Phase Sensitive Innovations (United States)

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 Vπ, high quality lasers and easy integration with Si photodetectors.

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.

Passive millimeter-wave (PmmW) imaging presents challenges in edge detection due to low contrast and high noise, which impact object recognition in security applications. Here, a selection of conventional edge detection techniques is cross-evaluated for their applicability to mmW imaging. Special attention is given to the size of the sliding window or box filter applied that takes advantage of the spatial oversampling obtained as a result of diffraction-limited resolution of the generated mmW images. Performance is assessed based on visual clarity, computational efficiency, and detection accuracy. While several algorithms have notable difficulties with imaging technologies at millimeter wavelengths, it has been found that simple standard deviation, when paired with adaptive mean thresholding, produces relatively lower clutter, and higher-quality edge maps compared to other methods.

In this work, we demonstrate the fabrication of various coupled optical ring resonator configurations on silicon on insulator (SOI) wafer via a foundry. We show that coupled optical ring resonator filters can have roll-off slopes greater than 6 dB/GHz with negligible loss, making it an attractive solution for RF over fiber applications. In addition, we show that this filter passband can be tuned up to 500 GHz and function as a programmable filter. Furthermore, we investigate the effect of increasing the number of rings on filter performance and report on different strategies to improve filter performance. Finally, in this paper we present a comprehensive theoretical and experimental study of these devices, including chip-to-chip, intra-chip, and run-to-run statistical analysis.

This paper presents an overview of the state-of-the-art in high-performance electro-optic modulators (EOM) based on thin-film lithium niobate on insulator (TFLNOI) material platform. By leveraging the advantage of capacitive loaded traveling wave electrodes (CL-TWEs) on a quartz handle, it is possible to engineer a modulator with low radio frequency (RF) loss and broadband index matching, expanding significantly the 3-dB limits of device. Herein we present the design, fabrication, and experimental demonstration of a Dual Output Mach-Zehnder Modulator (DO-MZM) with a 1V drive voltage (V_<i>&pi;</i>), 3-dB bandwidth around 125GHz, and over 40dB extinction ratio. The dual output architecture, when used with a balanced photodetector (PD), can reject common mode noise resulting from Relative Intensity Noise (RIN) in a microwave photonic link (MPL) to the point where it can become shot noise limited. Along with this development, we also experimentally demonstrate a compact sub-1 V<i>_&pi;</i> phase modulator using folded CL-TWEs. Furthermore, based on the high modulation efficiency and high bandwidth modulator design, we have designed, fabricated, and characterized a monolithic ultra-wideband antenna coupled photonic receiver, device that performs direct free space RF signal-to-optical conversion without the support of electronic components.

Tunable photonic radiofrequency (RF) signal generators are used to create RF carriers for applications in telecommunications, military, and satellite communications whose standards require a wide range of frequencies. For unmanned aerial vehicles (UAV), satellite data links, and other weight-sensitive applications, the need for a more compact and lightweight RF source generator is becoming more urgent. We report on the development of a compact tunable optical paired source (TOPS) that can be used to generate RF signals at frequencies between 5 and 110 GHz using compact free-space optics. Like earlier systems, this compact TOPS utilizes an optoelectronic scheme based on sideband-injection-locked lasers to generate RF carriers. By replacing the fiber-based components with their free-space counterparts, lower insertion loss can be achieved through the system. Fiber-based systems are also susceptible to acoustic noise, which is eliminated by switching to free-space optical components. Here, the component and system design, fabrication and assembly are discussed along with experimental results.

This paper presented to leverage thin-film Lithium Niobate (TFLN) technologies to develop high-speed high-efficiency electro-optic (EO) phase modulator for efficient up-conversion process in the millimeter wave (mmW) regime for the applications to passive mmW imaging applications. Compared with bulk LN modulators, TFLN modulators offer stronger EO interaction owing to tighter RF and optical mode sizes, thereby demonstrating significant modulation enhancement, i.e., &gt;50&times;. Various TFLN modulator designs, including hybrid SiN and ridge-etched TFLN, on the quartz and silicon substrates are investigated. Additionally, tighter optical waveguide bending allows single-end optical interface on one side and RF feed on the other side, thereby leading to more compact device packaging and easier system integration. Furthermore, capacitively loaded travelling wave electrodes (CL-TWE) are developed for better RF and optical index matching &lt;0.002, and lower RF loss of &lt;0.8dB/GHz^-1 for better conversion efficiency in W-band. The fabricated TFLN modulators on silicon handle are integrated with the RF module, and the packaged module was experimentally verified that the TFLN-based module demonstrates significantly improved performance, &gt;8dB in EO conversion efficiency, ~50% reduction in packaging size when packaged as a multiple channel blade.

We present a photonic-based approach for implementing a coherently distributed antenna system for multiple-input- multiple-output (MIMO) communication at millimeter-wave (mmWave) frequencies. This method utilizes RF-photonic links to enable antenna remoting, ensuring radio frequency (RF) phase coherence over extended distances with minimal loss. Different precoding schemes are applied, and the experimental results are compared with simulation results.

We present a method for the recovery of two-dimensional angle-of-arrival information by beamspace processing using only a linear array of elements in the beam-forming processor. The method exploits the presence of grating lobes in beam patterns formed when using phased arrays with regularly spaced antenna elements. Periodic distribution of grating lobes in the reciprocal space allows, for some arrays, ‘unrolling’ a two-dimensional beamspace pattern into a linear distribution of beams, which is amenable to recovery using a linear array of elements in the beamspace processor. We develop mathematical underpinning of the approach and analyze several explicit examples of such array-beamspace (AB) mapping.

In this work, angle-of-arrival (AoA) detection using a two-dimensional (2D) antenna array coupled to a planar photonic integrated circuit (PIC) is demonstrated. To detect AoA in azimuth and elevation (az-el) the received signal from each antenna element, in a 2D array, is up converted to the optical domain using an electro-optic modulator and transmitted to a PIC via optical fiber. To preserve the two-dimensional phase information captured by the array, a special array-beam space (AB) mapping is used to route the fibers to a linear array of input waveguides on the PIC. This paper presents the steps to generate such a mapping for the antenna elements, as well as an equivalent mapping for the array's beam space. We also present experimental results for beam detection using a 30-element hexagonally spaced array. The PIC-based approach promises to reduce system size and reduce latency for AoA detection.