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Intense laser propagation in sapphire

Tate, Jennifer Lynn
http://rave.ohiolink.edu/etdc/view?acc_num=osu1083179683

Abstract Details

2004, Doctor of Philosophy, Ohio State University, Physics.
When a sufficiently energetic short laser pulse propagates through a medium it can generate an explosive increase in bandwidth leading to the creation of white light; this is known as supercontinuum generation (SCG). Although it is frequently referred to as a single process, SCG is actually the result of many different parallel and competing processes. In this work we investigate the contribution of the individual physical processes underlying the SCG effect, focusing specifically on Raman processes and plasma formation in sapphire. For our experiments we use an amplified Ti:sapphire laser system producing nearly transform limited 60 fs pulses at 800 nm. Typical pulse energies for the experiments are 1 – 3 microJ/pulse. Using a new experimental technique, the spectrally resolved interferometric double pump, we study the contribution of non-instantaneous Raman effects. We see two distinct Raman contributions in sapphire which are much stronger than indicated in previous work. One Raman process has a period of approximately 185 fs and is related to an available optical phonon; the second Raman process has a period of 20 fs and is related to defect states caused by an oxygen vacancy in the sapphire crystal. Data from the same experiment show that the SCG light is not phase stable at low excitation energies, but that the phase stability is restored and saturates with increasing laser intensity. In a separate experiment we investigate the dynamics of plasma formation using a pump-probe technique. We observe that in sapphire both the formation and the decay of the plasma occur over time scales much longer than predicted by current theory. The plasma rise time is ~225 fs, while the decay time is ~150 ps; we also observe that these values do not depend on input pulse energy. In addition to these experiments, we perform a numerical integration of the extended (3+1) dimensional nonlinear Schrodinger equation, which models the propagation of a short laser pulse through a nonlinear medium. Although our data allow considerable direct physical interpretation, the comparison with numerical results provides further clarification of how the various physical processes contribute to SCG.
Douglass Schumacher (Advisor)
155 p.
Physics, Optics
nonlinear optics; supercontinuum generation

Recommended Citations

Citations

  • Tate, J. L. (2004). Intense laser propagation in sapphire [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1083179683

    APA Style (7th edition)

  • Tate, Jennifer. Intense laser propagation in sapphire. 2004. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1083179683.

    MLA Style (8th edition)

  • Tate, Jennifer. "Intense laser propagation in sapphire." Doctoral dissertation, Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1083179683

    Chicago Manual of Style (17th edition)

osu1083179683
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© 2004, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.