An optical-frequency synthesizer using integrated photonics

Abstract

Optical-frequency synthesizers, which generate frequency-stable light from a single microwave-frequency reference, are revolutionizing ultrafast science and metrology, but their size, power requirement and cost need to be reduced if they are to be more widely used. Integrated-photonics microchips can be used in high-coherence applications, such as data transmission , highly optimized physical sensors and harnessing quantum states , to lower cost and increase efficiency and portability. Here we describe a method for synthesizing the absolute frequency of a lightwave signal, using integrated photonics to create a phase-coherent microwave-to-optical link. We use a heterogeneously integrated III-V/silicon tunable laser, which is guided by nonlinear frequency combs fabricated on separate silicon chips and pumped by off-chip lasers. The laser frequency output of our optical-frequency synthesizer can be programmed by a microwave clock across 4 terahertz near 1,550 nanometres (the telecommunications C-band) with 1 hertz resolution. Our measurements verify that the output of the synthesizer is exceptionally stable across this region (synthesis error of 7.7 × 10 or below). Any application of an optical-frequency source could benefit from the high-precision optical synthesis presented here. Leveraging high-volume semiconductor processing built around advanced materials could allow such low-cost, low-power and compact integrated-photonics devices to be widely used.

Efficient second harmonic generation in nanophotonic GaAs-on-insulator waveguides

“…It is used to self-reference a frequency comb by comparing and controlling the difference between two sections of the comb spectra that are separated by an octave. This is referred to as f -2 f self-referencing and it produces low-noise optical frequency combs used for optical clocks [2][3][4], optical frequency synthesizers [5][6][7], low-phase-noise microwave generation [8], and molecular sensing [9,10].…”

“…Increasing the application space for stabilized frequency combs requires reducing the cost, size, weight, and power consumption while maintaining performance metrics [7]. Chip-scale integration is an attractive way to achieve these goals, particularly using heterogeneous integration to combine a suite of different materials into a compact package.…”

“…Chip-scale integration is an attractive way to achieve these goals, particularly using heterogeneous integration to combine a suite of different materials into a compact package. A promising approach to develop a chip-scale stabilized frequency comb is to pump a SiN microresonator with a continuous-wave (CW) near-IR laser [6,7,11]. This design is scalable to large-volume and high-yield manufacturing to reduce cost.…”

Imaging soliton dynamics in optical microcavities

“…Nonetheless, the compactness of microcavity-based soliton systems has practical importance for miniaturization of frequency comb technology 27 through chip-based microcombs 28,29 . Indeed, spectroscopy systems 30,31 , coherent communication 32 , ranging 33,34 , and frequency synthesis 35 demonstrations using the new miniature platform have already been reported. Moreover, the unique physics of the new soliton microcavity system has led to observation of many unforeseen physical phenomena involving compound soliton states, such as Stokes solitons 36 , soliton number switching 37 and soliton crystals 38 .…”

Universal isocontours for dissipative Kerr solitons

“…Referred to as dissipative Kerr solitons (DKs) in the microcavity system, soliton phenomena including the Raman self-shift [23][24][25], optical Cherenkov radiation [16,[25][26][27][28], multisoliton systems [29][30][31], and the cogeneration of new types of solitons [32] have been reported. Moreover, the compact soliton microcomb devices are being studied for systems-on-a-chip applications such as dual-comb spectroscopy [33,34], precision distance measurement [35,36], optical communications [37], and optical frequency synthesis [38].Regions of stability and existence are well known in driven soliton systems [39]. These properties of DKs and CSs have been studied using the Lugiato-Lefever (LL) equation [9,40] in a space of normalized pumping power and cavity-pump frequency detuning [14,[41][42][43].…”