Visible (400- to 700-nm) chirped-grating-coupled waveguide spectrometer

Area of Science:

• Photonics and Optical Engineering
• Integrated Optics
• Spectroscopy

Background:

• On-chip spectrometers are crucial for miniaturized optical analysis.
• Waveguide-based devices offer compact and efficient spectral measurement solutions.
• Chirped gratings enable wavelength-selective coupling in integrated photonic circuits.

Purpose of the Study:

• To demonstrate an integrable on-chip spectrometer.
• To utilize a transversely-chirped-grating waveguide-coupler for visible spectral range analysis (400-700 nm).
• To achieve high spectral resolution without post-processing.

Main Methods:

• Fabrication of a transversely-chirped-input grating on a SiO2-Si3N4-SiO2 waveguide atop a Si substrate using interferometric lithography.
• Integration of a uniform period grating for out-coupling to a 2048 element CMOS detector array.
• Coupling of incident visible light (400-700 nm) into the waveguide at a fixed angle of incidence (33.5°).

Main Results:

• Demonstration of an on-chip spectrometer operating in the 400-700 nm visible spectral range.
• Achieved spectral resolution of approximately 1.2 nm.
• Wavelength coupling is precisely controlled by local grating period and waveguide structure.

Conclusions:

• The developed on-chip spectrometer is a compact and effective solution for visible spectrum analysis.
• The transversely-chirped-grating waveguide-coupler design enables high-resolution spectral measurements.
• This technology holds promise for various applications requiring miniaturized spectroscopic capabilities.