Improvement on Direct Modulation Responses and Stability by Partially Corrugated Gratings Based DFB Lasers With Passive Feedback

Abstract

DFB lasers with ultrashort cavities or integrated DFB lasers with passive waveguide reflectors are frequently proposed to realize directly modulated lasers (DMLs) for carrying ultrahigh data rate signals. The former suffers from poor heatsink and laser cleavage yield, while the single-mode stability of the latter scheme is seldom addressed. The mode selection and device performance of a DFB laser is well known to be very sensitive to the facet reflection and external optical feedback. The DFB lasers with partial corrugated gratings and passive feedback (PCG-PFL) are proposed here to overcome the challenging issues for the aforementioned two schemes. With PCG structure, the DFB lasers can maintain high single-mode yield (SMY) even with a high-reflection-coating on the rear facet and strong reflection from the integrated passive section. This provides the robustness in applying the integrated passive reflector to reshape the modulation response or to enhance the 3-dB bandwidth by using the photon-photon resonance (PPR) effect. By designing the PCG-PFL to have 150-m long laser section, 50-m long passive section, and 30% front-facet reflectivity, it can have about 86% of SMY, reduced resonant peak in the intensity modulation response, and reduced waveform overshoot and undershoot for transmitting 56-Gbaud/s PAM-4 signals. By using a longer passive reflector, enhanced bandwidth can be achieved by the PPR effect.

Coupled mode analysis of high-speed transverse coupled cavity vertical-cavity surface-emitting laser for low frequency chirp operations

“…We present the small signal response including the bandwidth enhancement and chirp reduction dependent on the coupling parameters and the coupling phase tolerance. The bandwidth enhancement and chirp reduction can be explained by the increased frequency of carrier-photon resonance (CPR) due to detuned-loading effect [18,19], and additionally the photon-photon resonance (PPR) at a frequency higher than CPR due to beating between different modes in coupled cavities [20][21][22][23][24][25]. We also present a comparison between the Lang-Kobayashi model and coupled mode model.…”

Suppressing DFB Lasers Relaxation Oscillations by High-Order Continuous Shaping Current With CNN Prediction

“…This technique is relatively mature but high-cost. Compared with external modulation, direct modulation has the advantages of simple structure and the cost is cheap [7,8]. The disadvantage of direct modulation is that the output waveform will produce relaxation oscillations (ROs).…”

Parameter Extraction For Quantum Well DFB Lasers Based on 1D Traveling Wave Model

“…uantum well distributed feedback (DFB) lasers are important light sources for high-speed optical communication systems owing to the advantages of large differential gain, low threshold current, wide direct modulation bandwidth and narrow linewidth [1]- [3]. To fulfill the growing demands of directly modulated DFB lasers, great effort has been put into improving the modulation bandwidth, single longitudinal mode stability, and emission efficiency for a long time [4]- [5].…”