SEM, Chemical Etching and THz Wave Generation of 4-Dimethylamino-N-methyl-4-stilbazolium Tosylate (DAST) Single Crystals
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RYSTAL GROWTH
SEM, Chemical Etching and THz Wave Generation of 4-Dimethylamino-N-methyl-4-stilbazolium Tosylate (DAST) Single Crystals1 Qing Suna,b, Bing Tenga,b,*, Lifeng Caoa,b, Shaohua Jia,b, Degao Zhonga,b, Lun Haoa,b, Han Xua,b, and Yingtao Zhaoa,b aCollege
of Physics Science, Qingdao University, Qingdao, 266071 China Key Laboratory of Photonics Materials and Technology in University of Shandong, Qingdao University, Qingdao, 266071 China *e-mail: [email protected]; [email protected]
b
Received January 29, 2016
Abstract—The 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) crystal which was candidate for generating and detecting terahertz (THz) wave was grown by slope nucleation method (SNM). The functional groups of DAST were identified by Fourier Transform Infrared (FTIR) studies. Macroscopic steps and streaks on the (00 1 ) face were found by scanning electron microscope (SEM). Different patterns of etch pits under different chemical etchants were studied by optical microscope. Widely tunable THz waves ranging from 0.38 to 18.10 THz were generated from 0.5 mm-thick DAST crystal. The maximum output energy was 345.4 nJ/pulse at 3.39 THz and the conversion efficiency was 8.44 × 10–5. DOI: 10.1134/S1063774517070215
INTRODUCTION High-power single-cycle terahertz (THz) pulses have great potential for exploring frequency-domain spectroscopy, ultrafast magnetic switching, THzimaging applications, and others [1–3]. THz waves occupy a spectrum region of 0.3–10 THz or 10–333 cm–1, but only in the range 10–100 cm–1 is accessible in practice [1]. For efficient THz wave generation and detection, DAST crystal as a kind of nonlinear optical (NLO) material, has been a kind of promising candidate [4, 5]. Tuning the pump wavelength in the range between 1000–1200 and 1300–1700 nm, the THz conversion efficiencies were obtained using DAST in the frequency range between 0.4–0.8 and 1.5–5 THz, respectively [6, 7]. Due to the transverse optical phonon in DAST, the frequencies around ~1.1 THz is limited [8]. However, the technique to generate and detect THz waves using DAST crystals is not mature compared to using inorganic crystals such as LiNbO3 [9]. The application of this organic crystal is limited by lack of the large-size and high-quality DAST crystals. Thus, it is urgent to improve the growth technology or polish technology to obtain high-quality DAST crystals, which can be widely used in practice. In our work, the crystals were grown by slope nucleation method 1 The article is published in the original.
(SNM), which combines spontaneous nucleation and the subsequent growth of a single crystal into one process. The sizes of grown crystal were larger and thinner than that of the ones obtained by other works. Then the functional groups in DAST structure were identified by FTIR studies. The growth mechanism was preliminarily discussed by employing scanning electron microscopy (SEM) and etching investigation. What’s more, the THz wave from 0.38–18.10 THz was generated from the grown DAST crystal while it is difficult to ge
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