s-AFPF External-Cavity Diode Laser for Fast Wavelength Modulation
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Solution Overview
Problem
Tunable external-cavity diode lasers in TDLAS-WMS systems have slow modulation speeds, limiting their popularity and effectiveness in gas sensing applications compared to tunable monolithic diode lasers.
Innovation Solution
A single-mode external-cavity diode laser based on a circular single-cavity all-dielectric film Fabry-Perot filter (s-AFPF) is developed, utilizing a piezoelectric ceramic actuator to control the rotation and movement of optical components, ensuring mode hop-free tuning and high-precision wavelength modulation, replacing the traditional tunable monolithic diode laser.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a tunable external-cavity diode laser is used in TDLAS-WMS system, then wavelength tuning capability is improved, but modulation speed becomes slow
Solution Approach 1:
The patent employs dynamic control of the external cavity length through a piezoelectric actuator that rapidly adjusts the position of the output mirror. This dynamic adjustment mechanism enables fast wavelength modulation while maintaining the external cavity configuration, resolving the contradiction between wavelength tuning capability and modulation speed.
Solution Approach 2:
The patent changes the physical parameters of the external cavity (cavity length, mirror position) to achieve rapid wavelength modulation. By controlling the piezoelectric actuator to adjust the output mirror position, the system achieves fast modulation speeds while maintaining the wavelength tuning capability provided by the external cavity structure.
2Speed
If a tunable monolithic diode laser is used, then modulation speed is fast, but wavelength tuning range is limited
Solution Approach 1:
The patent segments the laser system into two functional parts: a monolithic diode laser module that provides fast modulation capability, and an external cavity that provides wide wavelength tuning range. This segmentation allows each component to perform its optimal function, combining the advantages of both fast modulation and broad tuning range.
Solution Approach 2:
The external cavity structure serves multiple functions: it extends the wavelength tuning range beyond the monolithic laser's capabilities, provides wavelength selection through the grating, and enables fast modulation through piezoelectric actuator control. This multi-functionality resolves the contradiction by making the external cavity system capable of both wide tuning and fast modulation.
3Adaptability or versatility
If external cavity components are added for wavelength tuning, then wavelength tuning range is improved, but device complexity increases
Solution Approach 1:
The patent merges the wavelength selection function and wavelength modulation function into a single external cavity structure. The grating and output mirror work together as an integrated wavelength control system, reducing the number of separate components needed while achieving both wide tuning range and fast modulation capability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables accurate sensing of gas types and concentrations with improved modulation speed, replacing the need for tunable monolithic diode lasers in TDLAS-WMS systems, enhancing precision and applicability in gas sensing.
Implementation Method 1
the actuator is a piezoelectric ceramic actuator; the actuator is used to move the second totally reflecting plane mirror forward and backward, and control the s-AFPF to rotate anticlockwise
Implementation Method 2
a high refractive index dielectric of the s-AFPF is Ta2O5 film; a low refractive index dielectric of the s-AFPF is SiO2 film
Implementation Method 3
a circular single-cavity all-dielectric film Fabry-Perot filter (s-AFPF)
Implementation Method 4
a first orthogonal bi-cylindrical lens and a second orthogonal bi-cylindrical lens are disposed on two sides of the Fabry-Perot laser diode respectively
Implementation Method 5
the wire grid polarizer is a wire grid polarizing film with a diameter of 20 mm, used to generate TE polarized light or TM polarized light
Implementation Method 6
a Fabry-Perot laser diode as a light source
Implementation Method 7
two cleavage surfaces of the Fabry-Perot laser diode as a light source are plated with a first AR film for eliminating longitudinal modes
Data Source
AI summary
The disclosure provides a single-mode external-cavity diode laser based on an s-AFPF, relates to the technical field of tunable diode laser absorption spectroscopy. A piezoelectric ceramic actuator is used to change and modulate an output center wavelength of the laser, so that the center wavelength of laser light can periodically scan an absorption spectrum band of a gas to be detected. To better apply tunable diode laser absorption spectroscopy-wavelength modulation spectroscopy to the apparatus of the disclosure, a curved groove structure is further proposed, and this structure can limit a ping-pong effect of a steel ball when vibration of KHz level from the tunable diode laser absorption spectroscopy-wavelength modulation spectroscopy appears on the piezoelectric ceramic actuator. The tunable external-cavity diode laser based on a narrow-band interference filter designed by the disclosure accurately senses the types and concentrations of various gases.