Lasers ♦ news digest
constantly energising and emitting synchronised photons, but on average, very few - less than one photon, in fact - stick around between the mirrors.
This average, which scientists calculate indirectly, based on the laser beam’s output power, is just enough to maintain an oscillating electric field to sustain the atoms’ synchronised behaviour. Nearly all photons escape before they have a chance to become scrambled by the mirrors and disrupt the synchronized atoms—thus averting the very effect that causes laser frequency to wobble in a normal laser.
Thompson engineered a system that first traps the atoms in laser light between two mirrors and then uses other low-power lasers to tune the rate at which the atoms switch back and forth between two energy levels.
The atoms emit photons each time their energy level drops. The atoms ordinarily would emit just one photon per second, but their correlated action boosts that rate 10,000-fold - making the light superradiant, Thompson says. This “stimulated emission” meets the definition of a laser (Light Amplification by the Stimulated Emission of Radiation).
“This superradiant laser is really, really dim - about a million times weaker than a laser pointer,” Thompson says. “But it is much brighter than one would expect from the ordinary uncoordinated emissions from individual atoms.”
Thompson’s measurements show that the stability of the laser beam frequency is less than 1/10,000th as sensitive to mirror motion as in a normal optical laser. This result suggests the new approach might be used in the future to improve the best lasers developed at NIST as much as 1,000-fold. Just as important, such lasers might be moved out of the vibration- controlled laboratory environment to be used in real-world applications.
Despite its dim light, the extraordinary stability of the superradiant laser can be transferred by using it as part of a feedback system to “lock” a normal laser’s output. The bright laser, potentially 100 to 1,000 times more stable than today’s best lasers, could then be used in the most advanced atomic clocks to induce the atomic oscillations that are the pendulum ticks of super-accurate clocks.
The added stability allows for a better match to the atoms’ exact frequency, significantly boosting the precision of the clock. The improvement would extend to atomic clock-based technologies such as GPS, optical communications, advanced geodetic surveys and astronomy.
Thompson’s work confirms predictions made several years ago by JILA/NIST Fellow Jun Ye and JILA/CU theorist Murray Holland, who is also a co-author of a new paper, describing this work. Thompson stresses that for the new laser design to achieve its highest potential stability and be of practical use, it will need to be re-created using different atoms, such as strontium, which are better suited for use in advanced atomic clocks.
The research is supported in part by the National Science Foundation, NIST, the Army Research Office and the Defence Advanced Research Projects Agency.
This work is further described in the paper, “ A steady state superradiant laser with fewer than one intracavity photon,” by J.G. Bohnet et al Nature, 484, 78-81 . DOI:10.1038/ nature1092099
Opto Diode releases “super high-power” AlGaAs IR emitter
The first in the series of aluminium gallium arsenide based devices is suited to night vision and other military imaging applications
California based Opto Diode is releasing the first in a new series of super high-power AlGaAs infrared emitters.
The new OD-110L device features an ultra high optical output with a very narrow optical beam, making it ideal for night vision (NV) and other military imaging applications.
The OD-110L is housed in a standard 3-lead, hermetically- sealed TO-39 package to accommodate the compact (0.026” x 0.026”) chip. There are four wire bonds on die corners and all surfaces are gold-plated for added durability.
Typically, the total power output (at 250C) is 110mW and the minimum output is 55mW with a peak emission wavelength of 850nm.
The absolute maximum rating at 250C (case) for power dissipation is 1000mW, with a continuous-forward-current rating set at 500mW. The OD-110L lead-soldering temperature (0.0625” from the case for 10 seconds) is 2600 C.
Storage and operating temperatures range from -400 C to 1000 C, making the devices suitable for harsh environments and for integration into illuminators and markers, and systems utilising NV goggles and cameras.
Emcore to sell VCSEL-based product line assets to SEDU for $17 million
The firm is selling fixed assets, inventory and intellectual property for the VCSEL-based product lines within Emcore’s fibre optics business unit. The transaction will allow the company to invest further in telecom, broadband and specialty photonics products
Emcore is to sell certain assets and transfer certain obligations of its Vertical Cavity Surface Emitting Lasers (VCSEL)-based product lines to Sumitomo Electric Device Innovations USA, Inc. (SEDU).
Subject to closing adjustments, the consideration for this sale will be $17 million in cash.
April/May 2012
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