Timothy Creazzo

Thin-film lithium niobate (TFLN) electro-optic modulators have been widely explored at 1550 nm, achieving ultra-low driving voltages, broad bandwidths, and compact footprints. Yet, development at 1064 nm has remained comparatively limited, despite its growing importance for applications that demand high power and cost-effective integration with CMOS-compatible silicon photodetectors such as free-space optics, frequency combs and biophotonics. In this work, we demonstrate a high-efficiency TFLN modulator operating at 1064 nm contributing to fulfilling this gap. The device employs a 1 cm-long interaction region with capacitively loaded traveling-wave electrodes designed to minimize the velocity mismatch between RF and optical modes, achieving an index mismatch as low as 0.05. This careful optimization enables a high frequency half-wave voltage of 1.45 V and a 40 GHz 3-dB bandwidth, representing the best performance reported to date for 1064 nm operation. These results highlight the potential of TFLN modulators to extend beyond traditional telecom wavelengths leveraging lower V $\pi $ , high quality lasers and easy integration with Si photodetectors.

This paper demonstrates concurrent spatial and spectral signal classification using two photonic integrated circuits (PICs) implemented in a 30-element Ka-band (26.5-40 GHz) antenna array. The received signals are coherently up-converted to the optical-domain using lithium niobate phase modulators. The up-converted RF signal is beamformed in a star-coupler PIC to instantaneously image angle-of-arrival to a single output channel that is amplified and input to an arrayed waveguide grating (AWG) PIC, which instantaneously channelizes the RF frequency into increments of approximately 1 GHz. A switching scheme is used to calibrate the AWG as well as alternate between frequency and beam location measurement. This work implements these devices in a radiometer that can localize RF beams both spatially and spectrally with minimal latency and computational requirements. Future applications will include advanced wireless communications and sensing.

In this work, angle-of-arrival (AoA) detection using a radio frequency (RF) 2-D planar antenna array receiver coupled to a photonic integrated circuit (PIC) is demonstrated. Optical upconversion identically preserves the RF phase-front information received by the antenna array and relays each upconverted RF signal to the linear array of inputs of a beamforming PIC. To convert from the 2-D planar array to a linear optical fiber array without loss of phase information, array-beamspace (AB) mapping is used in the signal routing. In the PIC, an optical spatial Fourier transform operation is performed via a star coupler, similar to the action of a Rotman lens. The signal measured at each output of the star coupler corresponds to a unique beam location in the RF beamspace. By applying AB mapping to the linear output array, the azimuth and elevation of the received signal can be fully recovered. This article presents the system architecture of the passive AoA detection system, as well as the steps to create an AB mapping scheme. The experimental results are presented for a 30-element triangularly spaced array for multiple source locations and multiple simultaneous sources. The PIC-based approach demonstrates a major reduction in latency as well as size, weight, and power (SWaP) for passive AoA detection.

We describe an RF-photonic system architecture to measure microwave spectrum over a wide bandwidth with high resolution. The approach relies on the up-conversion of the electronic signal to the optical domain using a high-speed electro-optic modulator (EOM), and an arrayed-waveguide (AWG) grating for spectral analysis. The modulator is implemented in lithium niobate whereas the AWG takes the form of a photonic integrated circuit fabricated in a silicon-on-insulator material platform. We present experimental results showing high-frequency response, in excess of 200 GHz, for the modulator, and broadband response of the AWG with the free spectral range of 81 GHz. The system is suitable for the measurement of atmospheric radiation between the oxygen and water vapor absorption lines for the monitoring of the planetary boundary layer (PBL) to aid in weather prediction and the modeling of climate dynamics.