Temperature dependent refractive index and absorption coefficient of congruent lithium niobate crystals in the terahertz range

Wu, Xiaojun; Zhou, Chun; Huang, Wei-Chin; Ahr, Frederike; Kärtner, Franz X.

doi:10.1364/oe.23.029729

Cited by 83 publications

(48 citation statements)

References 32 publications

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“…We performed numerical simulations that successfully reproduced the experimental results which allowed identifying THz absorption in lithium niobate at room temperature (absorption coefficient at 500 GHz α RT = 6 cm -1 ) as the cause for limiting the THz yield and also explain the absence of increase in THz energy when increasing crystal length. Changing the absorption coefficient at 500 GHz to α Cryo = 2 cm -1 in the numerical simulations -an absorption coefficient value that can be experimentally obtained via cryogenic cooling of the lithium niobate crystal [26] -, we find that, the crystal length can be scaled up to 4 cm and efficiencies up to the percent level can be reached (Figure 4 -right). …”

Section: Cascaded Optical Parametric Amplifiermentioning

confidence: 87%

Frequency-shifted sources for terahertz-driven linear electron acceleration

Hemmer

Cirmi

Ravi

et al. 2018

Nonlinear Frequency Generation and Conversion: Materials and Devices XVII

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The generation of THz-frequency radiation via nonlinear parametric frequency down-conversion has long been driven by the spectroscopy and imaging communities. As a result, little efforts have been undertaken toward the generation of high energy THz-frequency pulses. THz-frequency radiation has however recently been identified has a promising driver for strong-field physics and an emerging generation of compact particle accelerators. These accelerators require THzfrequency pulses with energies in the multi-millijoule range therefore demanding orders of magnitude improvements from the current state-of-the-art. Much can be gained by improving the intrinsically low efficiency of the down-conversion process while still resorting to existing state-of-the-art lasers. However, the fundamental Manley-Rowe limit caps the efficiency of parametric downconversion from 1-µm wavelength lasers to sub-THz frequency to the sub-percent range. We present methods that promise boosting the THz radiation yield obtained via parametric down-conversion beyond the Manley-Rowe limit. Our method relies on cascaded nonlinear three-wave mixing between two spectrally neighboring laser pulses in periodically poled Lithium Niobate. Owing to favorable phase-matching, the down-conversion process avalanches, resulting in spectral broadening in the optical domain. This allows in-situ coherent multiplexing of multiple parametric down-conversion stages within a single device and boosting the efficiency of the process beyond the ManleyRowe limit. We experimentally demonstrated the concept using either broadband, spectrally chirped optical pulses from a Joule-class laser or using two narrowband lasers with neighboring wavelengths. Experimental results are backed by numerical simulations that predict conversion efficiencies from 1 µm to sub-THz radiation in the multi-percent range.

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Section: Cascaded Optical Parametric Amplifiermentioning

confidence: 87%

Frequency-shifted sources for terahertz-driven linear electron acceleration

Hemmer

Cirmi

Ravi

et al. 2018

Nonlinear Frequency Generation and Conversion: Materials and Devices XVII

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“…the terahertz electric field period. The simulation parameters are tabulated in Table (1). The refractive index and absorption (α) of terahertz radiation at 80 K and 0.3 THz are obtained from linear interpolation of the experimental data between temperatures 50 K and 100 K from [56]. The material absorption at optical wavelengths, i.e.…”

Section: Numerical Methods and Simulation Parametersmentioning

confidence: 99%

High efficiency terahertz generation in a multi-stage system

et al. 2018

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We describe a robust system for laser-driven narrowband terahertz generation with high conversion efficiency in periodically poled Lithium Niobate (PPLN). In the multi-stage terahertz generation system, the pump pulse is recycled after each PPLN stage for further terahertz generation. By out-coupling the terahertz radiation generated in each stage, extra absorption is circumvented and effective interaction length is increased. The separation of the terahertz and optical pulses at each stage is accomplished by an appropriately designed out-coupler. To evaluate the proposed architecture, the governing 2-D coupled wave equations in a cylindrically symmetric geometry are numerically solved using the finite difference method. Compared to the 1-D calculation which cannot capture the self-focusing and diffraction effects, our 2-D numerical method captures the effects of difference frequency generation, self-phase modulation, self-focusing, beam diffraction, dispersion and terahertz absorption. We found that the terahertz generation efficiency can be greatly enhanced by compensating the dispersion of the pump pulse after each stage. With a two-stage system, we predict the generation of a 17.6 mJ terahertz pulse with total conversion efficiency η total = 1.6% at 0.3 THz using a 1.1 J pump laser with a two-line spectrum centered at 1 µm. The generation efficiency of each stage is above 0.8% with the out-coupling efficiencies above 93.0%.

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“…6, where the idler angular density corresponding to collinear signal angles, s 0   , is plotted for three different pump beam waists. Here, the angular density has been evaluated using the refractive indices (22,23) for 5 mol.% MgO-doped LiNbO3 and the crystal parameters are L=1 mm and  = 90 µm.…”

Section: Calculation Of the Interference Signalmentioning

confidence: 99%

Terahertz quantum sensing

et al. 2020

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Quantum sensing is highly attractive for accessing spectral regions in which the detection of photons is technically challenging: sample information is gained in the spectral region of interest and transferred via biphoton correlations into another spectral range, for which highly sensitive detectors are available. This is especially beneficial for terahertz radiation, where no semiconductor detectors are available and coherent detection schemes or cryogenically cooled bolometers have to be employed. Here, we report on the first demonstration of quantum sensing in the terahertz frequency range in which the terahertz photons interact with a sample in free space and information about the sample thickness is obtained by the detection of visible photons. As a first demonstration, we show layer thickness measurements with terahertz photons based on biphoton interference. As non-destructive layer thickness measurements are of high industrial relevance, our experiments might be seen as a first step towards industrial quantum sensing applications.

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Temperature dependent refractive index and absorption coefficient of congruent lithium niobate crystals in the terahertz range

Cited by 83 publications

References 32 publications

Frequency-shifted sources for terahertz-driven linear electron acceleration

Frequency-shifted sources for terahertz-driven linear electron acceleration

High efficiency terahertz generation in a multi-stage system

Terahertz quantum sensing

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