Direct Measurement of Group Delay Dispersion in Metamagnetics for Ultrafast Pulse Shaping Page: 4
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103 nm (a) 0
E 37-nmA 5nm 0.6
52-nm AI203 Al203 Q0.4
37-nm Ag 15-nm
192. n 315 nm 0.0
315 nm v
- - FEMssim
0.5 0.6 0.7 0.8 0.9 1
Fig. 1. Metamagnetic structure diagram, transmission, and sample appearance. (a) Schematic
for metamagnetic structure with layer materials and thicknesses as given. (b) Transmission
spectra calculated using FEM (dot-dash blue line), calculated using SHA (dashed red line), and
obtained from measurements (solid orange line). (c) FE-SEM and (d) AFM images of the
The spectral phase and the GDD of the transmitted light for the structure dimensions given
in Fig. 1(a) was calculated using FEM, and these are shown in Fig. 2. The materials used were
air (n = 1, k = 0), glass (n = 1.52, k = 0), A1203 (dispersion from ), and Ag (Drude-Lorentz
model with a loss factor of 3 from , which is typical for nanomaterials with internal
grained structure ). An electric resonance near 500 nm and a magnetic resonance near 800
nm are evident from the transmission spectra (Fig. 1(b)) and in the phase and GDD curves
(Figs. 2(a), 2(b)). Near these resonances the spectral dispersion of the material changes
quickly and this results in large GDD values.
To experimentally measure the GDD of a metamagnetic material, we used the MIIPS
technique  with an ultrafast oscillator, the Griffin-5, from KMLabs that had a 100 nm
root-mean-squared (RMS) spectral bandwidth capable of transform limited pulses below 15fs.
The RMS bandwidth is defined as the full width at half of the average maximum across the
spectrum, and the shape of the spectral bandwidth was rounded on the sides but roughly flat
on top. As a control experiment the dispersive glass SF5 of 3.2 mm in thickness was
characterized. Good agreement was obtained between MIIPS and spectroscopic ellipsometry
followed by calculation of GDD from the refractive index dispersion. At 800 nm, MIIPS
retrieved a GDD of 442 52 fs2, and the derived GDD from ellipsometry was
429 2 fs2. This agrees well with a Cauchy model using data from Schott that gives a GDD
of 429 fs2 at 800 nm. The GVD using the ellipsometry and Schott value is 134 fs2/mm.
0.6 0.8 1
-30w00g 0.8 0.82 0.84
Fig. 2. FEM simulation of the spectral phase and GDD of a metamagnetic structure. (a)
Simulated phase spectrum. (b) GDD spectrum. GDD of metamagnetic material. (c) MIIPS
measured GDD of a magnetic grating (green line) compared with calculated GDD from both
FEM (orange line) and SHA (red circles) simulations.
3. Results and discussion
The measured GDD for our metamagnetic material is shown in Fig. 2(c) (solid green line) and
is compared with the FEM and SHA simulations (orange line and red circles, respectively).
#173167 - $15.00 USD Received 24 Jul 2012; revised 15 Sep 2012; accepted 17 Sep 2012; published 24 Sep 2012
(C) 2012 OSA 8 October 2012 / Vol. 20, No. 21 / OPTICS EXPRESS 23085
-- MIIPS experiment
1 SHA simulation
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Brown, Dean P.; Walker, Mark A.; Urbas, Augustine M.; Kildishev, Alexander V.; Xiao, Shumin & Drachev, Vladimir P. Direct Measurement of Group Delay Dispersion in Metamagnetics for Ultrafast Pulse Shaping, article, September 24, 2012; Washington, DC. (digital.library.unt.edu/ark:/67531/metadc1212007/m1/4/: accessed October 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT College of Arts and Sciences.