Finesse is a critical parameter for describing the characteristics of an optical enhancement cavity(OEC). This paper first presents a review of finesse measurement techniques, including a comparative analysis of the a...Finesse is a critical parameter for describing the characteristics of an optical enhancement cavity(OEC). This paper first presents a review of finesse measurement techniques, including a comparative analysis of the advantages, disadvantages, and potential limitations of several main methods from both theoretical and practical perspectives. A variant of the existing method called the free spectral range(FSR) modulation method is proposed and compared with three other finesse measurement methods, i.e., the fast-switching cavity ring-down(CRD) method, the rapidly swept-frequency(SF) CRD method, and the ringing effect method. A high-power OEC platform with a high finesse of approximately 16000 is built and measured with the four methods. The performance of these methods is compared, and the results show that the FSR modulation method and the fast-switching CRD method are more suitable and accurate than the other two methods for high-finesse OEC measurements. The CRD method and the ringing effect method can be implemented in open loop using simple equipment and are easy to perform. Additionally, recommendations for selecting finesse measurement methods under different conditions are proposed, which benefit the development of OEC and its applications.展开更多
Moisture measurement is of great needs in semiconductor industry, combustion diagnosis, meteorology, and atmospheric studies. We present an optical hygrometer based on cavity ring-down spectroscopy （CRDS）. By using ...Moisture measurement is of great needs in semiconductor industry, combustion diagnosis, meteorology, and atmospheric studies. We present an optical hygrometer based on cavity ring-down spectroscopy （CRDS）. By using different absorption lines of H20 in the 1.56 and 1.36 gm regions, we are able to determine the relative concentration （mole fraction） of water vapor from a few percent down to the 10-12 level. The quantitative accuracy is examined by comparing the CRDS hygrometer with a commercial chilled-mirror dew-point meter. The high sensitivity of the CRDS instrument allows a water detection limit of 8 pptv.展开更多
Near-infrared continuous wave cavity ring-down spectroscopy was applied to mea- sure the OH radicals in dielectric barrier discharge plasmas, which play an important role in combustion systems, atmospheric chemistry a...Near-infrared continuous wave cavity ring-down spectroscopy was applied to mea- sure the OH radicals in dielectric barrier discharge plasmas, which play an important role in combustion systems, atmospheric chemistry and the removal of air pollutants by non-thermal plasmas. The P-branches of OH X2YIi （vI ： 2 ＋-- it 0） bands were used for number density measurements. The OH number density and plasma temperature were determined for different applied voltages, gas pressures and concentrations of both oxygen and water. The temporal evolu- tion of the OH number density was obtained by using the ＂time window＂ method, which was used to extract individual ring-down times at different times in a half period of the sine wave applied voltage in dielectric barrier discharge plasmas.展开更多
The absorption spectrum of NiI between 445 and 510 nm has been investigated using the technique of laser vaporization/reaction with free jet expansion and cavity ring down laser absorption spectroscopy. Two new transi...The absorption spectrum of NiI between 445 and 510 nm has been investigated using the technique of laser vaporization/reaction with free jet expansion and cavity ring down laser absorption spectroscopy. Two new transitions namely,[21.3]^2△5/2-X^2△5/2 and [21.9]^2Ⅱ3/2-X^2△5/2 systems were identified and studied. Spectra of both ^58NiI and ^60NiI isotopic molecules were observed. Equilibrium molecular constants for both electronic states are reported and the equilibrium bond length for the [21.3]^2△5/2 state and the[21.9]^2Ⅱ3/2 state was respectively determined to be 2.431 and 2.481 A.展开更多
The effect of resonant cavity structure on the performance operation of In As/Ga As quantum ring intersubband photodetector is studied for detection of terahertz radiations range.In order to confinement of optical fie...The effect of resonant cavity structure on the performance operation of In As/Ga As quantum ring intersubband photodetector is studied for detection of terahertz radiations range.In order to confinement of optical field w ithin active region and consequently enhancement in responsivity of device,tw o periods of Al2O3/Ga As distributed bragg reflectors are used as bottom dielectric mirror and a thin layer of Au material as top mirror of device.For further improvement in detectivity,Al0.3Ga0.7As/In0.3Ga0.7As resonant tunneling barriers are included in absorption layers to reduce dark current of device.Proposed photodetector show s a peak responsivity of about 0.4(A/W)and quantum efficiency of 1.2%at the w avelength of 80μm(3.75 THz).Furthermore,specific detectivity(D*)of device is calculated and results are compared to conventional quantum ring inter-subband photodetector.Results predict a D*of^1011(cm.Hz1/2/W)for device at T=80 K and V=0.4 V w hich is tw o orders of magnitude higher than that of conventional QRIPs.展开更多
腔衰荡光谱技术(Cavity Ring Down Spectroscopy,CRDS)具有高精度和高灵敏度,是一种常应用于微量气体浓度检测的方法,而采用这项技术的关键就是衰荡时间的准确获取。本文为此设计一种基于LabVIEW的腔衰荡信号在线处理系统,实现对衰荡信...腔衰荡光谱技术(Cavity Ring Down Spectroscopy,CRDS)具有高精度和高灵敏度,是一种常应用于微量气体浓度检测的方法,而采用这项技术的关键就是衰荡时间的准确获取。本文为此设计一种基于LabVIEW的腔衰荡信号在线处理系统,实现对衰荡信号的实时采集、平均、拟合、显示和保存。采用外部调制二极管激光器和高反腔搭建CRDS装置,获取实际的衰荡信号,用该系统处理测得的衰荡信号与其他软件的处理结果对比。实验表明,所编写的在线腔衰荡信号处理系统,可实现对衰荡时间的准确获取。展开更多
基金Project supported by National Key Research and Development Program of China (Grant No.2022YFA1603403)。
文摘Finesse is a critical parameter for describing the characteristics of an optical enhancement cavity(OEC). This paper first presents a review of finesse measurement techniques, including a comparative analysis of the advantages, disadvantages, and potential limitations of several main methods from both theoretical and practical perspectives. A variant of the existing method called the free spectral range(FSR) modulation method is proposed and compared with three other finesse measurement methods, i.e., the fast-switching cavity ring-down(CRD) method, the rapidly swept-frequency(SF) CRD method, and the ringing effect method. A high-power OEC platform with a high finesse of approximately 16000 is built and measured with the four methods. The performance of these methods is compared, and the results show that the FSR modulation method and the fast-switching CRD method are more suitable and accurate than the other two methods for high-finesse OEC measurements. The CRD method and the ringing effect method can be implemented in open loop using simple equipment and are easy to perform. Additionally, recommendations for selecting finesse measurement methods under different conditions are proposed, which benefit the development of OEC and its applications.
基金This work was supported by the National Basic Research Program of China （No.2013BAK12B00 and No.2013CB834602） and the National Natural Science Foundation of China （No.21225314 and No.21427804）.
文摘Moisture measurement is of great needs in semiconductor industry, combustion diagnosis, meteorology, and atmospheric studies. We present an optical hygrometer based on cavity ring-down spectroscopy （CRDS）. By using different absorption lines of H20 in the 1.56 and 1.36 gm regions, we are able to determine the relative concentration （mole fraction） of water vapor from a few percent down to the 10-12 level. The quantitative accuracy is examined by comparing the CRDS hygrometer with a commercial chilled-mirror dew-point meter. The high sensitivity of the CRDS instrument allows a water detection limit of 8 pptv.
基金supported by National Natural Science Foundation of China (Nos.10475015, 10975029)
文摘Near-infrared continuous wave cavity ring-down spectroscopy was applied to mea- sure the OH radicals in dielectric barrier discharge plasmas, which play an important role in combustion systems, atmospheric chemistry and the removal of air pollutants by non-thermal plasmas. The P-branches of OH X2YIi （vI ： 2 ＋-- it 0） bands were used for number density measurements. The OH number density and plasma temperature were determined for different applied voltages, gas pressures and concentrations of both oxygen and water. The temporal evolu- tion of the OH number density was obtained by using the ＂time window＂ method, which was used to extract individual ring-down times at different times in a half period of the sine wave applied voltage in dielectric barrier discharge plasmas.
文摘The absorption spectrum of NiI between 445 and 510 nm has been investigated using the technique of laser vaporization/reaction with free jet expansion and cavity ring down laser absorption spectroscopy. Two new transitions namely,[21.3]^2△5/2-X^2△5/2 and [21.9]^2Ⅱ3/2-X^2△5/2 systems were identified and studied. Spectra of both ^58NiI and ^60NiI isotopic molecules were observed. Equilibrium molecular constants for both electronic states are reported and the equilibrium bond length for the [21.3]^2△5/2 state and the[21.9]^2Ⅱ3/2 state was respectively determined to be 2.431 and 2.481 A.
文摘The effect of resonant cavity structure on the performance operation of In As/Ga As quantum ring intersubband photodetector is studied for detection of terahertz radiations range.In order to confinement of optical field w ithin active region and consequently enhancement in responsivity of device,tw o periods of Al2O3/Ga As distributed bragg reflectors are used as bottom dielectric mirror and a thin layer of Au material as top mirror of device.For further improvement in detectivity,Al0.3Ga0.7As/In0.3Ga0.7As resonant tunneling barriers are included in absorption layers to reduce dark current of device.Proposed photodetector show s a peak responsivity of about 0.4(A/W)and quantum efficiency of 1.2%at the w avelength of 80μm(3.75 THz).Furthermore,specific detectivity(D*)of device is calculated and results are compared to conventional quantum ring inter-subband photodetector.Results predict a D*of^1011(cm.Hz1/2/W)for device at T=80 K and V=0.4 V w hich is tw o orders of magnitude higher than that of conventional QRIPs.
基金supported by the National Natural Foundation of China(No.21827804,No.22103075,No.22173089)the National Key R&D Program of China(No.2021YFA0716801,No.2017YFA0303502)。
基金jointly supported by the National Natural Science Foundation of China(No.22273093,No.41905018,No.21903080)the Ministry of Science and Technology of China(No.2022YFF0606500)。
文摘腔衰荡光谱技术(Cavity Ring Down Spectroscopy,CRDS)具有高精度和高灵敏度,是一种常应用于微量气体浓度检测的方法,而采用这项技术的关键就是衰荡时间的准确获取。本文为此设计一种基于LabVIEW的腔衰荡信号在线处理系统,实现对衰荡信号的实时采集、平均、拟合、显示和保存。采用外部调制二极管激光器和高反腔搭建CRDS装置,获取实际的衰荡信号,用该系统处理测得的衰荡信号与其他软件的处理结果对比。实验表明,所编写的在线腔衰荡信号处理系统,可实现对衰荡时间的准确获取。
