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.

scholarly journals Design Methodology for Reducing RIN Level in DFB Lasers

2016 ◽  
Vol 12 (2) ◽  
pp. 207-213
Author(s):  
Hisham Hisham
Keyword(s):  
Numerical Simulations ◽  
Temperature Variation ◽  
Relative Intensity ◽  
Oscillation Frequency ◽  
Design Methodology ◽  
Relaxation Oscillation ◽  
Distributed Feedback ◽  
Model Parameters ◽  
Intensity Noise ◽  
Gain Compression

The relative intensity noise (RIN) characteristics in distributed feedback (DFB) lasers are analyzed theoretically by proposing a new methodology. In addition to temperature variation (T), the effect of other model parameters such as injection current (Iinj), active layer volume (V), spontaneous emission (βsp) and gain compression (ε) factors on RIN characteristics is investigated. The numerical simulations shows, the peak RIN level can be reduced to around –150 dB/Hz, while relaxation oscillation frequency (ROF) is shifted towards 5.6 GHz. In addition, the RIN level is increased with temperature by the rate of 0.2 dB/ºC and ROF is reduced by the rate of 0.018 GHz/ºC. Results show, the low RIN level can be obtained by selecting model parameters reasonably.

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.

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.

scholarly journals Characterization of InGaN/GaN-Based Multi-Quantum Well Distributed Feedback Lasers

1998 ◽  
Vol 537 ◽  
Author(s):  
Daniel Hofstetter ◽  
Robert L. Thornton ◽  
Linda T. Romano ◽  
David P. Bour ◽  
Michael Kneissl ◽  
...  
Keyword(s):  
Ion Beam ◽  
Device Fabrication ◽  
Distributed Feedback ◽  
Coupling Scheme ◽  
Optically Pumped ◽  
Ion Beam Etching ◽  
Measurement Results ◽  
Dfb Laser ◽  
First Time

AbstractWe present a device fabrication technology and measurement results of both optically pumped and electrically injected InGaN/GaN-based distributed feedback (DFB) lasers operated at room temperature. For the optically pumped DFB laser, we demonstrate a complex coupling scheme for the first time, whereas the electrically injected device is based on normal index coupling. Threshold currents as low as 1. 1 A were observed in 500 μm long and 10 μm wide devices. The 3rd order grating providing feedback was defined holographically and dry-etched into the upper waveguiding layer by chemically-assisted ion beam etching. Even when operating these lasers considerably above threshold, a spectrally narrow emission (3.5 Å) at wavelengths around 400 nm was seen.

scholarly journals Time and Space Scales in the Tropical Cyclone Boundary Layer, and the Location of the Eyewall Updraft

2017 ◽  
Vol 74 (10) ◽  
pp. 3305-3323 ◽  
Author(s):  
Jeffrey D. Kepert
Keyword(s):  
Boundary Layer ◽  
Tropical Cyclone ◽  
Nonlinear Models ◽  
Vertical Motion ◽  
Oscillation Period ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Radial Profiles ◽  
Sinusoidal Oscillations ◽  
Tropical Cyclone Boundary Layer

Abstract The transient response of the tropical cyclone boundary layer is studied using linearized and nonlinear models, with particular focus on the frictionally forced vertical motion. The impulsively started, linearized tropical cyclone boundary layer is shown to adjust to its equilibrium solution via a series of decaying oscillations with the inertial period . In the nonlinear case, the oscillation period is slightly lengthened by inward advection of the slower-evolving flow from larger radii, but the oscillations decay more quickly. In an idealized cyclone with small sinusoidal oscillations superimposed on the gradient wind, the equilibrium nonlinear boundary layer acts as a low-pass filter with pass length scaling as , where is the 10-m frictional inflow. This filter is absent from the linearized boundary layer. The eyewall frictional updraft is similarly displaced inward of the radius of maximum winds (RMW) by a distance that scales with , owing to nonlinear overshoot of the inflowing air as it crosses the relatively sharp increase in I near the eyewall. This displacement is smaller (other things being equal) when the RMW is small, and greater when it is large, including in secondary eyewalls. The dependence of this distance on may explain, at least partially, why observed RMW are seldom less than 20 km, why storms with relatively peaked radial profiles of wind speed can intensify more rapidly, and why some secondary eyewalls initially contract rapidly with little intensification, then contract more slowly while intensifying.

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.

scholarly journals Engineered protein-based functional nanopatterned materials for bio-optical devices

2019 ◽  
Vol 1 (10) ◽  
pp. 3980-3991 ◽  
Author(s):  
Daniel Sanchez-deAlcazar ◽  
David Romera ◽  
Jose Castro-Smirnov ◽  
Ahmad Sousaraei ◽  
Santiago Casado ◽  
...  
Keyword(s):  
Protein Engineering ◽  
Optical Devices ◽  
Simple Approach ◽  
Distributed Feedback ◽  
Dfb Laser

A simple approach for the fabrication of functional nanopatterned protein materials using protein engineering and soft-nanolithography and its implementation in optical devices based on distributed feedback (DFB) laser phenomena.

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