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Spectroscopic gas detection using a Bragg grating - stabilized external cavity laser, custom written in planar
Optics Express
|November 6, 2019
Summary
We developed a new tunable diode laser spectroscopy (TDLS) laser using a silica-on-silicon chip with a Bragg grating. This compact, stable laser achieves high performance for methane detection.
Area of Science:
- Photonics and Spectroscopic Instrumentation
- Integrated Optics and Photonics
- Gas Sensing Technologies
Background:
- Tunable diode laser spectroscopy (TDLS) requires stable, narrow-linewidth lasers for accurate gas detection.
- Traditional external cavity lasers can be bulky and mechanically unstable.
- Integrated photonic platforms offer potential for miniaturized and robust laser solutions.
Purpose of the Study:
- To develop and characterize a novel external cavity Bragg grating stabilized laser on a silica-on-silicon platform.
- To evaluate the laser's suitability for methane (CH4) spectroscopic measurements.
- To demonstrate a compact and stable laser source for gas sensing applications.
Main Methods:
- Design and fabrication of a silica-on-silicon integrated laser incorporating a custom Bragg grating.
- Characterization of a prototype singlemode laser operating at 1651 nm.
- Performance evaluation using a 25 cm single-pass cell for methane detection.
Main Results:
- Achieved mode hop-free tuning of 0.13 nm at frequencies up to 10 kHz.
- Demonstrated a single-point limit of detection of 8.3 × 10⁻⁵ AU for TDLS.
- Obtained a side-mode suppression ratio of -40 dB and RIN <-150 dB/Hz, indicating high stability.
Conclusions:
- The developed laser offers performance comparable to standard distributed feedback lasers but with enhanced stability and compactness.
- The silica-on-silicon platform enables potential low-volume manufacturing of custom lasers for gas detection.
- This technology presents a promising alternative to conventional, larger external cavity laser systems.
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