Crossed-beam phase matching

Eckbreth, A. C. 1978. BOXCARS Crossed-beam phase-matched CARS generation in gases. Appl. Phys. Lett. 32 421-23. 

Fig. 1. Coherent anti-Stokes Raman spectroscopy (CARS) from a diagnostic perspective. Crossed-beam phase matching is employed for high spatial precision, broadband Stokes sources for high temporal resolution.

A.C. Eckbreth BOX CARS Crossed-beam phase matched CARS generation. Appl. Rhys. Lett. 32, 421 (1978)... 

Fig. 18. Schematic of apparatus used to measure fluorescence kinetics with a streak camera. The Nd glass laser emits a train of one hundred 1.06 pm pulses separated by 6 ns. A single pulse in the earlier portion of the train is selected by a Pockels cell and crossed polarizers (Pi and P2). The high voltage pulse ( 5 ns) at the Pockels cell is supplied by a laser triggered spark gap and a charged line. The single pulse ( 8 ps, 109 W) can be amplified. The second harmonic is generated from a phase matched KDP crystal. Beam splitters provide two side beams beam (1) triggers the streak camera beam (2) arriving at the streak camera at an earlier time acts as a calibrating pulse. The main 0.53 pm beam excites the sample for fluorescence measurement. The fluorescence collected with f/1.25 optics is focused into the 30 pm slit of the streak camera. The streak produced at the phosphorescent screen is recorded by an optical multichannel analyzer. (After ref. 67.)...

In the major part of the experimental set-ups, the pump beam has a fixed frequency, while the Stokes frequency is tuned in order to match the beating frequency. The phase matching is achieved if the laser beams are crossed at angle 0, that is, the phase-matching angle (Figure 14.2b). 

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