Laser beam combiner for simultaneously detecting various types of gas of TDLAS (Tunable Diode Laser Absorption Spectroscopy)

Abstract

The invention provides a laser beam combiner for simultaneously detecting various types of gas of a TDLAS (Tunable Diode Laser Absorption Spectroscopy) and belongs to the technical field of laser gas detection. In the prior art, the attenuation is high, the work wavelength range is narrow and the construction cost of a beam combining part is high. The laser beam combiner is characterized by being provided with a plurality of paths of incidence optical fibers; an emergent end of each path of the incidence optical fiber is connected with a collimating mirror and each incidence optical fiber is a single-core and single-mode optical fiber; mutually-parallel optical axes of the plurality of collimating mirrors of the plurality of paths of incidence optical fibers are parallel to the optical axis of a concave spherical surface reflection mirror; the mutually-parallel optical axes of the plurality of collimating mirrors intersect with a reflection surface of the concave spherical surface reflection mirror; an incidence end face of an emergent optical fiber is located on a reflection surface focus point F of the concave spherical surface reflection mirror and is vertical to the optical axis of the concave spherical surface reflection mirror; the emergent optical fiber is a single-core and multi-mode optical fiber; the numerical aperture of the concave spherical surface reflection mirror is less than that of the emergent optical fiber.

Description

technical field [0001] The invention relates to a laser beam combiner used for simultaneous detection of multiple gases in TDLAS. The laser beam combiner can realize simultaneous detection of multiple gases. The same laser gas detection device can be used according to the different molecular absorption lines of different gases. Simultaneously adopting laser detection with different wavelengths belongs to the technical field of laser gas detection. Background technique [0002] In the field of gas spectral absorption, TDLAS (tunable diode laser absorption spectroscopy, tunable semiconductor laser absorption spectroscopy technology) can realize the simultaneous detection of multiple gases. This technology consists of several DFB lasers (distributed feedback lasers) with different central wavelengths to form a multi-wavelength light source. The mode optical fiber guides the combined beam detection laser into the gas cell containing the gas to be tested from the light inlet por...

AI Technical Summary

Problems solved by technology

[0005] 1. After multiple detection lasers with different wavelengths pass through the wavelength division multiplexer, they will be attenuated to varying degrees, and the more laser beams with different wavelengths to be coupled, the more serious the attenuation will be;

[0006] 2. The applicable wavelength range of the wavelength division multiplexer is relatively narrow. This is because it is difficult to have a transflective film suitable for a large wavelength range at present. Therefore, the existing wavelength division multiplexer has a working range of 1310-1610nm. And the detection laser center wavelength of many gases is greater than 1610nm, such as CH 4 Gas 1654nm, HCl gas 1742nm, NO gas 1800nm / 2650nm, CO 2 Gas 2004nm / 2680nm, N 2 O gas 2257nm, C 3 h 8 Gas 3370nm, therefore, the wavelength division multiplexer can not be suitable for the needs of these gas analysis;

[0007] 3. The wavelength division multiplexer used in the field of gas detection needs to be customized, and the cost is high

[0010] 2. The light intensity distribution in the cross-section of the outgoing light is scattered and uneven, and the beam divergence angle is large, which makes it more difficult to collimate and focus the outgoing light of the fiber bundle, which requires the length of the gas cell to be short and the detector to be short. The detection area needs to be large, and the short length of the gas pool results in a short optical path, light interaction between the detection laser and the gas to be detected, low detection sensitivity, and decreased detection accuracy; the large detection area of ​​the detector leads to high cost of the detector

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