Photonically integrated gain‐switched lasers for optical frequency comb generation

Abstract

The authors present the complete characterization of two cost-efficient photonically integrated slotted lasers that offer regrowth free manufacturing. Furthermore, the application of these devices, as multi-carrier transmitters is also investigated. In particular, the authors employ gain switching, an optical frequency comb (OFC) generation technique based on the direct modulation. The first device used is a dual section discrete mode index patterned device. It comprises two sections, implemented in a master-slave configuration to achieve optical injection locking (OIL) of the slave section. The second, a foursection device, consists of two regrowth-free Fabry-Perot lasers, also forming a master-slave configuration. The authors demonstrate that the additional sections give finer control over the OIL parameters of the device. Results show that the OIL leads to the enhancement of the modulation bandwidth, which in turn can be used to generate a broader OFC. The generated OFC is characterized to demonstrate additional improvements brought

Optical Frequency Comb Expansion Using Mutually Injection-Locked Gain-Switched Lasers

“…In other words, the FSR of the MIL-GS OFC can be tuned from GHz to MHz, without the need to re-optimize the GSL. Additionally, the average OFC power remains unchanged across the tuning range, thus overcoming the reduction of comb output power for low FSRs [31].…”

“…In recent years, the EI-GSL OFC has been extensively studied for various applications and some of the notable demonstrations include: (i) the realization of a superchannel transmitter employing spectrally efficient schemes such as Co-OFDM [22,23], coherent Nyquist WDM [6]; (ii) directly modulated DMT/PAM 4 for data center interconnects [24,25]; (iii) dual comb gas sensing spectroscopy [15,16,26]; (iv) soliton generation [27]; (v) absolute distance measurement [28] and (vi) analog radio-over-fiber distribution [14]. Furthermore, some of the photonic integrated circuit (PIC) versions of GSL sources are also realized in the form of a two-section device [29] and a four-section device [30,31]. This PIC realization highlights the huge potential of EI-GSL OFC and its suitability for commercial deployment.…”

Gain Switched Frequency Comb Enhancement Using Monolithically Integrated Mutually Coupled Lasers

“…Stable phase locking was achieved in both cases as the slave was optically phase locked to the emission of the master laser, thereby approximating a master-slave configuration. Alternative coupling techniques, whereby this biasing asymmetry is discarded while maintaining stable phase locking, have been demonstrated in [9], [10] and [11]. In each of these cases, both coupled lasers were biased above threshold current, therefore operating in a mutually coupled system.…”