Ultra-Low V Pi L Modulator for Low NF, High Linearity Microwave Photonic Links
Abstract
In the last decade, Si has become a popular material platform for photonic integrated circuits (PICs) mainly due to low cost, high index and mature manufacturing processes that leverage very large-scale integration (VLSI) processes developed in the electronics communities. Using the free-carrier plasma dispersion effect, where the material index is changed by changing carrier concentrations, light modulation in Silicon is achievable but limited in terms of high frequency response and power consumption. As a comparison, nonlinear optical materials offer simple, fast, and low power consumption light modulations based on the Pockels effect, which derivesfrom their non-inversion symmetry crystal structures. However, the footprint required to achieve a low V# modulator is still an order of magnitude larger than a typical Si PIC component. To this end, an ultra-low V#L modulator that can be integrated to Si PIC platform is in urgent demand. The use of such an ultra-low V#L modulator on DODapplications is also imminent. The modern warfare environment is fast becoming a battlefield of electromagnetic, or RF, signals where communication, radar, surveillance and electronic support signals all compete for available spectrum and bandwidth. For this reason, there is a natural migration to higher frequencies, namely microwave and mmWs which can offer currently underutilized bandwidth. However, with these frequencies comes excessive loss in the cables used to connect these systems, especially over long distances. To address this limitation, microwave photonic links (MPLs), where analog signals can be distributed over long distances with almost no propagation loss, are being developed to replace conventional metal cables for many defense applications such as antenna remoting. Along with low propagation loss, the small size, weightand power (SWaP) of an MPL offer exceptional flexibility in system design, deployment and service. The wide application of MPLs is,however, often limited by the system noise figure (NF). An MPL with a large NF requires a front-end LNA, which often limits the overall system dynamic range and is susceptible to high power microwave (HPM) attack. Therefore, an MPL approaching 3dB NF is highly desired. At this point, the photonic link acts effectively as a distributed broadband LNA (with a large distance between the input andamplified signals) but offers better dynamic range and is immune to EMI. To achieve <3dB NF, an ultra-low V# modulator is the key. Herein, PSI propose two approaches to significantly reduce V#L of state-of-the-art modulators. The first approach is to reduce V#L of an TFLN modulator with a recycled carrier design together with high K RF cladding in the traveling-wave electrode. The recycled carrier modulator enhances the sideband power by reusing the optical carrier in a high finesse microring resonator (MRR). Since the sidebands are not coupled into the MRR, this modulator structure preserves the broadband characteristics of a push-pull Mach-Zehnder modulator (MZM). In addition, high K RF cladding material will be selected and applied to the push-pull electrode structure, which substantially increases the field strength across the LN waveguide. The second approach is based on a thin film BTO modulator. We willacquire thin-film BTO wafers and build test setups to test and pull the thin-film BTO substrates. We will investigate modulator structures based on different thin-film BTO waveguide designs. We will design, fabricate and experimentally demonstrate an ultra-low V#L modulator with <0.5Vcm V#L and <0.5V V#. We will package the developed modulator chip and use it in a bench-top MPL setup. We willcharacterize the MPL to meet critical link specs including ~3dB NF and >116dB-Hz2/3 SFDR. In addition, as a trusted DoD foundry, PSI will provide MPW services to other domestic research teams and fabricate advanced TFLN modulators based on their design.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Dec 15, 2023
- Source ID
- N000142412067
Entities
People
- Peng Yao
Organizations
- Office of Naval Research
- United States Navy