Spectral extent and pulse shape of the supercontinuum for ultrashort laser pulse

Manassah, Jamal T.; Mustafa, Muhammad A.; Alfano, R. R.; Ho, P. P.

doi:10.1109/jqe.1986.1072850

Cited by 66 publications

(11 citation statements)

References 15 publications

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“…Extension of the theory to high conversion efficiency by including the second equation for the fundamental beam is also straightforward. Note that a similar frequency-domain approach to ultrashort-pulse propagation in optical fibers [62] helped solve a long-standing question of the magnitude of the shock term [50], [63].…”

Section: Sincementioning

confidence: 99%

Second-harmonic generation frequency-resolved optical gating in the single-cycle regime

Baltuška

Pshenichnikov

Wiersma

1999

IEEE J. Quantum Electron.

125

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The problem of measuring broad-band femtosecond pulses by the technique of second-harmonic generation frequency-resolved optical gating (SHG FROG) is addressed. We derive the full equation for the FROG signal, which is valid even for single-optical-cycle pulses. The effect of the phase mismatch in the second-harmonic crystal, the implications of the beam geometry, and the frequency-dependent variation of the nonlinearity are discussed in detail. Our numerical simulations show that, under carefully chosen experimental conditions and with a proper spectral correction of the data, the traditional FROG inversion routines work well even in the single-cycle regime. The developed description of the SHG FROG signal was applied to measure the white-light continuum pulses in the spectral region of 500-1100 nm. The obtained spectral phase of these pulses served as a target function for the pulse compressor design. The pulses produced by compression around 800 nm were also characterized by SHG FROG. The resulting pulse duration measures 4.5 fs which corresponds to 2.5 optical cycles.

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Section: Sincementioning

confidence: 99%

Second-harmonic generation frequency-resolved optical gating in the single-cycle regime

Baltuška

Pshenichnikov

Wiersma

1999

IEEE J. Quantum Electron.

125

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“…A value of Q ^ 1 is required for the generation of a broad (8v~~ v) supercontinuum. 2,3 Experimentally, self-focusing (the spatial analog of self-phase modulation) is difficult to avoid. Self-focusing limits the validity of current rj2 continuum theories to e<(4/r)(r ?2 P/cW) 1/2 , (1) where P is the laser power.…”

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confidence: 99%

“…Experimentally, the two thresholds agree within 20%. The absence of self-focusing in low y (3) gases accounts for the lack of continuum generation in neon.…”

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confidence: 99%

Supercontinuum Generation in Gases

1986

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Supercontinua extending from the ultraviolet to the infrared are observed from high-pressure (1-40 atm) Ar, Kr, Xe, H2, N2, or CO2 illuminated with 2-psec or 70-fsec, 0.6-/xm pulses with an energy ;$500 /xJ. The blue spectral component is shown to display a nearly universal behavior for all gases and pulse durations. Although the maximum intensity of the focused, femtosecond pulse in an evacuated cell was -10 B W/cm 2 , continuum generation was only observed with the femtosecond pulse when the threshold for self-focusing was exceeded. PACS numbers: 42.65.Jx, Discovered in 1970, supercontinuum generation has now been demonstrated in a wide variety of solids and liquids. Self-phase modulation, four-wave mixing, and plasma production (for the blue spectral component) are the processes most commonly invoked to explain continuum generation. 2 Recent plane-wave theoretical models based on cubic nonlinearities 2 ' 3 describe continuum generation in terms of a parameter Q :as rf2E 2 z/cr, where 172 is the nonlinear refractive index, E is the incident laser field amplitude, z is the interaction length, T is the pulse duration, and c is the speed of light. For small Q, the continuum bandwidth is given by Aco -Qco. A value of Q ^ 1 is required for the generation of a broad (8v~~ v) supercontinuum. 2,3 Experimentally, self-focusing (the spatial analog of self-phase modulation) is difficult to avoid. Self-focusing limits the validity of current rj2 continuum theories to e<(4/r)(r ?2 P/cW) 1/2 , (1) where P is the laser power. Equation (1) is obtained by the requirement that the interaction length be less than the self-focusing length for a Gaussian beam and by the assumption of only full-beam self-focusing. Mierofilamentation lowers Q even further. 4 Although no continuum-generation experiments have clearly satisfied the inequality in Eq. (1), the parameter Q is used as a guide to estimate the expected spectral broadening. Based on this parameter, gases are not likely to be sources of supercontinua. For example, xenon, a highly nonlinear gas, has a nonresonant 772 "^x 10~~2 6 m 2 /V 2 at atmospheric pressure 5 (r] 2 of water is 1.5x 10~2 2 m 2 /V 2 ). If we consider the maximum field that can be applied to Xe in the absence of breakdown 6 (/ -10 13 W/cm 2 ) then, even with a 100-fsee (2 psec) pulse, an interaction length of 2=6 xlO 3 cm (1.2xl0 5 cm) is required for

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“…29. of approximately 400-1200 nm, as shown in Figure 3. 21,[31][32][33][34] As mentioned above, the spectral broadening in the dielectric material is highly nonlinear in its dependence on the laser intensity, 21,32,34,35 requiring the generation of independent spectral references for each of the time delayed pulses, as will be discussed in more detail below. The white light was collimated using a 500-mm achromat and, after passing through a notch filter to remove the excess fundamental laser light at 800 nm, injected into a 1-m-long 200-µm-diameter core high-damage threshold fiber using a 40× microscope objective.…”

Section: Figmentioning

confidence: 99%

Development of a broadband reflectivity diagnostic for laser driven shock compression experiments

Ali

Bolme

Collins

et al. 2015

Review of Scientific Instruments

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Articles you may be interested inAnalysis of nanopatterning through near field effects with femtosecond and nanosecond lasers on semiconducting and metallic targets J. Appl. Phys. 107, 074305 (2010) A normal-incidence visible and near-infrared shock wave optical reflectivity diagnostic was constructed to investigate changes in the optical properties of materials under dynamic laser compression. Documenting wavelength-and time-dependent changes in the optical properties of laser-shock compressed samples has been difficult, primarily due to the small sample sizes and short time scales involved, but we succeeded in doing so by broadening a series of time delayed 800-nm pulses from an ultrafast Ti:sapphire laser to generate high-intensity broadband light at nanosecond time scales. This diagnostic was demonstrated over the wavelength range 450-1150 nm with up to 16 time displaced spectra during a single shock experiment. Simultaneous off-normal incidence velocity interferometry (velocity interferometer system for any reflector) characterized the sample under laser-compression and also provided an independent reflectivity measurement at 532 nm wavelength. The shock-driven semiconductor-to-metallic transition in germanium was documented by the way of reflectivity measurements with 0.5 ns time resolution and a wavelength resolution of 10 nm. C 2015 AIP Publishing LLC. [http://dx

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Spectral extent and pulse shape of the supercontinuum for ultrashort laser pulse

Cited by 66 publications

References 15 publications

Second-harmonic generation frequency-resolved optical gating in the single-cycle regime

Second-harmonic generation frequency-resolved optical gating in the single-cycle regime

Supercontinuum Generation in Gases

Development of a broadband reflectivity diagnostic for laser driven shock compression experiments

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