Prism Pellin-Broca

Figure 17.4 Schematic of the T-jump spectrometer described in the text. OAP, off-axis parabolic mirror PB, Pellin—Broca prism P, polarizer L, lens S, sample MCT, mercury cadmium telluride detector. The size of the pump relative to the probe at the point of overlap is shown in the lower left comer.

The T-jump pulse is generated by Raman shifting the fundamental output of a Q-switched Nd YAG laser (1 = 1.064 pm) in a 1-m-long Raman cell filled with H2 at 500 psi. The laser operates at a repetition rate of 10 Hz and has a pulse temporal width of <10 ns (FWHM). The Stokes shift in H2 is 4155 cm-1. As a result, the first Stokes line is at a wavelength of 1.9 pm that is partially absorbed by the D20 solvent, and thus serves as the T-jump pulse. A Pellin-Broca prism is used to separate the... 

This technique is critically dependent on the quality of the mirrors and cavity, respectively. Super polishing to <0.05 nm root-mean-square of surface roughness is essential. Under such conditions the arrangement with Pellin—Broca prism exhibits a base ring-down time of about 1 ps and yields a minimum detectable absorbance change of about 32 ppm. A ring-down time of about 800 ns is found for a 1 cm square mini-cavity. 

The Pellin-Broca prism also deviates beams by roughly 90° but is a dispersive prism, frequently used to separate laser beams of different colours after nonlinear frequency conversion (Sect. 8.6). By combining four Pellin-Broca prisms, beam separation with maintained direction of propagation can be achieved. In the straight-view prism colour d persion in the forward... 

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