Phase stability of terawatt-class ultrabroadband parametric amplification

Abstract

The phase stability of broadband (280 nm bandwidth) terawatt-class parametric amplification was measured, for the first time to our knowledge, with a combination of spatial and spectral interferometry. Measurements at four different wavelengths from 750 to 900 nm were performed in combination with numerical modeling. The phase stability is better than 1/23 rms of an optical cycle for all the measured wavelengths, depending on the phase-matching conditions in the amplifier. © 2007 Optical Society of America OCIS codes: 190.4970, 320.7090, 320.7160, 350.5030. The generation and amplification of phase-controlled few-cycle laser pulses is a necessity for applications such as quantum interference metrology [1], attosecond science [2], and quantum control of, e.g., molecular dynamics [3]. Intense, phase-stable few-cycle laser pulses have been produced by using Ti:sapphire amplifiers and subsequent spectral broadening in filaments. However, filamentation in gas-filled hollow fibers [4], or directly in a gas cell [5], is difficult to scale beyond Ϸ0.2 TW. In parametric amplification phase-stable pulses, albeit at moderate energies of a few hundred microjoules [6][7][8][9], have also been demonstrated. The generation of multimillijoule-level phase-controlled few-cycle pulses with terawatt (TW) intensity has not been demonstrated to date. In this Letter we report what is, to the best of our knowledge, the first measurement of the phase stability of TW-class ultrafast amplification. The amplifier is based on noncollinear optical parametric chirped pulse amplification (NOPCPA) and was described elsewhere in detail [10]. It consists of a double-pass preamplifier and a single-pass power amplifier using BBO crystals. The seed laser is a home-built 6.2 fs frequency comb oscillator, producing phase-locked 5.5 nJ pulses at a 75 MHz repetition rate. The carrier-envelope phase (CEP) stability of the oscillator is 1 / 46 rms of an optical cycle. The 532 nm pump laser provides 170 mJ pulses with a duration of 60 ps and is synchronized to the oscillator laser. The system operates at a repetition rate of 30 Hz and is capable of generating 7.6 fs pulses at 2 TW (15.5 mJ after compression) when the normal full seed energy of 1 nJ per pulse is available.The phase stability of the NOPCPA output is measured with linear interferometry. The advantage of this method over the frequently used f :2f technique [11] is that pulse intensity fluctuations (typically a few percent) do not influence the measurement; also the wavelength dependence can be measured. The system is based on a double interferometer, to be able to correct for optical path fluctuations due to external noise and drift (see Fig. 1). The interferometer path length variations, of the order of a wavelength, are too small to influence the CEP. Changes induced by thermal effects due to the 20 mm of optical material in the NOPCPA path are small and are in addition compensated by a similar amount of material in the reference arm. The interferometer compares interference [12] between...

High-accuracy deep-UV Ramsey-comb spectroscopy in krypton

“…The parametric amplification process and self-and cross-phase modulation between all interacting beams can imprint a phase shift on the amplified pulses, depending mostly on the pump intensity [31,34,35]. Any differential phase shift �Φ between different pulse pairs can lead to a frequency shift of the excited two-photon transition according to:…”

“…consisting of a Mach-Zehnder interferometer in combination with spectral interferometry [31,35]. The two amplified pulses are combined with their respective non-amplified FC pulses which are extracted before the amplification process using a combination of a wave plate and polarizing cube (see Fig.…”

Carrier-envelope phase control of Yb:KGW laser and parametric amplifiers

“…Theoretically, parametric amplification in the conditions of perfect phase matching maintains the phase of the amplified signal pulses [23]. However, for practical purposes, CEP variation caused by environmental instabilities and mechanical vibrations in the experiment set-up should be taken into account and requires to be mitigated.…”

“…An implementation of different OPA schemes, the methods of non-collinear broadband parametric amplification [11] and chirped pulse parametric amplification [12] allow us to produce pulses with durations down to a few optical cycles [13][14][15][16], generate the octave-spanning spectrum pulses in mid-IR with the central wavelength up to 6 µm [17], and to achieve the peak powers up to the PW-level [18]. The phase-preserving properties of OPAs have been confirmed in different experimental setups [19][20][21][22] and allowed for phase-stable pulse amplification to intensity levels exceeding 1 TW [23]. Another important feature of parametric frequency converters is the possibility to produce the pulses with a phase independent of the input pulse CEP.…”

The Generation and Characterisation of Ultrashort Mid-Infrared Pulses

“…Ti:Sapphire oscillator systems. The effect of imperfect phasematching is to couple the output CEP to fluctuations in the pump laser intensity via the f parameter, but for a stable pump laser and a correctly aligned OPA this does not affect the CEP stability in a drastic way (Renault et al (2007)). In our experimental realisation, the seed for our OPCPA system is derived from a two-color fibre laser system (Toptica Photonics) which delivers amplified and phase-coherent ultrashort pulses at 1050 nm (48 fs, 16 mW) and 1550 nm (75 fs, 180 mW).…”