scholarly journals Design for Distributed Feedback Laser Biosensors Based on the Active Grating Model

Sensors ◽  
2019 ◽  
Vol 19 (11) ◽  
pp. 2569 ◽  
Author(s):  
Bowen Wang ◽  
Yi Zhou ◽  
Zhihe Guo ◽  
Xiang Wu
Keyword(s):  
Duty Cycle ◽  
Theoretical Calculations ◽  
High Sensitivity ◽  
Distributed Feedback ◽  
Coupling Constant ◽  
Biomolecule Detection ◽  
Important Indicator ◽  
Sensor Performance ◽  
Duty Cycles ◽  
Dfb Laser

The distributed feedback (DFB) laser is widely used in sensing because of its portable size, simple fabrication and high sensitivity. Most theoretical design models are based on passive Bragg gratings. However, passive grating models cannot be used to predict sensor performance using the important indicator of figure of merit (FOM) through theoretical calculations. To solve this problem, we replaced the passive grating with an active grating by using the imaginary part of the coupling constant that represents the value of the gain. As a comparison, the influence of the full width at half maximum (FWHM) and sensitivity were analyzed for different grating duty cycles and depths in the passive grating sensors. To obtain a higher FOM in the active grating sensors, we systematically investigated the effects of duty cycle and gain value through numerical simulations. We found that the redshift caused by a duty cycle increase can improve the sensitivity of biomolecule detection by 1.7 times.

Acoustic-Reflex Dynamics for Pulsed Signals

1978 ◽  
Vol 21 (2) ◽  
pp. 295-308
Author(s):  
Terry L. Wiley ◽  
Raymond S. Karlovich
Keyword(s):  
Duty Cycle ◽  
Acoustic Impedance ◽  
Normal Hearing ◽  
Broadband Noise ◽  
Threshold Shift ◽  
Temporary Threshold Shift ◽  
Acoustic Reflex ◽  
Stapedius Muscle ◽  
Duty Cycles

Contralateral acoustic-reflex measurements were taken for 10 normal-hearing subjects using a pulsed broadband noise as the reflex-activating signal. Acoustic impedance was measured at selected times during the on (response maximum) and off (response minimum) portions of the pulsed activator over a 2-min interval as a function of activator period and duty cycle. Major findings were that response maxima increased as a function of time for longer duty cycles and that response minima increased as a function of time for all duty cycles. It is hypothesized that these findings are attributable to the recovery characteristics of the stapedius muscle. An explanation of portions of the results from previous temporary threshold shift experiments on the basis of acoustic-reflex dynamics is proposed.

DFB Lasers with Tilted Waveguide for Multi-Wavelength Generation

2007 ◽  
Vol 31 ◽  
pp. 36-38 ◽  
Author(s):  
Lip Fah Chong ◽  
Jing Hua Teng ◽  
Ee Leong Lim ◽  
Norman Soo Seng Ang ◽  
J.R. Dong ◽  
...  
Keyword(s):  
Single Mode ◽  
Distributed Feedback ◽  
Couple Mode ◽  
Threshold Condition ◽  
Couple Mode Theory ◽  
Gain Margin ◽  
Ridge Waveguides ◽  
Multi Wavelength ◽  
Dfb Laser ◽  
Lasing Frequency

In this paper, we present the theoretical investigation of index-coupled distributed feedback (DFB) laser with tilted single mode ridge waveguides. By tilting part of the ridge waveguide in various degrees, DFB laser with manifold effective grating periods can be realized. The structure is analyzed using couple mode theory in matrix form based on threshold analysis. Important parameters of DFB laser like resonant frequency and threshold gains are obtained by solving the eigen-equation. The results indicate not only that the lasing frequency is modulated by the waveguide titling angle, but also large Gain Margin (GM) can be achieved at the threshold condition which enhance the stable single mode operation in index-coupled DFB laser.

Controlling the Q-Point in Distributed Feedback Lasers Using a Numerical Optimization Methodology

2019 ◽  
Vol 37 (5A) ◽  
pp. 148-156
Author(s):  
Hisham K. Hisham
Keyword(s):  
Relaxation Oscillation ◽  
Oscillation Period ◽  
Distributed Feedback ◽  
Model Parameters ◽  
Gain Compression ◽  
Sinusoidal Oscillations ◽  
Bias Level ◽  
Dfb Laser ◽  
Optimization Methodology ◽  
Gain Compression Factor

In this paper, a new methodology for controlling the Q-point in the distributed feedback (DFB) lasers is proposed. The method based on reducing the DFB transient period (TP) by optimizing laser’s model parameters numerically. The analysis has taken into account investigated the effects of the laser injection current (Iinj), the dc-bias level (Ibias), the temperature (T) variation, and the gain compression factor (ε). Results showed that by optimizing the value of Iinj, Ibias, T and ε; the Q-point could be controlled effectively. Where increasing the current ratio (i.e., Iinj/Ith) leads to reduce the TP value. In addition, by increasing Iinj and/or Ibias, the relaxation oscillation period (TRO) and the laser delay time (TDelay) are reduced significantly. From the other hand, the temperature varying may push the DFB laser to operate in an improper region through increasing the TP value; which may lead it to operate in the off-mode. Moreover, as ε is increased, the sinusoidal oscillations are dramatically damped results in a reduction in the TRO value and larger period of stabilized.

Integrated Distributed Feedback Laser and Optical Amplifier

1991 ◽  
Vol 240 ◽  
Author(s):  
N. K. Dutta ◽  
J. Lopata ◽  
R. Logan ◽  
T. Tanbun-Ek
Keyword(s):  
Active Region ◽  
Spectral Width ◽  
Optical Amplifier ◽  
Distributed Feedback ◽  
Performance Characteristics ◽  
Distributed Feedback Laser ◽  
Electrical Isolation ◽  
Current Confinement ◽  
Dfb Laser ◽  
And Performance

ABSTRACTThe fabrication and performance characteristics of an integrated distributed feedback (DFB) laser and optical amplifier structure are described. The structure utilizes semi-insulating Fe doped InP layers for current confinement to the active region, electrical isolation between the two sections and for lateral index guiding. The amplified output has a slope of 1 mW/mA of laser current with the amplifier biased at 150 mA which is a factor of 5 larger than that for a typical laser. The laser emits near 1.55 μm and the spectral width under modulation of the amplified output is considerably smaller than that for a DFB laser for the same on/off ratio.

scholarly journals Self-Aligned Emission of Distributed Feedback Lasers on Optical Fiber Sidewall

Nanomaterials ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 2381
Author(s):  
Tianrui Zhai ◽  
Xiaojie Ma ◽  
Liang Han ◽  
Shuai Zhang ◽  
Kun Ge ◽  
...  
Keyword(s):  
Optical Fiber ◽  
Coupling Effect ◽  
Wave Theory ◽  
Dip Coating ◽  
Distributed Feedback ◽  
Power Delivery ◽  
Fiber Axis ◽  
Fiber Waveguide ◽  
Multi Wavelength ◽  
Dfb Laser

This article assembles a distributed feedback (DFB) cavity on the sidewalls of the optical fiber by using very simple fabrication techniques including two-beam interference lithography and dip-coating. The DFB laser structure comprises graduated gratings on the optical fiber sidewalls which are covered with a layer of colloidal quantum dots. Directional DFB lasing is observed from the fiber facet due to the coupling effect between the grating and the optical fiber. The directional lasing from the optical fiber facet exhibits a small solid divergence angle as compared to the conventional laser. It can be attributed to the two-dimensional light confinement in the fiber waveguide. An analytical approach based on the Bragg condition and the coupled-wave theory was developed to explain the characteristics of the laser device. The intensity of the output coupled laser is tuned by the coupling coefficient, which is determined by the angle between the grating vector and the fiber axis. These results afford opportunities to integrate different DFB lasers on the same optical fiber sidewall, achieving multi-wavelength self-aligned DFB lasers for a directional emission. The proposed technique may provide an alternative to integrating DFB lasers for applications in networking, optical sensing, and power delivery.

The development of a representative multidimensional transient duty cycle for in-service switcher locomotives

2021 ◽  
pp. 095440972110418
Author(s):  
Mohamed A Hegazi ◽  
Andreas Hoffrichter ◽  
Jeffrey L Andrews ◽  
Gordon Lovegrove
Keyword(s):  
Duty Cycle ◽  
Electric Propulsion ◽  
Clustering Algorithm ◽  
Power Level ◽  
Time Data ◽  
Major Drawback ◽  
Model Based Clustering ◽  
Engine Efficiency ◽  
Duty Cycles ◽  
Acceleration And Deceleration

Switcher locomotives operate in railway yards where they shunt railcars and assemble trains. Shunting railcars requires frequent aggressive acceleration and deceleration events in order for the locomotive to push or pull railcars onto specific tracks. As a result, switcher locomotives rarely sustain tractive power for any significant period of time. Given that all switchers in North America rely on diesel-electric propulsion; the result is rapid and frequent transitions in engine power leading to a very low engine efficiency and high levels of emissions. Any attempt to quantify or remedy these issues will face a lack of a representative profile or test cycle. A locomotive duty cycle is a breakdown of time spent at each power level of the locomotive’s engine. A major drawback of current duty cycles is that they only account for steady power. Such cycles are not representative of real switcher locomotive operation. This paper presents a real-world transient duty cycle for switcher locomotives that accounts for the rapid power transitions and is argued to be more statistically representative of actual operations. The methodology adopted relies on real-time data collection, microtrip based trip segmentation, and a finite mixture model-based clustering algorithm. Measurements were collected on a EMD 16-645 GP9 locomotive. The duty cycle developed herein is representative of switching operations in Southern Railway of British Columbia’s New Westminster Yard as an example of the methodology which can be repeated in other cases as well.

scholarly journals Assessment of Effects of Laser Light Combining Three Wavelengths (450, 520 and 640 nm) on Temperature Increase and Depth of Tissue Lesions in an Ex Vivo Study

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5340
Author(s):  
Kamil Jurczyszyn ◽  
Witold Trzeciakowski ◽  
Zdzisław Woźniak ◽  
Piotr Ziółkowski ◽  
Mateusz Trafalski
Keyword(s):  
Duty Cycle ◽  
Temperature Increase ◽  
Ex Vivo ◽  
Visible Spectrum ◽  
Maximum Temperature ◽  
Lesion Depth ◽  
Single Beam ◽  
Duty Cycles ◽  
Rate Of Increase

Background: Lasers are widely used in medicine in soft and hard tissue surgeries and biostimulation. Studies found in literature typically compare the effects of single-wavelength lasers on tissues or cell cultures. In our study, we used a diode laser capable of emitting three components of visible light (640 nm, red; 520 nm, green; 450 nm, blue) and combining them in a single beam. The aim of the study was to assess the effects of laser radiation in the visible spectrum on tissue in vitro, depending on the wavelength and pulse width. Methods: All irradiations were performed using the same output power (1.5 W). We used various duty cycles: 10, 50, 80 and 100% with 100 Hz frequency. Maximum superficial temperature, rate of temperature increase and lesion depth were investigated. Results: Maximum superficial temperature was observed for 450 + 520 nm irradiation (100% duty cycle). The highest rate of increase of temperature was noted for 450 + 520 nm (100% duty cycle). Maximum lesion depth was observed in case of three-wavelength irradiation (450 + 520 + 640 nm) for 100, 80 and 50% duty cycles. Conclusions: The synergistic effect of two-wavelength (450 + 520 nm) irradiation was observed in case of maximum temperature measurement. The deepest depth of lesion was noted after three-wavelength irradiation (450 + 520 + 640 nm).

scholarly journals Vibrationally and Spin-Orbit-Resolved Inner-Shell X-ray Absorption Spectroscopy of the NH+ Molecular Ion: Measurements and ab Initio Calculations

Atoms ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 67
Author(s):  
Stéphane Carniato ◽  
Jean-Marc Bizau ◽  
Denis Cubaynes ◽  
Eugene T. Kennedy ◽  
Ségolène Guilbaud ◽  
...  
Keyword(s):  
Ab Initio ◽  
Density Functional ◽  
Theoretical Calculations ◽  
High Sensitivity ◽  
Open Shell ◽  
Field Configuration ◽  
High Spectral Resolution ◽  
Spin Orbit ◽  
Molecular Ion ◽  
Hartree Fock

This article presents N2+ fragment yields following nitrogen K-shell photo-absorption in the NH+ molecular ion measured at the SOLEIL synchrotron radiation facility in the photon energy region 390–450 eV. The combination of the high sensitivity of the merged-beam, multi-analysis ion apparatus (MAIA) with the high spectral resolution of the PLEIADES beamline helped to resolve experimentally vibrational structures of highly excited [N1s−1H]*+ electronic states with closed or open-shell configurations. The assignment of the observed spectral features was achieved with the help of density functional theory (DFT) and post-Hartree Fock Multiconfiguration Self-Consistent-Field/Configuration Interaction (MCSCF/CI) ab-initio theoretical calculations of the N1s core-to-valence and core-to-Rydberg excitations, including vibrational dynamics. New resonances were identified compared to previous work, owing to detailed molecular modeling of the vibrational, spin-orbit coupling and metastable state effects on the spectra. The latter are evidenced by spectral contributions from the 4Σ− electronic state which lies 0.07 eV above the NH+2Π ground state.

Diaphragmatic blood flow in the dog

1986 ◽  
Vol 60 (2) ◽  
pp. 554-561 ◽  
Author(s):  
H. Bark ◽  
S. M. Scharf
Keyword(s):  
Blood Flow ◽  
Duty Cycle ◽  
Stimulus Frequency ◽  
Phase Flow ◽  
Transdiaphragmatic Pressure ◽  
Relaxation Phase ◽  
Duty Cycles ◽  
Tension Time ◽  
Phrenic Artery ◽  
Electromagnetic Flow Probe

In anesthetized mongrel dogs we measured the blood flow in the left phrenic artery (Qdi), using an electromagnetic flow probe, before and during supramaximal phrenic nerve stimulation (pacing). This was done at constant respiratory rate (24/min) but at three different stimulation frequencies at a duty cycle of 0.4 (20, 50, and 100 Hz) and at three different duty cycles at a stimulation frequency of 50 Hz (duty cycle = 0.2, 0.4, and 0.8). Qdi was unchanged during diaphragm contraction until transdiaphragmatic pressure (Pdi) was greater than approximately 11 cmH2O, whereafter it began to decrease, reaching zero at Pdi approximately 20 cmH2O. Thus, when Pdi was greater than 21 cmH2O, all flow occurred during relaxation. Qdi averaged over the entire respiratory cycle (Qt) was less at duty cycle = 0.8 than under the other conditions. This was because of decreasing length of relaxation phase rather than a difference of relaxation phase flow (Qr), which was maximal during all conditions of phrenic stimulation. During pacing-induced fatigue, Qt actually rose slightly as Pdi fell. This was due to an increase in contraction phase flow while Qr remained constant. The relationship between Qt and tension-time index was not unique but varied according to the different combinations of duty cycle and stimulus frequency.

Sustainable inspiratory pressures over varying flows, volumes, and duty cycles

1990 ◽  
Vol 69 (5) ◽  
pp. 1875-1882 ◽  
Author(s):  
T. L. Clanton ◽  
B. T. Ameredes ◽  
D. B. Thomson ◽  
M. W. Julian
Keyword(s):  
Tidal Volume ◽  
Duty Cycle ◽  
Dynamic Pressure ◽  
Breathing Patterns ◽  
Transdiaphragmatic Pressure ◽  
Lung Inflation ◽  
Duty Cycles ◽  
Pressure Time ◽  
Endurance Tests ◽  
Normal Humans

This study identifies the influence of flow (0.5-2.0 l/s), duty cycle (0.29-0.57), and tidal volume (1.08-2.16 liters) on sustainable inspiratory muscle pressure (Pmus) and transdiaphragmatic pressure (Pdi) development. Six normal humans performed endurance tests using an isoflow method, which allowed for measurements of maximum dynamic Pmus and Pdi, with controlled lung inflation. The subjects repeated maximum dynamic voluntary inspirations for 10 min. Pressures dropped exponentially from initial measurements at rest (Pmusi or Pdi) to sustainable values (Pmus or Pdis). As flow and tidal volume increased, maximum initial and sustainable pressures decreased significantly. However, at a constant duty cycle, the sustainable dynamic pressures remained predictable fractions of initial dynamic pressures (i.e., Pmuss/Pmusi or Pdis/Pdii), regardless of changes in flow and tidal volume. In contrast, as duty cycle increased, the sustainable fractions significantly decreased for both Pdi and Pmus. For example, at a duty cycle of 0.29, Pmuss/Pmusi was approximately 0.71, and at a duty cycle of 0.57, Pmuss/Pmusi was approximately 0.62. Calculated sustainable pressure-time indexes varied significantly between 0.16 to 0.32 for Pmus and 0.11 to 0.22 for Pdi over the breathing patterns studied. We conclude that 1) the maximum dynamic pressure that can be sustained at a given duty cycle is a predictable fraction of the maximum dynamic pressure that can be generated at rest when measured under the same conditions of inspiration and 2) the sustainable fraction of initial dynamic pressure significantly decreases with increasing duty cycle.

Sign in / Sign up

Export Citation Format

Share Document