Megawatt pulses from an all-fiber and self-starting femtosecond oscillator

Henry Haig, Pavel Sidorenko, Robert Thorne, and Frank Wise, “Megawatt pulses from an all-fiber and self-starting femtosecond oscillator,” Opt. Lett. 47, 762-765 (2022)

Mamyshev Oscillators are a relatively new type of fiber laser with extraordinary pulse performance— these lasers generate the highest peak-power pulses from femtosecond fiber lasers by over a factor of 10. Mamyshev oscillators should be excellent tools for applications like microscopy and micromachining, but there’s a catch: most Mamyshev oscillators are impractical for applications outside laser labs since they need another mode-locked laser to start and are relatively complicated and expensive. In this project we designed a Mamyshev oscillator that solves these practical problems and comes in a totally fiber-integrated, ready-for-applications format. The laser generates pulses on par with those from much more complex Mamyshev oscillators, and remarkably starts with some simple electronics rather than an additional mode-locked laser. The pulse energy (80 nJ) and duration (40 fs) advances the state-of-the-art for all-fiber, self-starting lasers by 20x, and should be scalable by another factor of 5 with large-mode-area fiber.

Starting dynamics of a linear-cavity femtosecond Mamyshev oscillator

Yi-Hao Chen, Pavel Sidorenko, Robert Thorne, Frank Wise “Starting dynamics of a linear-cavity femtosecond Mamyshev oscillator,” J. Opt. Soc. Am. B, 38, 743-748 (2021) 

This paper is chosen as Spotlight on Optics.

Mamyshev oscillator is a laser that not only generates strong pulses but is also capable of maintaining environmental stability. However, starting becomes a challenge due to the suppression of noise from continuous-wave (CW) lasing. Solutions to starting are to start with an external seed pulse, overlapped filter passbands to allow CW lasing, or self-seeding with a NPE starting arm described by Pavel et al. Here we proposed another solution to starting with pump modulation. It requires no mechanical flipping such as self-seeding and is demonstrated with full electronic control (Please watch the demonstration video here). Furthermore, it is demonstrated to reach a higher pulse energy by later increasing the filter separation. The laser is found to start reliably with pump modulation of a high repetition rate (>70 kHz) due to the emergence of a modulated mode-locked state. Besides, we found that damage from SBS constantly occurred in a linear cavity such that adding Faraday rotators is required.