Broadband coherent light generation in Raman-active crystals driven by femtosecond laser fields

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Title: Broadband coherent light generation in Raman-active crystals driven by femtosecond laser fields
Author: Zhi, Miaochan
Abstract: I studied a family of closely connected topics related to the production and application of ultrashort laser pulses . I achieved broadband cascade Raman generation in crystals , producing mutually coherent frequency sidebands which can possibly be used to synthesize optical pulses as short as a fraction of a femtosecond (fs ) . Unlike generation using gases , there is no need for a cumbersome vacuum system when working with room temperature crystals . Our method , therefore , shows promise for a compact system . One problem for sideband generation in solids is phase matching , because the dispersion is significant . I solved this problem by using non -collinear geometry . I observed what to our knowledge is a record -large number of spectral sidebands generated in a popular Raman crystal PbWO4 covering infrared , visible , and ultraviolet spectral regions , when I applied two 50 fs laser pulses tuned close to the Raman resonance . Similar generation in diamond was also observed , which shows that the method is universal . When a third probe pulse is applied , a very interesting 2 -D color array is generated in both crystals . As many as 40 anti -Stokes and 5 Stokes sidebands are generated when a pair of time -delayed linear chirped pulses are applied to the PbWO4 crystal . This shows that pulses with picosecond duration , which is on the order of the coherence decay time , is more effective for sidebands generation than Fourier transform limited fs pulses . I also studied the technique of fs coherent Raman anti -Stokes scattering (CARS ) which is used as a tool for detecting dipicolinic acid , the marker molecule for bacterial spores . I observed that there is a maximum when the concentration dependence of the near -resonant CARS signal is measured . I presented a model to describe this behavior , and found an analytical solution that agrees with our experimental data . Theoretically , I explored a possible application for single -cycle pulses : laser induced nuclear fusion . I performed both classical and quantum mechanical calculations for a system of two nuclei moving under a superintense ultrashort field . From our calculation I noted that the nuclear collisions occur on a sub -attosecond time scale , and are predicted to result in an emission of zeptosecond bursts of light .
URI: http : / /hdl .handle .net /1969 .1 /ETD -TAMU -2578
Date: 2009-05-15

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Broadband coherent light generation in Raman-active crystals driven by femtosecond laser fields. Available electronically from http : / /hdl .handle .net /1969 .1 /ETD -TAMU -2578 .

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