The series of precisely spaced, sharp spectral lines that form an optical frequency comb is enabling unprecedented measurement capabilities and new applications in a wide range of topics that include precision spectroscopy, atomic clocks, ultracold gases, and molecular fingerprinting. A new optical frequency comb generation principle has emerged that uses parametric frequency conversion in high resonance quality factor (Q) microresonators. This approach provides access to high repetition rates in the range of 10 to 1000 gigahertz through compact, chip-scale integration, permitting an increased number of comb applications, such as in astronomy, microwave photonics, or telecommunications. We review this emerging area and discuss opportunities that it presents for novel technologies as well as for fundamental science.

http://science.sciencemag.org/content/sci/332/6029/555.full.pdf

Microresonator-Based Optical Frequency Combs

Temporal dissipative solitons are observed in a nonlinear, high-finesse, optical microresonator driven by a continuous-wave laser. This approach enables ultrashort pulses to be generated in spectral regimes lacking broadband laser gain media and saturable absorbers, making it potentially useful for applications in broadband spectroscopy, telecommunications, astronomy and low-phase-noise microwave generation.

Temporal solitons in optical microresonators

저작근 근전도에 관한 정상교합자와 ii급 부정교합자의 비교 연구

Nonlinear photonic chips can generate and process signals all-optically with far superior performance to that possible electronically — particularly with respect to speed. Although silicon-on-insulator has been the leading platform for nonlinear optics, its high two-photon absorption at telecommunication wavelengths poses a fundamental limitation. We review recent progress in non-silicon CMOS-compatible platforms for nonlinear optics, with a focus on Si3N4 and Hydex®. These material systems have opened up many new capabilities such as on-chip optical frequency comb generation and ultrafast optical pulse generation and measurement. We highlight their potential future impact as well as the challenges to achieving practical solutions for many key applications. This article reviews recent progress in the use of silicon nitride and Hydex as non-silicon-based CMOS-compatible platforms for nonlinear optics. New capabilities such as on-chip optical frequency comb generation, ultrafast optical pulse generation and measurement using these materials, and their potential future impact and challenges are covered.

New CMOS-compatible platforms based on silicon nitride and hydex for nonlinear optics

The control of the broadband frequency comb emitted from a mode-locked femtosecond laser has permitted a wide range of scientific and technological advances--ranging from the counting of optical cycles for next-generation atomic clocks to measurements of phase-sensitive high-field processes. A unique advantage of the stabilized frequency comb is that it provides, in a single laser beam, about a million optical modes with very narrow linewidths and absolute frequency positions known to better than one part in 10(15) (ref. 5). One important application of this vast array of highly coherent optical fields is precision spectroscopy, in which a large number of modes can be used to map internal atomic energy structure and dynamics. However, an efficient means of simultaneously identifying, addressing and measuring the amplitude or relative phase of individual modes has not existed. Here we use a high-resolution disperser to separate the individual modes of a stabilized frequency comb into a two-dimensional array in the image plane of the spectrometer. We illustrate the power of this technique for high-resolution spectral fingerprinting of molecular iodine vapour, acquiring in a few milliseconds absorption images covering over 6 THz of bandwidth with high frequency resolution. Our technique for direct and parallel accessing of stabilized frequency comb modes could find application in high-bandwidth spread-spectrum communications with increased security, high-resolution coherent quantum control, and arbitrary optical waveform synthesis with control at the optical radian level.

/pdf/molecular-fingerprinting-with-the-resolved-modes-of-a-54pbyogvoq.pdf

Molecular fingerprinting with the resolved modes of a femtosecond laser frequency comb

In this paper, we review spectral line-by-line pulse shaping, including examples of waveform generation, data demonstrating sensitivity to comb offset frequency, and requirements for high fidelity waveform generation. In order to achieve spectral line-by-line pulse shaping, we have improved the spectral resolution of grating-based pulse shapers to ~2.5 GHz, and performed experiments utilizing high repetition rate (~10 GHz) pulse sources, including harmonically mode-locked fiber lasers and strongly phase modulated CW lasers.

Spectral line-by-line pulse shaping

We demonstrate a method for all-optical, tunable pulse repetition-rate multiplication of a mode-locked laser based on spectral line-by-line control. In particular, two-to-five-times repetition-rate multiplication of a 9 GHz source is achieved with very high fidelity.

Tunable pulse repetition-rate multiplication using phase-only line-by-line pulse shaping

Spectral line-by-line shaping is a key enabler towards optical arbitrary waveform generation, which promises broad impact both in optical science and technology. In this paper, generation of optical and microwave arbitrary waveforms using the spectral line-by-line shaping technique is reviewed. Compared to conventional pulse shaping, significant new physics arises in the line-by-line regime, where the shaped pulse fields generated from one laser pulse now overlap with those generated from adjacent pulses. This leads to coherent interference effects related to the properties of optical frequency combs which serve as the source in these experiments. We explore such effects in a series of experiments using several different high-repetition-rate optical combs, including harmonically mode-locked lasers and continuous-wave lasers that are externally phase modulated either with or without the help of an optical cavity. As an application of line-by-line pulse shaping, we describe generation of microwave electrical arbitrary waveforms that can be reprogrammed at rates approaching 10 GHz.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/lpor.200810001

Spectral line‐by‐line shaping for optical and microwave arbitrary waveform generations

We report spatial and temporal dispersion compensation for fan-out of femtosecond pulses with a low-frequency diffraction grating by means of a hybrid diffractive-refractive lens triplet. In this way, we achieve a multifocal light structure with nearly diffraction-limited light spots even for 20 fs pulse duration. The spatial chromatic compensation, which drastically reduces the lateral walk-off of the various spectral components, also allows us to improve the available bandwidth at the dispersion-compensated diffraction orders. In fact, the temporal width of the output pulse is essentially limited by the group-delay dispersion term, which is shown to be small. The high spatiotemporal resolution provided by our proposal permits parallel multifocal processing of materials with femtosecond pulses.

High spatiotemporal resolution in multifocal processing with femtosecond laser pulses.

Recently, using parageometrical optics concepts, a hybrid, diffractive-refractive, lens triplet has been suggested to significantly improve the spatiotemporal resolution of light spots in multifocal processing with femtosecond laser pulses. Here, we carry out a rigorous wave-optics analysis, including the spatiotemporal nature of the wave equation, to elucidate both the spatial extent of the diffractive spots and the temporal duration of the pulse at the output plane. Specifically, we show nearly transform-limited behavior of diffraction maxima. Moreover, the temporal broadening of the pulse is related to the group velocity dispersion, which can be pre-compensated for in practical applications. Finally, some numerical simulations of the spatiotemporal wave field at the output plane in a realistic case are provided.

José Caraquitena

Papers

Spectral line-by-line pulse shaping

Tunable pulse repetition-rate multiplication using phase-only line-by-line pulse shaping

Spectral line‐by‐line shaping for optical and microwave arbitrary waveform generations

High spatiotemporal resolution in multifocal processing with femtosecond laser pulses.

Dispersion-compensated beam-splitting of femtosecond light pulses: Wave optics analysis.