezocomposite material mentioned above offer special benefits when the transducer is coupled to a material of low acoustic impedance. This especially applies to probes having plastic delay lines or wedges and to immersion and medical probes. These probes with piezocomposite elements can be designed to have not only a high sensitivity but also at the same time an excellent resolution and, in addition, the effort required for the probe s mechanical damping can be reduced. 

Figure B2.5.8. Schematic representation of laser-flash photolysis using the pump-probe technique. The beam splitter BS splits the pulse coming from the laser into a pump and a probe pulse. The pump pulse initiates a reaction in the sample, while the probe beam is diverted by several mirrors M tluough a variable delay line.

Figure 8-5. Transmission difference spectra of m-LPPP films at 7=77 K excited at 3.2 eV for various pump-probe delays. The inset zooms out the low energy region for 0 ps (solid line) and 400 ps (dashed line) delay. Doping induced absorption (D1A) data are also shown for comparison (from Ref. (251 with permission).

Figure 8-13. Field-induced differential transmission (-A7ZT)a - a 1-91 (solid line) and 2.53 eV (dots) as a function of pump-probe delay. In the upper panel we also show, as a dashed line, the pump-pulse autocorrelation (from Ref. [40] with permission).

Figure 8-14. (a) (—versus pump-probe delay al 1.91 eV lor VW.= -16 V and pump excitation intensities 1.2 mJ/ein2 (solid line) and 0.24 niJ /cm" (dashed line). The inset shows (-A7/T)Mr at 1.91 eV and 20 ps versus excitation intensity, (b) same as (a) Tor pump excitation intensity 1.2 nij/eni2 with V[1M =-16 V (solid line) and th, is=-8 V (dashed line). The inset shows ( A7//)/h/. at 1.91 eV and 20 ps versus field open squares=posilive bias filled eirclcs=negative bias (adapted from Ref. (40J). 

Fig. 3.5. Experimental apparatus for time-resolved THz transmission spectroscopy. The sample is excited with a visible laser pulse delivered by delay line 3. A singlecycle THz electric-field transient probes the polarization response of the sample after time delay tv scanned by delay line 1. The transmitted THz amplitude is monitored via ultrabroadband electro-optic sampling in a THz receiver as a function of time T scanned by delay line 2. From [13]...

Fig. 9 Experimental setup for pump-probe measurements 1 - beam splitters 2 - silver mirrors 3 - time delay line 4 - lenses 5 - filters Do, Di, D2 - photodetectors P - polarizers k 2 - wave plate...

Figure 6.12 Experimental two-color setup featuring an IR beamline, to generate intense shaped IR pump pulses, and a VIS probe beamline, to provide time-delayed probe pulses of a different color. Both beams are focused collinearly into a supersonic beam to interact with isolated K atoms and molecules. Photoelectrons released during the interaction are measured by an energy-calibrated TOE spectrometer. The following abbreviations are used SLM, spatial light modulator DL, delay line ND, continuous neutral density filter L, lens S, stretcher T, telescope DM, dichroic mirror MCP, multichannel plate detector.

Fig. 3. Reconstruction of the transient absorption spectra of HPTA in DCM in the presence of 9xlO 3 M DMSO at different pump-probe delays. The time-zero absorption and gain bands of the photoacids are moving toward each other following the relaxation of the solute-solvent interactions to their steady-state values. Full lines are the superposition of the individual absorption and gain bands of HPTA.

Fig. 1. (a) Differential absorbance spectra of native PYP, after excitation at 430 nm, at different pump-probe delays. The scattered pump light around 430 nm has been masked. Steady-state absorption and fluorescence spectra are represented with dotted lines, (b) Kinetics extracted from the transient spectra at selected wavelengths... 

Fig. 1-left gives a general overview of the differential absorption spectra recorded for the free chromophore, oxyblepharismin, dissolved in DMSO for reference the steady-state absorption and (uncorrected) fluorescence spectra are also given below, in dotted lines. At all pump-probe delay times, the overall picture is a superposition of the structured bleaching and gain bands, as expected from the steady-state spectra, and broad transient absorption bands around 530 nm and 750 nm (weaker). These apparently homothetic spectra are very similar to... 

Fig. 5 Absorption spectrum of AT DNA oligomers around 3300 cm-1 (solid line) and absorbance difference spectra for several pump-probe delay times after excitation at 1740 cm-1 (FWHM 170 cm-1). The picosecond OH stretching response of water ranges from 3600 to 3050 cm-1. The spectrum at 0 ps delay time was obtained by averaging from -200 to 200 fs to eliminate nonabsorbing signal contributions.

Each pulse was split with a beam splitter (9) into pump and probe parts with energies of 2 nJ and 0.04 nJ, respectively, that were directed onto the sample at angles of incidence of 7° and 27°, respectively. A variable optical delay line (10) in the pump path allowed the time delay between the two pulses to be varied with a minimum step size of 1.67 fs. The position of a hollow retro-reflecting prism (11) in the delay line was varied through a few wavelengths at high frequency in order to remove any coherence oscillations around the zero delay position. The maximum time delay was 2 ns. 

Fig. 7. Setup for the degenerate four wave mixing experiments. The input beam is split in three beams. The beam splitter BS3 deflects a part of one of the pump beams to a power meter, which detects laser power fluctuations. The delay line with the retro reflector R adjusts the temporal overlap of the two pump beams coming from the front side on the sample. The long delay line with retro reflector R2 is moved to probe the temporal behavior of the nonlinearity in the sample. The phase conjugated signal beam propagates from the sample back to BSj and is then deflected through a stack of attenuation filters on a second power meter. An iris in front of the power meter increases the signal to noise ratio by removing scattered light...

Fig. 1.18. Spectrally resolved pump-probe spectrum of pristine MDMO-PPV compared to highly fullerene-loaded MDMO-PPV/PCBM composites at various delay times, (a) Absorption spectrum of a pure MDMO-PPV film (solid line) and AT/T spectrum at 200 fs pump-probe delay (dashed line), (b) AT/T spectra of the MDMO-PPV/PCBM blend (1 3 wt. ratio) at various time delays following resonant photoexcitation by a sub-10-fs optical pulse. The CW PA of the blend ( ) was measured at 80 K and 10-5 mbar. Excitation was provided by the 488 nm line of an argon ion laser, chopped at 273 Hz...

Figure 13 Schematic of the setup of the pump-probe experiment with polarization resolution for the probing of the induced change in sample transmission. X/2 half-wave plate P1-P3 polarizers L1-L4 lenses D1-D5 detectors Ch chopper VD optical delay line. The sample is permanently moved in a plane perpendicular to the beams in order to avoid accumulative thermal effects.

Figure 27 Structural relaxation within the OH-stretching band of HDO in D2O at 273 K the peak amplitudes (isotropic signal) of species I (filled circles, solid line) and II (hollow circles, dashed curve) are plotted versus probe delay, as derived from the decomposition of the measured transient spectra with excitation at 3410 cm-1 experimental points, calculated lines.

The IR pulse is split into a weak probe beam, which passes down a computer-controlled variable delay line with up to 12 ns of delay and a strong pump beam. The pump and probe pulses are counterpropagating and focused into the center of the SCF cell. Typical spot sizes (1/e radius of E-field) were oj0 120 pm for the pump beam and oj0 60 pm for the probe beam. A few percent of the transmitted probe beam is split off and directed into an InSb detector. A reference beam is sent through a different portion of the sample. The reference beam is used to perform shot-to-shot normalization. The pump beam is chopped at half the laser repetition rate (900 Hz). The shot-to-shot normalized signal is measured with a lock-in amplifier and recorded by computer. 

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