II Shaping and Analysis of Picosecond Light Pulses

Froehly, Claude; Colombeau, B.; Vampouille, M.

doi:10.1016/s0079-6638(08)70277-4

Cited by 98 publications

(59 citation statements)

References 89 publications

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“…It has been successfully implemented to image biological samples [3,4], cellular dynamics [5,6], as well as for microfabrication [7][8][9]. TF2p microscopy is, in essence, simply a 4-f pulse shaper proposed by Froehly, Colombeau, and Vampouille [10] and Martinez, Gordon, and Fork [11] with the exception that there is no second grating to recombine the pulse. TF2p microscopy works because of the time-bandwidth product which states that the product of the pulse width and the spectral content is a constant.…”

Section: Introductionmentioning

confidence: 99%

Temporally focused wide-field two-photon microscopy: Paraxial to vectorial

Yew

Sheppard

2013

Opt. Express

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Temporal focusing allows for optically sectioned wide-field microscopy. The optical sectioning arises because this method takes a pulsed input beam, stretches the pulses by diffracting off a grating, and focuses the stretched pulses such that only at the focal plane are the pulses re-compressed. This approach generates nonlinear optical processes at the focal plane and results in depth discrimination. Prior theoretical models of temporal focusing processes approximate the contributions of the different spectral components by their mean. This is valid for longer pulses that have narrower spectral bandwidth but results in a systematic deviation when broad spectrum, femtosecond pulses are used. Further, prior model takes the paraxial approximation but since these pulses are focused with high numerical aperture (NA) objectives, the effects of the vectorial nature of light should be considered. In this paper we present a paraxial and a vector theory of temporal focusing that takes into account the finite spread of the spectrum. Using paraxial theory we arrive at an analytical solution to the electric field at the focus for temporally focused wide-field two-photon (TF2p) microscopy as well as in the case of a spectrally chirped input beam. We find that using paraxial theory while accounting for the broad spectral spread gives results almost twice vector theory. Experiment results agree with predictions of the vector theory giving an axial full-width half maximum (FWHM) of 2.1μm and1.8 μm respectively as long as spectral spread is taken into account. Using our system parameters, the optical sectioning of the TF2p microscope is found to be 8 μm . The optical transfer function (OTF) of a TF2p microscope is also derived and is found to pass a significantly more limited band of axial frequencies than a point scanning two-photon (2p) microscope or a single photon (1p) confocal microscope.

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Section: Introductionmentioning

confidence: 99%

Temporally focused wide-field two-photon microscopy: Paraxial to vectorial

Yew

Sheppard

2013

Opt. Express

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“…Although initially implemented for input pulses in the picosecond time scale [6], the socalled direct space-to-time (DST) pulse shaper has been adapted to the femtosecond range and promoted as a fast data encoder [7]. The idea is that the spatial mask itself acts as the temporal filter, in contrast to the behavior of a Fourier pulse shaper, where a Fourier transform operation is required for the design of the temporal filter.…”

Section: Introductionmentioning

confidence: 99%

Diffractive optics for quasi-direct space-to-time pulse shaping

et al. 2008

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Abstract:The strong chromatic behavior associated with a conventional diffractive lens is fully exploited to propose a novel optical device for pulse shaping in the femtosecond regime. This device consists of two optical elements: a spatially patterned circularly symmetric mask and a kinoform diffractive lens, which are facing each other. The system performs a mapping between the spatial position of the masking function expressed in the squared radial coordinate and the temporal position in the output waveform. This space-to-time conversion occurs at the chromatic focus of the diffractive lens, and makes it possible to tailor the output central wavelength along the axial location of the output point. Inspection of the validity of our device is performed by means of computer simulations involving the generation of femtosecond optical packets.

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“…This apparatus consists of a pair of 1700-line/mm gratings placed at the focal planes of a unit magnification confocal-lens pair. 6 The grating separation is 60 cm, and the lenses are achromats with focal lengths of 15 cm. Spatially patterned amplitude and phase masks are inserted midway between the lenses at the point where the optical spectral components experience maximal spatial separation.…”

mentioning

confidence: 99%

Encoding and decoding of femtosecond pulses

1988

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We demonstrate the spreading of femtosecond optical pulses into picosecond-duration pseudonoise bursts. Spreading is accomplished by encoding pseudorandom binary phase codes onto the optical frequency spectrum. Subsequent decoding of the spectral phases restores the original pulse. We propose that frequency-domain encoding and decoding of coherent ultrashort pulses could form the basis for a rapidly reconfigurable, code-division multiple-access optical telecommunications network.Diverse communication and signal-processing technologies utilize specially coded signal formats in order to achieve desirable capabilities such as error correction, interference rejection, and secrecy. The ability to encode and decode signals according to a specified format is a crucial component of such systems.In this Letter we demonstrate frequency-domain encoding and decoding (in the time domain, spreading and despreading) of femtosecond optical pulses. Previously we described the generation of arbitrarily shaped picosecond optical pulses, by spectral amplitude and phase filtering in a fiber and grating pulse compressor.1-3 Here we utilize a special dispersionfree grating apparatus to manipulate the phase spectra of femtosecond pulses. Specifically, by encoding pseudorandom binary phase codes onto the opticalfrequency spectrum, we spread femtosecond pulses into picosecond-duration pseudonoise bursts. Subsequent decoding of the spectral phases restores the original pulse.We propose that spectral encoding and decoding of coherent ultrashort pulses could form the basis for a rapidly reconfigurable, code-division multiple-access 4 (CDMA) optical telecommunications network. The system would provide tens to hundreds of users with asynchronously multiplexed, random access to a common fiber or free-space channel.Our experiments utilize 0.62-ym, 75-fsec pulses from a balanced, colliding-pulse mode-locked (CPM) ring dye laser, 5 which are shaped by using the special dispersion-free grating apparatus. This apparatus consists of a pair of 1700-line/mm gratings placed at the focal planes of a unit magnification confocal-lens pair. 6 The grating separation is 60 cm, and the lenses are achromats with focal lengths of 15 cm. Spatially patterned amplitude and phase masks are inserted midway between the lenses at the point where the optical spectral components experience maximal spatial separation. The pulse shape at the output of the grating is the Fourier transform of the pattern transferred by the mask onto the frequency spectrum. The shaped pulses are measured by cross correlation, using femtosecond pulses directly out of the CPM laser as the reference.We have verified the nondispersive nature of our grating apparatus by performing autocorrelation measurements of pulses incident upon and emerging from the apparatus. Figure 1 shows autocorrelations of 48-fsec pulses with no mask present. The pulse widths are identical. Without the lens pair, the temporal dispersion arising from the 60-cm grating separation would broaden the pulses by more than 3 or...

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II Shaping and Analysis of Picosecond Light Pulses

Cited by 98 publications

References 89 publications

Temporally focused wide-field two-photon microscopy: Paraxial to vectorial

Temporally focused wide-field two-photon microscopy: Paraxial to vectorial

Diffractive optics for quasi-direct space-to-time pulse shaping

Encoding and decoding of femtosecond pulses

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