A tunable rare-earth laser source that emits visible light
Opportunity
From LASIK eye surgery to LIDAR remote sensing, lasers have become ubiquitous in manufacturing, medicine and other fields over the past few decades. Lasers produce their beams when energy pumped into a laser cavity excites a reactive material known as the gain medium. As the gain medium’s atoms return to their ground state, they release photons in the process.
Although most lasers only produce a beam in a single wavelength, there is a growing demand for tunable lasers that can switch between wavelengths—representing a much more flexible choice compared to conventional lasers. However, it has proven difficult to easily switch among different wavelengths with current tunable lasers. Accordingly, such lasers often require highly specialised manpower to ensure that the light hits the right target.
Available tunable lasers also feature configurations where light propagates through open air, making the beam’s alignment and performance dependent on environmental conditions. When factoring in these lasers’ bulkiness and cost, it is apparent that there is a need to develop a cost-effective, tunable laser that bypasses all these current limitations.
Technology
This invention describes a tunable laser device comprised of optical fibres and the use of mechanical splicing to connect these fibres for minimal loss of propagated light. Mechanical splicing create a closed loop called a ring cavity. When light travels between mechanically spliced fibres, light propagation losses are as low as 0.01 dB—eliminating the misalignment caused by open-air configurations. The end result is a direct and effective pathway for generating laser light.
By using a Praseodymium (Pr3+) doped fluoride fibre as the gain medium, the resulting laser is also capable of simultaneously generating visible laser light in a wide range of wavelengths. Compared to lasers that use gas or solid materials, rare-earth gain mediums like Pr3+ are more physically flexible and energetically stable. Hence, the Pr3+ fluoride fibre is capable of emitting laser light at blue, green, yellow, orange, red, and infrared wavelengths. ind
In addition, thanks to a component called the Fibre Bragg Grating that acts as a mirror, users can modify the output wavelength of the device during operation—overcoming the tunability issues associated with other lasers. By forming the laser cavity entirely using optical fibres, the disclosed laser source is a promising means for creating simple, yet fully customised lasers with large tunability for different applications.
Design of the laser cavity configuration. The device's fibre components are depicted in the schematic, including the: pump-signal combiner, fluoride fiber, output coupler mirror, optical circulator and Fibre Bragg Grating.
Download
