Derryck T. Reid,
Christoph M. Heyl,
Robert R. Thomson,
Rick Trebino,
Guenter Steinmeyer,
Helen H. Fielding,
Ronald Holzwarth,
Zhigang Zhang,
Pascal Del'Haye, et al.
The year 2015 marked the 25th anniversary of modern ultrafast optics, since the demonstration of the first Kerr lens modelocked Ti:sapphire laser in 1990 (Spence et al 1990 Conf. on Lasers and Electro-Optics, CLEO, pp 619-20) heralded an explosion of scientific and engineering innovation. The impact of this disruptive technology extended well beyond the previous discipline boundaries of lasers, reaching into biology labs, manufacturing facilities, and even consumer healthcare and electronics. In recognition of such a milestone, this roadmap on Ultrafast Optics draws together articles from some of the key opinion leaders in the field to provide a freeze-frame of the state-of-the-art, while also attempting to forecast the technical and scientific paradigms which will define the field over the next 25 years. While no roadmap can be fully comprehensive, the thirteen articles here reflect the most exciting technical opportunities presented at the current time in Ultrafast Optics. Several articles examine the future landscape for ultrafast light sources, from practical solid-state/fiber lasers and Raman microresonators to exotic attosecond extreme ultraviolet and possibly even zeptosecond x-ray pulses. Others address the control and measurement challenges, requiring radical approaches to harness nonlinear effects such as filamentation and parametric generation, coupled with the question of how to most accurately characterise the field of ultrafast pulses simultaneously in space and time. Applications of ultrafast sources in materials processing, spectroscopy and time-resolved chemistry are also discussed, highlighting the improvements in performance possible by using lasers of higher peak power and repetition rate, or by exploiting the phase stability of emerging new frequency comb sources.
Phase-coherent microwave-to-optical link with a self-referenced microcomb
Pascal Del'Haye,
Aurelien Coillet,
Tara Fortier,
Katja Beha,
Daniel C. Cole,
Ki Youl Yang,
Hansuek Lee,
Kerry J. Vahala,
Scott B. Papp, et al.
Precise measurements of the frequencies of light waves have become common with mode-locked laser frequency combs(1). Despite their huge success, optical frequency combs currently remain bulky and expensive laboratory devices. Integrated photonic microresonators are promising candidates for comb generators in out-of-the-lab applications, with the potential for reductions in cost, power consumption and size(2). Such advances will significantly impact fields ranging from spectroscopy and trace gas sensing(3) to astronomy(4), communications(5) and atomic time-keeping(6,7). Yet, in spite of the remarkable progress shown over recent years(8-10), microresonator frequency combs ('microcombs') have been without the key function of direct f-2f self-referencing(1), which enables precise determination of the absolute frequency of each comb line. Here, we realize this missing element using a 16.4 GHz microcomb that is coherently broadened to an octave-spanning spectrum and subsequently fully phase-stabilized to an atomic clock. We show phase-coherent control of the comb and demonstrate its low-noise operation.
Broadband dispersion-engineered microresonator on a chip
Ki Youl Yang,
Katja Beha,
Daniel C. Cole,
Xu Yi,
Pascal Del'Haye,
Hansuek Lee,
Jiang Li,
Dong Yoon Oh,
Scott A. Diddams, et al.
The control of dispersion in fibre optical waveguides is of critical importance to optical fibre communications systems(1,2) and more recently for continuum generation from the ultraviolet to the mid-infrared(3-5). The wavelength at which the group velocity dispersion crosses zero can be set by varying the fibre core diameter or index step(2,6-8). Moreover, sophisticated methods to manipulate higher-order dispersion so as to shape and even flatten the dispersion over wide bandwidths are possible using multi-cladding fibres(9-11). Here we introduce design and fabrication techniques that allow analogous dispersion control in chip-integrated optical microresonators, and thereby demonstrate higher-order, wide-bandwidth dispersion control over an octave of spectrum. Importantly, the fabrication method we employ for dispersion control simultaneously permits optical Q factors above 100 million, which is critical for the efficient operation of nonlinear optical oscillators. Dispersion control in high-Q systems has become of great importance in recent years with increased interest in chip-integrable optical frequency combs(12-32).
