Laser-induced autofluorescence (LIAF) spectroscopy is a label-free optical technique sensitive to biochemical and structural tissue properties. Its application in upper aerodigestive tract malignancies is in its early stages. This study evaluates the feasibility of a matrix scan-based LIAF approach for examining differences between normal and malignant tissues. An exploratory case series involving three patients with oropharyngeal malignancies was conducted. Tissue sections from normal and tumor regions were analyzed using LIAF spectroscopy, including intensity and lifetime measurements, implemented through a matrix scanning protocol with fixed excitation, detection sensitivity, and sample thickness. Complementary Fourier-transform infrared (FTIR) spectroscopy was used to qualitatively assess biochemical variations, and spectroscopic findings were correlated with histopathological evaluation. Within individual cases, consistent differences in autofluorescence spectral and lifetime characteristics were observed between benign and malignant tissue regions. FTIR analysis revealed concurrent biochemical variations that qualitatively supported the autofluorescence observations. This exploratory study demonstrates the potential of combining LIAF matrix scan with FTIR spectroscopy to investigate tissue-specific spectral variations in upper aerodigestive tract lesions. The findings are preliminary and motivate further investigation using larger patient groups and clinically relevant acquisition conditions.

This paper reports results obtained using white light diffraction phase microscopy (wDPM) on captured images of breast and colon tissue samples, marking a contribution to the advancement in biomedical imaging. Unlike conventional brightfield microscopy, wDPM offers the capability to capture intricate details of biological specimens with enhanced clarity and precision. It combines high resolution, enhanced contrast, and quantitative capabilities with non-invasive, label-free imaging. These features make it a useful tool for tissue imaging, providing detailed and accurate insights into tissue structure and dynamics without compromising the integrity of the samples. Our findings underscore the potential of quantitative phase imaging in histopathology, in the context of automating the process of tissue analysis and diagnosis. Of particular note are the insights gained from the reconstructed phase images, which provide physical data regarding peripheral glandular cell membranes. These observations serve to focus attention on pathologies involving the basal membrane, such as early invasive carcinoma. Through our analysis, we aim to contribute to catalyzing further advancements in tissue (breast and colon) imaging.

Breast cancer remains a global health challenge, prompting interest in the anticancer properties of other drugs, including chlorpromazine (CPZ). This study presents a novel approach in breast cancer treatment using laser irradiated CPZ. CPZ dissolved in distilled water, was exposed to 266 nm laser irradiation for varying durations, characterized by UV-Vis and FTIR spectroscopy, followed by drug-likeness and ADME-Tox predictions. In vitro assays evaluated the cytotoxicity and cellular effects on MCF-7 breast cancer cells, and compared with MCF-12 A healthy cell line. Laser irradiation altered CPZ molecular structure resulting in photoproducts with favourable drug-like properties and ADME-Tox profiles. In vitro evaluations demonstrate dose and irradiation time-dependent cytotoxicity against breast cancer cells, and reduced toxicity on healthy cell line. Significant alterations in F-actin organization, and excessive ROS generation were also proved, suggesting the potential of laser-modified CPZ for breast cancer therapy. This study introduces a novel approach to breast cancer treatment through laser irradiated CPZ, highlighting promising advancements in therapy and emphasizing the role of laser-generated compounds.

The need to measure droplets temperature with high precision in moderate or extreme environments has driven the development of advanced methods. Here, we report, for the first time, the measurement of droplet temperature using optical fiber-based temperature sensors. Specifically, a fiber Bragg grating sensor was used as a non-invasive technique to determine the temperature behavior of single micro-volumetric pendant droplets. The fiber sensor method, which provides indirect measurements, was validated by experimental and simulation data from the literature, showing good agreement. The temperature measurements rely on monitoring the vapor layer temperature near the droplet at sub-millimeter fiber-to-droplet distances and on determining a coefficient that characterizes the temperature difference between the droplet and the surrounding vapor layer at the liquid-gas interface. We calibrated the method by conducting measurements under various relative humidities and fiberdroplet contact conditions. We found that the coefficient remains constant for a specific distance regardless of the relative humidity or the droplet volume. Furthermore, we observed the minor influences that the environmental relative humidity and droplet content has on the behavior of the recorded temperatures during the short period after droplet generation.

"We report secure data transmission performed using chaotic lasers with different external cavity geometries and applying the chaotic masking method based on subcarrier and phase modulations of the chaotic optical carrier. Two semiconductor lasers with similar multimode emission spectra and self-optical feedback provided, respectively, by ring and linear external cavities, were optically coupled and chaotically synchronized into a master – slave scheme. The transmitted message frequency modulates the radio frequency signal which modulates in phase the master chaotic carrier. Based on the robustness of the used encryption method and the synchronization characteristics of the two lasers, the decryption is conducted by the simple radio frequency spectrum monitoring of the slave emission."

The need to measure temperature with high precision in extreme environments has driven the development of advanced methods. One of these is the use of optical fiber-based temperature sensors. Here, we report for the first time the approach of temperature measurements by a fiber Bragg grating sensor as a non-invasive method to determine the temperature of single micro-volumetric pendant droplets. The temperature measurements of individual droplets rely on monitoring the solvent evaporation process and the parameterization of the temperature difference between droplet and the surrounding vapor layer at the liquid-gas interface. We characterize the temperature behavior by conducting measurements under varying relative humidity, in-contact, and no-contact conditions. The influences of the environment’s relative humidity and droplet content upon the behavior of the recorded temperatures at short period after droplet generation are reported.

High-resolution spectrum analysis of the lasing emission of mm3-sized pendant droplets that contain aqueous solutions of the Rhodamine 6G (Rh6G) dye is reported. Pumping was performed with a 532 nm pulsed laser beam. The lasing emission demonstrates a complex spectral structure that contains mode-cluster peaks spaced 2 nm apart and a ripple structure formed by periodic resonances, which are superimposed on the peak closest to the maximum of the dye gain curve. The periodic resonances are associated with the light-scattering resonances on a large sphere when light absorption in the sphere occurs.

Long-term space missions must be prepared to provide means to treat astronauts' illnesses that could occur at take-off, during flights or arriving on other planets. This could be achieved using multipurpose medicines. Phenothiazine derivatives, normally used to treat mental and emotional disorders, are photosensitive drugs and in solutions undergo molecular modifications by exposure to UV laser radiation, which leads to transformation of a parent-compound into photoproducts with increased antimicrobial activity when compared to unirradiated solutions. Since space missions involve, even if only for short durations, hypergravity environment transitions, their effects on unirradiated and laser irradiated chlorpromazine and promazine aqueous solutions were studied in this paper. The experiment was performed at the European Space Agency's Large Diameter Centrifuge, subjecting solutions at 20 times Earth's gravitational acceleration. Since, generally, little is known about medicines exposed to high-g levels, this research brings an insight into the impact of hypergravity on phenothiazines. To evaluate drug stability, samples were assessed pre- and post-hypergravity treatment by pH measurements, UV-Vis-NIR/FTIR spectroscopy and thin layer chromatography. No significant changes between uncentrifuged and centrifuged samples were evidenced subsequent to hypergravity exposure, emphasising the stability of unirradiated and laser irradiated phenothiazines, which may allow their use during future space missions.

A densitometry method based on steady-state and time-resolved fluorescence assessments for thioridazine and its photoproducts applied on HPTLC plates has been developed. The excitation source was a picosecond diode laser emitting at 375 nm. This method was used for the analysis of the photoproducts resulted from thioridazine irradiation with 266 nm nanosecond-pulsed laser. The validation of the developed method was performed for thioridazine in terms of linearity, precision, limits of detection and quantification. Furthermore, analysis of the photoproducts of irradiated thioridazine was performed by steady-state and time-resolved fluorescence. The fluorescence spectra and fluorescence lifetime of each photoproduct were obtained and the horizontal chromatograms of fluorescence maxima were generated.

This paper presents a spectroscopic study of emulsions generated with a laser-assisted device. Fourier transform infrared (FTIR), Raman and UV–Vis–NIR reflectance spectra of emulsions, recorded before and after exposure to laser radiation were used to characterize the effect of laser irradiation. The paper also presents a comparison between the calculated IR spectra and the experimental FTIR spectra of an emulsion’s components. FTIR measurements allowed the identification of absorption bands specific to each of the emulsions’ components. Moreover, it enabled the observation of destabilization of the emulsion in real-time. Raman spectroscopy allowed the observation of the modifications at a molecular level, by identifying the vibrations of the representative functional groups and the polymerization of sodium tetradecyl sulfate (STS) molecules by analyzing the evolution of the carbonyl band. UV–Vis–NIR reflectance spectra of emulsions before and after exposure to laser radiation showed that the physical characteristics of the emulsions changed during irradiation—the dimensions of the droplets decreased, leading to an emulsion with a better time stability. These results proved that the employed spectroscopy techniques were powerful tools in emulsion analysis.

Fluorescence and lasing emission that are produced separately in time during excitation laser pulse for an mm-sized Rhodamine 6G dye-water droplet are reported. The droplet acts as a quasi-spherical closed optical resonator and due to multiple internal reflections, the resonant amplified emission is delayed with respect to fluorescence emission. Measurements of the temporal evolution of the droplet's emission were performed by varying the signal acquisition gate width and gate delay with respect to the pumping pulse. The droplet emission spectra are structured in two bands which appear one after the other in time: first, the fluorescence emission band which follows pumping laser pulse time shape and then a second band, the lasing band, placed at shorter wavelengths and formed in time after the peak of the pumping laser pulse intensity, on the pulse tail. The lasing threshold pumping intensity is much lower than those for typical dye lasers.

A complex chaotic behavior can be found in nonlinear dynamics of laser diode emission, only under optical feedback conditions provided by an external reflector. One of the most studied issues on chaotic dynamics is low frequency fluctuations (LFF) which occur at laser diode operation near lasing threshold. In this paper an extensive analysis of LFF regime of an external cavity - semiconductor laser system has been carried out. Data about the stability of LFF regimes for different sets of experimental parameters are shown. The injection current was adjusted at values near and over laser threshold current. Stable LFF regimes were obtained at current values above the threshold current only in certain conditions. These depend on intrinsic properties of semiconductor active region, namely, instabilities of mode-hoping type that are observed when the laser emission is obtained without feedback.

Two semiconductor lasers operated under external optical feedback conditions in low-frequency fluctuations (LFF) chaotic regime were optically coupled into a master - slave synchronization scheme. The modulation of master injection current induces in the emission of two coupled systems power dropouts at two dominant frequencies. The dropouts rates were studied using the statistical analysis and were correlated with the modulation frequency and the frequencies of natural LFF oscillations of master and slave emissions. Modulation at a frequency included in the range bounded by master and slave natural LFF frequencies has, as effect, the clustering of slave dropouts on two frequencies: the driven and the master natural LFF ones. If modulation frequency is out of this range, it has only the role to group dropouts periods on two frequencies, different from the modulation one. This behavior is consistent with the phase correlation between master laser and external modulator at the used driven frequencies.

Emulsification methods are of interest for numerous fields and those that generate nanoemulsions are, particularly, of great interest for medical applications. This paper presents a new laser-assisted device that may generate pharmaceutical emulsions. One of its advantages is that allows the use of small quantities of solutions, as low as a few hundreds of mu l. It also allows to set the number of mixing cycles and mixing speeds. Emulsions of Sodium tetradecyl sulfate (STS) solution in water and oily vitamin A were generated without additional stabilizers. Optical microscopy, dynamic light scattering and surface tension analysis of a pendant drop were employed to compare the unirradiated emulsions with the ones exposed to laser radiation at 532 nm. Results showed that laser radiation decreases and homogenizes droplets dimensions. Furthermore, irradiation increases the stability of the emulsions. The wavelength of laser radiation is selected so that it is not absorbed by molecules in the immiscible solutions. In this way the energy of laser radiation leads to droplet break-up and generation of new, smaller droplets.

Laser induced autofluorescence (LIAF) lifetime is useful to distinguish between normal laryngeal tissues and squamous cell carcinoma (SCC) based on variations of their biochemical composition and structure alterations. LIAF was collected from samples constituted by pairs of normal and malignant tissue, which were excised from three patients. Exclusion criteria for samples harvest were: (i) macroscopic changes of normal vocal cord observed during surgery; (ii) previous surgical intervention on vocal cord, (iii) patients treated only with chemotherapy or radiotherapy for carcinoma. Inclusion conditions: men, aged 57-68, non-smokers. A pulsed laser diode excited LIAF at 375 nm and 31 MHz repetition rate; beam full-time width at half-maximum was 87 ps at an average power of 0.49 mW. Mean LIAF lifetime for normal tissues was (3.75 ± 0.49) ns and for malignant (4.37 ± 0.85) ns: it is longer in malignant than in normal tissue. Variance analysis made with Fisher's test has shown no significant difference between patients for normal tissues; the same was true for malignant. Though, when malignant tissue was compared to normal for the same patients as well as between patients, a significant difference (significance level of 5%) was evidenced. Time-resolved LIAF may allow better differentiation between normal and malignant tissues in patients diagnosed with larynx SCC.

In the emission dynamics of a semiconductor laser operated under double optical feedback conditions, mixing of high frequency oscillations was observed. This consists of high frequency oscillations modulated by low-frequency fluctuations. The external feedback is provided by a double reflector cavity consisting of one cavity bordered by a diffraction grating which assures the optical injection on -1 -diffraction order and the other one delimited by a mirror which returns the 0 - order of the diffraction grating. We show experimentally that by changing the feedback intensity of the long cavity, high frequency chaotic oscillations with tunable frequencies are obtained. The chaotic oscillations show function of the long cavity feedback intensity, frequency values bounded by those of the short cavity and first harmonic of the long cavity. Also, the value range of the oscillation frequencies increase with the short cavity feedback intensity increasing.

Results for the interaction of a 532 nm pulsed laser beam with individual pendant rhodamine 6G dye droplets of a large-size parameter, x approximate to 7300, are reported. By varying dye concentration and pumping energy, typical fluorescence bands detected in such cases are obtained, along with a narrow, instantly, or gradually blueshifted band assigned to the lasing effect at the droplet surface. The maximum blueshift value of the lasing peak wavelength is associated with the maximum of the dye fluorescence gain curve when self-absorption effects are not present. Lasing peak position is not further influenced by pumping energy or droplet diameter decrease after lasing reaches the gain curve peak wavelength. (C) 2018 Optical Society of America