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Broadband coherent light generation in Raman-active crystals driven by femtosecond laser fieldsZhi, Miaochan 15 May 2009 (has links)
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.
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Emotionerna stolthet och skam och de divergerande multiplexa sociala banden : En intervjustudie av tre ungdomars sociala nätverk av sociala band och dess oscillation mellan att existera på och utanför InternetFürst, Henrik January 2007 (has links)
<p>The purpose of this qualitative study has been; how social bonds are interlaced between thesocial worlds contained within the analytical division of “outside Internet” and “withinInternet”. What happens with the social bond as the individual oscillate between this analyticbisection? This purpose raises important questions of the use of Internet in everyday life.</p><p>A new stance is taken toward studying the Internets integration into everyday life. The focusis adjusted to the importance of emotions. Emotions of pride and shame will be treated as thesignals of social bonds state and will indicate the resistance or openness of this integration.Goffmans theory on face-work will be used as a complement. A cognitive approach on socialbonds will assist the emotional approach. This is interwoven with a perspective forunderstanding Internet as a medium in form rather than only to focus on the “content”.</p><p>The conclusion consists of a required consistency between the quality of the social bond onthe Internet and outside the Internet. The fear of inconsistency had to do with a threat of lossof face, not to come in conflict with established norms from outside the Internet.Development of close and intimate social bonds on the Internet that didn’t have a counterpartor was in inconsistency with the social bond outside Internet, lead to shame that threatenedthe social bond. The integration of Internet in everyday life is therefore not accomplished.Still, a new generation with instant access to the Internet is to be primary socialized undernew conditions.</p>
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Emotionerna stolthet och skam och de divergerande multiplexa sociala banden : En intervjustudie av tre ungdomars sociala nätverk av sociala band och dess oscillation mellan att existera på och utanför InternetFürst, Henrik January 2007 (has links)
<p>The purpose of this qualitative study has been; how social bonds are interlaced between the social worlds contained within the analytical division of “outside Internet” and “within Internet”. What happens with the social bond as the individual oscillate between this analytic bisection? This purpose raises important questions of the use of Internet in everyday life.</p><p>A new stance is taken toward studying the Internets integration into everyday life. The focus is adjusted to the importance of emotions. Emotions of pride and shame will be treated as the signals of social bonds state and will indicate the resistance or openness of this integration. Goffmans theory on face-work will be used as a complement. A cognitive approach on social bonds will assist the emotional approach. This is interwoven with a perspective for understanding Internet as a medium in form rather than only to focus on the “content”.</p><p>The conclusion consists of a required consistency between the quality of the social bond on the Internet and outside the Internet. The fear of inconsistency had to do with a threat of loss of face, not to come in conflict with established norms from outside the Internet. Development of close and intimate social bonds on the Internet that didn’t have a counterpart or was in inconsistency with the social bond outside Internet, lead to shame that threatened the social bond. The integration of Internet in everyday life is therefore not accomplished. Still, a new generation with instant access to the Internet is to be primary socialized under new conditions.</p>
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Emotionerna stolthet och skam och de divergerande multiplexa sociala banden : En intervjustudie av tre ungdomars sociala nätverk av sociala band och dess oscillation mellan att existera på och utanför InternetFürst, Henrik January 2007 (has links)
The purpose of this qualitative study has been; how social bonds are interlaced between the social worlds contained within the analytical division of “outside Internet” and “within Internet”. What happens with the social bond as the individual oscillate between this analytic bisection? This purpose raises important questions of the use of Internet in everyday life. A new stance is taken toward studying the Internets integration into everyday life. The focus is adjusted to the importance of emotions. Emotions of pride and shame will be treated as the signals of social bonds state and will indicate the resistance or openness of this integration. Goffmans theory on face-work will be used as a complement. A cognitive approach on social bonds will assist the emotional approach. This is interwoven with a perspective for understanding Internet as a medium in form rather than only to focus on the “content”. The conclusion consists of a required consistency between the quality of the social bond on the Internet and outside the Internet. The fear of inconsistency had to do with a threat of loss of face, not to come in conflict with established norms from outside the Internet. Development of close and intimate social bonds on the Internet that didn’t have a counterpart or was in inconsistency with the social bond outside Internet, lead to shame that threatened the social bond. The integration of Internet in everyday life is therefore not accomplished. Still, a new generation with instant access to the Internet is to be primary socialized under new conditions.
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Emotionerna stolthet och skam och de divergerande multiplexa sociala banden : En intervjustudie av tre ungdomars sociala nätverk av sociala band och dess oscillation mellan att existera på och utanför InternetFürst, Henrik January 2007 (has links)
The purpose of this qualitative study has been; how social bonds are interlaced between thesocial worlds contained within the analytical division of “outside Internet” and “withinInternet”. What happens with the social bond as the individual oscillate between this analyticbisection? This purpose raises important questions of the use of Internet in everyday life. A new stance is taken toward studying the Internets integration into everyday life. The focusis adjusted to the importance of emotions. Emotions of pride and shame will be treated as thesignals of social bonds state and will indicate the resistance or openness of this integration.Goffmans theory on face-work will be used as a complement. A cognitive approach on socialbonds will assist the emotional approach. This is interwoven with a perspective forunderstanding Internet as a medium in form rather than only to focus on the “content”. The conclusion consists of a required consistency between the quality of the social bond onthe Internet and outside the Internet. The fear of inconsistency had to do with a threat of lossof face, not to come in conflict with established norms from outside the Internet.Development of close and intimate social bonds on the Internet that didn’t have a counterpartor was in inconsistency with the social bond outside Internet, lead to shame that threatenedthe social bond. The integration of Internet in everyday life is therefore not accomplished.Still, a new generation with instant access to the Internet is to be primary socialized undernew conditions.
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