Bayrakli Ismail, Akman Hatice
J Biomed Opt. 2015 Mar;20(3):037001. doi: 10.1117/1.JBO.20.3.037001.
A robust biomedical sensor for ultrasensitive detection of biomarkers in breath based on a tunable external cavity laser (ECL) and an off-axis cavity-enhanced absorption spectroscopy (OA-CEAS) using an amplitude stabilizer is developed. A single-mode, narrow-linewidth, tunable ECL is demonstrated. A broadly coarse wavelength tuning range of 720 cm⁻¹ for the spectral range between 6890 and 6170 cm⁻¹ is achieved by rotating the diffraction grating forming a Littrow-type external-cavity configuration. A mode-hop-free tuning range of 1.85 cm⁻¹ is obtained. The linewidths below 140 kHz are recorded. The ECL is combined with an OA-CEAS to perform laser chemical sensing. Our system is able to detect any molecule in breath at concentrations to the ppbv range that have absorption lines in the spectral range between 1450 and 1620 nm. Ammonia is selected as target molecule to evaluate the performance of the sensor. Using the absorption line of ammonia at 6528.76 cm⁻¹, a minimum detectable absorption coefficient of approximately 1×10⁻⁸ cm⁻¹ is demonstrated for 256 averages. This is achieved for a 1.4-km absorption path length and a 2-s data-acquisition time. These results yield a detection sensitivity of approximately 8.6×10⁻¹⁰ cm⁻¹ Hz(-1/2). Ammonia in exhaled breath is analyzed and found in a concentration of 870 ppb for our example.
基于可调谐外腔激光器（ECL）和使用振幅稳定器的离轴腔增强吸收光谱技术（OA-CEAS），开发了一种用于超灵敏检测呼出气体中生物标志物的强大生物医学传感器。展示了一种单模、窄线宽、可调谐的ECL。通过旋转形成利特罗型外腔配置的衍射光栅，在6890至6170 cm⁻¹的光谱范围内实现了720 cm⁻¹的宽粗波长调谐范围。获得了1.85 cm⁻¹的无模式跳变调谐范围。记录了低于140 kHz的线宽。将ECL与OA-CEAS相结合以进行激光化学传感。我们的系统能够检测呼出气体中浓度在ppbv范围内、在1450至1620 nm光谱范围内有吸收线的任何分子。选择氨作为目标分子来评估传感器的性能。利用氨在6528.76 cm⁻¹处的吸收线，对于256次平均测量，展示了约1×10⁻⁸ cm⁻¹的最小可检测吸收系数。这是在1.4公里的吸收路径长度和2秒的数据采集时间下实现的。这些结果产生了约8.6×10⁻¹⁰ cm⁻¹ Hz⁻¹/²的检测灵敏度。对呼出气体中的氨进行了分析，在我们的示例中发现其浓度为870 ppb。
