ColdQuanta’s microShutter is a free-space, chip-scale mechanical shutter designed for laser shuttering applications. The microShutter breaks through the size constraints of MEMS fiber shutters by eliminating the optical fiber and operating on the beam inline and in free-space. The microShutter allows laser shuttering in a form factor and with a power budget that enables high performance optical applications in hand-held devices. Uniquely, each microShutter chip integrates a beam dump that captures stray light in an on-board light trap. The microShutter is designed to the power, performance, and size requirements of portable atomic clocks and other compact atomic systems requiring free-space optical distribution. The prototype chip has been demonstrated to draw less than 0.5 μA at 150 V. A low power driver circuit that can operate the microShutter with 2.5 mW with a 4V supply has been demonstrated. Early prototypes demonstrate extinction below -45 dB with insertion loss of -2 dB, an open-closed transition time of 12 μs and closed-open transition time of 14 µs.
We have shown that Rydberg states can be used for high-sensitivity, absolute sensing of microwave (MW) electric fields. We achieved a sensitivity of 3 μVcm<sup>-1</sup>Hz<sup>-1/2</sup> for two read-out strategies. Depending on the spectral resolution of the read-out, either the MW induced transmission line frequency splitting, the Autler-Townes regime, or a change in the on-resonant absorption, the amplitude regime, can be used to determine the MW electric field. Results using a Mach-Zehnder interferometer and frequency modulated spectroscopy both achieve similar photon shot noise limited sensitivity. In addition, we have also explored amplitude modulation and the displacement of a probe laser beam due to index of refraction changes in a prism shaped vapor cell. These latter methods were not able to achieve photon shot noise limited performance. Fundamental limits to the sensitivity of the Rydberg atom-based MW electric field sensing have been addressed, but it is important to clarify the differences between noise in different parts or subsystems of the sensor. Shot noise in the probe laser usually dominates the projection noise of the atoms participating in the measurement of the MW electric field because of the desire to operate at low effective Rydberg atom densities in order to avoid collisional dephasing and ionization.