Photonic Circuits for UV to IR

A photonic integrated circuit in which an ultralow loss 2-meter optical waveguide guiding visible light in the red spectrum is put on a silicon nitride chip smaller than a penny, important for applications such as strontium atomic clocks. (Source: N. Chauhan / DARPA MTO ApHI program)

The field of photonic integration – the area of photonics in which waveguides and devices are fabri­cated as an integrated system onto a flat wafer – is relatively young compared to electronics. Photonic integration has focused on communi­cations appli­cations tradi­tionally fabricated on silicon chips, because these are less expensive and more easily manufactured. Researchers are exploring promising new waveguide platforms that provide these same benefits for appli­cations that operate in the ultraviolet to the infrared spectrum. These platforms enable a much broader range of applications, such as spectro­scopy for chemical sensing, precision metrology and compu­tation.

Now, a researcher from University of California, Santa Barbara, provides a per­spective of the field of ultra-wide­band photonic waveguide platforms based on wide bandgap semi­conductors. These waveguides and integrated circuits can realize power-efficient, compact solutions, and move key portions of ultra-high-per­formance systems to the chip scale instead of large tabletop instruments in a lab.

Until now, key components and subsystems for appli­cations, such as atomic clocks, quantum communications and high-resolution spectro­scopy, are constructed in racks and on tabletops. This has been necessary because they operate at wave­lengths not accessible to silicon waveguides due to its lower bandgap and other absorption properties in the UV to near-IR that reduce the optical power handling capa­bilities, among other factors. Daniel J. Blumenthal and his team have researched photonic inte­gration platforms based on waveguides fabricated with wide bandgap semi­conductors that have ultralow propa­gation losses.

“Now that the silicon market has been addressed for tele­communications and LIDAR applications, we are exploring new materials that support an exciting variety of new appli­cations at wavelengths not accessible to silicon wave­guides,” said Blumenthal. “We found the most promising waveguide platforms to be silicon nitride, tantala (tantalum pentoxide), aluminum nitride and alumina (aluminum oxide).” Each platform has the potential to address different appli­cations such as silicon nitride for visible to near-IR atomic transitions, tantalum pentoxide for raman spectro­scopy or aluminum oxide for UV inter­actions with atoms for quantum computing.

Applications, such as atomic clocks in satel­lites and next-gene­ration high-capacity data center inter­connects, can also benefit from putting functions such as ultralow linewidth lasers onto lightweight, low-power chips. This is an area of increased focus as exploding data center capacity pushes traditional fiber inter­connects to their power and space limi­tations.

Blumenthal said next-gene­ration photonic inte­gration will require ultra-wideband photonic circuit platforms that scale from the UV to the IR and also offer a rich set of linear and nonlinear circuit functions as well as ultralow loss and high-power handling capa­bilities. (Source: AIP)

Source: D. J. Blumenthal: Photonic integration for UV to IR applications, APL Phot. 5, 020903 (2020); DOI: 10.1063/1.5131683

Link: Optical Communications and Photonic Integration Group (D. Blumenthal), University of California at Santa Barbara, Santa Barbara, USA

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