Monolithic Linewidth Narrowing of a Tunable SG-DBR Laser

Simple analytical model for low-frequency frequency-modulation noise of monolithic tunable lasers

“…This frequency noise can cause considerable degradation to the overall performance of coherent optical systems and needs to be suppressed. For example, electronic feedback control of the current applied to the phase section could reduce the FM noise [7]. N-doping the waveguide regions of the passive sections would increase the carrier lifetime and thus decrease the bandwidth and hence lessen the high-frequency part of this FM noise.…”

“…Despite their potential benefits as key components in constructing wavelength-agile systems, one of their drawbacks is the presence of additional frequency-modulation (FM) noise at low frequencies compared to conventional semiconductor lasers [2,5]. This is of crucial importance in coherent applications because FM noise at low frequencies leads to significant degradation in the transmission performance of systems using quadrature amplitude modulation (QAM) formats [5,6], requiring sophisticated high-speed digital signal processing (DSP) algorithms to track the carrier phase at the receiver or additional integrated high-speed electronic circuits embedded with the laser to suppress the phase noise [7].…”

“…The performance of coherent systems can be predicted by knowledge of the phaseerror variance; using simple phase noise models, we show how the complete phase-error variance can be calculated from measurable device parameters. Accurate and predictable knowledge of the entire FM-noise spectrum would be invaluable for the development of any laser phase noise tracking or suppression techniques for coherent optical systems [7].…”

Stabilization of heterogeneous silicon lasers using Pound-Drever-Hall locking to Si_3N_4 ring resonators

“…Additionally, the CRR laser cavity yields a nonlinear FM tuning response beyond the loop bandwidth of 200 kHz, most likely due to the combination of thermal and carrier plasma effects [19]. Programmable digital loop filters can design for these nonlinear effects and closer monolithic or system-in-package integration of the full optoelectronic loop [8,18,20] will keep the phase lag due to loop delay low. …”

“…Many wavelength locking systems on chip scale platforms utilize sideband, or "fringe", locking where the laser is positioned on an amplitude slope of an interferometer or resonator [7,8]. However, fringe locking has issues with S/N, AM versus FM discrimination, and low frequency flicker noise in the generation of the error signal at baseband.…”