Enhanced Terahertz Wave Generation from Cytop Antireflection–Coated DAST Crystal

Uchida, Hirohisa; Koyama, Chisa; Takagi, Toshihisa; Wang, Peibin; Kamei, Takayuki; Tripathi, Saroj R.; Kawase, Kodo; Takeya, Kei

doi:10.1007/s10762-020-00674-6

Cited by 5 publications

(3 citation statements)

References 18 publications

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“…Considering a possible thermal accumulation by absorption of the optical pump pulses, cooling or employing substrates with a high thermal conductivity [317] may be helpful to improve the crystal stability and reduce undesired thermal effect. In addition, similar as for other frequency up-and down-conversion materials, future investigations of organic NLO crystals crystal growth and processing to improve their bulk and surface optical quality are needed, as well as using, e.g., anti-reflection coatings [318] to reduce reflection losses for the pump beam.…”

Section: Wwwadvopticalmatdementioning

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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Section: Wwwadvopticalmatdementioning

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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“…When using terahertz wave generation and detection devices in actual environments, packaging of the system using various materials, not just optical components, is necessary. Utilizing the characteristics of silicon, metals, and polymer materials in the terahertz frequency has been reported to achieve optimal device structures [11][12][13][14]. However, materials that combine opacity to visible light with transparency to terahertz waves are in short supply.…”

Section: Introductionmentioning

confidence: 99%

Terahertz characterization Microcellular Polyethylene Terephthalate (MCPET) across broad temperature range

Uchida,

Miyamoto,

Takeya

2024

Preprint

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The optical properties of Microcellular Polyethylene Terephthalate (MCPET) towards light and terahertz waves were compared. Within the measurement range of 0.3–1.3 THz and 30 K to room temperature, the refractive index remained nearly constant at approximately 1.15, close to 1. It was observed that MCPET with a thickness of 0.5 mm transmits over 70% of terahertz waves, while blocking more than 99.9% of light in the 300–2000 nm range. These findings present significant advantages for the design of optical devices using MCPET, highlighting its potential for selective transparency and high opacity in specific applications.

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“…When a pump laser is incident on a crystal surface, a significant percentage of pump power is reflected from air-crystal interface given by Fresnel’s equation as , where n is the refractive index of a crystal at the excitation wavelength. However, this reflection loss can be reduced by using an anti-reflection coat on the surface of the crystal with an appropriate thickness 34 .…”

Section: Introductionmentioning

confidence: 99%

Optical thin film coated organic nonlinear crystal for efficient terahertz wave generation

Uchida

Kawauchi

Otake

et al. 2022

Sci Rep

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In the process of terahertz (THz) wave generation via optical rectification of infrared femtosecond pulses in a non-linear optical crystal, the power of terahertz wave is directly proportional to the square of the optical pump power. Therefore, high power terahertz wave can be generated using a high power femtosecond laser provided that the crystal has both high laser induced damage threshold and optical non-linear coefficient. However, a significant amount of pump power is lost in this process due to the Fresnel’s reflection at the air-crystal boundary. In this paper, we numerically and experimentally demonstrate that the coat of optical thin film called Cytop on the 4-N, N-dimethylamino-4’-N’-methyl-stilbazolium tosylate (DAST) crystal effectively reduces the reflection loss of pump power, thereby increasing the THz wave emission efficiency of the DAST crystal. We found that the average power of THz wave emitted by the thin film coated crystal is about 28% higher than the THz power emitted by the uncoated crystal when an equal amount of laser power is used. The thin film coated DAST crystals can be used not only in terahertz measurement systems but also in optical devices such as modulators and waveguides.

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Enhanced Terahertz Wave Generation from Cytop Antireflection–Coated DAST Crystal

Cited by 5 publications

References 18 publications

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

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

Terahertz characterization Microcellular Polyethylene Terephthalate (MCPET) across broad temperature range

Optical thin film coated organic nonlinear crystal for efficient terahertz wave generation

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