Enhanced Modulation Bandwidth by Delayed Push–Pull Modulated DFB Lasers

Abstract

The bandwidth of a distributed feedback (DFB) directly modulated laser (DML) is limited by its carrier–photon resonance (CPR) frequency. A viable approach to break the bottleneck is to introduce a photon–photon resonance (PPR), since the PPR can happen at a much higher frequency than the CPR. Among the many structures that can possibly generate the PPR, the dual-sectional push–pull modulated (PPM) DFB is of particular interest for its fabrication cost-effectiveness as no regrowth is required. The PPR in the PPM DFB, however, usually shows a rapid roll-off on both edges, which brings in an indentation on the lower frequency side of the PPR peak and, consequently, cuts off the bandwidth. To compensate for this dip, we introduce a detuned PPR and restart the CPR response by exploiting a time delay between the differential signals applied to the PPM DFB. Our simulation result shows that the broadened PPR peak and the restarted CPR response indeed mitigate the dip and effectively expand the PPM-DFB’s bandwidth to approximately 50 GHz, a value double that of the conventional (single-sectional) DFB DML.

Output Optical Power Enhancement of Push-Pull Modulated DFB Laser With Asymmetric Structure

“…The intensity modulation response dependence on the DFB laser cavity parameters, such as cavity length and grating coupling coefficient, has been studied in the prior work [41]. In this paper, all other laser parameters will remain fixed, except for the facet reflectivities and section lengths.…”

“…It turns out to be more cost-effective as it does not need any monolithic integration for the device structure in the two sections is identical [35], [36], [37], [38], [39], [40]. We previously studied the PPM DFB laser with a first order grating symmetric cavity structure [41]. The indentation of the intensity modulation response in the frequency band between the CPR and PPR is compensated by introducing a delay between the differential signals applied to the PPM DFB laser.…”

“…The asymmetric coating design targets to boost the output optical power, however, generates a new issue, i.e., a dip appears in a frequency band slightly lower than CPR peak. With a different 2 > REPLACE THIS LINE WITH YOUR MANUSCRIPT ID NUMBER (DOUBLE-CLICK HERE TO EDIT) < root-cause from the indentation studied in [41], this dip arises from the imbalance between the CPR responses of the rear and front sections due to the asymmetric coating. In an attempt to offset the dip, we further exploited an asymmetric section length design.…”

Editorial for the Special Issue on Micro/Nano-Structure Based Optoelectronics and Photonics Devices

“…This Special Issue, entitled "Micro/Nano-Structure Based Optoelectronics and Photonics Devices," includes some noteworthy studies: five research articles and one review article. The Special Issue covers a wide range of topics: near-infrared (NIR) liquid crystal multifunctional automated optical polarimeters [6], enhanced modulation bandwidth of distributed feedback (DFB) lasers [7], full-color reflective electrowetting displays (EWDs) [8], a threeport light flow controller enabled by a programmable multimode waveguide engine [9], a dye-sensitized solar cell (DSSC) electrolyte preparation method considering light path and light absorption [10], and a review of recent advances in electrically tunable lenses for imaging and light manipulation [11]. From the perspective of modulating and manipulating the polarization characteristics of light, Farrahi et al [6] designed, calibrated, and developed a NIR liquid crystal multifunctional automated optical polarimeter, aiming to study and characterize the polarimetric properties of optical polymer nanofilms.…”

“…Depending on the nanophotonic structure and composition of functionalized polymer nanomaterials, their optical properties can be tailored. In order to break the bottleneck of the carrier-photon resonance (CPR) frequency-limited bandwidth of the DFB directly modulated laser, Chi et al [7] introduced the detuned photon-photon resonance (PPR) and restarted the CPR response by exploiting a time delay between the differential signals applied to the push-pull modulated DFB. Yang et al [8] designed, fabricated, and measured a full-color reflective EWD system consisting of three layers of cyan, magenta, and yellow EWD elements.…”