Noncollinear phase-matching

We performed transient absorption measurements on BP(OH>2 with a spectrometer based on two noncollinearly phase matched optical parametric amplifiers (NOPAs) pumped by an homebuilt regenerative Ti Sapphire laser system or a CPA 2001 (Clark-MXR) [1,7]. The tunable UV pump pulses are generated by frequency doubling the output of one of the NOPAs. The other NOPA provides the visible probe pulses. The cross correlation between pump and probe pulses has a typical width (FWHM) of 40 fs. The sample is a cyclohexane solution of BP(OH)2 pumped through a flow cell with a 120 pm thick channel. 

Transient spectra of solvated indole are measured in a 120 Jim liquid jet with a crosscorrelation of 80 fs by means of a white light continuum (450 - 740 nm) generated in a sapphire disc. The molecules are excited at 270 nm with pump pulses generated by frequency doubling the output of a noncollinearly phase matched optical parametric amplifier [2], Due to the short pump pulses there is a small yet finite probability for two-photon ionization in pure solvents. This allows us to study the spectral properties of the generated solvated electrons by measurements in pure solvents. The transient spectra of the indole solution are corrected for these solvent contributions. 

Experiments were performed using a visible optical parametric amplifier based on noncollinear phase-matching in /3-barium borate, followed by a pulse compressor using chirped dielectric mirrors. This optical source provides ultrabroadband pulses, with bandwidth extending from 500 to 720 nm, compressed to an almost transform-limited duration of 5-6 fs. The pump-... 

The transient absorption setup used in our experiments is a versatile tool providing both the necessary time resolution and the tunability to investigate different compounds. The pump-probe spectrometer is based on two noncollinearly phase matched optical parametric amplifiers (NOPAs) (see Fig. 11.3) [21, 22]. The NOPAs are pumped by a regenerative Ti sapphire laser amplifier delivering approximately 100 fs NIR pulses at around 800 nm with a repetition rate of 1 kHz. 

Shuto, Y, Takara, H Amano, M., and Kaino, T., Noncollinearly phase-matched second harmonic generation in stilbene-dye-attached polymer thin films, Jpn. J. Appl. Phys., 28, 2508-2512 (1989). 

Noncollinear phase-matching (NCPM) schemes have been studied in their early stages in single crystals [192,193], but this method has not been extensively studied in poled polymer waveguides. Shuto et al. [194,195]... 

In the absence of dispersion in the index-of-refraction, this condition is satisfied for collinear pulses. In real liquids, noncollinear pulses are needed. If we choose to work with coplanar pulses for simplicity, there are three angles to choose to satisfy one phase-matching condition [Equation (9)]. The relevant angles ([Pg.409]

Fig. 5.100a,b. Phase-matching condition as momentum conservation for (a) noncollinear and (b) collinear propagation of the three waves... 

M. Seiter, D. Keller, M.W. Sigrist Broadly tunable difference-frequency spectrometry for trace gas detection with noncollinear critical phase-matching in LiNb03. Appl. Rhys. B 67, 351 (1998)... 

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