Recently, researchers at the National Institute of Standards and Technology (NIST) developed an on-chip system that can simultaneously control the direction and focus of multiple laser beams (different wavelengths) and polarization.
NIST researchers designed and built a system-on-a-chip to steer and control the polarization of multiple laser beams. The system-on-chip is mainly composed of three components: (1) evanescent coupler (EVC), which couples the light beam from one device to another; (2) metagrating (MG), in the tiny Millions of small holes are prepared on the surface, which can scatter light like a large diffraction grating; (3) metasurface (metasurface, MS), and millions of pillars used as lenses are prepared on a tiny glass surface.
The ability to tailor these properties using a single chip "is critical to creating new types of portable sensors that can measure fundamental physical quantities such as rotation, acceleration, time and magnetic fields with unprecedented precision outside the confines of the laboratory," NIST said.
Typically, a laboratory bench the size of a dining table is required to accommodate the various lenses, polarizers, mirrors, and other equipment required for manipulation. However, many quantum technologies, including tiny optical atomic clocks and some future quantum computers, will require simultaneous manipulation of multiple widely varying laser wavelengths within a small region of space.
Integrated photonic circuits and optical metasurfaces
To address the problems encountered above, NIST researcher Vladimir Aksyuk and his colleagues combined two broad categories of chip-scale beam manipulation techniques: (1) integrated photonic circuits that use tiny transparent channels and other tiny components to guide beams;( 2) Optical metasurfaces, whose surfaces consist of glass wafers integrating millions of tiny structures that can manipulate light beams without bulky optics.
Aksyuk and his team demonstrated that a single photonic chip can do the work of 36 optical devices while simultaneously controlling the direction of travel, focus and polarization of 12 laser beams split into four different wavelengths.
The research team, presenting their latest findings in the Nature sub-journal (Light: Science & Applications), shows that the tiny photonic chip can guide two beams of different colors to travel side by side, which is a step forward for certain types of advanced Atomic Clock Requirements.
Laying the groundwork for chip-based optical atomic clocks
"Replacing optical benches filled with bulky optics with semiconductor wafers (photonic chips) that can be fabricated in a clean room is a real game-changer," said NIST researcher Amit Agrawal. The fabricated photonic chip has the advantage of being reliable and compact, and can be easily reconfigured for different experiments under real-world conditions," he added.
Aksyuk notes that chip-based optical atomic clock systems are being developed because laser light is not yet powerful enough to cool atoms to the ultra-low temperatures needed for tiny advanced atomic clocks.
While laser light normally excites atoms, causing them to heat up and move faster, the opposite happens if the frequency and other properties of the light are carefully chosen. After hitting an atom, the laser photons induce the atom to release energy and cool down so that it can be captured by a magnetic field.
"Even without cooling capabilities, micro-optical systems are a key stepping stone to building advanced atomic clocks on a chip," Aksyuk said.
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