A Tunable IR Laser Source for Remote Sensing

一种宽调谐的紧凑型红外激光源， 9-12微米范围基于非常有效的相位调制的二氧化碳 将建造微波频率的激光器， 表征了 该激光源包括一条选择CO的线， 2激光器，其被稳定到4.3 μ m发射Lamb-dip，以及 一种行波CdTe缓冲BaAs微带电光器件 调制器 在20 W微波驱动功率下， 连续可调红外功率输出10至50毫瓦， 从激光载波频率偏移8至18 GHz的频率。 将对该来源的性能和有用性进行评估 并通过进行直接饱和和 吸收和外差测量。 饱和 吸收测量可以提供 亚多普勒分辨率的原子和分子跃迁。 这种可调谐激光器也将用作本机振荡器， 外差光谱仪可以提供显著 提高系统灵敏度。 超高分辨率， 需要极低噪声的红外外差光谱仪， 对行星大气层中有趣现象的研究 发生在低密度，低温地区，其中亚- 多普勒频谱分辨率需要完全解决线 形状，并在空间上映射源。 的信息 可从红外外差测量中准确地检索 确定压力、温度、激发和分子 行星大气的丰度。 同样的技术也将应用于遥感 地球大气中微量气体的测量。

A widely tunable and compact IR laser source emitting in the 9-12 um range based on very efficient phase modulation of CO 2 lasers at microwave frequencies will be constructed and characterized. This laser source consists of a line selecting CO 2 laser, which is stabilized to the 4.3 um emission Lamb-dip, and a traveling-wave CdTe buffered BaAs microstrip electrooptic modulator. With a 20 W microwave drive power, it can provide a continuously tunable IR power output of 10 to 50 mW at frequencies 8 to 18 GHz off-set from the laser carrier frequency. The performance and usefulness of this source will be evaluated and demonstrated by carrying out both direct saturation absorption and hererodyne measurements. The saturation absorption measurements can provide individual line profiles of atomic and molecular transitioons with sub-Doppler resolution. This tunable laser will also be used as a local oscillator in a heterodyne spectrometer which can provide a significant improvement in system sensitivity. An ultra-high resolution and extremely low noise IR heterodyne spectrometer is required for the study of interesting phenomena in the atmospheres of planets occurring in low density, low temperature regions, where sub- Doppler spectral resolution are needed to resolve fully the line shapes and to map spatially the source. The information retrievable from IR heterodyne measurements can accurately determine pressure, temperature, excitation, and molecular abundances of planetary atmospheres. The same technology will find applications in remote sensing measurements of trace gases in the earth's atmosphere.//