Two-photon absorption spectrometers for near infrared

Area of Science:

• Optics and Photonics
• Spectroscopy
• Materials Science

Background:

• Femtosecond pulse characterization is crucial for advanced optical applications.
• Existing spectrometers can be expensive and complex.
• Silicon-based Charge-Coupled Device (Si-CCD) sensors offer potential for cost-effective optical measurements.

Purpose of the Study:

• To develop and evaluate a cost-effective spectrometer for femtosecond pulse characterization in the Near Infrared (NIR) region.
• To investigate the performance of a Silicon-based Charge-Coupled Device (Si-CCD) sensor in two different spectrometer configurations.
• To analyze the nonlinear response of the Si-CCD sensor for spectroscopic applications.

Main Methods:

• Utilized a Silicon-based Charge-Coupled Device (Si-CCD) sensor as the core detection element.
• Implemented two spectrometer configurations: two-Fourier and Czerny-Turner setups.
• Employed femtosecond lasers (Optical Parametric Oscillator and Erbium-Doped Fiber Amplifier) for testing in the 1100-1700 nm range.
• Leveraged the Two-Photon Absorption (TPA) effect within the Si-CCD for nonlinear spectral detection.

Main Results:

• Achieved a spectral resolution of 0.6 ± 0.1 nm.
• Determined a threshold peak intensity of 2×10^6 W/cm^2 for nonlinear operation.
• Characterized the nonlinear response as a function of wavelength and analyzed saturation effects.

Conclusions:

• The Si-CCD sensor demonstrates viability as a cost-effective spectrometer for NIR femtosecond pulse characterization.
• The Two-Photon Absorption mechanism in Si-CCD enables nonlinear spectroscopy with good resolution.
• Understanding nonlinear response and saturation is key for optimizing spectrometer performance.