Detectors and sources for ultrabroadband electro-optic sampling: Experiment and theory

Leitenstorfer, Alfred; Hunsche, S.; Shah, Jagdeep; Nuss, M. C.; Knox, Wayne H.

doi:10.1063/1.123601

Cited by 413 publications

(293 citation statements)

References 14 publications

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“…The detector response function ℎ depends on the parameters of the electrooptic crystal and the sampling pulse used 47,58,59 . For the calculation of ℎ, the optical constants are taken from Refs.…”

Section: Methodsmentioning

confidence: 99%

“…For ZnTe and GaP, the electrooptic signal S(t) consists of a slowly and fast oscillating part which is, respectively, related to frequencies below and above the Reststrahlen band of these crystals. Strong wave attenuation in the Reststrahlen region 47 leads to considerable gaps from 3 to 10 THz and 7 to 13 THz in the ZnTe and GaP amplitude spectra |S()|, respectively (Fig. 4b).…”

Section: Performance Testmentioning

confidence: 99%

“…It covers the large bandwidth from about 1 to 18 THz. Note that spectral features such as the dip at 8 THz arise from the 50 m thick GaP electrooptic sensor and not from the emitter 44,47 . By deconvoluting the detector response function from the signal S(t), we obtain the THz electric field E det (t) directly in front of the detection crystal (see Methods).…”

Section: Spintronic Thz Emittermentioning

confidence: 99%

“…In our experiment, the THz source is excited by femtosecond pulses from a Ti:sapphire laser oscillator (duration 10 fs, center wavelength 800 nm, pulse energy 2.5 nJ, repetition rate 80 MHz). The transient electric field of the emitted THz pulse is measured by electrooptic sampling 1,2,47 in suitable materials (see Methods). We start with bilayers consisting of FM Co 20 Fe 60 B 20 (thickness of 3 nm) capped by either NM Ta or Ir (3 nm) (see Methods).…”

Section: Spintronic Thz Emittermentioning

confidence: 99%

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Efficient metallic spintronic emitters of ultrabroadband terahertz radiation

Seifert¹,

Jaiswal²,

Martens³

et al. 2016

Nature Photon

669

802

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Terahertz electromagnetic radiation is extremely useful for numerous applications such as imaging and spectroscopy. Therefore, it is highly desirable to have an efficient table-top emitter covering the 1-to-30-THz window whilst being driven by a low-cost, low-power femtosecond laser oscillator. So far, all solid-state emitters solely exploit physics related to the electron charge and deliver emission spectra with substantial gaps. Here, we take advantage of the electron spin to realize a conceptually new terahertz source which relies on tailored fundamental spintronic and photonic phenomena in magnetic metal multilayers: ultrafast photo-induced spin currents, the inverse spin-Hall effect and a broadband Fabry-Pérot resonance. Guided by an analytical model, such spintronic route offers unique possibilities for systematic optimization. We find that a 5.8-nm-thick W/CoFeB/Pt trilayer generates ultrashort pulses fully covering the 1-to-30-THz range. Our novel source outperforms laser-oscillatordriven emitters such as ZnTe(110) crystals in terms of bandwidth, terahertz-field amplitude, flexibility, scalability and cost. IntroductionThe terahertz (THz) window, loosely defined as the frequency range from 0.3 to 30 THz in the electromagnetic spectrum, is located between the realms of electronics and optics 1,2 . As this region coincides with many fundamental resonances of materials, THz radiation enables very selective spectroscopic insights into all phases of matter with high temporal 3,4 and spatial 5,6,7,8 resolution. Consequently, numerous applications in basic research 3,4 , imaging 5 and quality control 8 have emerged.To fully exploit the potential of THz radiation, energy-efficient and low-cost sources of ultrashort THz pulses are required. Most broadband table-top emitters are driven by femtosecond laser pulses that generate the required THz charge current by appropriately mixing the various optical frequencies 9,10 . Sources made from solids usually consist of semiconducting or insulating structures with naturally or artificially broken inversion symmetry. When the incident photon energy is below the semiconductor band gap, optical rectification causes a charge displacement that follows the intensity envelope of the incident pump pulse 9,10,11,12,13,14,15,16,17 . For above-band-gap excitation, the response is dominated by a photocurrent 18,19,20,21,22,23,24 with a temporally step-like onset and, thus, generally smaller bandwidth than optical rectification 9 . Apart from rare exceptions 14 , however, most semiconductors used are polar 1,2,12,13,15,16,17,21,22 and strongly attenuate THz radiation around optical phonon resonances, thereby preventing emission in the so-called Reststrahlen band located between ~1 and 15 THz.The so far most promising sources covering the full THz window are photocurrents in transient gas plasmas 9,10,25,26,27,28,29 . The downside of this appealing approach is that the underlying ionization process usually requires amplified laser pulses with high threshold energies on the order of 0....

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Section: Methodsmentioning

confidence: 99%

Section: Performance Testmentioning

confidence: 99%

Section: Spintronic Thz Emittermentioning

confidence: 99%

Section: Spintronic Thz Emittermentioning

confidence: 99%

See 2 more Smart Citations

Efficient metallic spintronic emitters of ultrabroadband terahertz radiation

Seifert¹,

Jaiswal²,

Martens³

et al. 2016

Nature Photon

669

802

View full text Add to dashboard Cite

show abstract

“…10 -15-fs exciting pulses at 800 nm, it was shown that terahertz pulses could be generated with detectable frequencies as high as 70 THz. 70 At these large bandwidths, it is unavoidable that the t-ray spectrum will overlap with a photon absorption band in the generating and detecting crystals, leading to large oscillations in the terahertz field trailing the main peak.…”

Section: Terahertz-pulse Generation and Detectionmentioning

confidence: 99%

Ultrafast Laser Technology and Spectroscopy

Reid

Wynne

2000

Encyclopedia of Analytical Chemistry

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Ultrafast laser technology and spectroscopy involves the use of femtosecond (10 −15 s) laser and other (particle) sources to study the properties of matter. The extremely short pulse duration allows one to create, detect and study very short‐lived transient chemical reaction intermediates and transition states. Ultrafast lasers can also be used to produce laser pulses with enormous peak powers and power densities. This leads to applications such as laser machining and ablation, generation of electromagnetic radiation at unusual wavelengths (such as millimeter waves and X‐rays), and multiphoton imaging. The difficulty in applying femtosecond laser pulses is that the broad frequency spectrum can lead to temporal broadening of the pulse on propagation through the experimental set‐up. In this article, we describe the generation and amplification of femtosecond laser pulses and the various techniques that have been developed to characterize and manipulate the pulses.

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Growth and Characterization of Large Diameter ZnTe Single Crystals

Arakawa¹,

Asahi²,

Satô³

2002

phys. stat. sol. (b)

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ZnTe crystals of 80 mm diameter were grown in melt by the vertical gradient freezing (VGF) method. B 2 O 3 was used to prevent evaporation of Zn and Te during the crystal growth. The mean dislocation density of the grown crystals was about 4000-7000 cm --2 . The lowest dislocation density was found to be less than 2000 cm --2 . Hole concentrations of more than 10 18 cm --3 were obtained using ZnP 2 as a dopant. When the indium concentration in ZnTe was 2.9 Â 10 18 cm --3 , the resistivity was around 1 Â 10 8 W cm. Thus, high quality large-diameter single crystals covering a wide range of resistivity were obtained.Introduction II-VI compound semiconductors have been expected for various applications such as electroluminescence and electrooptic devices.ZnTe is a direct transition type semiconductor with a band gap energy of 2.26 eV. It has been expected for optical devices such as yellow and green light emitting diodes (LEDs) and laser diodes (LDs). Low resistivity ZnTe crystals can be utilized as latticematching substrates for these electroluminescence devices.ZnTe also has a relatively high electrooptic coefficient and a relatively low dielectric constant. ZnTe electrooptic sensors are reported for the coherent detection in the frequency region above 30 THz with a high sensitivity [1-3]. Furthermore, the capability for mapping of time-resolved THz image was shown using ZnTe electrooptic detectors.To get electrooptic devices in the THz frequency region, high resistivity crystals are needed. On the other hand, to obtain optical devices, low resistivity crystals are required. In order to develop ZnTe-based devices, high quality large-diameter single crystals with a wide range of resistivity are necessary. But it is known that the crystal growth of II-VI materials is very difficult.In our previous studies, p-type ZnTe single crystals were grown successfully by the VGF method [4]. The carrier concentration ranges from 1 Â 10 17 to 5 Â 10 17 cm --3 with the resistivities from 4.46 to 0.14 W cm. Pure green LEDs were first realized with good reproducibility getting over the well-known self-compensation effect specific to II-VI materials using the conventional thermal diffusion process of Al [4]. Realizations of ntype ZnTe were also attempted by molecular beam epitaxy (MBE) and metal-organic vapor phase epitaxy (MOVPE) techniques using ZnTe substrates. N-type conductivity was obtained with carrier concentration in the range of 10 17 cm --3 [5][6][7]. The interest and studies for ZnTe-based optical devices are clearly increasing.In this work, 80 mm diameter ZnTe crystals were grown over a wide range of resistivity, and their electrical and optical properties were evaluated.

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Detectors and sources for ultrabroadband electro-optic sampling: Experiment and theory

Cited by 413 publications

References 14 publications

Efficient metallic spintronic emitters of ultrabroadband terahertz radiation

Efficient metallic spintronic emitters of ultrabroadband terahertz radiation

Ultrafast Laser Technology and Spectroscopy

Growth and Characterization of Large Diameter ZnTe Single Crystals

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