Wu Xiaojun, Carbajo Sergio, Ravi Koustuban, Ahr Frederike, Cirmi Giovanni, Zhou Yue, Mücke Oliver D, Kärtner Franz X
Opt Lett. 2014 Sep 15;39(18):5403-6. doi: 10.1364/OL.39.005403.
We experimentally investigate the limits of 800-nm-to-terahertz (THz) energy conversion in lithium niobate at room temperature driven by amplified Ti:sapphire laser pulses with tilted pulse front. The influence of the pump central wavelength, pulse duration, and fluence on THz generation is studied. We achieved a high peak efficiency of 0.12% using transform limited 150 fs pulses and observed saturation of the optical-to-THz conversion efficiency at a fluence of 15 mJ/cm(2) for this pulse duration. We experimentally identify two main limitations for the scaling of optical-to-THz conversion efficiencies: (i) the large spectral broadening of the optical pump spectrum in combination with large angular dispersion of the tilted pulse front and (ii) free-carrier absorption of THz radiation due to multi-photon absorption of the 800 nm radiation.
我们通过实验研究了室温下由倾斜脉冲前沿的放大钛宝石激光脉冲驱动的铌酸锂中800纳米到太赫兹（THz）能量转换的极限。研究了泵浦中心波长、脉冲持续时间和通量对太赫兹产生的影响。使用变换极限的150飞秒脉冲，我们实现了0.12%的高峰值效率，并观察到对于该脉冲持续时间，在通量为15毫焦/平方厘米时，光到太赫兹的转换效率达到饱和。我们通过实验确定了光到太赫兹转换效率缩放的两个主要限制：（i）光泵浦光谱的大幅光谱展宽与倾斜脉冲前沿的大角度色散相结合，以及（ii）由于800纳米辐射的多光子吸收导致的太赫兹辐射的自由载流子吸收。
