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Equipements: Laser fs amplifié Hurricane X 1 kHz Spectra-Physics OPA Spectra-Physics Caméra à balayage de fente Hamamatsu  C7700   Responsables: Serge LEFRANT Eric FAULQUES

 

Equipement:

 

• Since January 2006, the Institute of Materials is equipped with a spectroscopic setup allowing to map in 3 dimensions (energy, time, intensity) the ultrafast photoluminescence of advanced emerging materials in the visible and near IR spectrum (270 – 910 nm) and in a wide temporal range (2 ps – 1 ms).

  The setup consists of two main parts :

  -the excitation system.

  -the detection system.

 

• Ultrafast laser pulses are generated by a regenerative amplified laser system Hurricane X from Spectra Physics. The excitation wavelength can be tuned with an Optical Parametric Amplifier (OPA) and by a SHG/THG box. The setup is able to deliver 82 fs pulses at 1 kHz repetition rate (mean power 1 W) with wavelengths ranging between 266 nm and 10 microns.It is possible to work also in single shot mode.

 

• At the output of the OPA and the SHG, the laser beam impiging on the sample is properly filtered and cleaned in order to give a single, narrow exciting spectral line whose intensity can be varied for photon fluence measurements.Band pass filters are placed in front of the spectrometer slit to avoid the exciting laser light entering through the streak camera slit.

 

• The transient photoluminescence (PL) signal is collected by a confocal arrangement of lenses and mirrors. The spectral and spatial resolutions are 0.3 nm and 60 nm, respectively.Time-resolved photoluminescence spectra are dispersed through an Oriel MS260i imaging  spectrograph equipped with 3 gratings (150 – 2400 l/mm, f = 1/4). The 3D time-resolved emission spectra are spatio-temporally detected with a high dynamic range Hamamatsu C7700 streak camera of temporal resolution < 5 ps and read out with an ORCA II CCD camera (1344x1024 pixels) cooled at -60°C. The temporal sweep ranges of the streak camera can be set between 500 ps and 1 ms. The streak camera sweep can be directly triggered up to 290 ns by the synchronization delay generator of the Hurricane laser. In addition to the transient “operate” mode, the streak camera can be also set in focus mode in order to acquire stationary PL spectra. The dynamics is 10000:1. The setup is still in development, and other devices will be added soon (delay generator).

 

Examples :
Fig.1to increase the image	Typical short-lived fluorescence of a conjugated polymer Organic polymers containing phenyl rings and alternating C-C=C bonds can reveal very short and structured photoluminescence. An example is given in Fig. 1. Figure 1– 3D streak camera image captured with the setup of  Nantes. This is the ultrafast fluorescence emission of a thin poly-p-phenylene-vinylene film in a temporal window of 1000 ps. The region of interest is 1024x1024 pixels in size (no pixel binning). The fluorescence intensity increases from blue colors to red colors.   Zero time delay corresponds here to the beginning of the streak camera sweep. The CCD spans 303.9795 nm with a 150 l/mm grating. Excitation : 400 nm.
The long-lived fluorescence of  hackmanite
Fig.2to increase the image	Figure 2 – Time-resolved fluorescence of hackmanite for two sweep ranges (20 ns and 2 ms = 2000 ns) recorded on the setup of Nantes. The steady-state spectrum acquired in focus mode is also shown for comparison. Zero time delay corresponds to the beginning of the streak camera sweep. Insets display the corresponding raw streak images. In focus mode the spectral image is focussed onto the photocathode as a streak since there is no sweep in this case.  Sample provided by Y. Moëlo (IMN-LPC). Excitation : 400 nm.
Hackmanite Na8Al6Si6O24(Cl2,S) is a variety of the mineral species sodalite. The fluorescence  is long-lived as shown by the shots in Fig. 2. For the excitation 400 nm, the fluorescence is broad with a maximum in the red. In the early stage of the process, we observe a non-exponential decay component, up to 3.7 ns after the beginning of the streak camera sweep. After this time, the fluorescence decreases with a slow linear rate up to 2 microseconds.

Fig.3to increase the image	Fig.4to increase the image
	The streak camera Hamamatsu C7700 and the read-out CCD camera Orca II. Fig.5to increase the image