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In this work, we demonstrate a four-core multicore fiber photonic lantern tip/tilt wavefront sensor. To diagnose the low-order Zernike aberrations, we exploit the ability of the photonic lantern to encode the characteristics of a complex incoming beam at the multimode facet of the sensor to intensity distributions at the multicore fiber output. Here, we provide a comprehensive numerical analysis capable of predicting the performance of fabricated devices and experimentally demonstrate the concept. Two receiver architectures are implemented to discern tip/tilt information by (i) imaging the four-core fiber facet on a 2D detector and (ii) direct power measurement of the single mode outputs using a multicore fiber multiplexer and photodetectors. For both receiver schemes, an angular detection window of
at 1064 nm can be achieved. Our results are expected to further facilitate the development of intensity-based fiber wavefront sensors for adaptive optics systems. -
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Non-mode-selective (NMS) multiplexers (muxes) are highly desirable for coherent power combining to produce a high-power beam with a shaped profile (wavefront synthesis) from discrete, phase-locked emitters. We propose a design for a multi-plane light conversion (MPLC)-based NMS mux, which requires only a few phase masks for coherently combining hundreds of discrete input beams into an output beam consisting of hundreds of Hermite–Gaussian (HG) modes. The combination of HG modes as a base can further construct a beam with arbitrary wavefront. The low number of phase masks is attributed to the identical zero-crossing structure of the Hadamard-coded input arrays and of the output HG modes, enabling the practicality of such devices. An NMS mux supporting 256 HG modes is designed using only seven phase masks, and achieves an insertion loss of
, mode-dependent loss of 4.7 dB, and average total mode crosstalk of . Additionally, this design, featuring equal power for all input beams, enables phase-only control in coherent power combining, resulting in significant simplifications and fast convergence compared with phase-and-amplitude control. -
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High‐speed modulators with low driving voltage, low loss, and compact size are essential for future optical communication systems. Thin‐film lithium niobate modulators have met each of these criteria separately, but simultaneous achievement of all of them has been challenging on this platform. Low driving voltage electro‐optic modulators necessitate either a narrow gap between the electrodes or an elongated Mach–Zehnder arms, both of which adversely affect the microwave loss, hence the bandwidth. Herein, this trade‐off is alleviated by placing the optical waveguides nonsymmetrically with respect to the electrodes and by including a dielectric buffer layer beneath the electrodes. Exploiting this novel design yields a modulator with a measured roll‐off of only 2 dB from low frequencies up to 100 GHz, and with an extrapolated 3 dB bandwidth of 170 GHz. The measured voltage–length product of this subterahertz device is 3.3 V cm. Another device, optimized for a lower voltage–length product of 2.2 V cm, exhibits a 3 dB electro‐optic bandwidth of 84 GHz. The devices are also tested for eight‐level pulse‐amplitude modulation (PAM‐8) and demonstrate data rates of up to 240 Gb s−1at 80 Gbaud, validating that the modulators are a propitious candidate for next‐generation optical communication systems.
