Magneto-optical spectroscopies are increasingly powerful probes of spin excitations in quantum materials, but at cryogenic temperatures, the laser excitation can be highly non-perturbative. While balanced photodetection can be used to suppress classical noise sources, the photon shot noise limit fundamentally constrains the measurement sensitivity for a given laser power. Here, we have used a two-mode squeezed light source to suppress noise below the shot noise level for magnetic circular dichroism measurements, thus enabling lower power measurements with reduced photothermal effects. We also describe the fundamental sensitivity limits for quantum enhanced interferometric and intensity-difference magneto-optical Kerr effect and circular dichroism spectroscopies.
We describe the operation of a free-space confocal optical microscope operated in a dilution refrigerator. The microscope is installed on a cold insertable probe to enable fast sample exchange while the refrigerator is held at low temperatures. A vector magnet provides a 6 T field normal to the sample and 1 T fields at arbitrary angles. A variety of optical microscopies and spectroscopies, including photoluminescence, Raman, magneto-optical Kerr effect, and spin relaxometry measurements are described, and some of the challenges associated with performing these measurements at milliKelvin temperatures are explored.
KEYWORDS: Semiconductors, Near field, Silicon carbide, Semiconductor materials, Near field optics, Spectroscopes, Infrared imaging, Infrared radiation, Phonons, Near field scanning optical microscopy
We show how extended defects in wide bandgap semiconductors manifest in the nanoscale infrared phonon response probed by scattering-type scanning near-field optical microscopy (s-SNOM). We correlate the s-SNOM response of various defects in 4H-SiC with UV-photoluminescence, secondary electron and electron channeling contrast imaging, and transmission electron microscopy. We identify evidence of step-bunching, recombination-induced stacking faults, and threading screw dislocations, and also demonstrate the interaction of surface phonon polaritons with extended defects. Our s-SNOM results help to advance material growth efforts for electronic, photonic, phononic, and quantum optical applications.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.