scholarly journals Coupled-Cavity VCSEL with an Integrated Electro-Absorption Modulator: Small- and Large-Signal Modulation Analysis

2020 ◽  
Vol 10 (17) ◽  
pp. 6128
Author(s):  
Krassimir Panajotov ◽  
Richard Schatz
Keyword(s):  
Power Distribution ◽  
Oscillation Frequency ◽  
Relaxation Oscillation ◽  
Optical Power ◽  
Photon Density ◽  
Modulation Transfer ◽  
Signal Modulation ◽  
Large Signal ◽  
Eye Diagram ◽  
Coupled Cavity

We consider an integrated electro-absorption modulator within a coupled-cavity VCSEL structure (EAM-VCSEL). We derive expressions for the modulation transfer function (MTF) of the EAM-VCSEL for small-signal modulation of either VCSEL injection current or EAM losses. For current modulation, the cut-off frequency remains limited by relaxation oscillation frequency. For EAM loss modulation, the MTF curve is much flatter and its shape around the relaxation oscillation frequency displays either a well-pronounced maximum, both a maximum and a minimum or a sharp minimum only depending on the bias point of the EAM losses. Such features have been found experimentally in Marigo-Lombart et al., J. Physiscs: Photonics, 1, 2019, but remained unexplained hitherto. Furthermore, the cut-off frequency remains beyond 100 GHz for moderate and week coupling between the VCSEL and EAM cavities. Such ultrahigh bandwidth modulation is due to the fact that the changes of EAM impact much less the optical power distribution along the EAM-VCSEL and, consequently, the confinement factor and photon density in the VCSEL cavity. The three cases of strong, intermediate and weak coupling are also considered when carrying out the large-signal modulation response of the EAM-VCSEL and a clear open-eye diagram is demonstrated at 100 Gbs for an optimal EAM cavity length.

Use of various keratometry data (ring and zone) in trifocal IOL calculation

2021 ◽  
pp. 53-56
Author(s):  
A.D. Loginova ◽  
◽  
S.V. Shukhaev ◽  
S.S. Kudlakhmedov ◽  
E.V. Boiko ◽  
...  
Keyword(s):  
Power Distribution ◽  
Optical Power ◽  
Iol Implantation ◽  
Universal Formula ◽  
Significant Difference ◽  
Trifocal Iol ◽  
Iol Calculation ◽  
Km Value ◽  
Tomographic Data ◽  
Corneal Refractive Power

Purpose. To compare the results of trifocal IOL calculation using various corneal tomographic data (ring and zone). Methods. This retrospective study involved 46 patients (46 eyes), underwent cataract surgery with trifocal IOL implantation (AcrySof IQ PanOptix). The calculation was performed using Tomey OA-2000 according to 2 formulas (Barrett II Universal, Olsen). Keratometry values included Km (the average of two main meridians of a cornea) provided by Pentacam HR Power Distribution Apex map, which describes total corneal refractive power (TCRP) with diameter of 3.0, 4.0 and 5.0 mm on a ring and zone. Mean (MAE) and median (MedAE) predicted postoperative refraction errors were assessed after surgery. Results. Mean Km value on 3 mm zone and ring was: 42.75±1,46 D and 42,91±1,43 D, respectively (p<0,0001). Mean Km on 4 mm zone and ring was: 42.6±1.5 D and 43.3 ± 1.5 D, respectively (p <0.005). Mean Km value on 5 mm zone and ring was: 43,09±1,5 D and 43,55±1,48 D, respectively (p<0,0001). Calculations using the Barrett II Universal formula revealed significant difference between MAE and MedAE of the predicted postoperative refraction on 5mm zone and ring (p=0.045). When using the Olsen formula in the calculations, significant difference was revealed using the Km data with a diameter of 3 mm and 5 mm (p=0.001 и p=0.009, respectively). The calculation on 3 mm ring was more accurate than for 3 mm zone. With a 5 mm diameter, the calculation is more accurate according to the zone data. Conclusion. Mean Km value on Power Distribution Apex map according to ring is significantly greater then according to zone. 1) The calculation of the trifocal IOL based on the TCRP zone data is reliably more accurate than the ring data according to both formulas (Barrett II Universal and Olsen) with a diameter of 5 mm. 2) According to the Olsen formula with a diameter of 3 mm, the calculation of the optical power of trifocal IOL based on TCRP ring data is more accurate. Key words: IOL calculation, Trifocal IOL, corneal topography

Influence of depth of intermediate layer on optical power distribution in W-type optical fibers

2012 ◽  
Vol 51 (20) ◽  
pp. 4896 ◽  
Author(s):  
Ana Simović ◽  
Alexandar Djordjevich ◽  
Svetislav Savović
Keyword(s):  
Optical Fibers ◽  
Power Distribution ◽  
Intermediate Layer ◽  
Optical Power

scholarly journals Achieving beyond-100-GHz large-signal modulation bandwidth in hybrid silicon photonics Mach Zehnder modulators using thin film lithium niobate

APL Photonics ◽  
2019 ◽  
Vol 4 (9) ◽  
pp. 096101 ◽  
Author(s):  
Xiaoxi Wang ◽  
Peter O. Weigel ◽  
Jie Zhao ◽  
Michael Ruesing ◽  
Shayan Mookherjea
Keyword(s):  
Thin Film ◽  
Lithium Niobate ◽  
Silicon Photonics ◽  
Modulation Bandwidth ◽  
Signal Modulation ◽  
Large Signal ◽  
Hybrid Silicon

scholarly journals Measuring Linewidth Enhancement Factor by Relaxation Oscillation Frequency in a Laser with Optical Feedback

Sensors ◽  
2018 ◽  
Vol 18 (11) ◽  
pp. 4004 ◽  
Author(s):  
Yuxi Ruan ◽  
Bin Liu ◽  
Yanguang Yu ◽  
Jiangtao Xi ◽  
Qinghua Guo ◽  
...  
Keyword(s):  
Light Beam ◽  
Oscillation Frequency ◽  
Enhancement Factor ◽  
Optical Feedback ◽  
Relaxation Oscillation ◽  
Measurement Methods ◽  
Linewidth Enhancement Factor ◽  
Simulation And Experiment ◽  
Factor Alpha ◽  
Linewidth Enhancement

This paper presents a new method for measuring the linewidth enhancement factor (alpha factor) by the relaxation oscillation (RO) frequency of a laser with external optical feedback (EOF). A measurement formula for alpha is derived which shows the alpha can be determined by only using the RO frequencies and no need to know any other parameters related to the internal or external parameters associated to the laser. Unlike the existing EOF based alpha measurement methods which require an external target has a symmetric reciprocate movement. The proposed method only needs to move the target to be in a few different positions along the light beam. Furthermore, this method also suits for the case with alpha less than 1. Both simulation and experiment are performed to verify the proposed method.

Coupling. Non-Symmetric Behaviour of a Joint Between Multimode Fibers

1984 ◽  
Vol 5 (3) ◽  
Author(s):  
G. Cancellieri ◽  
U. Ravaioli
Keyword(s):  
Power Distribution ◽  
Dispersion Compensation ◽  
Coupling Efficiency ◽  
Optical Power ◽  
Optical Source ◽  
Multimode Fibers ◽  
Intermodal Dispersion ◽  
Intentional Mode ◽  
Different Characteristics ◽  
Mode Mixing

SummaryWhen two different multimode fibers are jointed together, mode mixing and mode filtering take place, with different characteristics in the two directions, leading to a non-symmetric behaviour. A detailed analysis of the power transitions among the guided modes at the joint is presented here. Explicit formulas for coupling efficiency and intermodal dispersion compensation are derived. The intentional mode mixing which is produced by suitable beam-launchers, in order to reach an optical power distribution independent of that of the optical source, is also investigated.

scholarly journals Design of a Four-Branch Optical Power Splitter Based on Gallium-Nitride Using Rectangular Waveguide Coupling for Telecommunication Links

2019 ◽  
Vol 2019 ◽  
pp. 1-9
Author(s):  
Retno W. Purnamaningsih ◽  
Nji R. Poespawati ◽  
Elhadj Dogheche
Keyword(s):  
Gallium Nitride ◽  
Power Distribution ◽  
Optical Power ◽  
Power Input ◽  
Input Power ◽  
Propagation Length ◽  
Power Splitter ◽  
Excess Loss ◽  
Total Input ◽  
Rectangular Waveguides

This paper reports design of a simple four-branch optical power splitter using five parallel rectangular waveguides coupling in a gallium-nitride (GaN) semiconductor/sapphire for telecommunication links. The optimisation was conducted using the 3D FD-BPM method for long wavelength optical communication. The result shows that, at propagation length of 925 μm, the optical power input was successfully split into four uniform output beams, each with 24% of total input power. It is also shown that the relative output power distribution is almost stable through the C-band range. At the operating wavelength of 1.55 μm, the proposed power splitter has an excess loss lower than 0.2 dB. This study demonstrates the opportunity to develop optical interconnections from UV-Visible to near IR wavelengths.

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