Nanophotonic Chip Enables World-Class Beam Scanning

Information moves through our universe primarily as light, from the vastness of space to the smallest particles. While our digital networks rely on photonic waveguides, an even greater torrent of photonic data flows freely through the air. Bridging these two realms, creating an efficient chip-to-world optical interface, is a critical challenge. Success unlocks transformative potential across fields like high-speed communications, advanced manufacturing, augmented reality displays, biomedical imaging, and the precise control of atoms for quantum computing. Yet, our current infrastructure falters under the sheer volume of data from the real world, where every pixel represents a channel demanding processing. Photonic integrated circuits (PICs) have grown remarkably sophisticated, but a fundamental bottleneck remains: the inefficient translation between the guided light modes on a chip and the boundless spatial modes of free space.

This mode mismatch has blocked the path to a seamless, scalable interface. Integrated waveguides excel at handling many time-bin modes through fast electro-optic interactions but offer very few spatial waveguide modes. Free space, conversely, provides a nearly infinite number of spatial modes. Although the total mode counts can be similar, existing technologies fail to connect them effectively. They are plagued by poor beam quality, narrow fields of view, slow scanning speeds, or an inability to integrate directly and scalably with programmable photonic chips. The ideal solution must project and steer a sharp, diffraction-limited beam to a vast number of resolvable points, do so rapidly, from a compact footprint, and directly from the chip surface. Current architectures force a difficult compromise. Programmable devices like optical phased arrays suffer from degraded beam quality, while continuous aperture scanners are limited by physical inertia and integration hurdles.

Evaluating laser scanning systems involves many factors, but a core metric is the number of resolvable spots per unit of chip area. This figure fundamentally influences device count per wafer and cascades into overall size, weight, power, and cost. For a clear comparison, we combine this area-adjusted spot count with the system’s refresh rate, yielding a performance figure of merit in spots per second per square millimeter. Conventional pupil-plane scanners need large apertures for high resolution, leading to slow, power-hungry mechanics that limit performance. Focal-plane scanners separate optical and mechanical dimensions but have been hamstrung by bulky components and the absence of a scalable, actuatable single-mode waveguide that can be built directly onto a photonic chip.

We now present a breakthrough: a new class of integrated device called the photonic ski-jump. This innovation overcomes these longstanding barriers. Fabricated on standard 200-millimeter wafers in a commercial CMOS foundry, the device features a nanoscale optical waveguide embedded on a piezoelectrically actuated microcantilever. This cantilever has a submicrogram mass, a thickness of roughly two micrometers, and a pronounced upward curvature. The minuscule mass and dimensions shatter the inertial limits that constrain technologies like scanning fibers. The large curvature is engineered by controlling the intrinsic stress between the thin film layers of the cantilever, a technique inspired by mechanical metamaterials. This design enables vertical, scannable, broadband light emission from anywhere on the wafer, with mechanical resonances from about 1 kHz to over 100 kHz. These high frequencies dramatically boost scanning speed and field of view.

The integrated submicrometer waveguides simultaneously minimize mass and the emitted beam’s spot size. The result is a performance leap orders of magnitude beyond current state-of-the-art. The photonic ski-jump achieves more than a thousand-fold improvement over existing fiber scanners and a greater than fifty-fold improvement over mature micro-electromechanical systems (MEMS) mirrors and acousto-optic deflectors.

The photonic ski-jump is part of a unified family of active components on a CMOS-compatible piezo-opto-mechanical photonic integrated circuit (POMPIC) platform. This platform already includes tunable couplers, high-speed phase shifters, programmable interferometers, and tunable ring resonators. This extensive toolkit allows for complex photonic processing to occur on the same monolithic chip before light is projected by the ski-jump. Furthermore, these devices are cryogenically compatible, enabling direct integration with solid-state quantum systems like diamond color centers, which have already been combined with this platform for control purposes. This creates new pathways for addressing and reading out spin qubits. Looking ahead, integration with advanced electro-optic thin films could enable modulation at 100 GHz, allowing the projection of optical pulses shorter than a nanosecond. The combined capabilities of the POMPIC platform and the chip-to-world projection of the ski-jump pave the way for scalable photonic and quantum control both on and off the chip.

(Source: Nature)