The generation of femtosecond optical vortex beams with megawatt powers directly from a fiber based Mamyshev oscillator

Abstract

Numerous approaches have been developed to generate optical vortex beams carrying orbital angular momentum (OAM) over the past decades, but the direct intracavity generation of such beams with practical output powers in the femtosecond regime still remains a challenge. Here we propose and experimentally demonstrate the efficient generation of high-peak-power femtosecond optical vortex pulses from a Mamyshev oscillator (MO) based on few-mode polarization-maintaining (PM) ytterbium-doped fibers (YDFs). By employing an appropriate intracavity transverse spatial mode selection technique, ultrafast pulses carrying OAM with selectable topological charge of l = ±1 are successfully generated with an average output power of ∼5.72 W at ∼24.35 MHz repetition rate, corresponding to a single pulse energy of ∼235 nJ. The chirped pulses can be compressed to ∼76 fs outside the cavity, leading to a pulse peak power of ∼2.2 MW. To the best of our knowledge, this is by far the highest pulse energy and peak power for optical vortex pulses ever generated directly from a fiber oscillator. This unprecedented level of performance should be of great interest for a variety of applications including materials processing and imaging.

Recent advance of high-energy ultrafast mode-locked oscillators based on Mamyshev mechanism with different starting modes

“…7 The Mamyshev oscillator of femtosecond optical vortex beams. 51 Today, the peak power of Mamyshev oscillator has reached a megawatt level, which is comparable to that of commercial solid-state lasers. Table 1 gives typical output characteristics of some Mamyshev oscillators with seed source injection start mode in recent years.…”

“…The ultrafast pulses carrying OAM were successfully generated with an average output power of 5.72 W at 24.35-MHz repetition rate, corresponding to a single pulse energy of 235 nJ. The chirped pulses could be compressed to 76 fs outside the cavity with a pulse peak power of 2.2 MW 51 . Mamyshev oscillator is further developing toward a variety of pulse forms and different transverse modes.…”

“…The chirped pulses could be compressed to 76 fs outside the cavity with a pulse peak power of 2.2 MW. 51 Mamyshev oscillator is further developing toward a variety of pulse forms and different transverse modes.…”

Twisted Light in a Single‐Crystal Fiber: Toward Undistorted Femtosecond Vortex Amplification

“…[12,13] Apparently most of these applications rely on the high average/peak power of the femtosecond optical vortices. Current methods used for generation of femtosecond optical vortices are mainly based on special phase elements to imprint an OAM onto a pre-existing fundamental (TEM 00 ) mode beam, [14][15][16][17][18] or alternatively direct generation from mode-locked bulk [19,20] or fiber [21] laser sources containing an intracavity mode selection element followed by external transformation. Unfortunately, limitations of the power handling capability due to pulse instabilities, beam distortion, and the phase elements themselves, seriously restrict the power scalability of these approaches.…”

Wavelength-Tunable and OAM-Switchable Ultrafast Fiber Laser Enabled by Intracavity Polarization Control

“…However, these lasers are mainly working in the continuous wave mode, which is not favorable for applications that need vortex beam with high peak power and short pulse duration, for example, material processing [19,20], electron accelerations [21] and nonlinear optical microscopies [22]. Recently, research groups have built mode-locked OAM fiber laser using s-waveplate [23], q-plate [24][25][26], acousto-optic mode converter (AOMC) [27], offset splicing structure (OSS) with a two-mode fiber Bragg grating [28]and nonlinear loop mirror (NOLM) device [29]. In those realizations, the center wavelength of the OAM laser cannot be freely tuned.…”