I am stretching ultrashort laser pulses by passing them through an SF11 plate. The pulses are stretched due to the introduction of different delays to the group velocities of the various frequency components. Does this process also produce new frequency components (on the red and blue ends of the spectrum) in the pulse?
Dear Rituparna,
I do not have a definite answer to you question, but flint glass (eg SF11) generally features a considerable nonlinear behaviour. Thus, it is also used for the production of photonic crystal fibres for supercontinuum generation (see: A. Husakou, J. Herrmann, Supercontinuum generation in photonic crystal fibers made from highly nonlinear glasses, Appl. Phys. B 77 (2003) 227–234)...so I can imagine that the effect you observed or mentioned is quite probable...
I hope this helps?
Best,
Christoph
Dear Christoph,
Yes, I expect new frequency components to be generated if the laser pulse passes through a nonlinear crystal. Since you mentioned SF11 has nonlinear properties, that must be the possible reason for producing new frequency components. Thank you for the answer; it was helpful.
Regards,
Rituparna.
Hello! No, new frequencies can only appear if it is a non-linear process.
Things depend a lot of the irradiance level you have, Dispersion by itself will only stretch the pulse, without producing new frequencies. However, as mentioned by the others, the material has a nonlinearity, that through the process of self phase modulation (SPM), can produce new frequencies, If you have an oscillator only, it is unlikely that you get SPM, but it you have amplified pulses you probably have it. You can calculate the dispersion length L_D, and the nonlinear length L_NL to see in which regime are you
Raul Rangel-Rojo sir, thank you for the suggestion. We are using an amplifier to obtain intense ultrashort pulses, so it might lead to SPM after the pulse passes through the medium. I shall calculate the dispersion length.
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