-
[show abstract]
[hide abstract]
ABSTRACT: We study the diffraction of Gaussian pulses and beams within the framework of boundary diffraction wave theory. For the first time the boundary diffraction wave theory is applied to pulsed Gaussian beams, and it is shown that the diffracted field of a pulsed Gaussian beam on a circularly symmetric aperture can be evaluated by a single 1D integration along the diffracting aperture at every point of interest. We compare theoretical simulations to experimental measurements of ultrashort pulses diffracted off a circular aperture, an opaque disc, an annular aperture, and a system of four concentric annular apertures. Using the recently developed SEA TADPOLE measurement technique, we obtain micron spatial and femtosecond temporal resolutions in the spatio-temporal measurements of the diffracted fields.
Journal of optics 12/2011; 14(1):015701. · 1.57 Impact Factor
-
01/2011;
-
[show abstract]
[hide abstract]
ABSTRACT: For essentially all applications, laser pulses must avoid variations in their intensity and phase within a pulse and from pulse to pulse. Currently available devices work very well for both long (>10ns) and short (<100ps) pulses. But intermediate (~ns) pulses remain difficult to measure and, not surprisingly, are the least stable. Here we describe a simple, elegant, complete, all-optical, single-shot device that measures ~ns pulses and that does not require a reference pulse or assumptions about the pulse shape. It simultaneously achieves a very high spectral resolution of <1pm and a very large delay range of ~10ns (several meters of light travel). It accomplishes both goals using high-efficiency, high-finesse etalons: one to generate high angular dispersion for a high-resolution spectrometer, and another to tilt the pulse front by ~89.9° without distorting it in time. Using this device, we completely measure microchip and fiber-amplifier pulses.
Optics Express 01/2011; 19(2):1367-77. · 3.59 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We measure the complete electric field of extremely complex ultrafast waveforms using the simple linear-optical, interferometric pulse-measurement technique, MUD TADPOLE. The waveforms were measured with ~40 fs temporal resolution over a temporal range of ~3.5 ns and had time-bandwidth products exceeding 65,000. The approach is general and could allow the measurement of arbitrary optical waveforms.
Optics Express 11/2010; 18(24):24451-60. · 3.59 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Angular dispersion—whether from prisms, diffraction gratings, or etalons—is well known to result in a pulse-front tilt. Focusing into a tilted etalon, in particular, generates a huge angular dispersion, which is very useful for high-resolution spectrometers and pulse shapers. Here we demonstrate experimentally that, due to the large angular dispersion 3° /nm, the pulse directly out of an etalon can have a huge pulse-front tilt— 89.9°—which can cause one side of a few-millimeter-wide beam to lead the other by 1 m, that is, several nano-seconds. We propagated a 700 ps near-transform-limited pulse through the etalon and measured the resulting spatiotemporal field, confirming this result. To make this measurement, we used a high-spectral-resolution version of crossed-beam spectral interferometry, which used a high-resolution etalon spectrometer. We also performed simulations, which we found to be in good agreement with our measurements. © 2010 Optical So-ciety of America OCIS codes: 320.5550, 300.6190, 320.7100, 320.4240.
08/2010;
-
[show abstract]
[hide abstract]
ABSTRACT: In this seedling project, we studied the feasibility of coherently combining the output beams of multiple pulse-seeded fiber-optical amplifiers. Our procedure was to begin with a nanosecond seed pulse from a micro-disk laser, amplify it, and then develop a device to measure it in order to determine whether the pulses produced by currently available fiberlaser sources are sufficiently stable and possess sufficiently clean waveforms that it is conceivable that they can be combined coherently. As a result, we developed new single-shot frequency-resolved-optical gating (FROG) pulsemeasurement techniques with unprecedented spectral resolution and temporal range, with the ability to measure potentially extremely complex pulses on a single shot. Using this technology, we studied the pulses produced by an Yt-fiber-amplified micro-disk laser. Although we found that the pulse shape became somewhat complex as amplification increased, we believe that the phase stability was sufficient.
05/2010;
-
[show abstract]
[hide abstract]
ABSTRACT: Using a recently developed technique (SEA TADPOLE) for easily measuring the complete spatiotemporal electric field of light pulses with micrometer spatial and femtosecond temporal resolution, we directly demonstrate the formation of theo-called boundary diffraction wave and Arago's spot after an aperture, as well as the superluminal propagation of the spot. Our spatiotemporally resolved measurements beautifully confirm the time-domain treatment of diffraction. Also they prove very useful for modern physical optics, especially in micro- and meso-optics, and also significantly aid in the understanding of diffraction phenomena in general.
Optics Express 05/2010; 18(11):11083-8. · 3.59 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We introduce a spectral-interferometry (SI) technique for measuring the complete intensity and phase of relatively long and very complex ultrashort pulses. Ordinarily, such a method would require a high-resolution spectrometer, but our method overcomes this need. It involves making multiple measurements using SI (in its SEA TADPOLE variation) at numerous delays, measuring many temporal pulselets within the pulse, and concatenating the resulting pulselets. Its spectral resolution is the inverse delay range--many times higher than that of the spectrometer used. Our simple proof-of-principle implementation of it provided 71 fs temporal resolution and a temporal range of 100 ps using a few-cm low-resolution spectrometer.
Optics Express 03/2010; 18(7):6583-97. · 3.59 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We present direct measurements of the spatiotemporal electric field of an ultrashort Bessel-X pulse generated using a conical lens (axicon). These measurements were made using the linear-optical interferometric technique SEA TADPOLE, which has micrometer spatial resolution and femtosecond temporal resolution. From our measurements, both the superluminal velocity of the Bessel pulse and the propagation invariance of the central spot are apparent. We verified our measurements with simulations.
Optics Letters 09/2009; 34(15):2276-8. · 3.40 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The evolution of the frequency chirp of a laser pulse inside a classical pulse compressor is very different for plane waves and Gaussian beams, although after propagating through the last (4th) dispersive element, the two models give the same results. In this paper, we have analyzed the evolution of the frequency chirp of Gaussian pulses and beams using a method which directly obtains the spectral phase acquired by the compressor. We found the spatiotemporal couplings in the phase to be the fundamental reason for the difference in the frequency chirp acquired by a Gaussian beam and a plane wave. When the Gaussian beam propagates, an additional frequency chirp will be introduced if any spatiotemporal couplings (i.e. angular dispersion, spatial chirp or pulse front tilt) are present. However, if there are no couplings present, the chirp of the Gaussian beam is the same as that of a plane wave. When the Gaussian beam is well collimated, the introduced frequency chirp predicted by the plane wave and Gaussian beam models are in closer agreement. This work improves our understanding of pulse compressors and should be helpful for optimizing dispersion compensation schemes in many applications of femtosecond laser pulses.
Optics Express 09/2009; 17(19):17070-81. · 3.59 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We measure the spatiotemporal field of ultrashort pulses with complex spatiotemporal profiles using the linear-optical, interferometric pulse-measurement technique SEA TADPOLE. Accelerating and decelerating ultrashort, localized, nonspreading Bessel-X wavepackets were generated from a approximately 27 fs duration Ti:Sapphire oscillator pulse using a combination of an axicon and a convex or concave lens. The wavefields are measured with approximately 5 microm spatial and approximately 15 fs temporal resolutions. Our experimental results are in good agreement with theoretical calculations and numerical simulations.
Optics Express 09/2009; 17(17):14948-55. · 3.59 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The chirp acquired by a Gaussian ultrashort pulse due to angular dispersion, unlike that of plane waves, increases nonlinearly with propagation distance and eventually asymptotes to a constant. However, this interesting result has never been directly measured. In this Letter, we use two-dimensional spectral interferometry to measure the propagation dependence of the chirp for Gaussian ultrashort pulses and beams with angular dispersion. The measured chirp as a function of propagation distance agreed well with theory. This work verifies both an equation and a measurement technique that will be useful for predicting or determining the pulse's chirp in ultrafast optics experiments that contain angular dispersion.
Optics Letters 05/2009; 34(7):962-4. · 3.40 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A method is reported for creating, generating, and measuring parametrically shaped pulses for time-bandwidth product >>5, which consists of a parametric pulse-shaping algorithm, a spatial light modulation system and a single shot interferometric characterization scheme (SEA TADPOLE) . The utilization of these tools marks the inception of a new method called SPECIFIC, shaped-pulse electric-field construction and interferometric characterization, capable of producing complex shaped laser pulses for coherent control experiments.
04/2009;
-
[show abstract]
[hide abstract]
ABSTRACT: We demonstrate a spectral interferometer with NSOM probes for measuring focusing ultrashort pulses with high spatial and spectral
resolution. We measure a 0.44 NA focus and, for the first time to our knowledge, we observe the forerunner pulse.
12/2008: pages 917-919;
-
[show abstract]
[hide abstract]
ABSTRACT: We demonstrate a powerful and practical spectral interferometer with near-field scanning microscopy (NSOM) probes for measuring the spatiotemporal electric field of tightly focused ultrashort pulses with high spatial and spectral resolution. Our measurements involved numerical apertures as high as 0.44 and yielded the spatiotemporal field at and around the foci produced by two microscope objectives and several different lenses. For the first time, we measure the spatiotemporal field of the Bessel-like X-shaped pulse caused by spherical aberrations and a "fore-runner pulse" due to chromatic aberrations. We observed spatial features smaller than 1 microm and verified these results with non-paraxial simulations.
Optics Express 10/2008; 16(18):13663-75. · 3.59 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We present the first technique for directly measuring (without assumptions) the spatio-temporal intensity and phase of a train of ultrashort pulses at and near a focus. Our method uses an experimentally simple and high-spectral resolution variant of spectral interferometry (SEA TADPOLE). To illustrate our technique, we measured the spatio-temporal electric field in and around the foci of several different types of lenses. To confirm our results, we also simulated these measurements by numerically propagating a pulse through each of the lenses used. From one set of measurements, we made a movie showing a focusing pulse with severe chromatic aberration.
Optics Express 09/2007; 15(16):10219-30. · 3.59 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We present a high-spectral-resolution and experimentally simple version of spectral interferometry using optical fibers and crossed beams, which we call SEA TADPOLE. Rather than using collinear unknown and reference pulses separated in time to yield spectral fringes-and reduced spectral resolution-as in current versions, we use time-coincident pulses crossed at a small angle to generate spatial fringes. This allows the extraction of the spectral phase with the full spectrometer resolution, which allows the measurement of much longer and more complex pulses. In fact, SEA TADPOLE achieves spectral super-resolution, yielding the pulse spectrum with even better resolution. Avoiding collinear beams and using fiber coupling also vastly simplify alignment. We demonstrate SEA TADPOLE by measuring a chirped pulse, a double pulse separated by 14 ps, and a complex pulse comprising two trains of pulses with a time-bandwidth product of ~400.
Optics Express 12/2006; 14(24):11892-900. · 3.59 Impact Factor
-
Pamela Bowlan
[show abstract]
[hide abstract]
ABSTRACT: In this thesis a powerful and practical method for characterizing ultrashort pulses in space and time is described (called SEA TADPOLE). First we focus on measuring pulses that are spatially uniform but very complicated in time or frequency. We demonstrate and verify that SEA TADPOLE can measure temporal features as small as 30 femtoseconds over durations as long as 14 picoseconds. The spectral resolution of this device is carefully studied and we demonstrate that for certain pulses, we achieve spectral super resolution. We also develop and test an algorithm for measuring polarization shaped pulses with SEA TADPOLE. Our simple interferometer can even be used to measure the spatiotemporal electric field of ultrashort pulses at a focus. This is because SEA TADPOLE samples the field with an optical fiber which has a small core size. Therefore this fiber can be used to spatially sample the beam, so that the temporal electric field can be measured at every position to obtain E(x, y, z, t). The single mode fiber can be replaced with an NSOM (Near Field Scanning Optical Microscopy) fiber so that spatial resolution as low as 500nm (and possibly lower) can be achieved. Using this device we make the first direct measurements of the compete field of focusing ultrashort pulses. These measurement can be viewed as "snap shots" in flight of the focusing pulse. Also, for the first time, we have observed some of the interesting distortions that have been predicted for focusing ultrashort pulses such as the "forerunner" pulse, radially varying group delay dispersion, and the Bessel-like X-shaped pulse. We have also made the first direct measurements of the electric field of Bessel X-pulses and their propagation invariance is demonstrated. We also use SEA TADPOLE to study the "boundary wave pulses" which are due to diffraction. Ph.D. Committee Chair: Rick Trebino; Committee Member: Jennifer Curtis; Committee Member: John Buck; Committee Member: Mike Chapman; Committee Member: Stephen Ralph
-
Journal of Optics, v.12 (2010).
-
[show abstract]
[hide abstract]
ABSTRACT: We introduce and demonstrate a simple, compact, and automatically aligned ultrashort-pulse compressor that uses only a single diffraction element—a grating or a grism (a grating on a prism). This design automatically has unity beam magnification and automatically contributes zero spatiotemporal distortions to the pulse, thus avoiding spatial chirp, angular dispersion, pulse-front tilt, and all other first-order spatiotemporal distortions. It is comprised of only three elements: a diffraction element, a corner cube, and a roof mirror. Half the size of comparable two-grating compressors, it can provide large amounts of negative group-delay dispersion with small translations of the corner cube. The device can operate on pulses with both large and small bandwidths by varying the corner-cube position. Using a grism as the diffraction element, material dispersion up to the third order can be compensated, and we demonstrated compensation for 10 m of optical fiber for 800 nm pulses.
