We report on the design and sensitivity of a new torsion pendulum for measuring the performance of ultra-precise inertial sensors and for the development of associated technologies for space-based gravitational wave observatories and geodesy missions. The apparatus comprises a 1 m-long, 50 μm-diameter tungsten fiber that supports an inertial member inside a vacuum system. The inertial member is an aluminum crossbar with four hollow cubic test masses at each end. This structure converts the rotation of the torsion pendulum into translation of the test masses. Two test masses are enclosed in capacitive sensors which provide readout and actuation. These test masses are electrically insulated from the rest of the crossbar and their electrical charge is controlled by photoemission using fiber-coupled ultraviolet light emitting diodes. The capacitive readout measures the test mass displacement with a broadband sensitivity of 30 nm∕Hz and is complemented by a laser interferometer with a sensitivity of about 0.5 nm∕Hz. The performance of the pendulum, as determined by the measured residual torque noise and expressed in terms of equivalent force acting on a single test mass, is roughly 200 fN∕Hz around 2 mHz, which is about a factor of 20 above the thermal noise limit of the fiber.

True-time delays are important building blocks in modern radio frequency systems that can be implemented using integrated microwave photonics, enabling higher carrier frequencies, improved bandwidths, and a reduction in size, weight, and power. Stimulated Brillouin scattering (SBS) offers optically-induced continuously tunable delays and is thus ideal for applications that require programmable reconfiguration but previous approaches have been limited by large SBS gain requirements. Here, we overcome this limitation by using radio-frequency interferometry to enhance the Brillouin-induced delay applied to the optical sidebands that carry RF signals, while controlling the phase of the optical carrier with integrated silicon nitride microring resonators. We report a delay tunability over 600 ps exploiting an enhancement factor of 30, over a bandwidth of 1 GHz using less than 1 dB of Brillouin gain utilizing a photonic chip architecture based on Brillouin scattering and microring resonators.

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As electrochromic polymers can switch with a high transmittance contrast in the sub‐second time frame, an analytical tool to rapidly probe the electrochemically‐induced optical transition is required for characterization of these materials for electronic displays and smart windows. A novel technique is described to synchronize the electrochemical and optical measurements by utilizing an external trigger to facilitate coordinated communication between the potentiostat, which applies a voltage to the electrode supported electrochromic polymers, and the optical spectrometer that records the induced optical transitions. By using a spectrometer containing a photodiode array detector, these measurements are capable of rapid data acquisition to track the electrochromic change in the polymer films, with as many as 500 spectra captured during a one‐second switch of the polymer from a colored, neutral to highly transmissive state. Additionally, with this rapid, full‐spectral measurement, it is possible to trace the temporal evolution of the electrochromic change to determine the presence of intermediate color tones, as well as their duration. Here, three polymers are shown, ECP‐Magenta, ECP‐Green, and ECP‐Black, which obtain high transmittance contrast between 40 to 50 Δ%T, with sub‐second switching times measured in the range of 400 to 700 ms, demonstrating their potential for use in electrochromic windows and displays where rapid transitions are desired.