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© Stefan Marzenell |
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To understand the effects which influence the pulse formation in the AgGaSe2-OPO, i.e. the pulse duration and pulse chirp of signal and idler pulses, a numerical simulation is in progress, at present. For the calculation of self and cross phase modulation the nonlinear refractive index of AgGaSe2 was measured using the Z-Scan method. |
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First the well known Z-Scan technique with an aperture and a detector was used to determine the nonlinear index of refraction. |
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With the known numbers of wavelength, beam waist, power, repetition rate and pulse duration the nonlinear index of refraction was determined to be g = ( 6.35 +/- 0.70 ) 10-18 m2/W or n2 = ( 4.00 +/- 0.45 ) 10-11 esu. |
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Second a new technique with an ir camera was used. The beam structure in the far field was measured using this camera while the AgGaSe2 crystal was moved through the beam waist. A few examples of these measurements are shown below. |
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From these measurements the maximum transmission and the integrated transmission are deduced. For a (nonlinear) absorption measurement the data of the integrated transmission are normalized. We found at a wavelength of 1.58 µm no nonlinear absorption. For the Z-Scan measurement the data of the maximum transmission are normalized. These data are shown below. |
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Again with the known numbers of wavelength, beam waist, power, repetition rate and pulse duration the nonlinear index of refraction was determined to be g = ( 6.07 +/- 1.05 ) 10-18 m2/W or n2 = ( 3.81 +/- 0.65 ) 10-11 esu. |
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Using these numbers of the nonlinear index of refraction the numerical prediction of pulse duration and pulse chirp shows good agreement with the measured values. |
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