On-chip optical comb sources

Abstract

On-chip integration of optical comb sources is crucial in enabling their widespread use. Integrated photonic devices that can be mass-manufactured in semiconductor processing facilities offer a solution for the realization of miniaturized, robust, low-cost, and energy-efficient comb sources. Here, we review the state of the art in on-chip comb sources, their applications, and anticipated developments.

Integrated narrow-linewidth laser source based on self-injection locking

“…So Si3N4 MRR is employed as the external cavity in our experiment. To miniaturize the device, the semiconductor laser is integrated with a photonic circuit in three different methods: monolithic integration, heterogeneous integration and hybrid integration 5 . Compared to the former two methods, the third method has the advantage of improving the performance of the III-V chip and passive chips separately 6 .…”

Extending hybrid integrated diode lasers to multi-frequency oscillation

“…Table 1 provides an overview of the lowest repetition rates to date for integrated mode-locked diode lasers based on standard (AM) mode-locking techniques [56,63,65,140,[169][170][171][172][173][174][175][176], adapted from the overviews provided in Ref. [63] and [177].…”

“…It is important to note that for comb generation, also alternatives to standard diode laser mode-locking have been reported that enable lower repetition rates (an extensive review is provided by Ref. [177]). For instance, using a 3.55 GHz mode-locked laser, a very low repetition rate of 55 MHz was realized via pulsepicking based on an on-chip Mach-Zehnder modulator [52].…”

“…A disadvantage of this method is that the linewidth of the m-th order sideband is m times higher than the linewidth of the modulation frequency [179]. There are also reports of comb generation via gain-switching at 6 GHz [54] and 5 GHz [55], however, this approach suffers from timing jitter [177].…”

“…Although with standard (AM) mode-locking techniques so far repetition rates down to 755 MHz have been achieved [56], we mentioned already a fundamental problem in diode lasers which hinders further reduction of the repetition rate Table 5.1 Low repetition rate, fully integrated mode-locked lasers with saturable absorber, adapted from the overviews of state-of-the-art mode-locked diode lasers provided in Refs. [63] and [177]. The repetition rate is labeled f r .…”