All-passive phase locking of a compact Er:fiber laser system.

Area of Science:

• Optics and Photonics
• Laser Physics
• Fiber Optics Technology

Background:

• Femtosecond lasers are crucial for precision measurements and nonlinear optics.
• Controlling the carrier-envelope offset frequency (f_ceo) is essential for frequency comb generation.
• Erbium-doped (Er:fiber) fiber lasers offer compact and robust solutions for ultrafast science.

Purpose of the Study:

• To introduce a passively phase-locked laser source utilizing compact femtosecond Er:fiber technology.
• To demonstrate a method for achieving zero carrier-envelope offset frequency.
• To achieve a broadband output with excellent phase stability.

Main Methods:

• Utilizing compact femtosecond Er:fiber laser technology.
• Employing difference frequency generation between a 2 µm soliton and an 860 nm dispersive wave in a highly nonlinear fiber.
• Seeding a second Er:fiber amplifier to boost pulse energy and maintain short pulse duration.
• Characterizing phase stability using f-to-2f spectral interferometry.

Main Results:

• A passively phase-locked laser source with zero carrier-envelope offset frequency was successfully demonstrated.
• Broadband output centered at 1.55 µm was achieved through nonlinear spectral manipulation.
• Amplified pulse energy reached 8 nJ with a pulse duration of 125 fs.
• Excellent phase stability was confirmed via f-to-2f spectral interferometry.

Conclusions:

• The developed laser source provides a compact and stable platform for applications requiring precise frequency control.
• The demonstrated method for achieving zero f_ceo is effective for generating broadband, phase-stable femtosecond pulses.
• This technology holds promise for advancements in optical metrology, spectroscopy, and nonlinear optics.