We first propose and demonstrate a polarimetric fiber laser system for relative humidity (RH) sensing based on the beat frequency demodulation. A graphene oxide-coated D-shaped fiber (GDF) with a low insertion loss of 0.8 dB was embedded into a laser cavity to form an RH sensing probe. The output of the fiber laser could generate mode splitting between two orthogonal polarization modes due to birefringence of the GDF device. Hence, two types of beat signals, i.e., longitudinal mode beat frequency (LMBF) and polarization mode beat frequency (PMBF) could be generated synchronously. The experimental results indicated that the LMBFs of the fiber laser had almost no response to the ambient humidity, and the PMBFs of the fiber laser were very sensitive to the various RH levels. There was a good linear relationship between the PMBF and RH changes in the range of 30% to 98%. This fiber-optic RH sensor exhibited a sensitivity of 34.7 kHz/RH% with a high quality of fit (R>0.997) during the ambient RH increase and decrease. Moreover, the average response and recovery times of the fiber-optic RH sensor were measured to be about 64.2 ms and 97.8 ms, respectively. Due to its long stability, reversibility, quick response time and low temperature cross-sensitivity (i.e., 0.12 RH%/°C), the proposed fiber-optic RH sensor could offer attractive applications in many fields, such as biology, chemical processing and food processing, etc.
Harvard Medical School, Boston, MA 02114, USA; Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Cardiology, Erasmus Medical Center, Rotterdam GD3015, The Netherlands; Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA 02142, USA.
Photoacoustic microscopy (PAM) is a high-resolution and non-invasive imaging modality that provides optical absorption contrast. By employing dual- or multiple-wavelength excitation, PAM extends its capabilities to offer valuable spectroscopic information. To achieve efficient multispectral PAM imaging, an essential requirement is a light source characterized by a high repetition rate and switching rate, a ≈microjoule pulse energy, and a ≈nanosecond pulse duration.
Objective: To evaluate and compare the accuracy of detection methods for the diagnosis of secondary caries around direct restorations in posterior teeth.
Data: Accuracy parameters including sensitivity, specificity, diagnostic odds ratio (DOR), area under curve (AUC), and partial AUC (pAUC) are generated from studies assessing the accuracy of detection methods for secondary caries.
Sources: Publications from PubMed, Web of Science, Scopus, Medline, EMBASE and Cochrane Library databases.
Cascaded Raman fiber lasers (CRFLs) with wavelength-independent feedback can provide power at any wavelength in near-IR regions. However, broad feedback leads to a broad output spectrum, decreasing spectral power density at a desired wavelength. The output characteristics of CRFLs can be controlled by controlling the feedback.
In this Letter, we present an all-fiber bismuth (Bi)-doped germanosilicate fiber laser that is continuously tunable within the range of 1425-1475 nm, enabled by a tunable optical filter. A maximum output power of 86.4 mW was achieved at 1450 nm with a slope efficiency of 13.
Holographically designed aperiodic lattices (ALs) have proven to be an exciting engineering technique for achieving electrically switchable single- or multi-frequency emissions in terahertz (THz) semiconductor lasers. Here, we employ the nonlinear transfer matrix modeling method to investigate multi-wavelength nonlinear (sum- or difference-) frequency generation within an integrated THz (idler) laser cavity that also supports optical (pump and signal) waves. The laser cavity includes an aperiodic lattice, which engineers the idler photon lifetimes and effective refractive indices.
