为了改善腔增强吸收光谱的探测灵敏度和光谱分辨率,通过将激光光束离轴注入光学谐振腔中,减小了谐振腔内振荡,提高了模式密度,使得谐振腔被近似看作为“怀特池”。采用记录波长在扫描过程中实际变化的方法,对光谱数据进行了非线性校正,省去了参考光路的布置,简化了实验光路。对二氧化碳在1.572 μm处的一条弱吸收谱线进行了测量,得到了大小为1.98×10-7 cm-1的最小探测灵敏度。实验结果表明同等实验条件下,光束离轴入射时比正轴入射时的腔增强吸收光谱具有更高的信噪比和光谱分辨率。

In order to improve the detection sensitivity and spectral resolution of cavity-enhanced absorption spectroscopy, off-axis alignment method was employed to lead laser beam into the optical resonant cavity. It reduced the cavity interference and increased the mode density, and almost made the cavity like a "White cell". By using a recorded actual scan variation the wavelength was obtained a non-linear correction so as to remove a reference light design in the experiment. The experimental scheme was simplified. With a measurement of weak absorption spectrum of CO2 in near 1.572 μm, the minimum detection sensitivity of 1.98×10-7 cm-1 was achieved. The experimental results indicate that under the same experimental conditions, off axis alignment has higher signal to noise ratio and better spectral resolution than those on axis alignment in cavity enhanced absorption spectroscopy.