Ultrabroadband 50-130 THz pulses generated via phase-matched difference frequency mixing in LiIO_3

Abstract

We report the generation of ultrabroadband pulses spanning the 50-130 THz frequency range via phase-matched difference frequency mixing within the broad spectrum of sub-10 fs pulses in LiIO 3 . Model calculations reproduce the octave-spanning spectra and predict few-cycle THz pulse durations less than 20 fs. The applicability of this scheme is demonstrated with 9-fs pulses from a Ti:sapphire oscillator and with 7-fs amplified pulses from a hollow fiber compressor as pump sources. c 2006 Optical Society of America OCIS codes: 160.4330, 190.2620, 320.7110 Ultrafast mid-infrared (mid-IR) and ultrabroadband terahertz (THz) spectroscopy has evolved into a powerful tool in chemistry and materials science. Femtosecond pulses in this range can probe e.g. molecular vibrational dynamics, electronic gaps in superconductors, plasma quantum kinetics and intersubband transitions in semiconductors, or phonon coupling in semimetals.

Extreme THz nonlinearities in bulk and nanostructured semiconductors

“…However, for increasing THz field strengths, a unipolar component which is superimposed on the transient is clearly discernible in the time-domain data. The component which oscillates with the carrier frequency of the THz pulse saturates while the unipolar signal (squares) increases quadratically, which indicates (3) and (4) processes involving two and three THz photons, respectively. At intensities beyond 5 MV/cm, we start to observe THz induced continuum generation, interband luminescence, and ultimately THz radiation damage of the detector, indicating a catastrophic divergence of the power series expansion of the nonlinear polarization.…”

“…This is mainly due to two unique benefits of THz optoelectronics: The possibility of generating inherently phase stable transients and the availability of field-sensitive detectors. Recently these technologies have been extended across an ultrabroad spectral window approaching the near infrared [2][3][4][5] . Thus, they are ideally applicable to resonant probing of low-energy elementary excitations in condensed matter on a sub-cycle time scale [6][7][8][9][10][11] .…”

Characterization of mid-infrared femtosecond pulses [Invited]

“…Mid-IR generation might be done by difference-frequency mixing between the two tunable pulses from an optical parametric amplifier pumped by a Ti:sapphire chirped-pulsed amplifier (CPA) [10,11]. Another approach is the optical rectification of 10 fs pulses, an extension of far-IR (or terahertz) techniques for generating single-cycle pulses in the mid-IR, and useful for both amplified and unamplified laser sources [12][13][14][15][16]. Although self-referenced methods can be used in the mid-IR, alternative characterization methods can take advantage of the other available pulses.…”

Femtosecond THz studies of intra‐excitonic transitions

“…While the idea was initially exploited for far-infrared transients with frequencies typically up to a few THz, recent years have seen a rapid extension towards the near-infrared domain. Ever shorter pump pulses, efficient and tuneable phase-matching schemes [21,22], and a variety of crystal materials with high χ (2) nonlinearities, such as ZnTe, GaP, GaSe, or LiIO 3 , have enabled this vast progress [20][21][22][23][24]. THz pulses with MV/cm peak electric fields in a broad range and precisely shape the wave form of multi-THz field transients [25,26].…”