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Phosphorene is a two-dimensional material, so it is usually constructed of layers of single atoms. It is an allotrope of phosphorus that was first worked within its single-layer form by several research groups in 2014. Before this, a layered semiconducting allotrope of phosphorus, known as black phosphorus, gained attention for its exhibition of high carrier mobility.
Black phosphorus was first synthesized in the 1960s, and many teams have tested the potential of its unique properties, leading to the synthesis of single-layer phosphorene, a monolayer of black phosphorus. Like black phosphorus, phosphorene gained the attention of research groups, who, for the past 5 years have explored its potential in the field of optoelectronics. This is due to its unique characteristics, such as its highly tunable bandgap, high carrier mobility, and anisotropic photoelectronic properties.
These characteristics make the material interesting to scientists creating ultrafast lasers. Scientists can adjust the thickness of phosphorene to allow them to tune the bandgap, which is beneficial to the development of ultrafast lasers.
Limitations of Current Ultrafast Lasers
Scientists have outlined the need for alternative materials to create ultrafast lasers. These materials must be developed with the capabilities of producing the optimum nonlinear properties so they can function as saturable absorbers in ultrafast lasers.
Current materials used for saturable absorbers are falling behind requirements to create optimum ultrafast lasers. Existing materials, like nonlinear polarization evolution (NPE) and semiconductor saturable absorber mirrors (SESAMs) can create ultrafast optical pulses, however, they have a narrow operating bandwidth, as well as the limitation of being difficult to manufacture. Therefore, scientists have begun to explore alternative materials, and given phosphorene’s unique properties, it has become a key focus.
Phosphorene’s Tunable Bandgap
The main advantage of phosphorene is that its bandgap can be adjusted by altering the thickness of the layers of black phosphorus. This bandgap can be controlled to be between 0.3 eV and 2 eV. Being able to control the bandgap impacts the field-effect mobility and current on/off ratio, both vital components of optoelectronic devices.
Optoelectronic devices convert electrical energy into light and light into energy through semiconductors and require ultrafast lasers to function. The highly tunable bandgap of phosphorene allows for the development of these ultrafast lasers. Researchers have demonstrated that the material holds nonlinear optical properties, making it suitable as a broadband saturable absorber.
Research into photonics benefits from this as it sits in-between graphene’s zero bandgap and the large bandgap of transition-metal dichalcogenides. Because of phosphorene’s nonlinear, optically saturable absorption, it can be used to create the optical fibers that are utilized in ultrafast lasers.
Advances in Quantum
In 2017, a Chinese research team published a paper in the journal Scientific Reports, describing how they fabricated ultra-small phosphorene quantum dots (PQDs) with properties that will enable ultrafast fiber lasers. The team created the PQDs using a liquid exfoliation method, resulting in a device with ultrafast nonlinear saturable absorption property, and an optical modulation depth of 8.1% at the telecommunication band.
The future of ultrafast photonic technologies is predicted to benefit greatly from this advancement in two-dimensional nanomaterial technology.
The Future for Phosphorene
Work with phosphorene will likely continue, it is only in its beginnings given that the material was only synthesized a few years ago. So far, research has demonstrated phosphorene’s use in the development of ultrafast lasers due to the benefit of its highly tunable bandgap. Soon, we can expect to see phosphorene become an established material used in ultrafast lasers.
References and Further Reading