Powerful 1-µm 1-GHz optical frequency comb.

Area of Science:

• Laser physics
• Nonlinear optics
• Frequency metrology

Background:

• Optical frequency combs are crucial for precise frequency measurements.
• Kerr-lens mode-locking (KLM) is a powerful technique for generating ultrashort laser pulses.
• Developing compact and robust KLM sources with high repetition rates is an ongoing challenge.

Purpose of the Study:

• To demonstrate a self-referenced optical frequency comb based on KLM in ytterbium-doped CALGO.
• To achieve a high repetition rate (GHz-level) for the generated optical frequency comb.
• To characterize the power, pulse duration, timing jitter, and phase noise of the comb.

Main Methods:

• Utilized Kerr-lens mode-locking in a ytterbium-doped Calcium Lithium Germanate (Yb:CALGO) crystal.
• Employed a multi-mode pumping scheme to achieve stable mode-locking at a high repetition rate.
• Characterized the output using power meters, autocorrelators, and frequency domain noise analysis.

Main Results:

• Generated a robust optical frequency comb with 3.5 W average power and 44 fs pulse duration.
• Achieved a 1 GHz repetition rate with residual root-mean-square timing jitter of 146 fs.
• Measured residual integrated phase noise of the carrier-envelope offset frequency at 107 mrad (1 Hz to 10 MHz span).
• Obtained 2.7 W of stabilized average power suitable for direct application.

Conclusions:

• Successfully demonstrated the first multi-mode pumped Kerr-lens mode-locked optical frequency comb at a gigahertz repetition rate.
• The developed Yb:CALGO laser source offers a robust and high-performance platform for various applications requiring precise frequency standards.
• The high average power and stabilized output pave the way for practical implementation in fields like spectroscopy and optical communications.