Spectral superbroadening of self-focused picosecond laser pulses in D2O

Triplet-triplet absorption of eosin Y in methanol determined by nanosecond excimer laser excitation and picosecond light continuum probing

“…The generated single pulses have a duration of At % 6 ps and an energy of W«4 mJ. These pulses are focused (lens Ll,/=25 cm) into a heavy water sample (cell CO, length /= 5 cm) in order to generate a picosecond light continuum [63][64][65]. Behind the heavy water cell the Nd: laser pulse is filtered off by an edge filter EF.…”

Theoretical investigation of noncollinear phase-matched parametric four-photon amplification of ultrashort light pulses in isotropic media

“…Only the small-signal approximation limit is considered where the pump pulse intensities remain constant. Neglecting optical absorption, the collinear parametric four-photon amplification in the slowly varying amplitude approximation is described by Equations 1 and 2 [1,10,12,14,15] where E s , 2s x , E x and E 2 are the amplitudes of the electrical field strengths at the angular frequencies u; s (signal), UJX (idler), UJX and UJ2 (pump pulses); c 0 is the light velocity in vacuum; z is the propagation direction; and Ak z = k Sz + k Xz -k x z -k 2z -k$ + k\ -k x -k 2 is the wavevector mismatch. The wavevectors k t (i = 1,2, S, I) are given by k t = HiUii/cQ = lirriii/i/cQ = lirriii/i == Inni/Xi, where the n t are the refractive indices at the angular frequencies uj i9 frequencies v i9 wavenumbers v t or wavelengths A;.…”

“…(see Equations 14,15,17a,19,22). Exact noncollinear phase-matching is only possible for monochromatic waves.…”

“…Parametric amplification is only possible when f3 0 > Ak z . The total transverse phase mismatch should be Ak x d^ = Ak x tan < 7r to avoid reduction of parametric amplification [15,37]. For Ak z -0 one speaks of longitudinally phase-matched interaction or Cerenkov-like interaction [15,[38][39][40] …”

“…Parametric four-photon interaction is possible in all media [1][2][3][4][5][6][7][8][9][10]. Parametric four-photon generation (also called stimulated four-photon mixing [10,11], stimulated parametric fourphoton interaction [12], or stimulated four-wave parametric emission [3]) plays an important role in the generation of picosecond light continua [3,[10][11][12][13][14][15] and references therein]. Four-photon parametric oscillators have been realized by applying optical fibres [16] and atomic vapours [6,[17][18][19][20][21].…”