Full mathematical description of electro-optic detection in optically isotropic crystals

Valk, N. C. J. van der; Wenckebach, Tom; Planken, Paul C. M.

doi:10.1364/josab.21.000622

Cited by 95 publications

(67 citation statements)

References 15 publications

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“…This configuration thus serves as an effective method to avoid the pump beam going into the detection crystal along with the THz beam. The synchronized sampling pulse is also focused onto the detection crystal [18]. The THz electric field elliptically polarizes the probe beam to an extent proportional to the instantaneous THz electric field value.…”

Section: Methodsmentioning

confidence: 99%

Surface plasmon-enhanced terahertz emission from a hemicyanine self-assembled monolayer

Ramakrishnan¹,

Kumar²,

Planken³

et al. 2012

Opt. Express

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Abstract:Emission of terahertz radiation is observed when surface plasmons are excited on a thin film of gold, in the Kretschmann geometry. When a hemicyanine-terminated alkanethiol self-assembled monolayer of thickness 1.2 nm is deposited on the gold film, stronger terahertz emission is observed. Our experimental results confirm that enhanced terahertz emission is possible from planar gold surfaces when surface plasmons are excited.

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Section: Methodsmentioning

confidence: 99%

Surface plasmon-enhanced terahertz emission from a hemicyanine self-assembled monolayer

Ramakrishnan¹,

Kumar²,

Planken³

et al. 2012

Opt. Express

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“…5(b). Note that the electro-optic detection system is polarization sensitive and only one polarization component of the generated THz is detected at a time [10]. Magnetic-field enhancement measurements could not be performed in this case.…”

Section: Edge-plane Surface Illuminationmentioning

confidence: 99%

“…1(b) and 1(c). In all cases, the THz radiation generated from the graphite sample is collected in the reflected direction using offaxis parabolic mirrors and focused onto an electro-optic detection crystal (ZnTe (110) or GaP (110)) [10]. The synchronized, co-propagating, sampling pulse is also focused onto the detection crystal.…”

Section: Introductionmentioning

confidence: 99%

Terahertz generation from graphite

2009

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Generation of subpicosecond terahertz pulses is observed when graphite surfaces are illuminated with femtosecond near-infrared laser pulses. The nonlinear optical generation of THz pulses from graphite is unexpected since, in principle, the material possesses a centre of inversion symmetry. Experiments with highly oriented pyrolytic graphite crystals suggest that the THz radiation is generated by a transient photocurrent in a direction normal to the graphene planes, along the c-axis of the crystal. This is supported by magnetic-field induced changes in the THz electric-field polarization, and consequently, the direction of the photocurrent. We show that other forms of graphite, such as a pencil drawing on paper, are also capable of emitting THz pulses.

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“…This crystal orientation results in 18% smaller signals compared with the more commonly used (110) orientation. 10 However, as we discuss below, this orientation allows for the detection of both electric field components with equal sensitivities without any rotation of the detection crystal. A signal proportional to the terahertz electric field is obtained by measuring the difference in the energy in the two orthogonal polarization directions of the probe beam with a Wollaston prism and a differential detector.…”

mentioning

confidence: 99%

“…The following expression is obtained for the power difference measured by the differential detector 10 :…”

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confidence: 99%

Terahertz polarization imaging

2005

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We present a new method to measure the polarization state of a terahertz pulse by using a modified electrooptic sampling setup. To illustrate the power of this method, we show two examples in which the knowledge of the polarization of the terahertz pulse is essential for interpreting the results: spectroscopy measurements on polystyrene foam and terahertz images of a plastic coin. Both measurements show a sampleinduced rotation of the terahertz electric field vector, which is surprisingly large and is a strong function of frequency. A promising aspect of our setup is the possibility of simultaneously measuring both transversal electric field components. © single-shot imaging, 4 and near-field imaging. 5 A characteristic of these techniques is that only one component of the electric field vector is measured. This makes the images obtained with these methods sometimes difficult to interpret. A decrease in the amplitude of the measured field, for instance, is commonly interpreted as being caused by absorption or scattering. However, such a decrease could also be caused by a rotation of the electric field vector induced by a birefringence present in the sample. Besides birefringence, there are various other effects that can change the direction of a terahertz electric field, such as not-normalincidence reflection and multiple scattering. 6 We note that in a recent experiment on the terahertz Hall effect a rotation of the terahertz polarization was observed when two orthogonally oriented photoconductive emitters were used. 7 Here, we report a method for measuring both the direction and the length of the transversal terahertz electric field vector by using electro-optic sampling in a (111)-oriented electro-optic crystal. We demonstrate the potential of this technique in terahertz imaging and spectroscopy with two examples. In the first example, we perform spectroscopic measurements on polystyrene foam. Surprisingly, this material shows an effective birefringence, which can be measured accurately with our new technique. In the second example, we show terahertz images of a plastic coin based on a measurement of the two transversal electric field components at each pixel. The images clearly show that scattering or reflection at the edges of the coin results in a change in the polarization state of the terahertz beam. Figure 1 shows a schematic drawing of the detection setup. We concentrate on the detection setup because the other details of our setup have been published previously. 8,9 The terahertz electric field is measured by using the electro-optic effect, which causes a birefringence of the detection crystal proportional to the electric field. The birefringence causes a polarization change of the optical probe pulse, which is measured with a differential detection setup. A quarter-wave plate is placed before the ZnTe detection crystal, oriented such that the originally linear polarization of the probe beam becomes circular. A key element in our setup is the use of a ZnTe detection crystal with a (111) crystal orie...

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Full mathematical description of electro-optic detection in optically isotropic crystals

Cited by 95 publications

References 15 publications

Surface plasmon-enhanced terahertz emission from a hemicyanine self-assembled monolayer

Surface plasmon-enhanced terahertz emission from a hemicyanine self-assembled monolayer

Terahertz generation from graphite

Terahertz polarization imaging

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