Talk:Chirped pulse amplification

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These pages help us a lot. I want to know one thing. Many scientists(Geindre,Scherer,Tokunaga etc., ) talked about spectral interferometry in which they discuss interference of two pulses separated in time (in frequency domain)(Optics letters 19 1997 (1994),OL 16 1131 (1992). As part of this, they say these two pulses overlap in time at the spectrometer grating stage. So I wish to know how much temporal stretching will occur. how to estimate? thank you - Prasad, India. — Preceding unsigned comment added by Ybsrprasad (talkcontribs) 04:57, 21 October 2011 (UTC)

I'm studying about chirped pulse amplification. Are there any books that discusses about CPA?

depletion[edit]

this edit Whether or not the gain medium is depleted depends on the pulse energy, not the pulse duration. Or am I overlooking something? Han-Kwang 23:36, 22 March 2007 (UTC) (copy from user talk)

For moderate energies (0.5 .. 1 mJ) the beam diameter could be expanded to 20 mm (still sort of table top). But sending a 20 fs pulse with the energy/area needed to deplete the gain material through a Ti:Sa amplifier will destroy the material (at least the rear face). In times of "wall plug efficiency" and because pump lasers are expensive, as much as possible of the pump energy is supposed to be converted. Even small regenerative amplifiers with 1 mm beam diameter happily accept the strecht due to GVD in Ti:Sa and pockels cell and compress afterwards. Arnero 16:38, 23 March 2007 (UTC)

You wrote: "Small amplifiers need long pulses to deplete the inversion in the gain medium." was a very confusing way to word it. To me, that implies that "A big amplifier can deplete the inversion with a short pulse". I don't see exactly what you mean by "big" and how full depletion would be possible in that case. Han-Kwang 22:42, 23 March 2007 (UTC)

Some related stuff: As I wrote on the page for OPA there the chirp is even more essential for depleting the pump, which in these cases is about 50 ps long. As I wrote (actual asking) on the page for modelocking is the difference between a Rhodamin 6G and a Ti:Sa oscillator. The Rhodamin oscillator can depelete its gain material by means of 10 fs pulses and therefore shorten the pulse on the trailing edge. The Ti:Sa needs a very fast saturable absorber. Arnero 16:38, 23 March 2007 (UTC)

I'm not sure what you are asking here. Han-Kwang 22:42, 23 March 2007 (UTC)

I am not asking anything. It is just that we have a number of lasers in our labs. Two of them (nitrogen laser, and a dye laser) make ns pulses and uses a single pass amplifier. One of them makes 100 ps and needs multiple passes through Nd:YLF. And then there are the Ti:Sa amplifiers who need multiple pulses and chirped pulses. So the shorter the pulses and the lower the stimulated emisson cross section the more effort is needed to deplete the medium. Any proposal for a better wording? Arnero 19:59, 24 March 2007 (UTC)

To be honest, I still don't fully understand what point you want to make. Is it that especially Ti:Sa needs high energy densities for efficient amplification? Han-Kwang 20:35, 24 March 2007 (UTC)

Density is not good, because it leads to self-phase modulation and other stuff which makes the laser or amplifier unstable. As you said energy is important. So as this article states: The chirp allows high energy pulses with low energy density. My point is, that even small Ti:Sa amplifiers which are used for example for high harmonic generation benefit from chirp. Arnero 07:34, 25 March 2007 (UTC)

Sorry, I meant energy density (in J/cm2) rather than (W/cm2). Anyway, maybe you are used to dealing with terawatt laser systems and consider anything smaller "small", but the point of the article is to explain CPA to someone new to the field. The first time I learnt about CPA (10 years ago) I was amazed by the idea that you could stuff 1 mJ in just 100 fs. Maybe the article should specify more clearly what "high energy" means then, how about "The chirp allows relatively high energy pulses (e.g. 1 mJ) with low energy density."? Han-Kwang 09:21, 25 March 2007 (UTC)


the function τ[edit]

On the page it says "the dispersion of an optical device is a function τ(ω), where τ is the time delay experienced by a frequency component ω". I don't know anything about lasers, but shouldn't this say "is a function τ, where τ(ω) is the time delay experienced by a frequency component ω" ? --jholman (talk) 18:41, 8 June 2011 (UTC)

If it's dispersed, why is Fig. 3 labeled as a compressor?[edit]

If it's dispersed, why is Fig. 3 labeled as a compressor? In Figure 3, input is shown as a narrow pulse entering the device from the left. the pulse exiting is shown as dispersed colored bands exiting the device downwards. Yet the drawing is labeled "Prism compressor". Shouldn't it be labeled "Prism stretcher"? 71.139.166.154 (talk) 22:53, 1 September 2013 (UTC)

Amplifying the dispersed pulse[edit]

If the frequency of expanded pulse varies along its length, how can the gain medium effectively amplify ALL of the pulse? Doesn't the gain medium respond only to a NARROW frequency range? 71.139.166.154 (talk) 21:34, 2 September 2013 (UTC)