Injecting radio frequency (RF) white noise to the current driving of the laser can broaden the laser emission linewidth and efficiently suppress cavity-mode noise in off-axis integrated cavity output spectroscopy (OA-ICOS). The effect of the injected RF noise level on the cavity-mode noise and the deformation of the absorption line shape in off-axis integrated cavity output spectroscopy (OA-ICOS) with a distributed feedback laser (DFB) at 1.65 µm were investigated. We measured methane at different concentrations between 0.1 ppmv and 2 ppmv associated with a −20 dBm RF noise injection. A linear spectral response of the intensity of the cavity output spectra with the CH₄ concentration was observed. A threefold improvement in the detection limit was achieved compared to unperturbed OA-ICOS. The response time of the improved OA-ICOS system is about 30 s and the minimum detectable concentration (MDC) of CH₄ is 7.6 ppbv, which corresponds to a minimum detectable fractional absorption scaled to the path length of 7.3 × 10⁻¹⁰ cm⁻¹. The noise equivalent absorption sensitivity of the system is 5.51 × 10⁻⁹ cm⁻¹Hz^-1/2.

In this Letter, a new method is proposed to further improve the detection sensitivity of the gas sensor based on off-axis integrated cavity spectroscopy (OA-ICOS) using a distributed feedback laser operating in the near-infrared at 1653 nm that relies on implementation of wavelength modulation and radio frequency (RF) white noise perturbation to diode laser current. More than sixfold improvement in detection limit is achieved for an RF noised wavelength-modulated OA-ICOS compared to the unperturbed conventional OA-ICOS approach.

Erythrocyte deformability correlates with various diseases. Single-cell measurements via optical tweezers (OTs) enable quantitative exploration but may encounter inaccuracies due to erythrocyte life cycle mixing. We present a three-step methodology to address these challenges. Firstly, density gradient centrifugation minimizes erythrocyte variations. Secondly, OTs measure membrane shear force across layers. Thirdly, MATLAB analyzes dynamic cell areas. Results combined with membrane shear force data reveal erythrocyte deformational capacity. To further characterize the deformability of diseased erythrocytes, the experiments used glutaraldehyde-fixed erythrocytes to simulate diseased cells. OTs detect increased shear modulus, while image recognition indicates decreased deformation. The integration of OTs and image recognition presents a comprehensive approach to deformation analysis, introducing novel ideas and methodologies for investigating erythrocytic lesions.

In this study, a gold nanocage composite perovskite quantum dot fluorescent probe (MB-GNCs-PQDs) was designed and constructed. The GNCs-PQDs composite system was formed by the combination of gold nanocages (GNCs) and perovskite quantum dots (PQDs). Spectral analysis confirmed that its fluorescence intensity was significantly enhanced by 15.38% compared with that of pure PQDs. Furthermore, amino modification was performed on the nanomaterial. Through the specific design of molecular beacons (MB), the fluorescence emission spectrum of the probe was matched with the absorption peak of the quencher group BHQ2, and the effective closure of the fluorescence signal was achieved based on the Fluorescence Resonance Energy Transfer (FRET) effect. Subsequently, MB was immobilized on the surface of the composite system via amino covalent conjugation to complete the probe preparation. The prepared probe was applied to the detection of miRNA-4529-3P and miR-301b-3p, which are tumor markers of non-small cell lung cancer (NSCLC). The hybridization of target molecules with MB could trigger the disruption of FRET and the recovery of fluorescence signal, exhibiting excellent recognition performance. This study provides an experimental basis for the preparation of composite fluorescent probes, and the developed probe has potential application value in the field of tumor marker detection.

Off-axis integrated cavity output spectroscopy (OA-ICOS) is an extremely sensitive technique for measuring trace gas concentrations. Nevertheless, recent research has indicated that when the reflectivity of the mirrors forming the cavity is excessively high, it affects the linearity between the absorption signal and concentration. In this study, the causes and limitations of this phenomenon are discussed based on the Beer-Lambert Law and the law of light propagation within the cavity. A new equation is derived to describe the nonlinear relationship between the integral area of absorption spectra and gas concentration. The absorption spectra of CO₂ and CH₄, measured under different experimental conditions and concentrations, were fitted with Voigt functions to obtain parameters such as peak values and integral areas, which were used to verify the theoretical derivation process and results. The experimental results demonstrate that the relationship between the area of the measured absorption spectra and the gas concentration is consistent with the new formula, with an average fitting correlation coefficient of 0.9998. Meanwhile, the experimental results also demonstrate that the effective optical path length indeed decreases with increasing concentration. Furthermore, the cavity reflectances (99.99644 % at 6242.6 cm^-1 and 99.99833% at 6046.96 cm^-1) derived from the fitting coefficient of the new concentration expression closely match the reflectances (99.99727% at 6242.6 cm^-1 and 99.99868% at 6046.96 cm^-1) obtained by applying the classical formula to the spectra of the lowest gas concentration. These experimental results validate the theoretical deduction process and expression. This research provides insights for the theoretical and practical advancements of OA-ICOS, which is significant for advancing high-precision trace gas detection technology.