Supercontinuum generation in OHQ-N2S organic crystal driven by intense terahertz fields

Giorgianni, F.; Puc, Uroš; Jazbinšek, Mojca; Cea, Tommaso; Koo, Min-Jeong; Han, Jae-Hyun; Kwon, O‐Pil; Vicario, C.

doi:10.1364/ol.44.004881

Cited by 6 publications

(6 citation statements)

References 21 publications

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“…[ 32 ] Instead we use the electro‐optic lensing effect, which also achieves a high electro‐optic sampling sensitivity. [ 23 ] We confirmed experimentally that the detection is in our case perfectly linear and the nonlinear THz effects occurring at very strong THz fields [ 33,34 ] do not play a role yet. For electro‐optic detection, the phase matching, i.e., matching between the phase velocity of the THz pulse and the group velocity of the probe optical pulse, is as important as for the THz wave generation part.…”

Section: Terahertz Bandwidth Limitations and Theoretical Thz Spectrasupporting

confidence: 68%

Ultra‐Broadband and High‐Dynamic‐Range THz Time‐Domain Spectroscopy System Based on Organic Crystal Emitter and Detector in Transmission and Reflection Geometry

Puc

Bach

Günter

et al. 2021

Advanced Photonics Research

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The terahertz range of the electromagnetic spectrum reveals important insights when studying material properties. An ultra‐broadband terahertz time‐domain spectroscopy system based on state‐of‐the‐art, high‐stability organic nonlinear optical crystals used as both THz wave generator and detector is presented. In transmission geometry, a broad spectrum exceeding 20 THz and a high dynamic range of more than 80 dB is achieved using a compact 100 MHz femtosecond laser working at telecom wavelength 1560 nm. In the normal‐incidence reflection geometry, a similar bandwidth with a dynamic range surpassing 60 dB is reported. The experimental results are supported by a complete theoretical model, which includes the pump pulse duration, THz phonon/vibrational modes of the organic crystals and optical/THz beam path optimizations. The effectiveness of the newly developed system is demonstrated by measuring pharmaceutical samples with distinct THz features in the ultra‐broadband THz range and by measuring narrow water vapor lines at a spectral resolution of 2.7 GHz (0.090 cm−1), resulting in an excellent accuracy with a frequency deviation of less than 0.05% from the reference values.

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Section: Terahertz Bandwidth Limitations and Theoretical Thz Spectrasupporting

confidence: 68%

Ultra‐Broadband and High‐Dynamic‐Range THz Time‐Domain Spectroscopy System Based on Organic Crystal Emitter and Detector in Transmission and Reflection Geometry

Puc

Bach

Günter

et al. 2021

Advanced Photonics Research

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“…Examples of such applications are THz wave generation and detection, cross‐phase modulation, and THz nonlinear optics. [ 1–7 ] Compared to inorganic crystals, the organic alternatives exhibit superior macroscopic second‐order optical nonlinearity, which often shows one order of magnitude larger nonlinear optical and electro‐optic coefficients. [ 8 ] There is still a strong demand for improving the macroscopic optical nonlinearity of organic crystals, which is presently below the level achieved in the organic poled polymers.…”

Section: Introductionmentioning

confidence: 99%

Organic THz Generators: A Design Strategy for Organic Crystals with Ultralarge Macroscopic Hyperpolarizability

Seok

Kim

et al. 2021

Advanced Optical Materials

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include the submillimeter wavelengths of terahertz (THz) frequencies. Examples of such applications are THz wave generation and detection, cross-phase modulation, and THz nonlinear optics. [1][2][3][4][5][6][7] Compared to inorganic crystals, the organic alternatives exhibit superior macroscopic second-order optical nonlinearity, which often shows one order of magnitude larger nonlinear optical and electro-optic coefficients. [8] There is still a strong demand for improving the macroscopic optical nonlinearity of organic crystals, which is presently below the level achieved in the organic poled polymers. For example, the electro-optic coefficient of benchmark organic crystals is at the level of ≈50 pm V −1 at 1.3 µm. [9][10][11] On the other hand, the poled polymer systems may exhibit much larger electro-optic coefficients, up to ≈500 pm V −1 at 1.3 µm. [12][13][14] However, progress on designing a strategy to exceed the limits of the state-of-the-art optical nonlinearity of current benchmark organic crystals seems to be slow. Moreover, besides the large macroscopic optical nonlinearity desired, many other crystal characteristics that make possible to grow high-quality bulk crystals with plate-like crystal morphology and high thermal stability are required for real-world photonic applications.Developing new organic crystals with large macroscopic second-order optical nonlinearity is a challenging issue Newly designed halogenated organic quinolinium crystals proposed in this work provide fully optimized molecular ordering for maximizing the optical nonlinearity and high-performance broadband terahertz (THz) wave generation. The ultralarge diagonal optical nonlinearity (almost 300 × 10 −30 esu) of the new halogenated crystals is approximately two times larger than that of state-of-the-art pyridinium-based crystals. In contrast, nonhalogenated analogous crystals exhibit very low (or vanishing) diagonal optical nonlinearity. This is attributed to halogen-induced unique interionic interactions and finetuning of the space-filling characteristics. In addition, the halogenated crystals show a good ability for bulk crystal growth of few millimeters lateral size with plate-like morphology and high thermal stability that are finally required for real-world applications. The new halogenated quinolinium crystals exhibit excellent THz wave generation characteristics, significantly surpassing the limit of conversion efficiency and spectral bandwidth of inorganic benchmark crystals. A 0.16 mm thick chlorinated crystal generates a 29-times larger THz field than 1.0 mm thick inorganic ZnTe crystals at 1500 nm pump wavelength with a flat and broadband spectrum extending up to ≈8 THz. Therefore, introducing halogen substituents is a potential design strategy for designing new organic crystals showing ultralarge macroscopic hyperpolarizability and high-performance THz wave generation.

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“…During the last two decades, several organic NLO crystals have been extensively investigated for applications in THz photonics and are gaining increasing importance in the field of THz waves. [2][3][4][5]30,31] For instance, the frequency conversion applications (e.g., optical rectification, and difference frequency generation processes) in organic NLO crystals leads to the generation of efficient and intense THz waves. Depending on experimental configurations with different optical parameters and laser systems, organic NLO crystals could generate strong THz electric fields of over few hundred kV cm −1 to MV cm −1 level and high conversion efficiencies.…”

Section: Introductionmentioning

confidence: 99%

Highly Nonlinear Optical Organic Crystals for Efficient Terahertz Wave Generation, Detection, and Applications

Kim

Kang

Puc

et al. 2021

Advanced Optical Materials

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ordering in the crystalline state should be simultaneously considered when designing organic π-conjugated crystals to achieve the desired physical properties. However, the prediction of the molecular ordering of organic π-conjugated chromophores in the crystalline state is still significantly difficult. This is because most organic π-conjugated chromophores exhibit several complex intermolecular and intramolecular interactions (and interionic interactions) with multiple possible molecular conformations during the self-assembling process in the crystalline state. [17,18] For each specific target application, a different targeted control of the molecular ordering of chromophores in the crystalline state is required, which is still an important issue in the molecular (and crystal) engineering of various organic π-conjugated crystalline materials.This issue is more critical for organic nonlinear optical (NLO) crystals and will be the focus of this review. Organic NLO crystals can be used in diverse nonlinear photonic applications, such as frequency down-and up-conversion, terahertz (THz) wave generation and detection, phase and amplitude electro-optic modulation, and high-speed telecommunication integrated optics. [19][20][21][22][23] Organic crystals must possess a noncentrosymmetric molecular ordering of chromophores to achieve second-order optical nonlinearity. However, in addition to the aforementioned complicated molecular interactions, the introduction of strong polar substituents (electron-donating groups (EDGs) and electron-withdrawing groups (EWGs)) on widely used push-pull π-conjugated chromophores to increase their molecular nonlinearity also increases their dipole moment. In many cases, a high dipole moment leads to a centrosymmetric ordering of chromophores with antiparallel dipole-dipole aggregation in the crystalline state (i.e., there is no macroscopic second-order optical nonlinearity). This tendency further complicates the development of new organic NLO crystals with large second-order optical nonlinearity. This is one of the reasons for only a few classes of organic crystals with state-of-theart optical nonlinearity being reported in the last few decades. Moreover, in addition to large macroscopic second-order optical nonlinearity, different NLO applications require different targeted physical properties (e.g., refractive index, dispersion of the refractive index, dielectric constant, and absorption coefficient) and crystal characteristics (e.g., direction of the polar axis, morphology, aperture size, thickness, and facets). Therefore, it Organic π-conjugated crystals with second-order optical nonlinearity are considerably attractive materials for diverse terahertz (THz) wave photonics. An overview of the research of organic nonlinear optical (NLO) crystals for THz wave generation, detection, and applications is provided here. First, the status of organic NLO crystals compared to other alternative THz materials is described. Second, the basic theory and requirements for organic THz generators and d...

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Supercontinuum generation in OHQ-N2S organic crystal driven by intense terahertz fields

Cited by 6 publications

References 21 publications

Ultra‐Broadband and High‐Dynamic‐Range THz Time‐Domain Spectroscopy System Based on Organic Crystal Emitter and Detector in Transmission and Reflection Geometry

Ultra‐Broadband and High‐Dynamic‐Range THz Time‐Domain Spectroscopy System Based on Organic Crystal Emitter and Detector in Transmission and Reflection Geometry

Organic THz Generators: A Design Strategy for Organic Crystals with Ultralarge Macroscopic Hyperpolarizability

Highly Nonlinear Optical Organic Crystals for Efficient Terahertz Wave Generation, Detection, and Applications

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