Electrically driven acousto-optic devices that provide beam deflection and optical frequency shifting have broad applications from pulse synthesis to heterodyne detection. Commercially available acousto-optic modulators are based on bulk materials and consume Watts of radio frequency power. Here, we demonstrate an integrated 3-GHz acousto-optic frequency shifter on thin-film lithium niobate, featuring a carrier suppression over 30 dB. Further, we demonstrate a gigahertz-spaced optical frequency comb featuring more than 200 lines over a 0.6-THz optical bandwidth by recirculating the light in an active frequency shifting loop. Our integrated acousto-optic platform leads to the development of on-chip optical routing, isolation, and microwave signal processing.
We demonstrate a 3-GHz acousto-optic frequency shifter on a thin-film lithium niobate platform, featuring over 30 dB carrier suppression. The active frequency shifting loop generates a frequency comb with 200 lines over 5 nm optical bandwidth.
Photonic integrated circuit (PIC) phased arrays can be an enabling technology for a broad range of applications including free-space laser communications on compact moving platforms. However, scaling PIC phased arrays to a large number of array elements is limited by the large size and high power consumption of individual phase shifters used for beam steering. In this paper, we demonstrate silicon PIC phased array beam steering based on thermally tuned ultracompact microring resonator phase shifters with a radius of a few microns. These resonators integrated with micro-heaters are designed to be strongly coupled to an external waveguide, thereby providing a large and adjustable phase shift with a small residual amplitude modulation while consuming an average power of 0.4 mW. We also introduce characterization techniques for the calibration of resonator phase shifters in the phased array. With such compact phase shifters and our calibration techniques, we demonstrate beam steering with a 1x8 PIC phased array. The small size of these resonator phase shifters will enable lowpower and ultra-large scale PIC phased arrays for long distance laser communication systems.
The required dynamic range of a practical undersea laser-based sensor is limited by its range-to-target. The dynamic range of the sensor needs to accommodate the variations in target reflectivity and specularity, water scattering and absorption, and mode of operation of the sensor at the target range. For example, the same sensor may be used to sense a diffuse flat black target and a shiny metallic mirror at normal incidence. Similarly, the same sensor may be deployed both in murky coastal waters and in clear deep oceanic waters. Since a detector used in a sensor has a limited (intrascene) dynamic range of perhaps 40 dB, methods of mitigating the required dynamic range at the sensor must be employed. Further, the required time scales of each specific dynamic range absorber must be considered. Therefore, a systematic optical budget approach considering time scales is employed.After considering maximum laser power out and minimum detectable power, the remaining available dynamic range is allocated to specific devices based on time responses matched to requirements. Devices are discussed and classified according to their parameters, and a final recommended system design is presented. The final system consists ofa continuously variable neutral density filter wheel, and a galvanometrically scanned variable neutral density filter wheel. Other devices and their merits are discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.