Enhanced nonlinear optical response of layered WSe1.4Te0.6 alloy in 1 μm passively Q-switched laser

Zhengting Du; Tianqi Zhang; Zhenda Xie; Jian Ning; Xinjie Lü; Jinlong Xu; Shining Zhu

doi:10.3788/COL201917.121404

Chinese Optics Letters, Volume. 17, Issue 12, 121404(2019)

Enhanced nonlinear optical response of layered WSe_1.4Te_0.6 alloy in 1 μm passively Q-switched laser

Zhengting Du¹, Tianqi Zhang¹, Zhenda Xie^2、*, Jian Ning¹, Xinjie Lü¹, Jinlong Xu^2、**, and Shining Zhu¹

¹College of Engineering and Applied Sciences, National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China

²School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, China

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Fig. 1. (a) Synthesis scheme of bulk crystals by CVT with dual-temperature zones. Photographs and atomic models of the formation of 2H ${WSe}_{1.4} {Te}_{0.6}$ . Photographs and atomic models of layer-structure bulks of (b) 2H ${WSe}_{2}$ and (c) Td ${WTe}_{2}$ . TEM and SEAD characterizations of few-layer nanosheets of (d) ${WSe}_{2}$ , (e) ${WSe}_{1.4} {Te}_{0.6}$ , and (f) ${WTe}_{2}$ . Corresponding full EDS scanning of (g) ${WSe}_{2}$ , (h) ${WSe}_{1.4} {Te}_{0.6}$ , and (i) ${WTe}_{2}$ . AFM images and thickness measurements of typical nanosheets of (j) ${WSe}_{2}$ , (k) ${WSe}_{1.4} {Te}_{0.6}$ , and (l) ${WTe}_{2}$ .

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$(a) Raman spectra of few-layer WSe2, WSe1.4Te0.6, and WTe2 nanosheets. (b) Comparison of recorded transmittance spectra and corresponding fitted lines. (c) The refractive index of WSe2, WSe1.4Te0.6, and WTe2 based on the relationship of Kramers–Kronig.$

Fig. 2. (a) Raman spectra of few-layer ${WSe}_{2}$ , ${WSe}_{1.4} {Te}_{0.6}$ , and ${WTe}_{2}$ nanosheets. (b) Comparison of recorded transmittance spectra and corresponding fitted lines. (c) The refractive index of ${WSe}_{2}$ , ${WSe}_{1.4} {Te}_{0.6}$ , and ${WTe}_{2}$ based on the relationship of Kramers–Kronig.

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Fig. 3. (a) Determination of the Tauc optical gap. The spectral dependence of $\sqrt{α ℏ ω}$ on $ℏ ω$ . (b) The open-aperture Z-scan results of ${WSe}_{2}$ , ${WSe}_{1.4} {Te}_{0.6}$ , and ${WTe}_{2}$ nanoflakes.

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Fig. 4. Experimental setup of the LD pumped passively $Q$ -switched laser.

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Fig. 5. (a) Output power with increasing incident pump powers. (b) Variations of pulse repetition rates and pulse duration with increasing pump powers. (c) Typical temporal pulse trains of $Q$ -switched lasers. (d) Single pulse traces.

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Fig. 6. Optical spectrum of a ${WSe}_{1.4} {Te}_{0.6}$ $Q$ -switched laser.

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Table 1. Results of Z-scan Measurements at 1070 nm
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Table 1. Results of Z-scan Measurements at 1070 nm
Sample $n$ $α$ _NL(10⁴ cm/GW) $Im χ^{(3)} (10^{- 9} esu)$ $FOM (10^{- 13} cm \cdot esu)$ I_s(GW/cm²) A_s(%)
${WSe}_{2}$ 23 $- 1.35$ $- 22.87$ 25.41 0.53 3
${WSe}_{1.4} {Te}_{0.6}$ 24 $- 1.60$ $- 29.26$ 25.73 0.08 7.8
${WTe}_{2.}$ 12 $- 1.50$ $- 6.46$ 5.97 4.43 2.2

Table 2. Parameters of WSexTe2−x Saturable Absorbers Based Q-switched Lasers
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Table 2. Parameters of WSexTe2−x Saturable Absorbers Based Q-switched Lasers
Parameter ${WSe}_{2}$ ${WTe}_{2}$ ${WSe}_{1.4} {Te}_{0.6}$
Pulse duration (ns) 1220 776 556
Repetition frequency (kHz) 117.1 172.1 164
Average power (mW) 30.3 50.2 82.3

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Zhengting Du, Tianqi Zhang, Zhenda Xie, Jian Ning, Xinjie Lü, Jinlong Xu, Shining Zhu, "Enhanced nonlinear optical response of layered WSe_1.4Te_0.6 alloy in 1 μm passively Q-switched laser," Chin.Opt.Lett. 17, 121404 (2019)

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