Simple technique of coupling a diode laser into a linear power buildup cavity for Raman gas sensing

Abstract

We report a novel, to the best of our knowledge, and simple technique to lock a 642 nm multi-quantum well diode laser to an external linear power buildup cavity by directly feeding the cavity reflected light back to the diode laser for enhancement of gas Raman signals. The dominance of the resonant light field in the locking process is achieved by reducing the reflectivity of the cavity input mirror and thus making the intensity of the directly reflected light weaker than that of the resonant light. Compared with traditional techniques, stable power buildup in the fundamental transverse mode TEM00 is guaranteed without any additional optical elements or complex optical arrangements. An intracavity exciting light of 160 W is generated with a 40 mW diode laser. Using a backward Raman light collection geometry, detection limits at the ppm level are achieved for ambient gases (N2, O2) with an exposure time of 60 s.

Fiber-Optic Photoacoustic CO Sensor for Gas Insulation Equipment Monitoring Based on Cantilever Differential Lock-In Amplification and Optical Excitation Enhancement

“…Second harmonic-wavelength modulation spectroscopy (2f -WMS) technology is utilized, which can effectively eliminate The high-frequency sine wave with frequency f 1 /2 generated by the lock-in amplifier is employed for wavelength modulation, and the low-frequency triangular wave is applied for spectrum scanning. 45 The excitation light enters the MDPAC after passing through a fiber-optic collimator (FOC). The MDPAC has the obvious advantage of reducing gas flow noise, which is the fundamental reason for realizing high-sensitivity dynamic detection of trace gases.…”

Adsorption and Sensing Performances of a TiO2 Cluster-Doped Graphene Monolayer toward SOF2 and SO2F2

“…Gas-insulated switchgear (GIS) mainly utilizes SF 6 gas as its insulating medium. Partial discharge faults inevitably occur in long-term operation, causing the breakdown of SF 6 into various low-fluorine sulfides. , Under microwater and microoxygen conditions, the low-fluorine sulfides produce various corrosive decomposition products which corrode insulating components and cause the electrical or thermal breakdown of the insulating medium. , Partial discharge is difficult to detect in the operations, preventative high-voltage tests, and maintenance due to its strong concealment . Using a gas sensor to detect the decomposition components of SF 6 is a common method for realizing online monitoring of the partial discharge in GIS. , …”

“…This article studied the adsorption and sensing performances of different amounts of the TiO 2 cluster doped into a graphene monolayer ( n TiO 2 -graphene, n = 1, 2, 3) toward SOF 2 and SO 2 F 2 based on density of states (DFT) calculations. The adsorption properties were analyzed by studying the adsorption energy, charge transfer, density of states (DOS), and partial density of states (PDOS). − This study enriches and develops the online monitoring methods of GIS and enhances the engineering application value of gas sensor detection technology for the online monitoring of electrical equipment …”

Ultrahigh Sensitive Trace Gas Sensing System with Dual Fiber-Optic Cantilever Multiplexing-Based Differential Photoacoustic Detection

“…Real-time monitoring of trace H 2 S concentrations is an urgent need for the safe and stable operation of the power system . The optical method , has certain advantages in H 2 S measurement. Utilizing tunable diode laser absorption spectroscopy (TDLAS) technology with an effective absorption path of 56.7 m, an H 2 S sensor with a detection limit of 224 ppb was designed .…”