For the first time, Fluorescent proteins from jellyfish are used to create a laser. These lasers could open up research avenues in quantum physics and optical computing. It is more effective and compact than conventional ones.
Traditional polariton lasers use inorganic semiconductors. They need to be cool in incredibly low temperatures. Latest designs depend on organic electronics materials.
Generally, it is used inside organic light-emitting diode (OLED) displays. They operate at room temperature but require being driven by picosecond (one-trillionth of a second) pulses of light. According to scientists, this breakthrough represents a major advance in so-called polariton lasers.
By refunctioning the fluorescent proteins, scientists create a polariton laser. The laser operates at room temperature, powered by nanosecond pulses (just billionths of a second). The proteins allow scientists to monitor processes inside cells and have revolutionized biomedical imaging.
Malte Gather said, “Picosecond pulses of a suitable energy are about a thousandfold more difficult to make than nanosecond pulses. Thus it really simplifies making these polariton lasers quite significantly.” ( Gather is a professor in the School of Physics and Astronomy at the University of St. Andrews in Scotland and one of the laser’s inventors.)
“The fluorescent proteins are currently being use as a marker in living cells or living tissue. But now the researchers have started using them as a material. This work shows for the first time that their molecular structure is actually favorable for operation at high brightness as required, for example, for turning them into lasers,” he said.
Scientists genetically engineer E. coli bacteria to produce enhanced green fluorescent protein (eGFP). Then, scientists filled optical microcavities with this protein before exciting them with optical pumping. The nanosecond flashes of light are used to bring the system up to the required energy to create laser light.
Pumping a large amount of energy into the device, primarily after reaching the onset of polariton lasing, leads to conventional lasing. According to Gather, it helps to confirm that the first emission was due to polariton lasing. This is what something other approaches using organic materials have been unable to demonstrate so far.
Through the fact that photons can be amplified by excited atoms in the laser’s gain medium, conventional lasers create their intense beams. This is composed of inorganic materials, such as glasses, crystals, or gallium-based semiconductors.
There is no huge difference between Polariton laser light and conventional laser light. But the physical process that generates it depends on a quantum phenomenon to amplify the light.
Conventional lasers need more than half of the atoms in the gain medium to enter an excited state before laser light is generated. This is not the case in polariton lasers. It means they require less energy to be pumped into the system.
One main advantage of the new approach is that the light-emitting part of the protein molecules is protected within a nanometer-scale cylindrical shell. It prevents them from interfering with each other.
Stéphane Kéna-Cohen said, “This overcomes a major problem that has plagued previous designs. This allows the laser to operate with much longer pump pulses, which are easier to generate and allows for simpler implementations. At the moment, many challenges remain for such lasers to be useful because the [excitation] threshold is so high. But they are a fascinating platform for studying physics that normally occur only at ultralow temperatures.”
Gather said, “The fundamental physics suggests design improvements should eventually allow polariton lasers with considerably lower thresholds than conventional ones. This will allow them to be much more efficient and compact.”
“This makes the new study promising for the field of optical computing. A tiny laser depends on biomaterials could also potentially be insert in the human body for medical applications. In the meantime, they are a useful model for investigating fundamental questions in quantum physics.”
