Scientists at Laval University in Canada have developed the first fiber laser that can generate femtosecond pulses in the visible range of the electromagnetic spectrum. The laser, which can produce ultra-short, bright visible-wavelength pulses, could be widely used in biomedical and materials processing fields.
While the usual equipment for generating visible femtosecond pulses is complex and inefficient, fiber lasers have the advantages of stability, reliability, small footprint, high efficiency, low cost and high brightness, making them a very promising alternative. But so far, such lasers have not been able to directly generate visible light pulses with durations in the femtosecond (10-15 seconds) range.
Research team leader Ryle Ware said they have developed the first femtosecond fiber laser that can operate in the visible range. The laser, based on a lanthanide-doped fluoride fiber that emits red light at 635 nanometers, achieved compressed pulses with a duration of 168 femtoseconds, a peak power of 0.73 kilowatts and a repetition frequency of 137 megahertz. Moreover, they used a commercial blue laser diode as the energy source in the device, making the overall design more robust, compact and cost-effective.
The team notes that if higher energy and power are available in the near future, it could be used in a wide range of applications. Potential applications include high-precision, high-quality biological tissue ablation and two-photon excitation microscopy. In addition, femtosecond laser pulses can also be used to cold ablate materials during processing, which is a cleaner way to make cuts than with longer pulses, given that there is no thermal effect from this process.
Next, the researchers plan to improve the technology by making the device completely monolithic, which means that the individual fiber optic components will be directly interconnected, which will reduce optical losses in the device, increase efficiency, and further improve the reliability, compactness, and robustness of the laser. They are also investigating different ways to increase the laser pulse energy, pulse duration and average power.
