We present progress towards demonstrating multi-passed stimulated Raman scattering microscopy and multi-passed transmission electron microscopy. A multi-pass microscope interrogates a sample multiple times in a cyclical and deterministic fashion. This can lead to a metrological advantage for imaging weak scatterers. The enhanced sensitivity can yield a significant reduction in damage imparted to biological samples or can reduce image acquisition time. The approach compares favorably with imaging techniques using squeezed or entangled probe states, but avoids the technical complexity associated with the production of such states.
Penning ion traps containing hundreds of ions held in a 2D crystal can be used to sense weak electric fields. We couple the crystal’s center-of-mass (CM) mode to the ions’ spin states, such that small perturbations of the crystal motion caused by external electric fields can be determined by measuring the spin precession. We have demonstrated a sensitivity to small displacements of 8.8 dB below the standard quantum limit (SQL), which enables an electric field sensitivity of 240 nV/m in 1 second. We plan to increase this sensitivity by parametrically amplifying the CM motion, which we expect to improve our sensitivity to displacements by a further 10 dB below the SQL.
Supported by an appointment to the Intelligence Community Postdoctoral Research Fellowship Program, AFOSR grant FA9550-20-1-0019, by DARPA ONISQ, and by DOE, Office of Science, NQIS Research Center QSA
We report the development of an intracavity-frequency-doubled vertical external-cavity surface-emitting laser (VECSEL) emitting at 571 nm for photoionization of magnesium. The laser employs a V-cavity geometry with a gain chip at the end of one cavity arm and a lithium triborate (LBO) crystal for second harmonic generation. The gain chip has a bottom-emitting design with ten GaInAs quantum wells of 7 nm thickness, which are strain compensated by GaAsP. The system is capable of producing up to 2.4 ± 0.1 W (total power in two separate output beams) in the visible. The free-running relative intensity noise was measured to be below −55 dBc/Hz over all frequencies from 1 Hz to 1 MHz. With acoustic isolation and temperature regulation of the laser breadboard, the mode-hop free operation time is typically over 5 hrs. To improve the long-term frequency stability, the laser can be locked to a Doppler-free transition of molecular iodine. To estimate the short-term linewidth, the laser was tuned to the resonance of a reference cavity. From analysis of the on-resonance Hänsch-Couillaud error signal we infer a linewidth of 50 ± 10 kHz. Light at 285 nm is generated with an external build-up cavity containing a β-barium borate (BBO) crystal. The UV light is used for loading 25Mg+ ions in a surface-electrode RF Paul trap. These results demonstrate the applicability and versatility of high-power, single-frequency VECSELs with intracavity harmonic generation for applications in atomic and molecular physics.
Experiments in atomic, molecular and optical (AMO) physics rely on lasers at many different wavelengths and with varying requirements on spectral linewidth, power and intensity stability. Optically pumped semiconductor lasers (OPSLs), when combined with nonlinear frequency conversion, can potentially replace many of the laser systems currently in use. We are developing a source for laser cooling and spectroscopy of Mg+ ions at 280 nm, based on a frequency quadrupled OPSL with the gain chip fabricated at the ORC at Tampere Univ. of Technology, Finland. This OPSL system could serve as a prototype for many other sources used in atomic and molecular physics.
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