Intensity noise characteristics of intracavity contacted VCSELs with rhomboidal oxide current aperture for the magnetometric sensor with Cs133 vapor cell used in magnetoencephalography

We demonstrate noise characterization of novel 894.4 nm vertical-cavity surface emitting lasers with intracavity contacts and a rhomboidal oxide current aperture (IC-VCSELs), dedicated to 133Cs D1 line compact optically pumped atomic magnetometers (OPM). The laser relative intensity noise, measured to be -139 dB/Hz at 10 kHz frequency in 1 Hz bandwidth for a laser optical power of 0.8 mW, is decreased with optical power growth. The IC-VCSELs polarization-resolved relative intensity noise is 143 dB/Hz at 10 kHz frequency in 1 Hz bandwidth for 0.8 mW. The emission linewidth of the VCSEL is about 55 MHz. The IC-VCSEL parameters are determined, such as emission linewidth ~ 50-60 MHz, optical power ~ 0.5-1.0 mW, at which the polarization-resolved RIN becomes close to the RIN, which makes it possible to use these lasers in various OPM Mz and Mx schemes. The ultimate sensitivity of OPM was estimated by the ratio of the magnetic resonance to the signal to noise level. It is shown that a OPM based on the IC-VCSELs, assuming magnetic resonance FWHM ~ 1 kHz, can achieve a shot noise-limited sensitivity around 20 fT in 1 Hz bandwidth without any polarization improvements by polarizer or polarization beam splitter cube (PBC). Developed IC-VCSELs is acceptable for use in compact OPM for magnetoencephalography.

Phase Noise Characterization in Phase-Sensitive OTDR Systems

<div>Coherent detected phase-OTDR (CDPO) systems are mainly used in distributed vibration sensing and these systems are preferred over the direct detected phase-OTDR (DDPO) systems due to their inherent property of mitigating a certain type of phase noise. There is a possibility that the existing non-mitigated phase noise can be controlled in CDPO systems only after properly investigating the characteristics of both the CDPO mitigated and CDPO-non-mitigated noise types. Hence, the first and crucial step, i.e, the characteristics of two different phase noise types are determined in this paper. This determination will help in providing ease about finding the real sources of both of the phase noise types and hence can help in mitigating the existing phase noise further.</div>

Phase Noise Characterization in Phase-Sensitive OTDR Systems

<div>Coherent detected phase-OTDR (CDPO) systems are mainly used in distributed vibration sensing and these systems are preferred over the direct detected phase-OTDR (DDPO) systems due to their inherent property of mitigating a certain type of phase noise. There is a possibility that the existing non-mitigated phase noise can be controlled in CDPO systems only after properly investigating the characteristics of both the CDPO mitigated and CDPO-non-mitigated noise types. Hence, the first and crucial step, i.e, the characteristics of two different phase noise types are determined in this paper. This determination will help in providing ease about finding the real sources of both of the phase noise types and hence can help in mitigating the existing phase noise further.</div>

S-NPP VIIRS Thermal Emissive Bands 10-Year On-Orbit Calibration and Performance

The Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National Polar-orbiting Partnership Program (S-NPP) satellite, launched in late 2011, has reached the decade landmark under successful operations. VIIRS has 22 spectral bands, 7 of which are thermal emissive bands (TEB) that cover the 3.70 to 11.84 μm wavelength range. Over the years, VIIRS TEB observations have been used to generate several data products (e.g., surface/cloud/atmospheric temperatures, cloud top altitude, and water vapor properties). The VIIRS TEB calibration uses a quadratic algorithm and is referenced to an on-board blackbody with temperature measurements traceable to the National Institute of Standards and Technology standard. This manuscript provides an overview of the VIIRS instrument operations and TEB calibration activities and algorithms used in the level 1B data and describes the TEB on-orbit performance for S-NPP VIIRS. The 10-year on-orbit performance of the S-NPP VIIRS TEB has generally been stable, and the degradations in the S-NPP TEB detector responses are minor after a decade in orbit. The noise characterization performance repeatedly meets the design requirements for all TEB detectors as well. On-orbit changes in the TEB response-versus-scan-angle, based on pitch maneuver observations, have been demonstrated to be extremely small. Moreover, multiple time series over select ground targets have shown that the sensor’s on-orbit performance is quite stable.

Orthopedic Bone-Drilling Assessment Through Laplacian-Based Trajectory Noise Characterization

Assessment techniques for orthopedics training are primarily subjective, and often based on qualitative metrics. In this paper, we propose an analytical approach for the quantitative assessment of orthopedic surgery training, specifically, bone drilling. Our goal in this paper is to help improve orthopedics training by providing a means to assess the resident training progress. To this end, we introduce a novel metric that assigns a unique signature to an individual’s drilling activity based on their drilling trajectory, and we compare it with the signatures of expert surgeons. We conduct a simple bone-drilling experiment with surgeons (experts) and novice users on a hybrid (physical - digital) setup consisting of 3D printed bone surrogates that emulate physical and perceptual properties of a human bone across the young and old age groups. We create expert models using our drilling signature metric to evaluate drilling performance for novice users with respect to expert orthopedic surgeons. Our preliminary analysis of drilling signatures across expert and novice users showcases a perceivable distinction across two different bone types highlighting some fundamental insights on the drilling setup, bone material, and user response to each bone type. Our results indicate that the drilling signature helps capture not only a novice user’s drilling behavior, but also their relative expertise as they progress with training.