Tunable 30 GHz laser frequency comb for astronomical spectrograph characterization and calibration

Area of Science:

• Astronomy and Astrophysics
• Optical Engineering
• Exoplanet Detection

Background:

• Precision spectroscopy, particularly the Doppler radial velocity (RV) technique, is crucial for discovering Earth-like exoplanets.
• Subpixel quantum efficiency (QE) variations in spectrograph detectors limit RV precision to 10⁻¹⁰ level.
• Accurate calibration requires mapping the point spread function (PSF) across the entire spectrograph bandwidth.

Purpose of the Study:

• To develop a tunable laser frequency comb for precise calibration of astronomical spectrographs.
• To quantify and correct detector artifacts affecting RV measurements.
• To enhance the accuracy of exoplanet detection using the RV method.

Main Methods:

• Demonstrated a tunable 30 GHz electro-optic comb with controlled laser frequency and mode spacing.
• Utilized supercontinuum generation for broadband frequency access (700-1300 nm).
• Developed techniques applicable to laser frequency combs (LFCs) for spectrograph calibration.

Main Results:

• Achieved full and deterministic tunability of the electro-optic comb.
• Enabled access to any optical frequency within the 700-1300 nm range.
• Provided a method to map the PSF and correct detector artifacts.

Conclusions:

• The developed tunable comb addresses a key instrumental limitation in high-precision RV measurements.
• This technique is vital for improving the accuracy of exoplanet detection, especially for Earth-like planets.
• The methodology is adaptable for various precision spectrographs and LFC applications.