Optical frequency synthesizer with an integrated erbium tunable laser

Abstract

Optical frequency synthesizers have widespread applications in optical spectroscopy, frequency metrology, and many other fields. However, their applicability is currently limited by size, cost, and power consumption. Silicon photonics technology, which is compatible with complementary-metal-oxide-semiconductor fabrication processes, provides a low-cost, compact size, lightweight, and low-power-consumption solution. In this work, we demonstrate an optical frequency synthesizer using a fully integrated silicon-based tunable laser. The synthesizer can be self-calibrated by tuning the repetition rate of the internal mode-locked laser. A 20 nm tuning range from 1544 to 1564 nm is achieved with ~10−13 frequency instability at 10 s averaging time. Its flexibility and fast reconfigurability are also demonstrated by fine tuning the synthesizer and generating arbitrary specified patterns over time-frequency coordinates. This work promotes the frequency stability of silicon-based integrated tunable lasers and paves the way toward chip-scale low-cost optical frequency synthesizers.

High-yield, wafer-scale fabrication of ultralow-loss, dispersion-engineered silicon nitride photonic circuits

“…While tight optical confinement can reduce the footprint, losses approaching even 1 dB m −1 have not been achieved in any nonlinear waveguide including thick-core Si 3 N 4 . Here, we demonstrate meter-long Si 3 N 4 waveguides featuring ultralow loss and small footprint, which can enable key applications such as traveling-wave parametric amplifiers 56 – 59 , rare-earth-doped mode-locked lasers 60 and optical coherence tomography (OCT) 75 .…”

“…Meanwhile, the fabrication of densely packed, meter-long PIC has not yet been realized, and neither has wafer-level fabrication yield, reliability and reproducibility, required for widespread adoption in CMOS foundries. Yet, densely packed, meter-long nonlinear Si 3 N 4 PIC could enable a new class of devices, ranging from integrated traveling-wave parametric amplifiers 56 – 59 to integrated mode-locked-lasers based on rare-earth doping 60 .

Fig.

…”

Spectral imaging and spectral LIDAR systems: moving toward compact nanophotonics-based sensing

“…The frequency comb generation originates from the nonlinear interaction between high-intensity optical field and material, which also can be a platform for optical soliton generation [138][139][140][141][142]. The optical frequency comb is a powerful tool in precision measurement [143], spectroscopy [144], optical frequency synthesis [145][146][147], distance measurement [148], microwave photonics [141,149] and many other applications [150][151][152]. The photonic-integrated optical frequency comb, which is able to provide a compact solution to a sensing system, has drawn a lot of research interests [153][154][155][156][157].…”

Tellurite glass microcavity resonators integrated on a silicon photonics platform

“…Aluminum oxide glass cavities fabricated in this manner and aligned to silicon nitride bus waveguides have demonstrated high Q factors of greater than 10 6 , 24 with demonstrations of rare earth lasing with erbium 25 and thulium dopants 26 and four wave mixing. 27 Advanced multilayer foundry processes can be used to vertically couple light from silicon nitride to silicon waveguides to combine these devices with electro-optic functionality, [28][29][30] but for lower cost fabrication technology, it would be preferable to be able to couple the resonator directly to the silicon waveguide layer. Although aluminum oxide resonators have been highly successful in combination with silicon nitride waveguides, it is much more difficult to phase match the low refractive index of aluminum oxide (1.65) to a silicon bus waveguide, making alternative glasses more preferable for direct silicon integration.…”