Custom fabrication and mode-locked operation of a femtosecond fiber laser for multiphoton microscopy

Nima Davoudzadeh,Bryan Q Spring,Guillaume Ducourthial

doi:10.1038/s41598-019-40871-5

Abstract

Solid-state femtosecond lasers have stimulated the broad adoption of multiphoton microscopy in the modern laboratory. However, these devices remain costly. Fiber lasers offer promise as a means to inexpensively produce ultrashort pulses of light suitable for nonlinear microscopy in compact, robust and portable devices. Although encouraging, the initial methods reported in the biomedical engineering community to construct home-built femtosecond fiber laser systems overlooked fundamental aspects that compromised performance and misrepresented the significant financial and intellectual investments required to build these devices. Here, we present a practical protocol to fabricate an all-normal-dispersion ytterbium (Yb)-doped femtosecond fiber laser oscillator using commercially-available parts (plus standard optical components and extra-cavity accessories) as well as basic fiber splicing and laser pulse characterization equipment. We also provide a synthesis of established protocols in the laser physics community, but often overlooked in other fields, to verify true versus seemingly (partial or noise-like) mode-locked performance. The approaches described here make custom fabrication of femtosecond fiber lasers more accessible to a wide range of investigators and better represent the investments required for the proper laser design, fabrication and operation.

Highlights

Commercial solid-state femtosecond lasers are central to the development of nonlinear microscopy as well as its applications to biology and medicine
The published pulse spectrum and duration data from this first report[17] indicate that the laser was not operating correctly, as has appeared frequently in the custom fiber laser literature. The performance of these lasers for multiphoton microscopy can be significantly improved with further consideration of fundamental, albeit non-trivial, aspects of the pulse shaping and mode-locking
Fig. 1) was built entirely using readily-available, commercial components (Supplementary Table 1) inspired by all-normal-dispersion (ANDi) dissipative soliton fs fiber laser technology invented by Wise and colleagues[21,22] that has been commercialized by KMLabs into a rugged, compact and portable system

Summary

Introduction

Commercial solid-state femtosecond (fs) lasers are central to the development of nonlinear microscopy as well as its applications to biology and medicine. Outstanding examples of commercial fiber laser technologies include several products offered by KMLabs (4.5 W at 1035 nm), Menlo Systems (0.3 W at 780, 1030, 1040 and 1560 nm) and Calmar Laser (0.5 W at 780, 920 and 1550 nm), where each individual fiber laser generates a single wavelength (sources available online: KMLabs Y-Fi series data sheet; Menlo Systems C-Fiber 780, ELMO, Orange, and YLMO data sheets; and, Calmar Laser Carmel X-series white paper) These fiber-based systems lack the tunability of solid-state lasers but are more economical for applications that require only a specific wavelength. These specifications match those of the commercial solid-state and fiber lasers mentioned above, albeit at a single wavelength

Methods

Results

Conclusion