Optical clocks at sea.

Deployed optical clocks will improve positioning for navigational autonomy, provide remote time standards for geophysical monitoring and distributed coherent sensing, allow time synchronization of remote quantum networks and provide operational redundancy for national time standards. Although laboratory optical clocks now reach fractional inaccuracies below 10 (refs. ), transportable versions of these high-performing clocks have limited utility because of their size, environmental sensitivity and cost.

Mid-infrared frequency combs at 10 GHz.

We demonstrate mid-infrared (MIR) frequency combs at 10 GHz repetition rate via intra-pulse difference-frequency generation (DFG) in quasi-phase-matched nonlinear media. Few-cycle pump pulses (≲15, 100 pJ) from a near-infrared electro-optic frequency comb are provided via nonlinear soliton-like compression in photonic-chip silicon-nitride waveguides. Subsequent intra-pulse DFG in periodically poled lithium niobate waveguides yields MIR frequency combs in the 3.

All-fiber frequency comb at 2 µm providing 1.4-cycle pulses.

We report an all-fiber approach to generating sub-2-cycle pulses at 2 µm and a corresponding octave-spanning optical frequency comb. Our configuration leverages mature erbium:fiber laser technology at 1.5 µm to provide a seed pulse for a thulium-doped fiber amplifier that outputs 330 mW average power at a 100 MHz repetition rate.

Mid-Infrared Frequency Comb Generation and Spectroscopy with Few-Cycle Pulses and χ^{(2)} Nonlinear Optics.

The mid-infrared atmospheric window of 3-5.5  μm holds valuable information regarding molecular composition and function for fundamental and applied spectroscopy. Using a robust, mode-locked fiber-laser source of <11  fs pulses in the near infrared, we explore quadratic (χ^{(2)}) nonlinear optical processes leading to frequency comb generation across this entire mid-infrared atmospheric window.

Mid-infrared frequency comb with 6.7 W average power based on difference frequency generation.

We report on the development of a high-power mid-infrared frequency comb with 100 MHz repetition rate and 100 fs pulse duration. Difference frequency generation is realized between two branches derived from an Er:fiber comb, amplified separately in Yb:fiber and Er:fiber amplifiers. Average powers of 6.

Infrared electric field sampled frequency comb spectroscopy.

Probing matter with light in the mid-infrared provides unique insight into molecular composition, structure, and function with high sensitivity. However, laser spectroscopy in this spectral region lacks the broadband or tunable light sources and efficient detectors available in the visible or near-infrared. We overcome these challenges with an approach that unites a compact source of phase-stable, single-cycle, mid-infrared pulses with room temperature electric field-resolved detection at video rates.

Tunable mid-infrared generation via wide-band four-wave mixing in silicon nitride waveguides.

We demonstrate wide-band frequency down-conversion to the mid-infrared (MIR) using four-wave mixing (FWM) of near-infrared (NIR) femtosecond-duration pulses from an Er:fiber laser, corresponding to 100 THz spectral translation. Photonic-chip-based silicon nitride waveguides provide the FWM medium. Engineered dispersion in the nanophotonic geometry and the wide transparency range of silicon nitride enable large-detuning FWM phase-matching and results in tunable MIR from 2.

Mid-infrared frequency comb generation via cascaded quadratic nonlinearities in quasi-phase-matched waveguides.

We experimentally demonstrate a simple configuration for mid-infrared (MIR) frequency comb generation in quasi-phase-matched lithium niobate waveguides using the cascaded-χ nonlinearity. With nanojoule-scale pulses from an Er:fiber laser, we observe octave-spanning supercontinuum in the near-infrared with dispersive wave generation in the 2.5-3 μm region and intrapulse difference frequency generation in the 4-5 μm region.

Quasi-Phase-Matched Supercontinuum Generation in Photonic Waveguides.

Supercontinuum generation (SCG) in integrated photonic waveguides is a versatile source of broadband light, and the generated spectrum is largely determined by the phase-matching conditions. Here we show that quasi-phase-matching via periodic modulations of the waveguide structure provides a useful mechanism to control the evolution of ultrafast pulses during supercontinuum generation. We experimentally demonstrate a quasi-phase-matched supercontinuum to the TE_{20} and TE_{00} waveguide modes, which enhances the intensity of the SCG in specific spectral regions by as much as 20 dB.

Quantum optical arbitrary waveform manipulation and measurement in real time.

We describe a technique for dynamic quantum optical arbitrary-waveform generation and manipulation, which is capable of mode selectively operating on quantum signals without inducing significant loss or decoherence. It is built upon combining the developed tools of quantum frequency conversion and optical arbitrary waveform generation. Considering realistic parameters, we propose and analyze applications such as programmable reshaping of picosecond-scale temporal modes, selective frequency conversion of any one or superposition of those modes, and mode-resolved photon counting.

Multichannel photon-pair generation using hydrogenated amorphous silicon waveguides.

We demonstrate highly efficient photon-pair generation using an 8 mm long hydrogenated amorphous silicon (a-Si:H) waveguide in far-detuned multiple wavelength channels simultaneously, measuring a coincidence-to-accidental ratio as high as 400. We also characterize the contamination from Raman scattering and show it to be insignificant over a spectrum span of at least 5 THz. Our results highlight a-Si:H as a potential high-performance, CMOS-compatible platform for large-scale quantum applications, particularly those based on the use of multiplexed quantum signals.

Experimental demonstration of interaction-free all-optical switching via the quantum Zeno effect.

We experimentally demonstrate all-optical interaction-free switching using the quantum Zeno effect, achieving a high contrast of 35:1. The experimental data match a zero-parameter theoretical model for several different regimes of operation, indicating a good understanding of the switch's characteristics. We also discuss extensions of this work that will allow for significantly improved performance, and the integration of this technology onto chip-scale devices, which can lead to ultra-low-power all-optical switching, a long-standing goal with applications to both classical and quantum information processing.