25 263 294 317 326 ° C a GLYPH<RParen1> GLYPH<Minus> 2 0 2 4 6 8 10 12 0 0.2 0.4 0.6 0.8 1 t GLYPH<LParen1> ps GLYPH<RParen1> cross GLYPH<Minus> correlation b GLYPH<RParen1> 150 200 250 300 0 2 4 6 8 T GLYPH<LParen1> °C GLYPH<RParen1> t D GLYPH<LParen1> ps GLYPH<RParen1> Fig. 4. (Color online) a) Comparison of experimental (solid line) and theoreti- cally predicted (dashed line) results for multiple 650-fs-long pulses at 25, 263, 294, 317, 326 ◦ C (from left to right, respectively) centered at λ$_{c}$ . b) Depen- dence of the experimental (points) and theoretical (solid line) values of the group delay on cell temperature. The error is the same for all points and is due to uncertainties in the measurement of the vapor temperature. incurring negligible distortion ( i.e. , D max < 0 . 05). This metric does an excellent job of quantifying the pulse distortion, but it is extremely conservative in that the entire pulse shape is considered. While this may be appropriate for applications where one needs to maintain the details of the pulse’s temporal profile (such as for biomedical imaging using pulse-shaping techniques), many applications are less sensitive to the exact pulse shape. To quantify pulse distortion in an alternative manner, we adopt two additional distortion metrics: the fractional broadening of the pulse and the power leakage (defined below). Figure 6 a) shows the fractional broadening as a function of the vapor temperature for a 250-fs-long pulse. We observe f$_{D}$ = 18 for f$_{B}$ = 0 . 65 (corresponding to a vapor temperature of 294 ◦ C), in good agreement with our theoretical predictions. To demonstrate the impact of the pulse shape and central wavelength, we show theoretical results for the case where the incident pulse has a rectangular spectrum centered at λ$_{c}$ and 787 nm, as well as a Gaussian spectrum centered at λ$_{c}$ . While the fractional broadening of the sinc pulses generally follows the trend set by the Gaussian pulse, it is clear that careful selection of pulse shape and central wavelength are crucial for minimizing broadening. 10