Enabling High-Performance CPO

As AI and cloud workloads scale, copackaged optics (CPO) is redefining data center architecture by integrating photonics directly with compute and switching ASICs. This approach dramatically increases bandwidth and energy efficiency, but it also introduces extreme thermal density and tight thermo-optic constraints that make advanced cooling essential.

In CPO systems, heat generation is no longer distributed across a board. Instead, it is concentrated within millimeters—or even microns—of sensitive photonic components and high-power ASICs. These conditions create steep thermal gradients, which are often more damaging than absolute temperature rise. Even small temperature variations can shift laser wavelength, alter refractive indices in photonic integrated circuits (PICs), and degrade modulation efficiency, leading to higher bit error rates and reduced signal integrity.

Phononic thermoelectric cooling addresses these challenges at the device level. Using the Peltier effect, thermoelectric coolers (TECs) pump heat across junctions when current is applied, enabling bidirectional heat control with better than -0.5°C precision. This deterministic control is critical for stabilizing laser junction temperatures and maintaining resonance alignment in ring modulators and other wavelength-sensitive structures.

A key advantage of Phononic’s approach to cooling is its ability to provide localized, fast-response thermal regulation. Unlike conventional air or liquid cooling—which primarily manage bulk temperature—TECs can dynamically respond to transient hotspots caused by bursty data traffic or switching activity. This closed-loop control minimizes laser thermal drift, reduces insertion loss, and preserves CPO optical link performance under varying workloads.

Additionally, Phononic’s solid state approach has no moving parts, eliminating vibration and improving mean time between failures (MTBF). This makes them especially well-suited for tightly integrated photonic-electronic packages where mechanical stability and reliability are critical.

As CPO scales from the demonstration phase into high volume deployments, achieving optimal performance requires co-optimization of thermal, electrical, and optical domains.