Mid-infrared optical frequency comb spectroscopy using an all-silica antiresonant hollow-core fiber.

We present the first mid-infrared optical frequency comb spectrometer employing an absorption cell based on self-fabricated, all-silica antiresonant hollow-core fiber (ARHCF). The spectrometer is capable of measuring sub-mL sample volumes with 26 m interaction length and noise equivalent absorption sensitivity of 8.3 × 10-8 cm-1 Hz-1/2 per spectral element in the range of 2900 cm-1 to 3100 cm-1. Compared to a commercially available multipass cell, the ARHCF offers a similar interaction length in a 1000 times lower gas sample volume and a 2.8 dB lower transmission loss, resulting in better absorption sensitivity. The broad transmission windows of ARHCFs, in combination with a tunable optical frequency comb, make them ideal for multispecies detection, while the prospect of measuring samples in small volumes makes them a competitive technique to photoacoustic spectroscopy along with the robustness and prospect of coiling the ARHCFs open doors for miniaturization and out-of-laboratory applications.

Direct performance comparison of antiresonant and Kagome hollow-core fibers in mid-IR wavelength modulation spectroscopy of ethane.

In this paper, we experimentally asses the performance of wavelength modulation spectroscopy-based spectrometers incorporating 1.3 m-long gas absorption cells formed by an antiresonant hollow core fiber (ARHCF) and a Kagome hollow core fiber. To evaluate the discrepancies with minimum methodology error, the sensor setup was designed to test both fibers simultaneously, providing comparable measurement conditions. Ethane (C2H6) with a transition located at 2996.88 cm-1 was chosen as the target gas. The experiments showed, that due to better light guidance properties, the ARHCF-based sensor reached a minimum detection limit of 4 ppbv for 85 s integration time, which is more than two times improvement in comparison to the result obtained with the Kagome fiber.

Quartz-Enhanced Photothermal Spectroscopy-Based Methane Detection in an Anti-Resonant Hollow-Core Fiber.

In this paper, the combination of using an anti-resonant hollow-core fiber (ARHCF), working as a gas absorption cell, and an inexpensive, commercially available watch quartz tuning fork (QTF), acting as a detector in the quartz-enhanced photothermal spectroscopy (QEPTS) sensor configuration is demonstrated. The proof-of-concept experiment involved the detection of methane (CH4) at 1651 nm (6057 cm-1). The advantage of the high QTF Q-factor combined with a specially designed low-noise amplifier and additional wavelength modulation spectroscopy with the second harmonic (2f-WMS) method of signal analysis, resulted in achieving a normalized noise-equivalent absorption (NNEA) at the level of 1.34 × 10-10 and 2.04 × 10-11 W cm-1 Hz-1/2 for 1 and 100 s of integration time, respectively. Results obtained in that relatively non-complex sensor setup show great potential for further development of cost-optimized and miniaturized gas detectors, taking advantage of the combination of ARHCF-based absorption cells and QTF-aided spectroscopic signal retrieval methods.

A Review of Antiresonant Hollow-Core Fiber-Assisted Spectroscopy of Gases.

Antiresonant Hollow-Core Fibers (ARHCFs), thanks to the excellent capability of guiding light in an air core with low loss over a very broad spectral range, have attracted significant attention of researchers worldwide who especially focus their work on laser-based spectroscopy of gaseous substances. It was shown that the ARHCFs can be used as low-volume, non-complex, and versatile gas absorption cells forming the sensing path length in the sensor, thus serving as a promising alternative to commonly used bulk optics-based configurations. The ARHCF-aided sensors proved to deliver high sensitivity and long-term stability, which justifies their suitability for this particular application. In this review, the recent progress in laser-based gas sensors aided with ARHCFs combined with various laser-based spectroscopy techniques is discussed and summarized.

Fabrication of Microchannels in a Nodeless Antiresonant Hollow-Core Fiber Using Femtosecond Laser Pulses.

In this work, we present femtosecond laser cutting of microchannels in a nodeless antiresonant hollow-core fiber (ARHCF). Due to its ability to guide light in an air core combined with exceptional light-guiding properties, an ARHCF with a relatively non-complex structure has a high application potential for laser-based gas detection. To improve the gas flow into the fiber core, a series of 250 × 30 µm microchannels were reproducibly fabricated in the outer cladding of the ARHCF directly above the gap between the cladding capillaries using a femtosecond laser. The execution time of a single lateral cut for optimal process parameters was 7 min. It has been experimentally shown that the implementation of 25 microchannels introduces low transmission losses of 0.17 dB (<0.01 dB per single microchannel). The flexibility of the process in terms of the length of the performed microchannel was experimentally demonstrated, which confirms the usefulness of the proposed method. Furthermore, the performed experiments have indicated that the maximum bending radius for the ARHCF, with the processed 100 µm long microchannel that did not introduce its breaking, is 15 cm.

Nitrous oxide detection at 5.26 µm with a compound glass antiresonant hollow-core optical fiber.

Laser-based gas sensors utilizing various light-gas interaction phenomena have proved their capacity for detecting different gases. However, achieving reasonable sensitivity, especially in the mid-infrared, is crucial. Improving sensor detectivity usually requires incorporating multipass cells, which increase the light-gas interaction path length at a cost of reduced stability. An unconventional solution comes with the aid of hollow-core fibers. In such a fiber, light is guided inside an air-core which, when filled with the analyte gas can serve as a low-volume and robust absorption cell. Here we report on the use of a borosilicate antiresonant hollow-core fiber for laser-based gas sensing. Due to its unique structure and guidance, this fiber provides low-loss, single-mode transmission $ {\gt} {5}\;{\unicode{x00B5}{\rm m}}$>5µm. The feasibility of using the fiber as a gas cell was verified by detecting nitrous oxide at 5.26 µm with a minimum detection limit of 20 ppbv.

Antiresonant Hollow-Core Fiber-Based Dual Gas Sensor for Detection of Methane and Carbon Dioxide in the Near- and Mid-Infrared Regions.

In this work, we present for the first time a laser-based dual gas sensor utilizing a silica-based Antiresonant Hollow-Core Fiber (ARHCF) operating in the Near- and Mid-Infrared spectral region. A 1-m-long fiber with an 84-µm diameter air-core was implemented as a low-volume absorption cell in a sensor configuration utilizing the simple and well-known Wavelength Modulation Spectroscopy (WMS) method. The fiber was filled with a mixture of methane (CH4) and carbon dioxide (CO2), and a simultaneous detection of both gases was demonstrated targeting their transitions at 3.334 µm and 1.574 µm, respectively. Due to excellent guidance properties of the fiber and low background noise, the proposed sensor reached a detection limit down to 24 parts-per-billion by volume for CH4 and 144 parts-per-million by volume for CO2. The obtained results confirm the suitability of ARHCF for efficient use in gas sensing applications for over a broad spectral range. Thanks to the demonstrated low loss, such fibers with lengths of over one meter can be used for increasing the laser-gas molecules interaction path, substituting bulk optics-based multipass cells, while delivering required flexibility, compactness, reliability and enhancement in the sensor's sensitivity.

Heterodyne interferometric signal retrieval in photoacoustic spectroscopy.

A new heterodyne interferometric method for optical signal detection in photoacoustic or photothermal spectroscopy is demonstrated and characterized. It relies on using one laser beam for the photoacoustic excitation of the gas sample that creates refractive index changes along the beam path, while another laser beam is used to measure these changes. A heterodyne-based detection of path-length changes is presented that does not require the interferometer to be balanced or stabilized, which significantly simplifies the optical design. We discuss advantages of this new approach to photoacoustic signal detection and the new sensing arrangements that it enables. An open-path photoacoustic spectroscopy of carbon dioxide at 2003 nm and a novel sensing configuration that enables three-dimensional spatial gas distribution measurement are experimentally demonstrated.

Laser-Based Monitoring of CH4, CO2, NH3, and H2S in Animal Farming-System Characterization and Initial Demonstration.

In this paper, we present a system for sequential detection of multiple gases using laser-based wavelength modulation spectroscopy (WMS) method combined with a Herriot-type multi-pass cell. Concentration of hydrogen sulfide (H2S), methane (CH4), carbon dioxide (CO2), and ammonia (NH3) are retrieved using three distributed feedback laser diodes operating at 1574.5 nm (H2S and CO2), 1651 nm (CH4), and 1531 nm (NH3). Careful adjustment of system parameters allows for H2S sensing at single parts-per-million by volume (ppmv) level with strongly reduced interference from adjacent CO2 transitions even at atmospheric pressure. System characterization in laboratory conditions is presented and the results from initial tests in real-world application are demonstrated.

High energy green nanosecond and picosecond pulse delivery through a negative curvature fiber for precision micro-machining.

In this paper we present an anti-resonant guiding, low-loss Negative Curvature Fiber (NCF) for the efficient delivery of high energy short (ns) and ultrashort (ps) pulsed laser light in the green spectral region. The fabricated NCF has an attenuation of 0.15 dB/m and 0.18 dB/m at 532 nm and 515 nm respectively, and provided robust transmission of nanosecond and picosecond pulses with energies of 0.57 mJ (10.4 kW peak power) and 30 µJ (5 MW peak power) respectively. It provides single-mode, stable (low bend-sensitivity) output and maintains spectral and temporal properties of the source laser beam. The practical application of fiber-delivered pulses has been demonstrated in precision micro-machining and marking of metals and glass.

Picosecond and nanosecond pulse delivery through a hollow-core Negative Curvature Fiber for micro-machining applications.

We present high average power picosecond and nanosecond pulse delivery at 1030 nm and 1064 nm wavelengths respectively through a novel hollow-core Negative Curvature Fiber (NCF) for high-precision micro-machining applications. Picosecond pulses with an average power above 36 W and energies of 92 µJ, corresponding to a peak power density of 1.5 TWcm⁻² have been transmitted through the fiber without introducing any damage to the input and output fiber end-faces. High-energy nanosecond pulses (>1 mJ), which are ideal for micro-machining have been successfully delivered through the NCF with a coupling efficiency of 92%. Picosecond and nanosecond pulse delivery have been demonstrated in fiber-based laser micro-machining of fused silica, aluminum and titanium.

Comparison of INTEGRA and the Manual Method to Determine the Axis for Intraocular Lens Implantation-A Case Series of 60 Eyes.

(1) Background: To compare the results of a new intraoperative contactless device (INTEGRA Optomed, Poland) with the result of a manual method for determining the axis for toric intraocular lens implantation. (2) Material and Methods: This retrospective observational study included 60 eyes of 40 patients (17 men, 23 women) who had toric intraocular lenses implanted. A video recording of each surgery that used the INTEGRA system was made for the analysis. Two researchers then independently assessed the location of the implant axes determined with both digital and manual slit-lamp methods, and compared the results between methods. (3) Results: The implantation axes suggested through the manual and INTEGRA methods were similar. The median axis disparities were 0.0 degrees for both groups. The standard deviation was 0.63 and 0.75 for researcher 1 and 2, respectively. The dominant value was 0.0 in both groups. The INTEGRA axis designation was statistically significantly different from the manual method for researcher 1 (p < 0.05), but it was statistically insignificant for researcher 2 (p = 0.79). (4) Conclusions: The INTEGRA system is a digital ink-free device for image tracking scleral vessels. It was helpful for determining the implantation axis in a precise manner, and the measurements were comparable with those obtained through a manual technique.

Validation of FES-I and Short FES-I Scales in the Polish Setting as the Research Tools of Choice to Identify the Fear of Falling in Older Adults.

Fear of falling is associated with a clear hazard to individual self-reliance, reduced physical activity, as well as a sense of shame and loss of self-confidence. The present study aimed to complete the applicable translation and validation protocol for the Falls Efficacy Scale-International (FES-I) tool, following its prior adaptation to ensure full compatibility with the Polish setting. The FES-I questionnaire, along with its abridged version, was translated in line with the recommended standards of the MAPI Institute, taking into account both the cultural fabric and pertinent language specifics of the country. The survey was attended by 740 individuals (N = 740; 463 women, 277 men), over 60 years old. All respondents were required to complete both the FES-I and FES-I (Short) questionnaires twice, following an intervening period, and subsequently had their responses statistically assessed. The FES-I questionnaire, along with its abridged version, may be recommended as an effective assessment tool for addressing the fear of falling issue among the older adults, consequently allowing the teams of attending physicians, physiotherapists, psychologists, or psychiatrists to complete an unambiguous diagnosis, with a view to helping the patients overcome this particular type of anxiety.

Manganese superoxide dismutase (MnSOD) gene (Ala-9Val, Ile58Thr) polymorphism in patients with age-related macular degeneration (AMD).

BACKGROUND: Oxidative stress is involved in the pathogenesis of many chronic disorders including cancer, inflammation, and neurologic diseases. Reactive oxygen species (ROS) may play a major role in age-related macular degeneration (AMD). This study investigated the mRNA and protein profiles of manganese superoxide dismutase MnSOD in patients with AMD and healthy controls, while examining its genetic sequence polymorphism (Ala-9Val, Ile58Thr). Our intent was to find a correlation between the expression of MnSOD genes and nucleotide sequence polymorphisms encoded in the gene of the dry and wet form of AMD. MATERIAL/METHODS: We examined 300 unrelated AMD patients and 300 unrelated healthy controls who gave free consent to participate in the study. The MnSOD gene polymorphisms were determined by PCR/RFLP method. We also used real-time RT-PCR and ELISA methods to estimate expression of MnSOD mRNA and protein. RESULTS: There were statistically significant differences in the genotype distribution between patients with AMD and controls. Our results showed positive correlations between gene sequence polymorphism and the level of MnSOD mRNA and protein expression. The Ala-9Ala genotype and alanine allele (Ala-9Val sequence polymorphism) is much more frequent in AMD patients than in healthy subjects. Healthy controls who are homozygotes Val/Val and heterozygotes Ala/Val showed lower expression of the MnSOD gene as compared to homozygote Ala/Ala. The lowest expression of MnSOD (homozygotes Val/Val and heterozygotes Ala/Val for wet and dry form of AMD) was noted in patients with AMD. CONCLUSIONS: These data suggest a genetic role of MnSOD polymorphism in the development of age-related degeneration.

Comparison between using INTEGRA and manual method in determining axis for intraocular lens implantation: Preliminary retrospective study.

The aim of this study was to explore the efficacy, repeatability, and efficiency of a new intraoperative contactless device (INTEGRA Optomed, Chorzów, Poland) for determining the axis for toric intraocular lens implantation and then to compare this with that determined using a manual method.This study was conducted at the Ophthalmological Center for Children and Adults Optomed, Chorzów, Poland.This nonrandomized, retrospective, observational study included 20 eyes of 12 patients (5 males and 7 females) who had toric intraocular lens implanted. A video recording of each surgery using the INTEGRA system was made showing the analysis. The surgeon and one of the researchers then independently assessed the location of the implant axes determined with both digital and manual slit-lamp methods, and compared them.The implantation axes suggested for both the manual and INTEGRA methods were similar. The median axis disparities were 0.0 degree and 0.5 degree, and standard deviations were 0.61 and 0.81 for researcher 1 and 2, respectively. The dominant value was 0.0 in both groups. The INTEGRA axis designation was not statistically different from the manual method (level of significance: α < 0.01).The INTEGRA system is a digital ink-free device for image tracking scleral vessels. It was helpful for determining the implantation axis in a precise and repeatable manner, and measurements were comparable with a manual technique.

Two sisters with microphthalmia and anterior segment dysgenesis secondary to a PAX6 pathogenic variant with clinically healthy parents: a case of gonadal mosaicism?

PURPOSE: Genetic analysis of two siblings with complex microphthalmia, with clinically healthy parents. STUDY DESIGN: Clinical and experimental. METHODS: The patients underwent a detailed ophthalmic evaluation, including visual acuity, fundus examination, gonioscopy, ultrasound examination, and optical coherence tomography. Lensectomy with anterior vitrectomy was conducted in both patients. Additionally, in patient p1, electroencephalography analysis was performed. Genetic analysis was carried out using array comparative genomic hybridization (aCGH) and whole exome sequencing (WES). Bidirectional Sanger sequencing was conducted for validation and segregation analysis of the identified variant in the family. RESULTS: The aCGH results were normal. The heterozygous PAX6 variant c.52G>C (p.Gly18Arg) was identified in the proband (p1) through WES analysis. Sanger sequencing of exon 5 of PAX6 confirmed the presence of the variant in the other affected sibling (patient p2) but did not allow for identification of the variant in the parents' DNA isolated from leukocytes and buccal cells. CONCLUSIONS: The description of the variant in PAX6 in two siblings with clinically healthy parents who are negative for the mutation in DNA from leukocytes and buccal cells represents the possibility of parental gonadal mosaicism. Detection of germ cell mosaicism in the parents is essential to provide genetic counseling to the family regarding the risk of reoccurrence. Furthermore, we also report a pathogenic variant in PAX6 that to our knowledge has not so far been reported in patients with partial aniridia and therefore broadens the spectrum of the variants associated with aniridia.

[Application of duo-systems (piggy back) in correction of keratoconus]. / Zastosowanie duosystemów (piggy back) w korekcji stozka rogówki.

The purpose of the paper was to determine possibilities and effectiveness of application of piggy back system in keratoconus and choosing the best soft contact lens to meet the demands of the system. 335 patients were examined (511 eyes), including 131 women (163 eyes) and 204 men (348 eyes). Retrospective method involved patients with chronic corneal erosion and symptoms of intolerance of hard contact lenses. It was found out that application of piggy back system is the best therapeutic method in cases of chronic corneal erosion and it improves comfort of wearing lenses. Sof Lens 66 proved to fulfill the assumed criteria best. Application of piggy back reduces opacity within keratoconus top and it prevents or delays necessity of penetrating keratoplasty.

[New possibilities of individual fitting of hard contact lenses with use of computer programs and videokeratography (CVK)]. / Nowe mozliwosci indywidualnego dopasowania soczewek kontaktowych twardych z uzyciem programów komputerowych oraz wideokeratografii (CVK).

The aim of the following paper is to evaluate possibilities of modern computer technologies and CVK in fitting of hard contact lenses in difficult cases of keratoconus or in order to improve their tolerance. 425 patients were examined (761 eyes) 289 men and 135 women, age - between 11 and 56 years of life, giving the average of 26 years. Evaluation was carried out by means of retrospective method, analyzing the effect of fitting in the 2nd and 3rd stage of keratoconus, advancement in the Amsler and Muckenchirn's scale. The procedure involved the technique of parallel application to the cornea. Computer technique enabled fast and precise fitting of lenses in difficult cases.

[Evaluation of eye total aberration in patients with keratoconus]. / Ocena aberracji ukladu optycznego oka u pacjentów ze stozkiem rogówki.

PURPOSE: Evaluation of total eye aberration in patients with I, II, III degree of keratoconus according to Amsler scale, and results compared with normal group patients, having only refractive error. MATERIAL AND METHOD: The analyzed group of patients consisted of 43 patients (55 eyes), who underwent examinations: visual acuity, subjective and objective refractive error, cornea keratometric power, pupil diameter and total eye aberration performed by System WASCA (Asclepion-Meditec). Our patients were divided in to two groups: group I--16 patients with keratoconus (25 eyes), group II--27 control patients (30 eyes). RESULTS: Comparison of all analyzed parameters in both groups were statistical significant. In eyes with keratoconus coma aberrations excel spherical aberrations.