Tunable high-power femtosecond yellow laser has biomedical uses

Sept. 11, 2020
The yellow-orange spectral range is highly absorbed by hemoglobin in the blood, making lasers with these wavelengths particularly useful for biomedical applications.

Researchers at the Physical Research Laboratory (Ahmedabad, India) have developed an ultrafast high-power yellow laser with utility in biomedical applications. The tunable laser exhibits excellent beam quality and helps fill the need for a practical yellow light source emitting ultrafast pulses of light.

"The yellow-orange spectral range is highly absorbed by hemoglobin in the blood, making lasers with these wavelengths particularly useful for biomedical applications, dermatology treatments, and eye surgery," says research team member Anirban Ghosh from the Photonic Sciences Lab at the Physical Research Laboratory. "A femtosecond, tunable yellow laser source might one day offer medical treatments that produce less thermal damage and are more selective." 

In a paper published in the journal Optics Letters, the research team led by Goutam K. Samanta describe how they used an optical phenomenon known as nonlinear frequency conversion to convert mid-infrared (mid-IR) laser light into yellow light that can be tuned from 570 nm to 596 nm. 

"We demonstrate a robust, high-power, ultrafast, tunable yellow radiation in a rather simple experimental configuration," says Ghosh. "In addition to biomedical applications, this is a sought-after wavelength range for full-color video projection and could be used for a variety of spectral applications." 

Although studies have shown that lasers emitting in the yellow spectral range are optimal for various medical treatments, such wavelengths are usually created using bulky and inefficient copper vapor lasers, dye lasers, and optical parametric oscillators. These sources have been used successfully for various applications, but they suffer from one or more drawbacks such as low average power, lack of good spatial beam profile, limited or no wavelength tunability, and broad output pulses. 

"Femtosecond lasers are important for many applications because they emit a large number of photons in a short period to provide a very high intensity and extremely high precision without causing any thermal damage," says Ghosh. "However, there is no commercially available femtosecond yellow laser that can provide all the desired parameters needed for the applications that would benefit from this wavelength range." 

To address these limitations in a single experimental configuration, the researchers used a recently developed ultrafast solid-state Cr2+:ZnS laser emitting in the mid-infrared range along with a two-stage frequency-doubling process. Frequency doubling an ultrafast laser is not an easy process and requires identifying the right crystal to produce a quality laser output with the desired properties. 

"We frequency-doubled the ultrafast mid-IR laser with a peak wavelength at 2360 nm in two different nonlinear crystals and used simple optical components available in any standard optics laboratory to achieve a high-power, tunable, ultrafast yellow laser source," says Ghosh. "As a byproduct, our source provides tunable ultrafast near-IR radiation with substantial average power useful for various fields, including spectroscopy, material processing and imaging." 

Tests of the new laser showed that it can provide a maximum output average power over 1 W with 130 fs pulses at a repetition rate of 80 MHz with an outstanding spatial beam profile. The researchers also observed excellent power stability over a long duration. 

The researchers plan to further improve the laser's pulse duration, efficiency, and compactness. They are also working to optimize the laser so that it can operate at room temperature to make it more practical for long-term use. 

Full details of the work appear in the journal Optics Letters

Source: OSA press release via EurekAlert! – September 9, 2020

About the Author

BioOptics World Editors

We edited the content of this article, which was contributed by outside sources, to fit our style and substance requirements. (Editor’s Note: BioOptics World has folded as a brand and is now part of Laser Focus World, effective in 2022.)

Sponsored Recommendations

Request a quote: Micro 3D Printed Part or microArch micro-precision 3D printers

April 11, 2024
See the results for yourself! We'll print a benchmark part so that you can assess our quality. Just send us your file and we'll get to work.

Request a free Micro 3D Printed sample part

April 11, 2024
The best way to understand the part quality we can achieve is by seeing it first-hand. Request a free 3D printed high-precision sample part.

How to Tune Servo Systems: The Basics

April 10, 2024
Learn how to tune a servo system using frequency-based tools to meet system specifications by watching our webinar!

Precision Motion Control for Sample Manipulation in Ultra-High Resolution Tomography

April 10, 2024
Learn the critical items that designers and engineers must consider when attempting to achieve reliable ultra-high resolution tomography results here!

Voice your opinion!

To join the conversation, and become an exclusive member of Laser Focus World, create an account today!