OH sensor based on ultraviolet, continuous-wave absorption spectroscopy utilizing a frequency-quadrupled,...

Area of Science:

• Spectroscopy
• Laser Physics
• Atmospheric Chemistry

Background:

• The hydroxyl radical (OH) is a key species in atmospheric chemistry and combustion processes.
• Accurate measurement of OH concentration is crucial for understanding these phenomena.
• Existing methods for OH detection face limitations in sensitivity or accessibility.

Purpose of the Study:

• To develop a robust and tunable all-solid-state continuous-wave (cw) laser system.
• To enable sensitive optical absorption measurements of the OH radical in the ultraviolet (UV) spectral region.
• To characterize the performance of the developed laser system for OH spectroscopy.

Main Methods:

• Utilized a tunable external-cavity diode laser operating at 1064 nm.
• Employed a Neodymium-doped (Nd) double-clad fiber amplifier to boost laser power.
• Implemented frequency doubling using a periodically poled lithium niobate (PPLN) crystal.
• Achieved frequency quadrupling via a beta-barium borate (BBO) crystal to reach UV wavelengths.
• Performed optical absorption measurements on the OH radical's (2, 0) band of the A(2)Σ⁺-X(2)Π electronic transition.

Main Results:

• Successfully developed and operated an all-solid-state cw laser system.
• Generated tunable UV radiation suitable for OH radical spectroscopy.
• Demonstrated the system's capability to measure OH absorption in the specified spectral band.
• Characterized the performance and design of the laser system.

Conclusions:

• The developed all-solid-state laser system is effective for OH radical optical absorption measurements.
• This system offers a promising tool for spectroscopic studies of OH in various applications.
• The advancements in laser technology pave the way for improved atmospheric and combustion diagnostics.