Enhancement cavities for zero-offset-frequency pulse trains

Abstract

The optimal enhancement of broadband optical pulses in a passive resonator requires a seeding pulse train with a specific carrier-envelope-offset frequency. Here, we control the phase of the cavity mirrors to tune the offset frequency for which a given comb is optimally enhanced. This enables the enhancement of a zero-offset-frequency train of sub-30-fs pulses to multi-kW average powers. The combination of pulse duration, power, and zero phase slip constitutes a crucial step toward the generation of attosecond pulses at multi-10-MHz repetition rates. In addition, this control affords the enhancement of pulses generated by difference-frequency mixing, e.g., for mid-infrared spectroscopy.

Cavity-enhanced ultrafast spectroscopy: ultrafast meets ultrasensitive

“…Based on previous work in suppressing noise in CE-DFCS [28,36], achieving shot-noise limited detection should be possible, which would reduce detection limit of the current system by one order of magnitude. Furthermore, the current probe cavity finesse of 370 is quite modest for cavity-enhanced spectroscopy, and this can also be improved along with the time-resolution and probe pulse bandwidths that can be achieved [37,38]. The methods can be extended to the UV and infrared [39], the probe light can be spectrally resolved as in conventional transient absorption spectroscopy, and multidimensional spectroscopy can be performed via phase cycling methods [40].…”

“…Based on previous work in suppressing noise in CE-DFCS [28,36], achieving shot-noise limited detection should be possible, which would reduce detection limit of the current system by one order of magnitude. Furthermore, the current probe cavity finesse of 370 is quite modest for cavity-enhanced spectroscopy, and this can also be improved along with the time-resolution and probe pulse bandwidths that can be achieved [37,38] Experiments are performed with a home-built Yb:fiber laser system consisting of a passively mode-locked fiber oscillator, a pulse stretcher, a fiber amplifier and a pulse compressor. The oscillator is similar to the one presented in ref.…”

Phase-stable, multi-µJ femtosecond pulses from a repetition-rate tunable Ti:Sa-oscillator-seeded Yb-fiber amplifier

“…For instance, the zero-offset-frequency pulse train can be used to drive HHG in a suitable femtosecond enhancement cavity [16,17] for the generation of attosecond pulse trains and, ultimately, for the generation of isolated attosecond pulses at multi-MHz repetition rates [18]. This will dramatically decrease the measurement times in photoelectron emission microscopy and spectroscopy, in particular allowing for the study of plasmonic fields with a unique combination of nm-scale spatial resolution with sub-femtosecond temporal resolution [20].…”

“…First, the high phase stability achieved with the Ti:Sa frontend is largely preserved upon amplification of a 10-nm band around 1030 nm by about 54 dB to 80 W. Additional phase fluctuations introduced by the multi-stage, chirped-pulse amplifier (CPA) and by subsequent nonlinear compression to about 30 fs were compensated for by a feed-back loop, resulting in an unprecedentedly small overall phase jitter of the highpower pulse train of less than 100 mrad (out-of-loop phase noise, integrated in the band between 0.4 Hz and 400 kHz). Due to its phase stability, this source is particularly well suited to drive cavity-enhanced highorder harmonic generation (HHG) for the generation of extreme ultraviolet (XUV) frequency combs [15,16] and of XUV attosecond pulses [16][17][18]. Second, the master oscillator power amplifier (MOPA) approach readily enables the use of a high-frequency pulse picker after the low-power oscillator [19], allowing for a tunable repetition frequency (18.5,24.7,37 and 74 MHz).…”

Ultrafast optomechanical pulse picking

“…With a length of 1.5 m, a distance between the rotating mirrors of 70 mm and an angle of incidence of 2 • , the diameter of the deflection beam circle on the imaging mirrors is about 100 mm. At an angle of incidence of 2 • , birefringent effects in typical broadband highly reflective mirrors are negligible even for the largest bandwidths yet demonstrated in high-finesse ECs [23]. The separation of a b Fig.…”