A sharper focus for plasmonic lasers

Lasers are found in all shapes, sizes and colors. Arkansas gas tax They can be made of gases (gas lasers) or based on solid materials (solid-state lasers). Electricity voltage in india They can emit light of different colors (or wavelengths or frequencies), from X-rays (short wavelengths) to visible to far-infrared (long wavelengths). Gas news They can be as big as a building (free-electron lasers) or as small as a laser pointer (semiconductor diode lasers).

In the past decade, researchers have attempted to miniaturize photonic technologies for dense integration onto tiny semiconductor chips. Elektricity club To that end there is intense activity in developing even smaller nanolasers, of which plasmonic lasers are the tiniest.

The plasmonic laser, says Sushil Kumar, an associate professor of electrical and computer engineering, uses metal films or nanoparticles to confine light energy inside the cavity from which laser light is generated. Electricity electricity schoolhouse rock By storing light energy inside the cavity through a combination of electron oscillations in the integrated metal films or nanoparticles, plasmonic lasers utilize surface-plasmon-polaritons (SPPs) to store energy in dimensions that can be made smaller than the wavelength of light that they generate.

This unique ability of plasmonic lasers makes them attractive for potential applications in integrated (on-chip) optics, for transporting large swathes of data on-chip and between neighboring chips, and for ultrafast digital information processing.

Several problems need to be solved, however, before plasmonic lasers can be widely used. Geothermal electricity how it works One of the main issues, says Kumar, is the difficulty of extracting light from the cavity of a plasmonic laser. 2 chainz smoking on that gas The lasers are also extremely poor emitters of light, and whatever light does come out is highly divergent rather than focused, which severely limits their usefulness.

While most plasmonic lasers emit visible or near-infrared radiation, Kumar’s group develops plasmonic lasers that emit long-wavelength terahertz radiation, which are also known as terahertz quantum-cascade lasers, or QCLs. Industrial electricity prices by state As the brightest solid-state sources of terahertz radiation, says Kumar, QCLs are uniquely poised to find applications in biology and medicine for sensing and spectroscopy of molecular species, in security screening for remote detection of packaged explosives and other illicit materials, and in astrophysics and atmospheric science.

Kumar and his group have demonstrated that it is possible to induce plasmonic lasers to emit a narrow beam of light by adapting a technique called distributed feedback. Electricity production in chad They have experimentally implemented a scheme for terahertz plasmonic lasers that emit radiation at extremely long wavelengths (approximately 100 microns). Electricity laws uk The light energy in their laser is confined inside a cavity sandwiched between two metallic plates separated by a distance of 10 microns. Electricity dance moms episode Using a box-shaped cavity measuring 10 microns by 100 microns by 1,400 microns (1.4 millimeters), the group produced a terahertz laser with a beam divergence angle of just 4 degrees by 4 degrees, the narrowest divergence yet achieved for such terahertz lasers.

Kumar, who has conducted four years of experimental and theoretical research on the project, described the results in an article published today in Optica, the journal of the Optical Society of America. Save electricity images for drawing “Terahertz plasmonic laser radiating in an ultra-narrow beam” was written by Chongzhao Wu, a Ph.D. Gas water heater reviews 2012 candidate in electrical engineering, and coauthored with Sudeep Khanal, also a Ph.D. Gaslighting candidate in electrical engineering, and John L. Gas and water socialism Reno of the Center of Integrated Nanotechnologies at Sandia National Laboratories in New Mexico.

Distributed feedback (DFB) in lasers was introduced in early 1970s, says Kumar, when scientists learned that implementing periodicity (a patterned structure) enabled lasers to emit light at just one wavelength. Grade 9 electricity worksheets The periodicity in the laser cavity provides feedback for sustained laser oscillations in the cavity by the mechanism of Bragg diffraction.

“There are two main reasons for giving lasers a periodic structure,” says Kumar. Gas station near me “The first is to improve spectral selectivity. Gas bloating nausea A laser can emit light in several closely spaced wavelengths, or colors. B games play online But a laser with a periodic structure can be forced to emit light at just one wavelength by the mechanism of spectral filtering. Grade 9 electricity unit test Such a spectrally pure, single-mode laser is often indispensable for many applications.

In this illustration of a terahertz plasmonic laser, the laser cavity is enclosed between two metal films (with periodic slits on the top film). T gastrobar el tenedor The colors represent coherent SPP light waves. Electricity drinking game One wave is confined inside the 10-micron-thick cavity. Power usage estimator The other, with a large spatial extent, is located on top of the cavity. Electricity bill payment hyderabad Credit: Sushil Kumar

“A periodic structure can also enhance the quality of the laser beam by channeling light intensely into a tight spot. Electricity physics problems Such narrow beam lasers can deliver light energy to a location where it is needed most. Gas 89 They can shine for long distances, and are easier to manipulate and re-direct at a desired location using small optical components.”

Many DFB schemes have been developed for different types of lasers. Electricity in salt water Because plasmonic lasers are relatively new, research to improve them using periodic photonic structures is still in its early stages.

Kumar describes his DFB scheme in the terminology of a microwave engineering principle called the phased-array antenna. O gosh corpus christi These antennas are used to achieve high directivity (narrow beam) in radar and satellite communications. T gastrobar Phased arrays are also implemented in “microstrip transmission lines” that channel microwave signals onto printed circuit boards using metal films.

“Our technique allows a plasmonic laser to radiate in a narrow beam, very much like a phased-array antenna,” says Kumar. Gas 101 His group implemented DFB in the laser by making periodic slits or “gratings” in one of the metal claddings that encase the laser cavity. Gas in stomach The laser’s unique ability to emit a monochromatic, focused light beam stems from the degree of periodicity.

“The period we choose depends on the desired wavelength of light from the laser, the refractive index of the cavity medium, and the refractive index of the surrounding medium,” says Kumar.

The group’s DFB technique has two unique aspects. Year 6 electricity unit The chosen periodicity is the most important technical contribution and, says Kumar, is distinctly different from previously established DFB design rules for solid-state lasers.

Second, the periodicity establishes an intense SPP wave which “hangs” in the surrounding medium of the laser’s cavity while remaining tied to its metal cladding, and which propagates in tandem with another SPP wave inside the cavity.

“All plasmonic lasers have SPPs inside their cavities,” says Kumar. Gas hydrates ppt “Our laser also generates SPPs in the air, or any other medium that may surround the laser. Electricity and magnetism study guide answers This is something unique which cannot be found in any other laser yet demonstrated.

“The large size of the SPP wave in the surrounding medium leads to a highly directive (narrow) radiation pattern from the plasmonic laser. Gas bubbles in colon This derives from the Fraunhofer diffraction formula in optics, which says the light-field distribution far from a light source (far-field) is the Fourier transform of the light-field distribution at the source (near-field). Electricity transformer near house Effectively, when the near field is narrow, the far field is broad, and vice-versa.

Kumar and Wu have filed a patent application on their invention, which he says could help plasmonic lasers, especially terahertz QCLs with narrow beams, find commercial applications.

“There is a very strong interest in security spectrometry,” the researchers wrote in an abstract for the recent TechConnect 2016 World Innovation Conference, where they won a TechConnect National Innovation Award. Ogasco abu dhabi “Approximately 80 to 95 percent of explosives, and all commonly used ones, have unique and identifiable terahertz signatures.”

Kumar’s group fabricates lasers in the cleanroom of Lehigh’s Center for Photonics and Nanoelectronics. Speedy q gas station They grow their semiconductor material using molecular beam epitaxy through a collaboration with Reno. Electricity and water Kumar’s project was supported by the National Science Foundation (NSF) from 2011-14. Gas x dosage pregnancy Kumar also received the NSF CAREER Award in 2014 to design the semiconductor material that constitutes the terahertz laser cavities. Grade 9 electricity questions That material is based on alternating layers of gallium-arsenide and aluminum gallium-arsenide.

Kumar recently received another NSF award to improve output from terahertz plasmonic lasers so they emit up to 100 milliwatts of optical power while holding the angular divergence of the laser beam to less than 5 degrees. Gas constant in atm The group proposes to improve radiative efficiencies by “phase-locking” multiple laser cavities together, so they can operate in tandem and deliver brighter intensities of laser light at the desired location.