Getting PICs Off The Ground
PICs based on InP and GaAs prepare to slash the size, weight and power of systems to be deployed in space and on-board aircraft for a variety of sensing applications.
BY Jonathan Klamkin, Paul Verrinder, Victoria Rosborough AND Fengqiao Sang FROM THE University of California Santa Barbara
One of the most powerful technologies of our time is the photonic integrated circuit(PIC). By integrating all the requiredfunctions on a single chip, the PIC significantly reduces the cost, size, andweight at the system level, while improving performance, stability, andreliability.
To produce this multi-faceted photonic device, wafers areprocessed in a manner that is similar to that employed for the electroniccircuits that have revolutionised our society. However, the materials that areused can be somewhat different. While silicon is the semiconductor of choicefor making electronic circuits, those employing photonics can also be formedfrom InP and GaAs. Both these III-Vs are attractive options, because theyenable monolithic integration of gain material for light sources and theiramplification.
Pioneers of the PIC developed this technology withtelecommunications applications in mind. They focused on the centre-band, orC-band, which spans the spectral range from 1530 nm to 1565 nm, a domainassociated with ultra-low-loss transmission of light through an optical fibre.Recently, though, PICs have gained traction in applications involving theO-band (1260 nm to 1360 nm), such as optical interconnects within and betweendata centres.
Note, though, that the potential for PICs is not limitedto these wavelengths, nor to communications, or even to terrestrialapplications. There are opportunities lying well beyond these boundaries, suchas those we are exploring at the University of California, Santa Barbara(UCSB). We are targeting space and airborne applications of PICs, namelyfree-space communications, remote lidar for gas sensing and topographicallidar. Our work on free-space communications has focused on extending the power-handlingcapabilities of InP PICs. Success on this front opens the door to higher datarates and/or longer link distances. Output powers with our InP PIC platformhave exceeded 250 mW, a value far higher than any previous demonstration.