Comments on the use of BOXCARS for gas‐phase CARS spectroscopy

Calculations of integrated intensity and 90% interaction length have been performed for planar and folded BOXCARS phase matching schemes for gas‐phase Coherent Anti‐Stokes Raman Scattering (CARS). These results show that, in general, for a half crossing angle of the pump laser beams of less than 20 degrees there is no difference between folded and planar BOXCARS. Further, the calculations indicate that the optimum Stokes beam diameter is 2/3 of the pump beam diameter; this result is also true for colinear CARS. The calculations also show that the interaction length can be accurately estimated from a simple geometric formula. The adaptation of planar and folded BOXCARS for ‘single‐ended’ operation (input and signal beams transmitted through the same observation window) is outlined and discussed.