- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Correlation of Small-Signal Modulation with Digital Modulation Characteristics of High-Speed Semiconductor Lasers
摘要： This paper introduces correlation of the small-signal modulation characteristics with those of digital modulation of high-speed multiple-quantum-well semiconductor laser. The accuracy of applying the common small-signal approximation to calculate the modulation bandwidth is evaluated by comparing the obtained values with those calculated by the reliable technique of time-integration of the rate equations. Also, we present correlation between the maximum bit rate and the small-signal bandwidth at given bias current and modulation index. We show that the bandwidth frequencies predicted by the small-signal approximation are higher than those calculated by the time integration. The difference increases with the increase of the bias current reaching 8 GHz when the current exceeds 3.5 times the threshold current. We predict also the modulation conditions required to achieve modulation speed as high as 40 Gbps. The ratio of the maximum bit rate to the small-signal bandwidth exceeds unity and reaches 1.6 under deep modulation with modulation index equal to 0.5.
关键词： high-speed semiconductor lasers,small-signal modulation,digital modulation,modulation bandwidth,maximum bit rate
更新于2025-09-23 15:21:01
-
Solution-processed QD-LEDs in visible range: Modulation bandwidth enhancement
摘要： Light-emitting diodes based on quantum dots (QD-LEDs) have attracted much attention not only due to their usage in lighting and display applications but also as the light sources in visible light communication (VLC). One of the most important parameters of a QD-LED as a light source is the improvement of modulation bandwidth in order to increase the data transfer rate. Here, three sets of QD-LEDs are presented for which some parameters such as frequency response are investigated, once for the devices with similar structure but different homogeneities and then for those with minor changes in the structure. It was found that by changing the homogeneity of QDs in the same structure based on CdSe/ZnS and using the ZnO shell instead of ZnS, the modulation bandwidth varied between 2 and 8 MHz. Furthermore, for the structure based on CdSe/ZnS, the modulation bandwidth of 8 MHz is achieved which is fairly a wide bandwidth for a QD-LED. The idea of manipulation in the structure of nanomaterials can be an important step toward increasing the modulation bandwidth. According to calculated results, the carrier density in different layers is calculated and then the recombination current-voltage characteristics are compared with the experimental results, indicating high conformity.
关键词： Light emitting diode,Frequency response,CdSe/ZnS,Quantum dots,Modulation bandwidth
更新于2025-09-16 10:30:52
-
[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - 25 GHz Small-Signal Modulation Bandwidth with a 7-Element Electrically-Parallel Vertical-Cavity Surface-Emitting Laser Array
摘要： Small arrays of VCSELs have emerging applications in free-space optical communications for a plethora of gadgets from smartphones to appliances to sensing systems within the realm of the Internet-of-Things. For data communication we require eye-safe line-of-sight beams or cones of light radiation that can reliably and inexpensively send data (as across optical fiber) from device-to-device or serve as an illumination source or both. Via our simplified VCSEL epitaxial designs [1] we investigate various configurations of top-emitting single 980 nm VCSELs and VCSEL arrays with varying VCSEL-to-VCSEL spacing, mesa shapes, and emitting diameters. We report record combinations of small-signal modulation bandwidth (f3dB) and optical output power (L) for an electrically-parallel compact VCSEL array with 7 VCSELs in a hexagonal configuration. The VCSELs in the array are identical with oxide aperture diameters estimated to be ? ~3.5 (cid:80)m ± 0.5 (cid:80)m. We summarize key room temperature (RT) performance figures-of-merit in Fig. 1. We achieve an f3dB of 20 GHz at a bias of about I ~35 mA with an operating L exceeding 25 mW. The f3dB is as high as 24.8 GHz with L ~50 mW when I ~65 mA. The maximum wall plug efficiency (WPE) is 0.32 at I ~16 mA. We anticipate increased WPE and optical output power for a given I with heat sinking, advanced packaging, and substrate-emitting array designs. Previous best array results include an f3dB of 7.5 GHz at L = 120 mW for a 28-element 850 nm array [2] and an f3dB of 23 GHz at L = 25 mW for a single 980 nm VCSEL. In our presentation we include additional experimental results on our large ? single VCSELs and on our triple, septuple, and novemdecuple VCSEL arrays from RT to 85 °C.
关键词： optical output power,VCSEL,electrically-parallel,small-signal modulation bandwidth,hexagonal configuration
更新于2025-09-12 10:27:22
-
Regimes of bandwidth enhancement in coupled-cavity semiconductor laser using photon–photon resonance
摘要： In the last decade, different solutions were proposed to boost the transmission bitrate of semiconductor lasers. Here, we focus on applying optical feedback to a semiconductor laser from an external cavity in order to induce enhancement of the modulation bandwidth up to 50 GHz as well as resonant modulation (RM) around frequencies approaching 60 GHz. High-speed modulation up to 90 Gbps under none-return to zero operation and a 45 Gbaud using pulse amplitude modulation-4 signals are predicted. Both types of improving the modulation performance of the laser are attributed to the photon–photon resonance (PPR) effect. The regimes of the external power reflectivity that correspond to both types of modulation response are specified. Comprehensive simulations are introduced to correlate the PPR frequency to the RM frequencies of the non-modulated coupled-cavity laser. Dependencies of the enhanced BW and PPR frequency on the cavity length and bias current are elucidated.
关键词： optical feedback,photon–photon resonance,modulation bandwidth,high-speed modulation,semiconductor lasers
更新于2025-09-11 14:15:04