1.1-µm Band Extended Wide-Bandwidth Wavelength-Swept Laser Based on Polygonal Scanning Wavelength Filter.
Ontology highlight
ABSTRACT:
SUBMITTER: Lee GH
PROVIDER: S-EPMC8141112 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:Innovations in laser engineering have yielded several novel configurations for high repetition rate, broad sweep range, and long coherence length wavelength swept lasers. Although these lasers have enabled high performance frequency-domain optical coherence tomography, they are typically complicated and costly and many require access to proprietary materials or devices. Here, we demonstrate a simplified ring resonator configuration that is straightforward to construct from readily available materials at a low total cost. It was enabled by an insight regarding the significance of isolation against bidirectional operation and by configuring the sweep range of the intracavity filter to exceed its free spectral range. The design can easily be optimized to meet a range of operating specifications while yielding robust and stable performance. As an example, we demonstrate 240 kHz operation with 125 nm sweep range and >70 mW of average output power and demonstrate high quality frequency domain OCT imaging. The complete component list and directions for assembly of the laser are posted on-line at www.octresearch.org.
| S-EPMC4247181 | biostudies-other
Project description:Undersampling and pixelation affect a number of imaging systems, limiting the resolution of the acquired images, which becomes particularly significant for wide-field microscopy applications. Various super-resolution techniques have been implemented to mitigate this resolution loss by utilizing sub-pixel displacements in the imaging system, achieved, for example, by shifting the illumination source, the sensor array and/or the sample, followed by digital synthesis of a smaller effective pixel by merging these sub-pixel-shifted low-resolution images. Herein, we introduce a new pixel super-resolution method that is based on wavelength scanning and demonstrate that as an alternative to physical shifting/displacements, wavelength diversity can be used to boost the resolution of a wide-field imaging system and significantly increase its space-bandwidth product. We confirmed the effectiveness of this new technique by improving the resolution of lens-free as well as lens-based microscopy systems and developed an iterative algorithm to generate high-resolution reconstructions of a specimen using undersampled diffraction patterns recorded at a few wavelengths covering a narrow spectrum (10-30 nm). When combined with a synthetic-aperture-based diffraction imaging technique, this wavelength-scanning super-resolution approach can achieve a half-pitch resolution of 250 nm, corresponding to a numerical aperture of ~1.0, across a large field of view (>20 mm2). We also demonstrated the effectiveness of this approach by imaging various biological samples, including blood and Papanicolaou smears. Compared with displacement-based super-resolution techniques, wavelength scanning brings uniform resolution improvement in all directions across a sensor array and requires significantly fewer measurements. This technique would broadly benefit wide-field imaging applications that demand larger space-bandwidth products.
| S-EPMC6059953 | biostudies-literature
Project description:Light can be used to facilitate alertness, task performance and circadian adaptation during night work. Novel strategies for illumination of workplaces, using ceiling mounted LED-luminaires, allow the use of a range of different light conditions, altering intensity and spectral composition. This study (ClinicalTrials.gov Identifier NCT03203538) investigated the effects of short-wavelength narrow-bandwidth light (?max = 455 nm) compared to long-wavelength narrow-bandwidth light (?max = 625 nm), with similar photon density (~2.8 × 1014 photons/cm2/s) across light conditions, during a simulated night shift (23:00-06:45 h) when conducting cognitive performance tasks. Light conditions were administered by ceiling mounted LED-luminaires. Using a within-subjects repeated measurements study design, a total of 34 healthy young adults (27 females and 7 males; mean age = 21.6 years, SD = 2.0 years) participated. The results revealed significantly reduced sleepiness and improved task performance during the night shift with short-wavelength light compared to long-wavelength light. There was also a larger shift of the melatonin rhythm (phase delay) after working a night shift in short-wavelength light compared to long-wavelength light. Participants' visual comfort was rated as better in the short-wavelength light than the long-wavelength light. Ceiling mounted LED-luminaires may be feasible to use in real workplaces, as these have the potential to provide light conditions that are favorable for alertness and performance among night workers.
| S-EPMC7712639 | biostudies-literature
Project description:We propose a novel filter circuit that incorporates a double ring resonator with a balanced Mach-Zehnder interferometer (MZI). The circuit has a response equivalent to a conventional ring loaded MZI filter, but with added flexibility in terms of configurability. The second-order filter can also be cascaded to realize higher-order filters. The circuit incorporates a two-stage input and output coupler to further reduce the effect of dispersion. A combination of local and global optimization strategies to program the filter, using tailored objective functions, have been tested in simulation and experiments. To our best knowledge, this is the first time a global optimization strategy is directly used in ARMA filter synthesis and simulation without any additional requirement. We further extend the optimization strategy into experiments and demonstrated its use in practical case for programmable filter circuits.
| S-EPMC8795437 | biostudies-literature
Project description:The current paradigm for tuning synthetic biological systems is through re-engineering system components. Biological systems designed with the inherent ability to be tuned by external stimuli will be more versatile. We engineered Escherichia coli cells to behave as an externally tunable band-pass filter for enzyme activity and small molecules. The band's location can be positioned within a range of 4 orders of magnitude simply by the addition of compounds to the growth medium. Inclusion in the genetic network of an enzyme-substrate pair that functions as an attenuator is a generalizable strategy that enables this tunability. The genetic circuit enabled bacteria growth to be patterned in response to chemical gradients in nonintuitive ways and facilitated the isolation of engineered allosteric enzymes. The application of this strategy to other biological systems will increase their utility for biotechnological applications and their usefulness as a tool for gaining insight into nature's underlying design principles.
| S-EPMC2700907 | biostudies-literature
Project description:Light-induced toxicity is a fundamental bottleneck in microscopic imaging of live embryos. In this article, after a review of photodamage mechanisms in cells and tissues, we assess photo-perturbation under illumination conditions relevant for point-scanning multiphoton imaging of live Drosophila embryos. We use third-harmonic generation (THG) imaging of developmental processes in embryos excited by pulsed near-infrared light in the 1.0-1.2 µm range. We study the influence of imaging rate, wavelength, and pulse duration on the short-term and long-term perturbation of development and define criteria for safe imaging. We show that under illumination conditions typical for multiphoton imaging, photodamage in this system arises through 2- and/or 3-photon absorption processes and in a cumulative manner. Based on this analysis, we derive general guidelines for improving the signal-to-damage ratio in two-photon (2PEF/SHG) or THG imaging by adjusting the pulse duration and/or the imaging rate. Finally, we report label-free time-lapse 3D THG imaging of gastrulating Drosophila embryos with sampling appropriate for the visualisation of morphogenetic movements in wild-type and mutant embryos, and long-term multiharmonic (THG-SHG) imaging of development until hatching.
| S-EPMC4128758 | biostudies-literature
Project description:Visible light communication requires III-nitride LEDs with a high modulation bandwidth but have c-plane limitations. General illumination requires green/yellow III-nitride LEDs with high optical efficiency that are difficult to achieve on c-plane substrates. Micro-LEDs with a low efficiency are used to obtain a high modulation bandwidth. This paper demonstrates a record modulation bandwidth of 540 MHz for our semipolar green LEDs with a broad area. Semipolar yellow and amber LEDs with modulation bandwidths of 350 and 140 MHz, respectively, have also been reported, and are the longest wavelength III-nitride LEDs. These results agree with differential carrier lifetime measurements.
| S-EPMC7461145 | biostudies-literature
Project description:This paper presents the design and realization of a compact ultra-wideband (UWB) antenna with a rectangular notch wireless area network (WLAN) band that has controllable notched bandwidth and center frequency. The UWB characteristics of the antenna are achieved by truncating the lower ends of the rectangular microstrip patch, and the notch characteristics are obtained by using electromagnetic bandgap (EBG) structures. EBGs consist of two rectangular metallic conductors loaded on the back of the radiator, which is connected to the patch by shorting pins. A rectangular notch at the WLAN band with high selectivity is realized by tuning the individual resonant frequencies of the EBGs and merging them. Furthermore, the results show that the bandwidth and frequency of the rectangular notch band could be controlled according to the on-demand rejection band applications. In the demonstration, the rectangular notch band was shifted to X-band satellite communication by tuning the EBG parameters. The simulated and measured results show that the proposed antenna has an operational bandwidth from 3.1-12.5 GHz for |S11| < -10 with a rectangular notch band from 5-6 GHz, thus rejecting WLAN band signals. The antenna also has additional advantages: the overall size of the compact antenna is 16 × 25 × 1.52 mm3 and it has stable gain and radiation patterns.
| S-EPMC7038389 | biostudies-literature
Project description:We proposed perfect absorbers of ultra-wide bandwidths based on prism coupling with wavelength-insensitive phase matching, which consists of three dielectric layers (Prism-Cavity-Air) with monolayer graphene embedded in the cavity layer. Due to inherent material dispersion of the dielectric layers, with the proper choice of the incidence angle and the cavity thickness, the proposed perfect absorbers can satisfy the phase matching condition over a wide wavelength range, inducing enormous enhancement of the absorption bandwidth. The requirement on the material dispersions of the prism and the cavity layer for the wavelength-insensitive phase matching over a wavelength range of the interest has been derived, and it has been demonstrated that the various kinds of materials can meet the requirement. Our theoretical investigation with the transfer matrix method (TMM) has revealed that a 99% absorption bandwidth of ~300?nm with perfect absorption at ? ?=?1.51 ?m can be achieved when BK7 and PDMS are used as the prism and the cavity layer, respectively, which is ~7 times wider than the conceptual design based on the non-dispersive materials. The full width at half maximum of our designed perfect absorber is larger than 1.5 ?m.
| S-EPMC6700108 | biostudies-literature
Project description:BackgroundPreference for speech and music processed with nonlinear frequency compression (NFC) and two controls (restricted bandwidth [RBW] and extended bandwidth [EBW] hearing aid processing) was examined in adults and children with hearing loss.PurposeThe purpose of this study was to determine if stimulus type (music, sentences), age (children, adults), and degree of hearing loss influence listener preference for NFC, RBW, and EBW.Research designDesign was a within-participant, quasi-experimental study. Using a round-robin procedure, participants listened to amplified stimuli that were (1) frequency lowered using NFC, (2) low-pass filtered at 5 kHz to simulate the RBW of conventional hearing aid processing, or (3) low-pass filtered at 11 kHz to simulate EBW amplification. The examiner and participants were blinded to the type of processing. Using a two-alternative forced-choice task, participants selected the preferred music or sentence passage.Study sampleParticipants included 16 children (ages 8-16 yr) and 16 adults (ages 19-65 yr) with mild to severe sensorineural hearing loss.InterventionAll participants listened to speech and music processed using a hearing aid simulator fit to the Desired Sensation Level algorithm v5.0a.ResultsChildren and adults did not differ in their preferences. For speech, participants preferred EBW to both NFC and RBW. Participants also preferred NFC to RBW. Preference was not related to the degree of hearing loss. For music, listeners did not show a preference. However, participants with greater hearing loss preferred NFC to RBW more than participants with less hearing loss. Conversely, participants with greater hearing loss were less likely to prefer EBW to RBW.ConclusionsBoth age groups preferred access to high-frequency sounds, as demonstrated by their preference for either the EBW or NFC conditions over the RBW condition. Preference for EBW can be limited for those with greater degrees of hearing loss, but participants with greater hearing loss may be more likely to prefer NFC. Further investigation using participants with more severe hearing loss may be warranted.
| S-EPMC4269381 | biostudies-literature