Normal-dispersion fiber optical parametric chirped-pulse amplification
Walter Fu and Frank W. Wise, “Normal-dispersion fiber optical parametric chirped-pulse amplification,” Opt. Lett. 43, 5331-5334 (2018).
An ongoing limitation of fiber lasers is their lack of broad wavelength tunability. Here, we address this problem using fiber optical parametric chirped-pulse amplification (FOPCPA), which combines the energy capacity of chirped pulse amplification with the spectral flexibility of optical parametric amplification and the practical benefits of fiber. Notably, this is the first FOPCPA to be pumped in the normally-dispersive regime, which permits phase-matching far from the pump wavelength.
The system operates by coupling a stretched, broadband pump pulse and a continuous-wave signal into a photonic crystal fiber. At each point in time, the monochromatic signal interacts via four-wave-mixing with a different wavelength of the chirped pump, resulting in an idler that is chirped in exactly the same manner as the pump. Scalability follows from the timescale-invariance of this process: stretching the pump at constant peak power likewise stretches the idler at constant peak power, increasing the energy without affecting the dechirped duration. By exploiting this property, we are able to convert pulses from the Yb-band to the important bio-imaging window near 1300 nm, with energies of >100 nJ and femtosecond-scale durations.
9/11/2018 – Walter travels to the far-away country of Canada to visit colleagues and friends at Université Laval! Pictured below in the company of Réal Vallée and Simon Duval.
Self-seeded, multi-megawatt, Mamyshev oscillator
P. Sidorenko, W. Fu, L. G. Wright, M. Olivier, and F. W. Wise, “Self-seeded, multi-megawatt, Mamyshev oscillator,” Opt. Lett. 43, 2672-2675 (2018).
As was shown by Liu et al., the pulses from a Mamyshev oscillator can be enhanced by increasing the spectral separation between the two bandpass filters. However, this comes at a cost: the same mechanism that strongly stabilizes the pulse against continuous-wave breakthrough also suppresses the weak electric field fluctuations that are needed to initiate pulse formation. Thus, a Mamyshev oscillator may be constructed that supports very high-energy pulses, but which can be mode-locked only with the aid of an external seed source. In this paper, we address this problem by showing how a simple auxiliary cavity–a “starting arm”–may be embedded into a Mamyshev oscillator, enabling the oscillator to seed itself at the flip of a mirror. A video of this process can be viewed here. We have furthermore scaled part of the cavity to fiber with a 10-micron core diameter. The result is a fiber oscillator with self-starting-like behavior that can deliver 190-nJ, 35-fs pulses without any external amplification, for an unprecedented peak power of 3 MW after dechirping.
7/1/2018 – Zimu Zhu returns from attending Nonlinear Photonics in Zurich with fond memories, new ideas, and the Best Student Paper Prize. Congratulations!
5/26/2018 – Congratulations to the Wise group’s latest graduate – Dr. Logan Wright! It’s clear that his parents couldn’t be prouder, and neither could we!
High-power femtosecond pulses without a modelocked laser
Walter Fu, Logan G. Wright, and Frank W. Wise. “High-power femtosecond pulses without a modelocked laser” Optica, Vol. 4, Issue 7, pp. 831-834 (2017).
Modelocked lasers have long been a mainstay of ultrafast optics. However, they face ongoing challenges regarding long-term reliability, and can only emit pulses at regular intervals. Here, we present an alternative approach by seeding a fiber amplifier with a gain-switched diode. Gain-switched diodes emit pulses that are much longer and less coherent than those from modelocked oscillators. We address these issues using fiber nonlinearities: a Mamyshev regenerator isolates a coherent component of the pulse, and subsequent parabolic amplification allows the pulses to be compressed to 140 fs with 13 MW of peak power. Starting with a gain-switched diode means our system is highly robust and can in principle be electronically triggered in arbitrary pulse patterns. This flexibility may facilitate machining or microscopy sources (where pulses must be synchronized to scanning optics) or enable new types of functional neuroimaging (where specific neurons must be illuminated without saturating an entire sample).
6/12/2017 – Congratulations to Yuxing Tang, who will soon start his new job as an associate at Wells Fargo, and Zhanwei Liu, who will do the same at CoAdna Photonics! Yuxing recently attended convocation, and is the 27th PhD student to graduate from the Wise group.
05/29/2016 – Congratulations to Dr. Jun Yang on a successful PhD! Best of luck in the future!
01/15/2016 – Zimu wins Best Talk at Sibley Graduate Research Symposium 2016!
12/16/2015 – Congratulations to Yuxing on passing his A Exam!