Low Noise Heterogeneous III‐V‐on‐Silicon‐Nitride Mode‐Locked Comb Laser

Abstract

Generating optical combs in a small form factor is of utmost importance for a wide range of applications such as datacom, LIDAR, and spectroscopy. Electrically powered mode-locked diode lasers provide combs with a high conversion efficiency, while simultaneously allowing for a dense spectrum of lines. In recent years, a number of integrated chip scale mode-locked lasers have been demonstrated. However, thus far these devices suffer from significant linear and nonlinear losses in the passive cavity, limiting the attainable cavity size and noise performance, eventually inhibiting their application scope. Here, we leverage the ultra-low losses of silicon-nitride waveguides to demonstrate a heterogeneously integrated III-V-on-silicon-nitride passively mode-locked laser with a narrow 755 MHz line spacing, a radio frequency linewidth of 1 Hz and an optical linewidth below 200 kHz. Moreover, these comb sources are fabricated with wafer scale technology, hence enabling low-cost and high volume manufacturable devices.

A Review of Capabilities and Scope for Hybrid Integration Offered by Silicon-Nitride-Based Photonic Integrated Circuits

“…Recent advances in telecom-wavelength lasing based on high-gain GaAs QDs heteroepitaxially grown on Si and SOI substrates with low thresholds and high temperature stability [282], indicate that it is a promising gain material for III-V/SiN monolithic integration and there is a strong possibility that 100 mW level heterogeneous/monolithic III-V/SiN lasers are achievable in the near future. [239,, (c) schematic layout of a heterogeneous III-V/SiN laser and its optical taper between SiN and III-V gain sections [245] and (d) development of linewidth of III-V/SiN lasers [244,246,248,249,252,254,[256][257][258][261][262][263][264]266,267,270,[272][273][274][275][276]279,280,[283][284][285].…”

“…Benefiting from the fast-developing SiN devices, especially resonators with Q up to >200 M [294], a highly precise phase (factor A) and spectral (factor B) feedback [295,296] is achievable in addition to an extended cavity length (thereby reducing ∆ω 0 ), likely to generate ultranarrow linewidth. Figure 11d displays the state-of-the-art linewidth of III-V/SiN-coupled lasers in terms of integration method [244,246,248,249,252,254,[256][257][258][261][262][263][264]266,267,270,[272][273][274][275][276]279,280,[283][284][285]]. It appears that significant progress has been made with hybrid integration when compared to heterogenous/monolithic integration, though the latter started its development at a later stage.…”

“…Figure 11. Development of (a) threshold current and (b) maximum output power of III-V/SiNcoupled lasers[239,, (c) schematic layout of a heterogeneous III-V/SiN laser and its optical taper between SiN and III-V gain sections[245] and (d) development of linewidth of III-V/SiN lasers[244,246,248,249,252,254,[256][257][258][261][262][263][264]266,267,270,[272][273][274][275][276]279,280,[283][284][285].…”

Miniaturization of Laser Doppler Vibrometers—A Review

“…No report 12 [76] 8 dB [77] Butt coupler loss (dB) <2 (to lensed fiber) [78] 1.5 (to lensed fiber) [42] <2 [79] <1 [56] 0.4 [47] 6 [76] 0.8 [80] Laser sorce Hetero integration [59]/MOB [60] Monolithic Monolithic [81] Hybrid [59] and Hetero Integration [82] Hybrid integration Hybrid integration Hybrid integration Optical isolator MOB/monolithic [83] No report Monolithic [84] Monolithic [85]…”

A hybrid integrated dual-microcomb source

“…Today, the performance of low-loss silicon-based photonic systems has become comparable with that of free-space optic systems. In addition, high-level compatibility with CMOS fabrication processes [35][36][37] and also with the III-V semiconductor platform [38][39][40] have been demonstrated. Recent progress in silicon photonics, combined with the self-injection locking (SIL) effect [41][42][43][44][45][46][47][48][49], enabled optical microcomb generation using semiconductor laser diodes (LDs) instead of bulky narrow-linewidth lasers, thereby greatly simplifying the process of microcomb generation and paving the way for the development of fully integrated chip-scale single microcomb sources based on high-Q microresonators (MRs) [38,39,[50][51][52].…”