Four-channel silicon nitride wavelength beam combiners for multi-gas absorption spectroscopy

Area of Science:

• Photonics
• Optical Engineering
• Spectroscopy

Background:

• Laser absorption spectroscopy requires tunable lasers across multiple wavelength bands for trace gas detection.
• Existing methods for combining multiple wavelengths can be complex and bulky.

Purpose of the Study:

• To develop an integrated, on-chip wavelength beam combiner for multi-band laser sources.
• To demonstrate the device's capability in multiplexing different wavelengths for spectroscopy applications.

Main Methods:

• Utilizing silicon nitride Mach-Zehnder interferometers (MZIs) and a modified multimode interferometer (MMI) structure.
• Implementing digital multiplexing of two wavelengths with ~100 nm spacing using MZI.
• Employing a compact modified MMI for multiplexing broader wave bands with several hundred nanometers spacing.

Main Results:

• Achieved multiplexing of light with different wavelength spacings on a single chip.
• Measured low insertion losses of approximately 2.5 dB across all four channels from 1650 nm to 2050 nm.
• Successfully demonstrated tunable diode laser absorption spectroscopy (TDLAS) for multi-gas detection using the developed combiner.

Conclusions:

• The on-chip wavelength beam combiner offers an efficient solution for multi-band laser sources in spectroscopy.
• The device enables compact and versatile multi-gas sensing systems.
• This integrated approach advances the field of laser absorption spectroscopy for trace gas analysis.