[Paper Review] Ultra-broadband, few cycle pulses directly from a Mamyshev fiber oscillator

Chunyang Ma, Ankita Khanolkar+2 more|arXiv (Cornell University)|May 24, 2019

Advanced Fiber Laser Technologies26 references4 citations

TL;DR

This paper presents a novel Mamyshev fiber oscillator that directly generates ultra-broadband, few-cycle pulses (~5 cycles, ~400 nm bandwidth) by leveraging self-similar nonlinear evolution and intrinsic saturable absorption in a gain fiber. The method achieves the shortest pulse width and broadest spectrum reported directly from a fiber laser, overcoming traditional gain bandwidth limitations through nonlinear dynamics as a stable attractor.

ABSTRACT

While the performance of mode-locked fiber lasers has been improved significantly, the limited gain bandwidth restricts them to generate ultrashort pulses approaching a few cycles or even shorter. Here we present a novel method to achieve few cycle pulses (~5 cycles) with ultra-broad spectrum (~400 nm). To our best knowledge, this is the shortest pulse width and broadest spectrum directly generated from fiber lasers. It is noteworthy that a dramatic ultrashort pulse evolution can be stabilized in a laser oscillator by the unique nonlinear processes of a self-similar evolution as a nonlinear attractor in the gain fiber and a perfect saturable absorber action of the Mamyshev oscillator.

Motivation & Objective

• Overcome the gain bandwidth limitation in mode-locked fiber lasers that restricts ultrashort pulse generation.
• Develop a method to directly generate few-cycle pulses with ultra-broad spectral bandwidth from a fiber oscillator.
• Stabilize dramatic ultrashort pulse evolution using intrinsic nonlinear dynamics and saturable absorption in a single fiber cavity.
• Demonstrate a self-sustaining mechanism for few-cycle pulse generation without external compression.
• Achieve the shortest pulse width and broadest spectrum reported from a fiber laser oscillator.

Proposed method

• Utilize a Mamyshev oscillator configuration where self-phase modulation and anomalous dispersion drive self-similar nonlinear evolution in the gain fiber.
• Leverage the inherent saturable absorber behavior of the Mamyshev oscillator to stabilize ultrashort pulse formation.
• Employ a nonlinear fiber with tailored dispersion and nonlinearity to support self-similar pulse evolution as a nonlinear attractor.
• Design the laser cavity to support spectral broadening to ~400 nm bandwidth through nonlinear phase accumulation.
• Optimize pump power and fiber length to balance nonlinear compression and gain saturation for stable few-cycle pulse emission.
• Use spectral and autocorrelation measurements to confirm pulse duration and bandwidth directly from the oscillator output.

Experimental results

Research questions

• RQ1 Can self-similar nonlinear evolution in a fiber oscillator generate few-cycle pulses with ultra-broad spectral bandwidth?
• RQ2 Can the intrinsic saturable absorption of a Mamyshev oscillator stabilize ultrashort pulse formation without external components?
• RQ3 What is the shortest pulse width and broadest spectrum achievable directly from a fiber laser oscillator?
• RQ4 How does the interplay between nonlinearity and dispersion enable stable few-cycle pulse generation in a single cavity?
• RQ5 Can the self-similar evolution dynamics serve as a nonlinear attractor to ensure robust pulse formation?

Key findings

• The system directly generates few-cycle pulses with a duration of approximately 5 cycles, representing the shortest pulse width reported from a fiber laser oscillator.
• The output spectrum spans ~400 nm, the broadest bandwidth achieved directly from a fiber oscillator to date.
• The pulse formation is stabilized by the self-similar nonlinear evolution as a nonlinear attractor in the gain fiber.
• The Mamyshev oscillator provides intrinsic saturable absorption, eliminating the need for external nonlinear or absorptive elements.
• The method achieves direct generation of few-cycle pulses without external compression, enabling compact and stable source design.
• The results demonstrate a significant advancement in fiber laser technology for generating ultrashort, broadband pulses.