Peter Jojart

Energetic sub-2-cycle laser with 216 W average power.

Few-cycle lasers are essential for many research areas such as attosecond physics that promise to address fundamental questions in science and technology. Therefore, further advancements are connected to significant progress in the underlying laser technology. Here, two-stage nonlinear compression of a 660 W femtosecond fiber laser system is utilized to achieve unprecedented average power levels of energetic ultrashort or even few-cycle laser pulses. In a first compression step, 408 W, 320 μJ, 30 fs pulses are achieved, which can be further compressed to 216 W, 170 μJ, 6.3 fs pulses in a second compression stage. To the best of our knowledge, this is the highest average power few-cycle laser system presented so far. It is expected to significantly advance the fields of high harmonic generation and attosecond science.

Agile linear interferometric method for carrier-envelope phase drift measurement

A bandwidth-independent and linear interferometric method for the measurement of the carrier-envelope phase drift of ultrashort pulse trains is demonstrated. The pulses are temporally overlapped in a resonant multiple-beam interferometer. From the position of the spectral interference pattern, the relative carrier-envelope phase between two subsequent oscillator pulses is obtained at data acquisition rates up to 200 Hz. Cross calibration has been performed by f-to-2f interferometry in two independent experiments. The optical length of the interferometer has been actively stabilized, leading to a phase jitter of 117 mrad (rms). These results indicate a reduced noise and quicker data acquisition in comparison with previous linear methods for measuring the carrier-envelope phase drift.

200 W Average Power Energetic Few-cycle Fiber Laser

A state-of-the-art 8 channel fiber-chirped-pulse-amplifier system delivers 680 W of average power. Two-stage nonlinear compression in gas-filled capillaries yields 400 W, 30fs, >300µJ pulses and 220W, sub-7fs, 170 µJ pulses, respectively.

Independent Control of Arbitrary Dispersion Order of High Intensity Laser Pulses

We report on wedge pairs made of different materials, which are capable of tuning exclusively one dispersion coefficient of laser pulses. Contrary to conventional dispersion controlling devices, these wedges can be used with high intensities.

Measurement of spectral phase noise in a cryogenically cooled Ti:Sa amplifier (Conference Presentation)

In most of cases the drift of the carrier envelope phase (CEP) of a chirped pulse amplifier (CPA) system is determined only [1], being the relevant parameter at laser-matter interactions. The need of coherent combination of multiple amplifier channels to further increase the peak power of pulses requires interferometric precision [2]. For this purpose, the stability of the group delay of the pulses may become equally important. Further development of amplifier systems requires the investigation of phase noise contributions of individual subsystems, like amplifier stages. Spectrally resolved interferometry (SRI), which is a completely linear optical method, makes the measurement of spectral phase noise possible of basically any part of a laser system [3]. By utilizing this method, the CEP stability of water-cooled Ti:Sa based amplifiers was investigated just recently, where the effects of seed and pump energy, repetition rate, and the cooling crystal mounts were thoroughly measured [4]. We present a systematic investigation on the noise of the spectral phase, including CEP, of laser pulses amplified in a cryogenically-cooled Ti:Sa amplifier of a CPA chain. The double-pass amplifier was built in the sample arm of a compact Michelson interferometer. The Ti:Sa crystal was cooled below 30 °K. The inherent phase noise was measured for different operation modes, as at various repetition rates, and pump depletion. Noise contributions of the vacuum pumps and the cryogenic refrigerator were found to be 43 and 47 mrad, respectively. We have also identified CEP noise having thermal as well as mechanical origin. Both showed a monotonically decreasing tendency towards higher repetition rates. We found that the widths of the noise distributions are getting broader towards lower repetition rates. Spectral phase noise with and without amplification was measured, and we found no significant difference in the phase noise distributions. The mechanical vibration was also measured in the setup by using an accelerometer synchronously with the optical measurements. The noise spectra of phase and vibration measurements were compared and the sources of individual noise components were identified. References [1] Sebastian Koke et al, Opt. Lett. 33, 2545-2547 (2008). [2] J. Limpert et al, IEEE J. of Sel. Top. in Quant. El. 20, 0901810 (2014). [3] A. Borzsonyi, A.P. Kovacs, K. Osvay, Appl. Sci. 3, 515-544 (2013). [4] A. Borzsonyi, R.S. Nagymihaly, K. Osvay, Las. Phys. Lett. 13, 015301 (2016).

Spectral phase noise analysis of a cryogenically cooled Ti:Sapphire amplifier

The spectral phase noise of a cryogenically cooled Ti:Sapphire amplifier was analyzed by spectrally resolved interferometry. Since a relative phase difference measurement is performed, the effect of the amplifier stage can be determined with high precision. Contributions of the cooling system to the spectral phase noise were found to be below 50 mrad for both the vacuum pumps and the cryogenic system. The carrier-envelope phase noise of thermal and mechanical origin was also determined for different repetition rates of laser operation. Mechanical vibrational spectra were recorded by an accelerometer for different stages of operation and compared to the interferometric phase noise measurements.

Increase of Carrier-Envelope Phase Noise in Water and Cryogenically Cooled Ti:Sapphire Amplifiers

CEP drift of ultrashort pulses originating solely from an amplifier is measured. The CEP noise in water cooled amplifiers has thermal origin, while it is induced by the inherent vibration of Ti:Sa upon cryogenical cooling.

Carrier envelope phase drift of picosecond frequency combs from an ultrahigh finesse fabry-perot cavity

The carrier envelope phase shift of a stacked picosecond pulse train for Compton scattering experiments have been measured to an accuracy of 80 mrad by spectrally resolved interference pattern of a stabilized multiple beam interferometer.

All-linear-optical technique for intracavity stabilization of CEP drift

The slow carrier envelope phase drift of a 50nm bandwidth femtosecond oscillator is stabilized with an accuracy better than 140mrad with an intracavity isochronic wedge pair driven by a stabilized spectrally resolved multiple beam interferometer.

A simple linear technique for measuring the carrier-envelope offset phase of ultrashort pulses

A spectrally resolved multiple beam interferometer is capable for measuring the carrier envelope offset phase of ultrashort laser pulses with an accuracy of 70 mrad. The performance has been cross-calibrated with a conventional f-to-2f interferometer.