Ultra-broadband terahertz pulses generated in the organic crystal DSTMS

Somma, Carmine; Folpini, Giulia; Gupta, Jyotsana; Reimann, K.; Woerner, M.; Elsaesser, Thomas

doi:10.1364/ol.40.003404

Cited by 42 publications

(27 citation statements)

References 35 publications

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“…This fact has made LN the most commonly used THz generation approach so far.There have been reports extending the use of organic crystals to the Ti:Sa wavelengths for intense THz sources. However, in these experiments, the maximum conversion efficiency was limited to 5x10 -5 [19,20] and the emitted 1-5 THz radiation did not cover the scientifically interesting low-frequency THz range between 0.2-1 THz [21,22]. These studies focused on adapting the mid-IR phasematched crystals (DAST, DSTMS, TMS) to the 800 nm pump wavelength.BNA is a highly nonlinear organic crystal well-suited for intense THz generation pumped at Ti:Sa wavelength [23][24][25][26].…”

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confidence: 99%

Intense THz source based on BNA organic crystal pumped at Ti:sapphire wavelength

et al. 2016

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We report on high energy terahertz pulses by optical rectification (OR) in the organic crystal N-benzyl-2-methyl-4-nitroaniline (BNA) directly pumped by a conventional Ti:Sapphire (Ti:Sa) amplifier. The simple scheme provides an optical to terahertz conversion efficiency of 0.25% when pumped by a collimated laser pulses with duration of 50 fs and central wavelength of 800nm. The generated radiation spans frequencies between 0.2 and 3 THz. We measured the damage threshold as well as the dependency of the conversion efficiency on the pump fluence, pump wavelength, and pulse duration.High field terahertz (0.1-10 THz) generation is a topic of numerous ongoing researches due to its wide range of science applications [1][2][3][4][5][6][7][8][9][10][11]. Presently, optical rectification (OR) in nonlinear crystals is the preferred generation technique as it allows the realization of the most intense THz source. The figures of merit of a high-field THz source are the pump-to-THz conversion efficiency, THz spectrum, focusability and the applicable pump wavelength. The wide use of Ti:Sa laser technology in ultrafast THz spectroscopy has inspired the development of a THz emitter which can be pumped directly by those powerful lasers. Presently, for the most intense THz sources Ti:Sapphire needs to be converted to the short wavelength midinfrared spectral range to provide efficient phase-matching [11][12][13][14].In this letter, we report on THz generation in the organic crystal BNA which is pumped at the Ti:Sa 800 nm wavelength. The conversion efficiency and spectral density offered by BNA surpasses other organic crystals pumped at conventional Ti:Sa wavelength in the range of 0.1-3 THz by a factor 10-100. It thus represents a valuable option to the widely used Ti:Sa pumped Lithium Niobate (LN) crystal as the generation scheme is simpler and does not require pulse front tilting.Among all nonlinear crystals, LN [10] and organic crystals (DAST, DSTMS, OH1) [11][12][13][14][15] provide most efficient OR. The typical conversion efficiency for LN pumped at 800 nm [10] and 1030 nm reaches 0.1-0.2 % that can thus be further increased by a factor of three by cryo-cooling the LN [15,16]. However, the reported conversion efficiency is still debated as other research groups [15,16] who repeated the experiment obtained conversion efficiency smaller by an order of magnitude than ref. [17,18]. Due to the notorious focusing issues of LN, which are partly caused by the asymmetric beam quality and the complex geometry, the maximum reported THz field strength has not surpassed 1 MV/cm [10]. LN-based sources emit in the low-THz range (0.1-3 THz). Until now, this range has been difficult to access by organic crystals.Organic crystals offer excellent phase-matching for OR in a simple pump beam configuration and superior THz focusability. The high 2-3% conversion efficiency is achieved for a pump wavelength between 1.2-1.5 µm [11,13]. Such a scheme allows for extreme focusing peak fields reaching up to 83 MV/cm [11]. Yet, the main drawback of or...

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Intense THz source based on BNA organic crystal pumped at Ti:sapphire wavelength

et al. 2016

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“…Future experimental developments should aim both at scaling up the pump fluence without damaging these fragile organic crystals, as well as extending the frequency bandwidth of the detection apparatus without losing dynamical range. Pulse-shaping techniques [89,141] controlling the radiation wavefront [71,94] and/or the spatiotemporal chirp [65] of the laser beams could possibly be optimized to broaden the THz spectrum.…”

Section: Discussionmentioning

confidence: 99%

“…OR typically allows us to generate intense THz radiation below 5 THz (sketched in light green and light red in Figure 1c), while DFG covers higher frequencies (dark green and dark red in Figure 1c). Both inorganic (LiNbO 3 [66][67][68][69][70][71][72][73][74][75][76][77], GaSe [78][79][80], ZnTe [81,82], LiGaS 2 [83], GaP [84][85][86][87][88][89]) as well as organic (DSTMS [89][90][91][92], OH1 [93][94][95][96][97], DAST [98,99], DPFO [100], HMQ-TMS [101], OHQ-N2S [102]) crystals are phase-matched in the NIR and can emit pulsed THz fields with peak amplitudes in excess of 1 MV/cm. The approximate spectrum of the strongest THz pulses generated to date by non-linear optical methods in inorganic [62,64] and organic [63,65] crystals are shown in green and in red in Figure 1c, respectively.…”

Section: Introductionmentioning

confidence: 99%

“…Both techniques operate in a limited frequency range and can detect THz radiation up to~7 THz. Broader THz spectra can be measured with thin crystals [89,105], via more exotic detection schemes employing organic crystals with large linear birefringence [106][107][108][109][110], or with air-biased coherent detection (ABCD) at a cost of reduced DR (~30 dbm) [111][112][113]. While the detection techniques described above allow measuring both the amplitude as well as the phase of a THz field, power or intensity detectors are also available over the entire THz range [114,115].…”

Section: Introductionmentioning

confidence: 99%

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Towards Intense THz Spectroscopy on Water: Characterization of Optical Rectification by GaP, OH1, and DSTMS at OPA Wavelengths

2020

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Water is the most prominent solvent. The unique properties of water are rooted in the dynamical hydrogen-bonded network. While TeraHertz (THz) radiation can probe directly the collective molecular network, several open issues remain about the interpretation of these highly anharmonic, coupled bands. In order to address this problem, we need intense THz radiation able to drive the liquid into the nonlinear response regime. Firstly, in this study, we summarize the available brilliant THz sources and compare their emission properties. Secondly, we characterize the THz emission by Gallium Phosphide (GaP), 2–{3–(4–hydroxystyryl)–5,5–dimethylcyclohex–2–enylidene}malononitrile (OH1), and 4–N,N–dimethylamino–4′–N′–methyl–stilbazolium 2,4,6–trimethylbenzenesulfonate (DSTMS) crystals pumped by an amplified near-infrared (NIR) laser with tunable wavelength. We found that both OH1 as well as DSTMS could convert NIR laser radiation between 1200 and 2500 nm into THz radiation with high efficiency (> 2 × 10−4), resulting in THz peak fields exceeding 0.1 MV/cm for modest pump excitation (~ mJ/cm2). DSTMS emits the broadest spectrum, covering the entire bandwidth of our detector from ca. 0.5 to ~7 THz, also at a laser wavelength of 2100 nm. Future improvements will require handling the photothermal damage of these delicate organic crystals, and increasing the THz frequency.

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“…To fully exploit the utilization of the THz band, ultra-broadband THz sources [8,9] and detectors [10] are intensively studied. Compared with the significant research focusing on these active THz components, the development of antireflection (AR) coatings, especially very broadband AR coatings, still lags behind.…”

Section: Introductionmentioning

confidence: 99%

Ultra-Broadband THz Antireflective Coating with Polymer Composites

Cai

Chen

et al. 2017

Polymers

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Abstract:Achieving an ultra-broadband range is an essential development direction in terahertz techniques; however, a method to cover the full terahertz band by using a highly efficient antireflection (AR) coating that could greatly increase the efficiency of terahertz radiation is still lacking. It is known that structures possessing a graded-index profile can offer a broadband AR effect, and such structures have been widely used, especially in the visible range. In this paper, first, we tuned the refractive index of a cyclo-olefin polymer (COP) by using a TiO 2 dopant, and a polymer-TiO 2 composite with a refractive index of 3.1 was achieved. We then fabricated a surface-relief structure with a graded-index profile by using a hot-embossing method. The structure on the silicon substrate can provide an excellent AR effect, but the working band is still limited by its scale of sag and swell. To obtain an ultra-broadband AR effect, we then proposed a flat six-layer structure; a graded-index profile was obtained by casting epoxy-TiO 2 composites in the order of a high index to lower indices. With a very well controlled refractive index and thickness of each layer, we achieved an AR effect of <2% in the ultra-broadband of 0.2-20 THz.

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Ultra-broadband terahertz pulses generated in the organic crystal DSTMS

Cited by 42 publications

References 35 publications

Intense THz source based on BNA organic crystal pumped at Ti:sapphire wavelength

Intense THz source based on BNA organic crystal pumped at Ti:sapphire wavelength

Towards Intense THz Spectroscopy on Water: Characterization of Optical Rectification by GaP, OH1, and DSTMS at OPA Wavelengths

Ultra-Broadband THz Antireflective Coating with Polymer Composites

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