Mërtiri Alket, Jeys Thomas, Liberman Vladimir, Hong M K, Mertz Jerome, Altug Hatice, Erramilli Shyamsunder
Appl Phys Lett. 2012 Jul 23;101(4):44101. doi: 10.1063/1.4737942.
We report a technique to measure the mid-infrared photothermal response induced by a tunable quantum cascade laser in the neat liquid crystal 4-octyl-4'-cyanobiphenyl (8CB), without any intercalated dye. Heterodyne detection using a Ti:sapphire laser of the response in the solid, smectic, nematic and isotropic liquid crystal phases allows direct detection of a weak mid-infrared normal mode absorption using an inexpensive photodetector. At high pump power in the nematic phase, we observe an interesting peak splitting in the photothermal response. Tunable lasers that can access still stronger modes will facilitate photothermal heterodyne mid-infrared vibrational spectroscopy.
我们报道了一种在纯液晶4-辛基-4'-氰基联苯（8CB）中测量由可调谐量子级联激光器诱导的中红外光热响应的技术，无需任何插入染料。使用钛宝石激光器对固态、近晶相、向列相和各向同性液晶相中的响应进行外差检测，能够使用廉价的光电探测器直接检测微弱的中红外简正模吸收。在向列相的高泵浦功率下，我们在光热响应中观察到一个有趣的峰分裂。能够探测更强模式的可调谐激光器将推动光热外差中红外振动光谱学的发展。
