Fibre laser based mid infrared source development

气体分子表现出特征振动，导致在电磁光谱的中红外(MID-IR)区域产生高度结构化但具有特征的光吸收光谱。因此，通过测量气体样品对光的吸收作为波长的函数，可以确定样品中不同分子物种的存在和浓度。这使得传感在生物、医学、环境监测和制造业等领域的广泛应用成为可能。为了利用这种传感方法，对工作在中红外的激光光源提出了新的要求。使用传统的激光材料和设计很难实现这些目标。在这个项目中，我们将开发一系列中红外光源，在中红外范围内提供前所未有的波长覆盖和功率水平(波长范围从2-15微米，可以检测到大多数气体的“指纹”吸收光谱)。该项目将包括开发在传统近红外波长(例如1和2微米)下工作的高功率短脉冲光纤激光器，并利用特殊设计的晶体和/或光纤中的非线性光学效应将输出光的波长转换为中红外波长。我们将瞄准可用于探测单个气体吸收的宽波长调谐范围和窄光谱线宽的高功率源，以及具有超高光谱功率密度的宽带超连续谱源，可以在无需调谐的情况下一次测量记录全部气体吸收光谱。该项目的最终目标是为中红外开发一个突破性的新技术平台，并与其他人合作，展示该平台在上述几个重要应用领域提供的使能能力，特别是生命科学。

Gas molecules exhibit characteristic vibrations that lead to highly structured but characteristic light absorption spectra in the mid-infrared (mid-IR) regions of the electromagnetic spectrum. Consequently, by measuring the absorption of light through a gas sample as a function of the wavelength the presence and concentration of different molecular species within the sample can be determined. This is enabling for a wide range of sensing applications in biology, medicine, environmental monitoring and manufacturing amongst others. In order to exploit this sensing approach there is an emerging requirement for laser sources operating in the mid-IR. These are difficult to realise using traditional laser materials and designs. In this project we will develop a range of mid-IR sources offering unprecedented levels of wavelength coverage and power within the mid-IR (wavelengths range from 2-15 um where the "fingerprint" absorption spectra of most gases can be detected).The project will involve the development of high power short pulse fibre lasers operating at conventional near-IR wavelengths (e.g. 1 and 2um) and converting the wavelength of the output light to the mid-IR wavelengths using nonlinear optical effects in specially engineered crystals, and/or optical fibres. We will target both high-power sources with a wide wavelength tuning range and a narrow spectral linewidth that can be used to probe individual gas absorption, as well as broadband supercontinuum sources with ultrahigh spectral power densities that can be used to record the full gas absorption spectra in one measurement without tuning.The ultimate goal of the project is to develop a ground-breaking new technology platform for the mid-IR and to work with others to demonstrate the enabling capabilities provided by the platform in several of the important application areas above, with a particular focus on the life sciences.