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Propagation of short pulses Jörgen Larsson, Fysiska Instutionen Lunds Tekniska Högskola
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Propagation of short pulses Jörgen Larsson, Fysiska Instutionen Lunds Tekniska Högskola
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Distributed feedback laser
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Femtosecond X-Ray and Electron Source at the SLAC Linac 80 fs 8-10 keV 1x10 7 ph./pulse (2% bw.) 10 Hz Bending compress. <100 fsec ~1 Å Add 12-meter chicane compressor in linac at 1/3-point (9 GeV) Damping Ring 9 ps 0.4 ps 50 ps 1 GeV 20-50 GeV FFTB undulator femtosecond laser (synchronized) Short-pulse accelerator sources SPPS www-ssrl.slac.stanford.edu/jhhome.html
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Femtosecond fiber laser
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Splitters/Couplers
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Femtosecond fiber laser
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Wavelength Division Multiplexers
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Bragg grating
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Bandpass filter for fiber optics
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Manufacturing Bragg gratings
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Representation of short pulses Gaussian pulses Carrier EnvelopeAmplitude Frequency
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Representing ”chirp”
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Time-bandwidth product- Transform limited pulses If the pulse is chirped it is wider in the temporal domain Gaussian pulse
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Propagation of a range of frequencies After the pulse has propagated the distance x
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Propagation of a range of frequencies
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Group velocity dispersion
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Propagation of a range of frequencies
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GVD wavelength form Whiteboard
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Group velocity dispersion compensation All matererials show a positive GVD in the visible range – hence various set-ups have been deviced for GVD compensation
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GVD compensation using prisms
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Chirped mirrors
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Dispersion compensation using Bragg gratings
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Time-varying refractive indes Self-phase modulation FIG 2.18
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Time-varying refractive indes Self-phase modulation
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Passive modelocking Kerr lens
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Matrix representaiton of beam propagation
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Beam propagation in a linear cavity
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Stability analysis of Kerr-lens mode- locked laser Propagation matrix General stability criterion 2-mirror cavity Stability criterion
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Beampropagation in a folded cavity (out of plane – approx for in-plane)
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Beampropagation including Kerr- lens
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