Abstract
Modulation bandwidth enhancement of directly modulated semiconductor lasers (DMLs) has attracted broad interest to accommodate the tremendously growing demand for network traffic. In this paper, a monolithically integrated mutually coupled (IMC) laser for the O-band is demonstrated both numerically and experimentally. The direct modulation bandwidth was enhanced utilizing a photon–photon resonance (PPR) effect based on the mutual injection-locking technique. The IMC laser consisted of two distributed feedback (DFB) laser sections with a semiconductor optical amplifier (SOA) section in between. The relationship between the PPR frequency and SOA length was analyzed numerically to achieve a flat modulation response by optimizing the SOA length. Then, an enhanced 3-dB bandwidth of 38.7 GHz was realized experimentally, a nearly threefold enhancement over the modulation bandwidth of a solitary DFB laser at the same bias. Moreover, clear open eyes up to 40 Gb/s transmission over a 25-km single-mode fiber were achieved. Although the dynamic extinction ratio of the eye diagram was 1.1 dB, it can be further improved by increasing the mutual injection locking range of the IMC laser.
Highlights
Data traffic has been growing rapidly due to the increasing demand for high-definition video streaming, cloud computing, and a massive internet-of-things
We demonstrate modulation bandwidth enhancement and large-signal modulation performance of integrated mutually coupled (IMC) lasers for the O-band with identical multiple quantum well (MQW) layers under mutual injection-locking (MIL)
The IMC laser works under the MIL state by adjusting the current of three sections, which leads to an appropriate detuning frequency, coupling strength, and coupling phase
Summary
Data traffic has been growing rapidly due to the increasing demand for high-definition video streaming, cloud computing, and a massive internet-of-things. One approach to achieving this is to increase the carrier-photon resonance (CPR) frequency by increasing the differential gain through optimizing multiple quantum well (MQW) structures, reducing the photon lifetime via shortening the cavity length [3,4,5,6] or reducing parasitic parameters [7] Another approach entails utilizing the photon–photon resonance (PPR) effect based on optical feedback [8,9,10] or optical injection-locking techniques [11,12,13]. An enhanced modulation bandwidth of 18.7 GHz has been demonstrated in our previous work [29], the tuning range of the laser section for the mutually injection-locked state was only 4 mA due to poor single-mode stability resulting from the uniform grating and laser facets without AR coatings.
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