Phase-locked multi-terahertz electric fields exceeding 13  MV/cm at a 190  kHz repetition rate

Abstract

We demonstrate a compact source of energetic and phase-locked multi-terahertz pulses at a repetition rate of 190 kHz. Difference frequency mixing of the fundamental output of an Yb:KGW amplifier with the idler of an optical parametric amplifier in GaSe and LiGaS2 crystals yields a passively phase-locked train of waveforms tunable between 12 and 42 THz. The shortest multi-terahertz pulses contain 1.8 oscillation cycles within the intensity FWHM. Pulse energies of up to 0.16 µJ and peak electric fields of 13 MV/cm are achieved. Electro-optic sampling reveals a phase stability better than 0.1 π over multiple hours combined with free CEP tunability. The scalable scheme opens the door to strong-field terahertz optics at unprecedented repetition rates. OCIS codes: (140.3070) Infrared and far-infrared lasers; (190.4970) Parametric oscillators and amplifiers; (320.7100) Ultrafast measurements; (320.7100) Ultrafast nonlinear optics; (120.5050) Phase measurementUltrashort pulses in the terahertz (THz) and mid-infrared region of the electromagnetic spectrum have attracted tremendous interest in the past few years as resonant probes of low-energy elementary excitations in condensed matter [1,2]. The combination of CEP-stable pulses with ultrabroadband electro-optic sampling [3][4][5][6][7][8] has allowed for studies of electronic and structural dynamics of molecules and solids, on time scales faster than a single cycle of the carrier wave [1,2]. The recent advent of high-power sources [9][10][11][12][13] has prompted an ongoing revolution of ultrabroadband THz nonlinear optics and resonant THz quantum control of condensed matter [14][15][16][17][18][19][20]. In particular, when the ponderomotive energy exceeds the fundamental bandgap of semiconductors or dielectrics, the carrier wave acts like an AC bias field that can accelerate and recollide quasiparticles [15,16]. It can drive dynamical Bloch oscillations and highharmonic generation [17], or induce tunneling of electrons out of sharp metal tips [18] or through the tunneling junction of a scanning tunneling microscope (STM) [19,20]. In the multi-THz range, non-perturbative dynamics of this nature, often dubbed 'lightwave electronics', have occurred for field amplitudes typically above 10 MV/cm.Optical rectification, i.e. difference frequency generation (DFG) within the broad spectrum of a single femtosecond near-infrared (NIR) pulse, gives rise to passively phaselocked THz pulses [3][4][5][6][7][8]21]. While this concept warrants a particularly stable carrier-envelope phase (CEP), its observed low quantum efficiency has made it a popular choice for the generation of probe pulses [1,2]. Difference frequency mixing between the signal waves of two optical parametric amplifiers driven by the same pump laser, in contrast, has generated CEP-stable few-and single-cycle multi-THz pulses with field amplitudes in excess of 10 MV/cm or even above 100 MV/cm [9][10][11]22]. An innovative in-line scheme of two-color parametric amplification in a single OPA has further improved the long...

Octave-spanning single-cycle middle-infrared generation through optical parametric amplification in LiGaS2

“…Researchers are therefore invoking nonlinear optical conversions, for example difference frequency generation or optical rectification in nonlinear crystals [10][11][12][13] such as GaSe or AgGaS 2 [14,15], filaments [16,17] or plasmas [18]. A quite new material is LiGaS 2 (LGS) [19][20][21][22][23][24] which offers a broadband transparency range (0.32-11.6 µm) and a large bandgap of ∼4 eV that leads to very weak two-photon absorption for Ti:sapphire-based (∼800 nm) or Yb-based (∼1030 nm) laser pulses.…”

Generalized Gross-Pitaevskii model for intersubband polariton lasing

“…4. A more in depth experimental investigation can benefit from electro-optic sampling techniques, allowing the real time measurement of the actual reflected electric fieldẼ refl (k, t) [34][35][36][37][38][39][40]. The direct measurement of both amplitude and phase of the reflected radiation allows to study more subtle optical features such as the temporal shape of wavepackets or the coherence properties of the emission.…”

Towards Intense THz Spectroscopy on Water: Characterization of Optical Rectification by GaP, OH1, and DSTMS at OPA Wavelengths

“…OR typically allows us to generate intense THz radiation below 5 THz (sketched in light green and light red in Figure 1c), while DFG covers higher frequencies (dark green and dark red in Figure 1c). Both inorganic (LiNbO 3 [66][67][68][69][70][71][72][73][74][75][76][77], GaSe [78][79][80], ZnTe [81,82], LiGaS 2 [83], GaP [84][85][86][87][88][89]) as well as organic (DSTMS [89][90][91][92], OH1 [93][94][95][96][97], DAST [98,99], DPFO [100], HMQ-TMS [101], OHQ-N2S [102]) crystals are phase-matched in the NIR and can emit pulsed THz fields with peak amplitudes in excess of 1 MV/cm. The approximate spectrum of the strongest THz pulses generated to date by non-linear optical methods in inorganic [62,64] and organic [63,65] crystals are shown in green and in red in Figure 1c, respectively.…”