Third-Order Nonlinear Spectrum of GaN under Femtosecond-Pulse Excitation from the Visible to the Near Infrared
Third-Order Nonlinear Spectrum of GaN under Femtosecond-Pulse Excitation from the Visible to the Near Infrared
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DOI：
10.3390/photonics6020069
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发表时间：
2019-06-01
期刊：
影响因子：
2.4
通讯作者：
Mendonca, Cleber R.
中科院分区：
文献类型：
--
作者：
Almeida, Gustavo E. B.;Santos, Sabrina N. C.;Mendonca, Cleber R.
氮化镓（GaN）已被确定为集成电光和光子器件的有前途的候选者，旨在从光开关到信号处理的应用。然而，对其光学非线性的研究缺乏频谱覆盖，特别是在电信范围内。在本研究中，我们利用飞秒激光脉冲测量了GaN在可见光到近红外波段的双光子吸收系数（beta）和非线性折射率（n(2)）。我们观察到，当光子能量接近带隙从1.77到2.25 eV （700-550 nm）时，beta从（1.0 +/- 0.2）增加到（2.9 +/- 0.6）x10(-11) m/W，而n(2)在宽光谱范围内从（90 +/- 30）x10（-20）到（265 +/- 80）x10(-20) m(2)/W，从0.80到2.25 eV （1550-550 nm）。应用基于二阶微扰理论和直接间隙半导体的Kramers-Kronig关系的理论对结果进行了建模，这对gan基非线性光子器件的发展具有重要意义。
Gallium nitride (GaN) has been established as a promising candidate for integrated electro-optic and photonic devices, aiming at applications from optical switching to signal processing. Studies of its optical nonlinearities, however, lack spectral coverage, especially in the telecommunications range. In this study, we measured the two-photon absorption coefficient (beta) and the nonlinear index of refraction (n(2)) of GaN from the visible to the near-infrared by using femtosecond laser pulses. We observed an increase of beta from (1.0 +/- 0.2) to (2.9 +/- 0.6) x10(-11) m/W as the photon energy approached the band gap from 1.77 up to 2.25 eV (700-550 nm), while n(2) varied from (90 +/- 30) x10(-20) up to (265 +/- 80) x10(-20) m(2)/W within a broad spectral range, from 0.80 up to 2.25 eV (1550-550 nm). The results were modeled by applying a theory based on the second-order perturbation theory and the Kramers-Kronig relationship for direct-gap semiconductors, which are important for the development of GaN-based nonlinear photonic devices.