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 LiIO3. Model calculations reproduce the octave-spanning spectra and predict few-cycle THz pulse durations less than 20 fs. The broad 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.

© 2007 Optical Society of America

1. Introduction

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 [1, 2, 3, 5, 6].

Mid-IR femtosecond pulses are often generated via intricate cascades of optical parametric amplification and difference frequency mixing stages [7, 8, 9]. While the latter provide high pulse energies, a significantly simpler route involves mixing the components within the broad spectrum of individual fs pulses (henceforth called visible pulses). This was demonstrated by optical rectification of Ti:sapphire oscillator pulses on various semiconductors [10, 11]. Phase-matched difference frequency mixing within the broad spectrum of single 13-fs pulses was reported in GaSe [12, 13], providing mid-IR fs pulses tunable from 7–20 μm and a significant boost of IR power. Direct ultrabroadband electro-optic sampling of such few-cycle pulses revealed an inherent stability of the electric field profile [14]. This finding corresponds to a precisely locked carrier-envelope phase that results from difference frequency mixing within a single pulse spectrum [15, 16]. Thin naturally-cleaved GaSe emitters were shown to generate detectable frequency components spanning several octaves throughout the far- and mid-IR [17, 18]. However, the center frequencies could not be tuned beyond 50 THz due to exceedingly large angles of incidence required in this phase-matching scheme. This motivates the search for new compact fs sources to cover all of the mid-IR.

In this paper, we demonstrate the first phase-matched source of ultrabroadband 50-130 THz pulses, generated in LiIO3 via difference frequency mixing within broad visible pulse spectra. THz pulse energies and spectra are characterized for different sub-10 fs Ti:sapphire pump sources. We present calculations of the THz electric field and the phase-matching conditions for this nonlinear process. This constitutes a novel compact and broadband THz source around λ ≈ 3 – 7 μ, resonant to important molecular vibrations and electronic excitations in solids.

In LiIO3, difference frequency mixing can be phase-matched as a type-I nonlinear process with ∆v (o) = v 2 (eo) - v 1 . Here, v 1, v 2 are frequencies of the visible pulse, ∆v is the THz difference frequency, while o and eo designate the ordinary and extraordinary polarizations. In the following, we investigate a 113-μm thick, free-standing LiIO3 crystal cut at θ = 21.5° for phase-matching at normal incidence.

 

Fig. 1. (a) Oscillator-based setup for THz pulse generation in LiIO3 and for interfero-metric field correlations. W: 1-mm thick fused-silica window, CM: chirped mirrors with ≈ -200 fs2 group delay dispersion, Ge: Germanium window. (b) interferogram generated with a 113-μm thick crystal near normal incidence.

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2. Oscillator-based difference frequency mixing in LiIO3

In a first set of experiments, a 78-MHz Ti:sapphire oscillator is used to deliver 9-fs pulses around 790 nm wavelength. The setup is shown in Fig. 1(a). Several reflections off a pair of negatively chirped mirrors compensate for the dispersion of the optical components, where fine tuning is achieved by tilting a fused silica window. The laser polarization is rotated by 45° using a half-wave plate, to provide both o and eo-polarized components for the type-I phase-matching scheme while ensuring a well-defined horizontal THz polarization [12]. A spherical mirror (focal length f = 100 mm) focuses the visible beam to a spot size of 30 μm on the LiIO3 crystal. The emitted THz radiation is collimated with a BaF2 lens and refocused onto a liquid-N2 cooled HgCdTe detector, with remaining visible beam components blocked with a Ge window.

Spectra of the broadband THz pulses are obtained from interferometric field correlations [11]. As illustrated in Fig. 1(a), two visible beams are focused on the LiIO3 crystal for this purpose. This generates two independent THz beams, which overlap due to divergence and interfere on the detector. An interferogram, as shown in Fig. 1(b), results from scanning the time delay ∆t between the two visible pulses. The THz spectrum is then obtained from the Fourier transform of the interferogram.

As shown in Fig. 2(a), we observe generation of ultrabroadband THz pulses with the 113 -μm crystal near normal incidence. The spectrum extends more than an octave from ≈ 40-90 THz. In contrast, Fig. 2(b) shows the spectrum obtained with a 1-mm thick LiIO3 crystal, which by comparison exhibits a much narrower bandwidth. About 1 μ W of THz power is generated from the thin crystal for 160 mW of incident visible power, as estimated from the calibrated detector sensitivity.

 

Fig. 2. Spectra of THz pulses generated in LiIO3 with a 9-fs Ti:sapphire oscillator: (a) measured spectrum from a 113-μm thick crystal (dots) and model curve (line) at θ = 19°. (b) as above, but for a 1-mm thick crystal and θ = 19.3°.

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3. Simulations of pulse parameters

To elucidate the ultrabroadband phase-matching process in LiIO3, we simulate difference frequency mixing of ultrashort pulses using the model of Ref. [13]. The latter ensures a correct representation of the few-cycle electric fields beyond the slowly-varying envelope approximation. Our calculation takes into account the dispersion of LiIO3 [19], the measured pump spectra shown in Fig. 3(a), and the THz transmission of our crystal displayed in Fig. 3(b). Results are shown in Fig. 3(c)–(e) for two different combinations of the pump source and the internal phase-matching angle θ: pulses from the 9-fs oscillator with θ = 19° (solid lines), and amplified pulses from a hollow-fiber compressor with θ = 21.5° (dashed lines) discussed further below. For simplicity, a flat pump-pulse spectral phase is employed. The calculated THz spectrum for the oscillator-based source is shown in Fig 3(c) (solid line) and confirms the ultra-broadband phase-matching condition. It closely follows the experiment as seen from the comparison in Fig. 2(a). The calculations also provide the full time-domain THz electric field ETHz(t) shown in Fig. 3(e). It reveals a few-cycle THz transient, corresponding to only τP ≈ 19 fs pulse width (FWHM) of the intensity envelope.

Phase-matching for the type-I process is governed by the wavevector mismatch ∆k(v 1, ∆v, θ) ≡ (2π/c) × {ne(v 2,θ)v 2 - no(v 1)v 1 - no(∆v)∆v}, which must be minimized. Here, no and ne are the ordinary and extraordinary refractive indices of LiIO3. A convenient measure of phase-matching is the coherence length LC = 2/∆k. The shaded areas in Fig. 3(d) indicate visible and THz frequency pairs v 1, ∆v where LC > 100 μm, i.e. where efficient phase-matching occurs in our crystal. The large extent of these regions underscores the potential of LiIO3 for ultrabroadband frequency mixing. The THz bandwidth is thus optimized by matching the frequency-pair area in Fig. 3(d) to the pump spectrum. A second limitation of the interaction is the group velocity mismatch (GVM) between o and eo-polarized visible pulse components. Calculations show that while this mismatch vanishes for ∆v ≈ 60 THz, it can approach 100 fs/mm at higher frequencies. These aspects, along with broadening of the sub-10 fs visible pulses, contribute to the choice of ≈ 100 μm as an ideal crystal thickness for ultrabroadband THz generation.

 

Fig. 3. (a) Spectra of 9-fs Ti:sapphire oscillator pulses (solid line) and of 7-fs pulses from a hollow fiber compressor, HFC (dashed). (b) normal incidence transmission of 113-mm thick LiIO3. (c)-(e) Calculations of phase-matched difference frequency mixing in this crystal. Results are for θ = 19° pumped by the oscillator (solid lines), and for θ = 21.5° pumped by the HFC (dashed): (c) THz spectra, (d) frequency space (shaded) with LC > 100 μm, (e) time-domain THz electric fields.

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4. Difference frequency mixing of pulses from a hollow-core fiber compressor

With higher pulse energy and bandwidth, these THz pulses may also act as a broadband seed for phase-preserving chirped-pulse optical parametric amplifiers [20], extending comparable schemes around 2 μm wavelength [21, 22] towards the mid-IR. Such arguments, in turn, motivate the use of even shorter and more intense visible driving pulses. In a second experiment, we employ 7-fs pulses generated with a commercial 1-kHz multi-pass Ti:sapphire amplifier coupled to a hollow-fiber and chirped mirror compressor (HFC) [23]. With the fiber filled with Ne at 1.7 bar, the pulse spectrum extends from 600–900 nm [dashed line, Fig. 3(a)]. A train of 200 μJ pulses with 7 mm 1/e 2 beam diameter is transmitted unfocused through the 113-μm thick LiIO3 crystal. We observe generation of THz radiation, characterized with a grating-based spectrometer.

 

Fig. 4. Octave-spanning THz spectrum (circles) generated in LiIO3 with 7-fs pulses from a hollow fiber compressor (inset). The visible pulses from the hollow-core fiber are re-compressed using chirped mirrors (CM) and thin fused silica wedges [23]. The dips in the spectrum arise from absorption in the spectrometer path. Model curves with θ = 21.5° are shown for unchirped pump pulses (dashed line) as in Fig. 3, and for 6 fs2 quadratic chirp (thick solid line). Both theory curves are scaled equally.

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Figure 4 shows the resulting extremely broadband THz spectrum (circles), which extends from 50 to beyond 130 THz. The spectral width far exceeds that achieved with two-color mixing schemes [8, 9]. Note that the interferometric technique is not suitable for this measurement, because the interference contrast decreases too quickly as the THz wavelength approaches that of the generation pulse [11]. A model calculation is shown for θ = 21.5° for an unchirped pump pulse (dashed line) and for 6 fs2 positive quadratic chirp (thick solid line). The latter ensures optimal THz generation around 90 THz and mimics the experiment, where optimization occured by varying the insertion of thin fused silica wedges. Thus, excellent agreement between experiment and theory is achieved over most of the spectrum. Deviations below 50 THz are explained by long-wavelength limitations of our spectrometer.

A comment is in order on the effect of the positive chirp in the model calculation: THz generation with ∆v ≈ 90 THz involves mixing the blue part of the eo-polarized with the red part of the o-polarized visible pulse. Due to GVM, the eo-polarized pulse is faster than the o-polarized. A positive chirp (red components arriving before the blue ones for each polarization) partially compensates this GVM effect and, hence, increases the interaction length and thus the conversion efficiency around 90 THz.

In Fig. 3(d), the coherence length area for θ = 21.5° is well adapted to the visible HFC spectrum. This clearly leads to a broadening and shift to higher frequencies. The calculated time-domain field in Fig. 3(e) predicts even shorter THz pulses with τP ≈ 16 fs. We measure a THz pulse energy of ≈ 8 nJ, corresponding to a quantum efficiency of 2 × 10-4. This entails MV/cm field strengths when focused to a 100-μm spot size, with interesting perspectives for heterodyne mixing in high-harmonic generation or as streak fields in attosecond spectroscopy [24].

5. Conclusion

In conclusion, we report the generation of ultrabroadband 50-130 THz pulses via phase-matched difference frequency mixing in LiIO3. The broad applicability of this compact scheme is demonstrated using different sub-10 fs pump sources. Model calculations give insight into the phasematching conditions, provide octave-spanning spectra that agree with experiment, and predict underlying few-cycle pulses with sub-20 fs duration. We envision that these intrinsically phase-stable THz pulses will open new possibilities for ultrafast photonics, coherent time-domain spectroscopy, and optical parametric processes in the important 3–7 μm wavelength range.

Acknowledgments

We thank A. Cavalleri and R. W. Schoenlein for stimulating discussions, and Z. Hao and M.C. Martin for IR materials characterization. This study was sponsored by a MURI program of the Air Force Office of Scientific Research, grant FA9550-04-1-0242. Part of the work was supported by the U.S. Department of Energy, contract DE-AC02-05CH11231. R. H. and T.Z. acknowledge fellowships from the Alexander von Humboldt Foundation and German Academic Exchange Service, respectively.

Footnotes

*Present address, Department of Physics, University of Konstanz, 78464 Konstanz, Germany.

References and links

1. S. Woutersen, U. Emmerichs, and H. J. Bakker, “Femtosecond mid-IR pump-probe spectroscopy of liquid water: Evidence for a two-component structure,” Science 278, 658–660 (1997). [CrossRef]  

2. R. A. Kaindl, M. Woerner, T. Elsaesser, D. C. Smith, J. F. Ryan, G. A. Farnan, M. P. McCurry, and D. G. Walmsley, “Ultrafast mid-infrared response of YBa2Cu3O7-δ ,” Science 287, 470–473 (2000). [CrossRef]   [PubMed]  

3. R. Huber, F. Tauser, A. Brodschelm, M. Bichler, G. Abstreiter, and A. Leitenstorfer, “How many-particle interactions develop after ultrafast excitation of an electron-hole plasma,” Nature 414, 286–289 (2001). [CrossRef]   [PubMed]  

4. R. Huber, C. Kübler, S. Tübel, A. Leitenstorfer, Q. T. Vu, H. Haug, F. Köhler,, and M.-C. Amann, “Femtosecond formation of phonon-plasmon coupled modes in InP: ultrabroadband THz experiment and quantum kinetic theory,” Phys. Rev. Lett. 94, 027401 (2005). [CrossRef]   [PubMed]  

5. C. W. Luo, K. Reimann, M. Woerner, T. Elsaesser, R. Hey, and K. H. Ploog, “Phase-Resolved Nonlinear Response of a Two-Dimensional Electron Gas under Femtosecond Intersubband Excitation,” Phys. Rev. Lett. 92, 047402 (2004). [CrossRef]   [PubMed]  

6. T. Kampfrath, L. Perfetti, F. Schapper, Ch. Frischkorn, and M. Wolf, “Strongly Coupled Optical Phonons in the Ultrafast Dynamics of the Electronic Energy and Current Relaxation in Graphite,” Phys. Rev. Lett. 95, 187403 (2005). [CrossRef]   [PubMed]  

7. G. Cerullo and S. De Silvestri, “Ultrafast optical parametric amplifiers,” Rev. Sci. Instrum. 74, 1–18 (2003). [CrossRef]  

8. A. Sugita, K. Yokoyama, H. Yamada, N. Inoue, M. Aoyama, and K. Yamakawa, “Generation of Broadband Mid-Infrared Pulses by Noncollinear Difference Frequency Mixing,” Jpn. J. Appl. Phys. 46, 226–228 (2007). [CrossRef]  

9. R. A. Kaindl, M. Wurm, K. Reimann, P. Hamm, A. M. Weiner, and M. Woerner, “Generation, shaping, and characterization of intense femtosecond pulses tunable from 3 to 20μm,” J. Opt. Soc. Am. B 17, 2086–2094 (2000). [CrossRef]  

10. A. Bonvalet, M. Joffre, J.-L. Martin, and A. Migus, “Generation of ultrabroadband femtosecond pulses in the mid-infrared by optical rectification of 15 fs pulses at 100 MHz repetition rate,” Appl. Phys. Lett. 67, 2907–2909 (1995). [CrossRef]  

11. M. Joffre, A. Bonvalet, A. Migus, and J.-L. Martin, “Femtosecond diffracting Fourier-transform infrared interferometer,” Opt. Lett. 21, 964–966 (1996). [CrossRef]   [PubMed]  

12. R. A. Kaindl, D. C. Smith, M. Joschko, M. P. Hasselbeck, M. Woerner, and T. Elsaesser, “Femtosecond infrared pulses tunable from 9 to 18 μm at an 88-MHz repetition rate,” Opt. Lett. 23, 861–863 (1998). [CrossRef]  

13. R. A. Kaindl, F. Eickemeyer, M. Woerner, and T. Elsaesser, “Broadband phase-matched difference frequency mixing of femtosecond pulses in GaSe: Experiment and theory,” Appl. Phys. Lett. 75, 1060–1062 (1999). [CrossRef]  

14. R. Huber, A. Brodschelm, F. Tauser, and A. Leitenstorfer, “Generation and field-resolved detection of femtosecond electromagnetic pulses tunable up to 41 THz,” Appl. Phys. Lett. 76, 3191–3193 (2000). [CrossRef]  

15. T. Fuji, A. Apolonski, and F. Krausz, “Self-stabilization of carrier-envelope offset phase by use of difference-frequency generation,” Opt. Lett. 29, 632–634 (2004). [CrossRef]   [PubMed]  

16. M. Zimmermann, C. Gohle, R. Holzwarth, T. Udem, and T. W. Hänsch, “Optical clockwork with an offset-free difference frequency comb: accuracy of sum- and difference frequency generation,” Opt. Lett. 29, 310–312 (2004). [CrossRef]   [PubMed]  

17. K. Liu, J. Xu, and X.-C. Zhang, “GaSe crystals for broadband terahertz wave detection,” Appl. Phys. Lett. 85, 863–865 (2004). [CrossRef]  

18. C. Kübler, R. Huber, S. Tübel, and A. Leitenstorfer, “Ultrabroadband detection of multi-terahertz field transients with GaSe electro-optic sensors: Approaching the near infrared,” Appl. Phys. Lett. 85, 3360–3362 (2004). [CrossRef]  

19. M. M. Choy and R. L. Byer, “Second-order susceptibility measurements of visible and infrared nonlinear crystals,” Phys. Rev. B 14, 1693–1706 (1976). [CrossRef]  

20. C. P. Hauri, P. Schlup, G. Arisholm, J. Biegert, and U. Keller, “Phase-preserving chirped-pulse optical parametric amplification to 17.3 fs directly from a Ti:sapphire oscillator,” Opt. Lett. 29, 1369–1371 (2004). [CrossRef]   [PubMed]  

21. T. Fuji, N. Ishii, C. Y. Teisset, X. Gu, Th. Metzger, A. Baltuska, N. Forget, D. Kaplan, A. Galvanauskas, and F. Krausz, “Parametric amplification of few-cycle carrier-envelope phase-stable pulses at 2.1 μm,” Opt. Lett. 31, 1103–1105 (2006). [CrossRef]   [PubMed]  

22. C. Manzoni, C. Vozzi, E. Benedetti, G. Sansone, S. Stagira, O. Svelto, S. De Silvestri, M. Nisoli, and G. Cerullo, “Generation of high-energy self-phase stabilized pulses by difference frequency generation followed by optical parametric amplification,” Opt. Lett. 31, 963–965 (2006). [CrossRef]   [PubMed]  

23. S. Sartania, Z. Cheng, M. Lenzner, G. Tempea, Ch. Spielmann, F. Krausz, and K. Ferencz, “Generation of 0.1-TW 5-fs optical pulses at a 1-kHz repetition rate,” Opt. Lett. 22, 1562–1564 (1997). [CrossRef]  

24. T. Pfeifer, L. Gallman, M. Abel, P. Nagel, D. Neumark, and S. R. Leone, “Heterodyne Mixing of Laser Fields for Temporal Gating of High-Harmonic Generation,” Phys. Rev. Lett. 97, 163901 (2006). [CrossRef]   [PubMed]  

References

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  1. S. Woutersen, U. Emmerichs, and H. J. Bakker, "Femtosecond mid-IR pump-probe spectroscopy of liquid water: Evidence for a two-component structure," Science 278, 658-660 (1997).
    [CrossRef]
  2. R. A. Kaindl, M. Woerner, T. Elsaesser, D. C. Smith, J. F. Ryan, G. A. Farnan, M. P. McCurry, and D. G. Walmsley, "Ultrafast mid-infrared response of YBa2Cu3O7−δ," Science 287, 470-473 (2000).
    [CrossRef] [PubMed]
  3. R. Huber, F. Tauser, A. Brodschelm, M. Bichler, G. Abstreiter, and A. Leitenstorfer, "How many-particle interactions develop after ultrafast excitation of an electron-hole plasma," Nature 414, 286-289 (2001).
    [CrossRef] [PubMed]
  4. R. Huber, C. Kübler, S. Tübel, A. Leitenstorfer, Q. T. Vu, H. Haug, F. Köhler, and M.-C. Amann, "Femtosecond formation of phonon-plasmon coupled modes in InP: ultrabroadband THz experiment and quantum kinetic theory," Phys. Rev. Lett. 94, 027401 (2005).
    [CrossRef] [PubMed]
  5. C. W. Luo, K. Reimann, M. Woerner, T. Elsaesser, R. Hey, and K. H. Ploog, "Phase-resolved nonlinear response of a two-dimensional electron gas under Femtosecond intersubband excitation," Phys. Rev. Lett. 92, 047402 (2004).
    [CrossRef] [PubMed]
  6. T. Kampfrath, L. Perfetti, F. Schapper, Ch. Frischkorn, and M. Wolf, "Strongly coupled optical phonons in the ultrafast dynamics of the electronic energy and current relaxation in graphite," Phys. Rev. Lett. 95, 187403 (2005).
    [CrossRef] [PubMed]
  7. G. Cerullo and S. De Silvestri, "Ultrafast optical parametric amplifiers," Rev. Sci. Instrum. 74, 1-18 (2003).
    [CrossRef]
  8. A. Sugita, K. Yokoyama, H. Yamada, N. Inoue, M. Aoyama, and K. Yamakawa, "Generation of broadband mid-infrared pulses by noncollinear difference frequency mixing," Jpn. J. Appl. Phys. 46, 226-228 (2007).
    [CrossRef]
  9. R. A. Kaindl, M. Wurm, K. Reimann, P. Hamm, A. M. Weiner, M. Woerner, "Generation, shaping, and characterization of intense femtosecond pulses tunable from 3 to 20μm," J. Opt. Soc. Am. B 17, 2086-2094 (2000).
    [CrossRef]
  10. A. Bonvalet, M. Joffre, J.-L. Martin, and A. Migus, "Generation of ultrabroadband femtosecond pulses in the mid-infrared by optical rectification of 15 fs pulses at 100 MHz repetition rate," Appl. Phys. Lett. 67, 2907-2909 (1995).
    [CrossRef]
  11. M. Joffre, A. Bonvalet, A. Migus, and J.-L. Martin, "Femtosecond diffracting Fourier-transform infrared interferometer," Opt. Lett. 21, 964-966 (1996).
    [CrossRef] [PubMed]
  12. R. A. Kaindl, D. C. Smith, M. Joschko, M. P. Hasselbeck, M. Woerner, and T. Elsaesser, "Femtosecond infrared pulses tunable from 9 to 18 μm at an 88-MHz repetition rate," Opt. Lett. 23, 861-863 (1998).
    [CrossRef]
  13. R. A. Kaindl, F. Eickemeyer, M. Woerner, and T. Elsaesser, "Broadband phase-matched difference frequency mixing of femtosecond pulses in GaSe: experiment and theory," Appl. Phys. Lett. 75, 1060-1062 (1999).
    [CrossRef]
  14. R. Huber, A. Brodschelm, F. Tauser, and A. Leitenstorfer, "Generation and field-resolved detection of femtosecond electromagnetic pulses tunable up to 41 THz," Appl. Phys. Lett. 76, 3191-3193 (2000).
    [CrossRef]
  15. T. Fuji, A. Apolonski, and F. Krausz, "Self-stabilization of carrier-envelope offset phase by use of differencefrequency generation," Opt. Lett. 29, 632-634 (2004).
    [CrossRef] [PubMed]
  16. M. Zimmermann, C. Gohle, R. Holzwarth, T. Udem, and T. W. Hänsch, "Optical clockwork with an offset free difference frequency comb: accuracy of sum- and difference frequency generation," Opt. Lett. 29, 310-312 (2004).
    [CrossRef] [PubMed]
  17. K. Liu, J. Xu, and X.-C. Zhang, "GaSe crystals for broadband terahertz wave detection," Appl. Phys. Lett. 85, 863-865 (2004).
    [CrossRef]
  18. C. Kübler, R. Huber, S. Tübel, and A. Leitenstorfer, "Ultrabroadband detection of multi-terahertz field transients with GaSe electro-optic sensors: approaching the near infrared," Appl. Phys. Lett. 85, 3360-3362 (2004).
    [CrossRef]
  19. M. M. Choy and R. L. Byer, "Second-order susceptibility measurements of visible and infrared nonlinear crystals," Phys. Rev. B 14, 1693-1706 (1976).
    [CrossRef]
  20. C. P. Hauri, P. Schlup, G. Arisholm, J. Biegert, and U. Keller, "Phase-preserving chirped-pulse optical parametric amplification to 17.3 fs directly from a Ti:sapphire oscillator," Opt. Lett. 29, 1369-1371 (2004).
    [CrossRef] [PubMed]
  21. T. Fuji, N. Ishii, C. Y. Teisset, X. Gu, Th. Metzger, A. Baltuska, N. Forget, D. Kaplan, A. Galvanauskas, and F. Krausz, "Parametric amplification of few-cycle carrier-envelope phase-stable pulses at 2.1 μm," Opt. Lett. 31, 1103-1105 (2006).
    [CrossRef] [PubMed]
  22. C. Manzoni, C. Vozzi, E. Benedetti, G. Sansone, S. Stagira, O. Svelto, S. De Silvestri, M. Nisoli, and G. Cerullo, "Generation of high-energy self-phase stabilized pulses by difference frequency generation followed by optical parametric amplification," Opt. Lett. 31, 963-965 (2006).
    [CrossRef] [PubMed]
  23. S. Sartania, Z. Cheng, M. Lenzner, G. Tempea, Ch. Spielmann, F. Krausz, and K. Ferencz, "Generation of 0.1-TW 5-fs optical pulses at a 1-kHz repetition rate," Opt. Lett. 22, 1562-1564 (1997).
    [CrossRef]
  24. T. Pfeifer, L. Gallman, M. Abel, P. Nagel, D. Neumark, and S. R. Leone, "Heterodyne mixing of laser fields for temporal gating of High-Harmonic Generation," Phys. Rev. Lett. 97, 163901 (2006).
    [CrossRef] [PubMed]

2007 (1)

A. Sugita, K. Yokoyama, H. Yamada, N. Inoue, M. Aoyama, and K. Yamakawa, "Generation of broadband mid-infrared pulses by noncollinear difference frequency mixing," Jpn. J. Appl. Phys. 46, 226-228 (2007).
[CrossRef]

2006 (3)

2005 (2)

T. Kampfrath, L. Perfetti, F. Schapper, Ch. Frischkorn, and M. Wolf, "Strongly coupled optical phonons in the ultrafast dynamics of the electronic energy and current relaxation in graphite," Phys. Rev. Lett. 95, 187403 (2005).
[CrossRef] [PubMed]

R. Huber, C. Kübler, S. Tübel, A. Leitenstorfer, Q. T. Vu, H. Haug, F. Köhler, and M.-C. Amann, "Femtosecond formation of phonon-plasmon coupled modes in InP: ultrabroadband THz experiment and quantum kinetic theory," Phys. Rev. Lett. 94, 027401 (2005).
[CrossRef] [PubMed]

2004 (6)

C. W. Luo, K. Reimann, M. Woerner, T. Elsaesser, R. Hey, and K. H. Ploog, "Phase-resolved nonlinear response of a two-dimensional electron gas under Femtosecond intersubband excitation," Phys. Rev. Lett. 92, 047402 (2004).
[CrossRef] [PubMed]

K. Liu, J. Xu, and X.-C. Zhang, "GaSe crystals for broadband terahertz wave detection," Appl. Phys. Lett. 85, 863-865 (2004).
[CrossRef]

C. Kübler, R. Huber, S. Tübel, and A. Leitenstorfer, "Ultrabroadband detection of multi-terahertz field transients with GaSe electro-optic sensors: approaching the near infrared," Appl. Phys. Lett. 85, 3360-3362 (2004).
[CrossRef]

M. Zimmermann, C. Gohle, R. Holzwarth, T. Udem, and T. W. Hänsch, "Optical clockwork with an offset free difference frequency comb: accuracy of sum- and difference frequency generation," Opt. Lett. 29, 310-312 (2004).
[CrossRef] [PubMed]

T. Fuji, A. Apolonski, and F. Krausz, "Self-stabilization of carrier-envelope offset phase by use of differencefrequency generation," Opt. Lett. 29, 632-634 (2004).
[CrossRef] [PubMed]

C. P. Hauri, P. Schlup, G. Arisholm, J. Biegert, and U. Keller, "Phase-preserving chirped-pulse optical parametric amplification to 17.3 fs directly from a Ti:sapphire oscillator," Opt. Lett. 29, 1369-1371 (2004).
[CrossRef] [PubMed]

2003 (1)

G. Cerullo and S. De Silvestri, "Ultrafast optical parametric amplifiers," Rev. Sci. Instrum. 74, 1-18 (2003).
[CrossRef]

2001 (1)

R. Huber, F. Tauser, A. Brodschelm, M. Bichler, G. Abstreiter, and A. Leitenstorfer, "How many-particle interactions develop after ultrafast excitation of an electron-hole plasma," Nature 414, 286-289 (2001).
[CrossRef] [PubMed]

2000 (3)

R. A. Kaindl, M. Woerner, T. Elsaesser, D. C. Smith, J. F. Ryan, G. A. Farnan, M. P. McCurry, and D. G. Walmsley, "Ultrafast mid-infrared response of YBa2Cu3O7−δ," Science 287, 470-473 (2000).
[CrossRef] [PubMed]

R. Huber, A. Brodschelm, F. Tauser, and A. Leitenstorfer, "Generation and field-resolved detection of femtosecond electromagnetic pulses tunable up to 41 THz," Appl. Phys. Lett. 76, 3191-3193 (2000).
[CrossRef]

R. A. Kaindl, M. Wurm, K. Reimann, P. Hamm, A. M. Weiner, M. Woerner, "Generation, shaping, and characterization of intense femtosecond pulses tunable from 3 to 20μm," J. Opt. Soc. Am. B 17, 2086-2094 (2000).
[CrossRef]

1999 (1)

R. A. Kaindl, F. Eickemeyer, M. Woerner, and T. Elsaesser, "Broadband phase-matched difference frequency mixing of femtosecond pulses in GaSe: experiment and theory," Appl. Phys. Lett. 75, 1060-1062 (1999).
[CrossRef]

1998 (1)

1997 (2)

S. Sartania, Z. Cheng, M. Lenzner, G. Tempea, Ch. Spielmann, F. Krausz, and K. Ferencz, "Generation of 0.1-TW 5-fs optical pulses at a 1-kHz repetition rate," Opt. Lett. 22, 1562-1564 (1997).
[CrossRef]

S. Woutersen, U. Emmerichs, and H. J. Bakker, "Femtosecond mid-IR pump-probe spectroscopy of liquid water: Evidence for a two-component structure," Science 278, 658-660 (1997).
[CrossRef]

1996 (1)

1995 (1)

A. Bonvalet, M. Joffre, J.-L. Martin, and A. Migus, "Generation of ultrabroadband femtosecond pulses in the mid-infrared by optical rectification of 15 fs pulses at 100 MHz repetition rate," Appl. Phys. Lett. 67, 2907-2909 (1995).
[CrossRef]

1976 (1)

M. M. Choy and R. L. Byer, "Second-order susceptibility measurements of visible and infrared nonlinear crystals," Phys. Rev. B 14, 1693-1706 (1976).
[CrossRef]

Abel, M.

T. Pfeifer, L. Gallman, M. Abel, P. Nagel, D. Neumark, and S. R. Leone, "Heterodyne mixing of laser fields for temporal gating of High-Harmonic Generation," Phys. Rev. Lett. 97, 163901 (2006).
[CrossRef] [PubMed]

Abstreiter, G.

R. Huber, F. Tauser, A. Brodschelm, M. Bichler, G. Abstreiter, and A. Leitenstorfer, "How many-particle interactions develop after ultrafast excitation of an electron-hole plasma," Nature 414, 286-289 (2001).
[CrossRef] [PubMed]

Amann, M.-C.

R. Huber, C. Kübler, S. Tübel, A. Leitenstorfer, Q. T. Vu, H. Haug, F. Köhler, and M.-C. Amann, "Femtosecond formation of phonon-plasmon coupled modes in InP: ultrabroadband THz experiment and quantum kinetic theory," Phys. Rev. Lett. 94, 027401 (2005).
[CrossRef] [PubMed]

Aoyama, M.

A. Sugita, K. Yokoyama, H. Yamada, N. Inoue, M. Aoyama, and K. Yamakawa, "Generation of broadband mid-infrared pulses by noncollinear difference frequency mixing," Jpn. J. Appl. Phys. 46, 226-228 (2007).
[CrossRef]

Apolonski, A.

Arisholm, G.

Bakker, H. J.

S. Woutersen, U. Emmerichs, and H. J. Bakker, "Femtosecond mid-IR pump-probe spectroscopy of liquid water: Evidence for a two-component structure," Science 278, 658-660 (1997).
[CrossRef]

Baltuska, A.

Benedetti, E.

Bichler, M.

R. Huber, F. Tauser, A. Brodschelm, M. Bichler, G. Abstreiter, and A. Leitenstorfer, "How many-particle interactions develop after ultrafast excitation of an electron-hole plasma," Nature 414, 286-289 (2001).
[CrossRef] [PubMed]

Biegert, J.

Bonvalet, A.

M. Joffre, A. Bonvalet, A. Migus, and J.-L. Martin, "Femtosecond diffracting Fourier-transform infrared interferometer," Opt. Lett. 21, 964-966 (1996).
[CrossRef] [PubMed]

A. Bonvalet, M. Joffre, J.-L. Martin, and A. Migus, "Generation of ultrabroadband femtosecond pulses in the mid-infrared by optical rectification of 15 fs pulses at 100 MHz repetition rate," Appl. Phys. Lett. 67, 2907-2909 (1995).
[CrossRef]

Brodschelm, A.

R. Huber, F. Tauser, A. Brodschelm, M. Bichler, G. Abstreiter, and A. Leitenstorfer, "How many-particle interactions develop after ultrafast excitation of an electron-hole plasma," Nature 414, 286-289 (2001).
[CrossRef] [PubMed]

R. Huber, A. Brodschelm, F. Tauser, and A. Leitenstorfer, "Generation and field-resolved detection of femtosecond electromagnetic pulses tunable up to 41 THz," Appl. Phys. Lett. 76, 3191-3193 (2000).
[CrossRef]

Byer, R. L.

M. M. Choy and R. L. Byer, "Second-order susceptibility measurements of visible and infrared nonlinear crystals," Phys. Rev. B 14, 1693-1706 (1976).
[CrossRef]

Cerullo, G.

Cheng, Z.

Choy, M. M.

M. M. Choy and R. L. Byer, "Second-order susceptibility measurements of visible and infrared nonlinear crystals," Phys. Rev. B 14, 1693-1706 (1976).
[CrossRef]

De Silvestri, S.

Eickemeyer, F.

R. A. Kaindl, F. Eickemeyer, M. Woerner, and T. Elsaesser, "Broadband phase-matched difference frequency mixing of femtosecond pulses in GaSe: experiment and theory," Appl. Phys. Lett. 75, 1060-1062 (1999).
[CrossRef]

Elsaesser, T.

C. W. Luo, K. Reimann, M. Woerner, T. Elsaesser, R. Hey, and K. H. Ploog, "Phase-resolved nonlinear response of a two-dimensional electron gas under Femtosecond intersubband excitation," Phys. Rev. Lett. 92, 047402 (2004).
[CrossRef] [PubMed]

R. A. Kaindl, M. Woerner, T. Elsaesser, D. C. Smith, J. F. Ryan, G. A. Farnan, M. P. McCurry, and D. G. Walmsley, "Ultrafast mid-infrared response of YBa2Cu3O7−δ," Science 287, 470-473 (2000).
[CrossRef] [PubMed]

R. A. Kaindl, F. Eickemeyer, M. Woerner, and T. Elsaesser, "Broadband phase-matched difference frequency mixing of femtosecond pulses in GaSe: experiment and theory," Appl. Phys. Lett. 75, 1060-1062 (1999).
[CrossRef]

R. A. Kaindl, D. C. Smith, M. Joschko, M. P. Hasselbeck, M. Woerner, and T. Elsaesser, "Femtosecond infrared pulses tunable from 9 to 18 μm at an 88-MHz repetition rate," Opt. Lett. 23, 861-863 (1998).
[CrossRef]

Emmerichs, U.

S. Woutersen, U. Emmerichs, and H. J. Bakker, "Femtosecond mid-IR pump-probe spectroscopy of liquid water: Evidence for a two-component structure," Science 278, 658-660 (1997).
[CrossRef]

Farnan, G. A.

R. A. Kaindl, M. Woerner, T. Elsaesser, D. C. Smith, J. F. Ryan, G. A. Farnan, M. P. McCurry, and D. G. Walmsley, "Ultrafast mid-infrared response of YBa2Cu3O7−δ," Science 287, 470-473 (2000).
[CrossRef] [PubMed]

Ferencz, K.

Forget, N.

Frischkorn, Ch.

T. Kampfrath, L. Perfetti, F. Schapper, Ch. Frischkorn, and M. Wolf, "Strongly coupled optical phonons in the ultrafast dynamics of the electronic energy and current relaxation in graphite," Phys. Rev. Lett. 95, 187403 (2005).
[CrossRef] [PubMed]

Fuji, T.

Gallman, L.

T. Pfeifer, L. Gallman, M. Abel, P. Nagel, D. Neumark, and S. R. Leone, "Heterodyne mixing of laser fields for temporal gating of High-Harmonic Generation," Phys. Rev. Lett. 97, 163901 (2006).
[CrossRef] [PubMed]

Galvanauskas, A.

Gohle, C.

Gu, X.

Hamm, P.

Hänsch, T. W.

Hasselbeck, M. P.

Haug, H.

R. Huber, C. Kübler, S. Tübel, A. Leitenstorfer, Q. T. Vu, H. Haug, F. Köhler, and M.-C. Amann, "Femtosecond formation of phonon-plasmon coupled modes in InP: ultrabroadband THz experiment and quantum kinetic theory," Phys. Rev. Lett. 94, 027401 (2005).
[CrossRef] [PubMed]

Hauri, C. P.

Hey, R.

C. W. Luo, K. Reimann, M. Woerner, T. Elsaesser, R. Hey, and K. H. Ploog, "Phase-resolved nonlinear response of a two-dimensional electron gas under Femtosecond intersubband excitation," Phys. Rev. Lett. 92, 047402 (2004).
[CrossRef] [PubMed]

Holzwarth, R.

Huber, R.

R. Huber, C. Kübler, S. Tübel, A. Leitenstorfer, Q. T. Vu, H. Haug, F. Köhler, and M.-C. Amann, "Femtosecond formation of phonon-plasmon coupled modes in InP: ultrabroadband THz experiment and quantum kinetic theory," Phys. Rev. Lett. 94, 027401 (2005).
[CrossRef] [PubMed]

C. Kübler, R. Huber, S. Tübel, and A. Leitenstorfer, "Ultrabroadband detection of multi-terahertz field transients with GaSe electro-optic sensors: approaching the near infrared," Appl. Phys. Lett. 85, 3360-3362 (2004).
[CrossRef]

R. Huber, F. Tauser, A. Brodschelm, M. Bichler, G. Abstreiter, and A. Leitenstorfer, "How many-particle interactions develop after ultrafast excitation of an electron-hole plasma," Nature 414, 286-289 (2001).
[CrossRef] [PubMed]

R. Huber, A. Brodschelm, F. Tauser, and A. Leitenstorfer, "Generation and field-resolved detection of femtosecond electromagnetic pulses tunable up to 41 THz," Appl. Phys. Lett. 76, 3191-3193 (2000).
[CrossRef]

Inoue, N.

A. Sugita, K. Yokoyama, H. Yamada, N. Inoue, M. Aoyama, and K. Yamakawa, "Generation of broadband mid-infrared pulses by noncollinear difference frequency mixing," Jpn. J. Appl. Phys. 46, 226-228 (2007).
[CrossRef]

Ishii, N.

Joffre, M.

M. Joffre, A. Bonvalet, A. Migus, and J.-L. Martin, "Femtosecond diffracting Fourier-transform infrared interferometer," Opt. Lett. 21, 964-966 (1996).
[CrossRef] [PubMed]

A. Bonvalet, M. Joffre, J.-L. Martin, and A. Migus, "Generation of ultrabroadband femtosecond pulses in the mid-infrared by optical rectification of 15 fs pulses at 100 MHz repetition rate," Appl. Phys. Lett. 67, 2907-2909 (1995).
[CrossRef]

Joschko, M.

Kaindl, R. A.

R. A. Kaindl, M. Woerner, T. Elsaesser, D. C. Smith, J. F. Ryan, G. A. Farnan, M. P. McCurry, and D. G. Walmsley, "Ultrafast mid-infrared response of YBa2Cu3O7−δ," Science 287, 470-473 (2000).
[CrossRef] [PubMed]

R. A. Kaindl, M. Wurm, K. Reimann, P. Hamm, A. M. Weiner, M. Woerner, "Generation, shaping, and characterization of intense femtosecond pulses tunable from 3 to 20μm," J. Opt. Soc. Am. B 17, 2086-2094 (2000).
[CrossRef]

R. A. Kaindl, F. Eickemeyer, M. Woerner, and T. Elsaesser, "Broadband phase-matched difference frequency mixing of femtosecond pulses in GaSe: experiment and theory," Appl. Phys. Lett. 75, 1060-1062 (1999).
[CrossRef]

R. A. Kaindl, D. C. Smith, M. Joschko, M. P. Hasselbeck, M. Woerner, and T. Elsaesser, "Femtosecond infrared pulses tunable from 9 to 18 μm at an 88-MHz repetition rate," Opt. Lett. 23, 861-863 (1998).
[CrossRef]

Kampfrath, T.

T. Kampfrath, L. Perfetti, F. Schapper, Ch. Frischkorn, and M. Wolf, "Strongly coupled optical phonons in the ultrafast dynamics of the electronic energy and current relaxation in graphite," Phys. Rev. Lett. 95, 187403 (2005).
[CrossRef] [PubMed]

Kaplan, D.

Keller, U.

Köhler, F.

R. Huber, C. Kübler, S. Tübel, A. Leitenstorfer, Q. T. Vu, H. Haug, F. Köhler, and M.-C. Amann, "Femtosecond formation of phonon-plasmon coupled modes in InP: ultrabroadband THz experiment and quantum kinetic theory," Phys. Rev. Lett. 94, 027401 (2005).
[CrossRef] [PubMed]

Krausz, F.

Kübler, C.

R. Huber, C. Kübler, S. Tübel, A. Leitenstorfer, Q. T. Vu, H. Haug, F. Köhler, and M.-C. Amann, "Femtosecond formation of phonon-plasmon coupled modes in InP: ultrabroadband THz experiment and quantum kinetic theory," Phys. Rev. Lett. 94, 027401 (2005).
[CrossRef] [PubMed]

C. Kübler, R. Huber, S. Tübel, and A. Leitenstorfer, "Ultrabroadband detection of multi-terahertz field transients with GaSe electro-optic sensors: approaching the near infrared," Appl. Phys. Lett. 85, 3360-3362 (2004).
[CrossRef]

Leitenstorfer, A.

R. Huber, C. Kübler, S. Tübel, A. Leitenstorfer, Q. T. Vu, H. Haug, F. Köhler, and M.-C. Amann, "Femtosecond formation of phonon-plasmon coupled modes in InP: ultrabroadband THz experiment and quantum kinetic theory," Phys. Rev. Lett. 94, 027401 (2005).
[CrossRef] [PubMed]

C. Kübler, R. Huber, S. Tübel, and A. Leitenstorfer, "Ultrabroadband detection of multi-terahertz field transients with GaSe electro-optic sensors: approaching the near infrared," Appl. Phys. Lett. 85, 3360-3362 (2004).
[CrossRef]

R. Huber, F. Tauser, A. Brodschelm, M. Bichler, G. Abstreiter, and A. Leitenstorfer, "How many-particle interactions develop after ultrafast excitation of an electron-hole plasma," Nature 414, 286-289 (2001).
[CrossRef] [PubMed]

R. Huber, A. Brodschelm, F. Tauser, and A. Leitenstorfer, "Generation and field-resolved detection of femtosecond electromagnetic pulses tunable up to 41 THz," Appl. Phys. Lett. 76, 3191-3193 (2000).
[CrossRef]

Lenzner, M.

Leone, S. R.

T. Pfeifer, L. Gallman, M. Abel, P. Nagel, D. Neumark, and S. R. Leone, "Heterodyne mixing of laser fields for temporal gating of High-Harmonic Generation," Phys. Rev. Lett. 97, 163901 (2006).
[CrossRef] [PubMed]

Liu, K.

K. Liu, J. Xu, and X.-C. Zhang, "GaSe crystals for broadband terahertz wave detection," Appl. Phys. Lett. 85, 863-865 (2004).
[CrossRef]

Luo, C. W.

C. W. Luo, K. Reimann, M. Woerner, T. Elsaesser, R. Hey, and K. H. Ploog, "Phase-resolved nonlinear response of a two-dimensional electron gas under Femtosecond intersubband excitation," Phys. Rev. Lett. 92, 047402 (2004).
[CrossRef] [PubMed]

Manzoni, C.

Martin, J.-L.

M. Joffre, A. Bonvalet, A. Migus, and J.-L. Martin, "Femtosecond diffracting Fourier-transform infrared interferometer," Opt. Lett. 21, 964-966 (1996).
[CrossRef] [PubMed]

A. Bonvalet, M. Joffre, J.-L. Martin, and A. Migus, "Generation of ultrabroadband femtosecond pulses in the mid-infrared by optical rectification of 15 fs pulses at 100 MHz repetition rate," Appl. Phys. Lett. 67, 2907-2909 (1995).
[CrossRef]

McCurry, M. P.

R. A. Kaindl, M. Woerner, T. Elsaesser, D. C. Smith, J. F. Ryan, G. A. Farnan, M. P. McCurry, and D. G. Walmsley, "Ultrafast mid-infrared response of YBa2Cu3O7−δ," Science 287, 470-473 (2000).
[CrossRef] [PubMed]

Metzger, Th.

Migus, A.

M. Joffre, A. Bonvalet, A. Migus, and J.-L. Martin, "Femtosecond diffracting Fourier-transform infrared interferometer," Opt. Lett. 21, 964-966 (1996).
[CrossRef] [PubMed]

A. Bonvalet, M. Joffre, J.-L. Martin, and A. Migus, "Generation of ultrabroadband femtosecond pulses in the mid-infrared by optical rectification of 15 fs pulses at 100 MHz repetition rate," Appl. Phys. Lett. 67, 2907-2909 (1995).
[CrossRef]

Nagel, P.

T. Pfeifer, L. Gallman, M. Abel, P. Nagel, D. Neumark, and S. R. Leone, "Heterodyne mixing of laser fields for temporal gating of High-Harmonic Generation," Phys. Rev. Lett. 97, 163901 (2006).
[CrossRef] [PubMed]

Neumark, D.

T. Pfeifer, L. Gallman, M. Abel, P. Nagel, D. Neumark, and S. R. Leone, "Heterodyne mixing of laser fields for temporal gating of High-Harmonic Generation," Phys. Rev. Lett. 97, 163901 (2006).
[CrossRef] [PubMed]

Nisoli, M.

Perfetti, L.

T. Kampfrath, L. Perfetti, F. Schapper, Ch. Frischkorn, and M. Wolf, "Strongly coupled optical phonons in the ultrafast dynamics of the electronic energy and current relaxation in graphite," Phys. Rev. Lett. 95, 187403 (2005).
[CrossRef] [PubMed]

Pfeifer, T.

T. Pfeifer, L. Gallman, M. Abel, P. Nagel, D. Neumark, and S. R. Leone, "Heterodyne mixing of laser fields for temporal gating of High-Harmonic Generation," Phys. Rev. Lett. 97, 163901 (2006).
[CrossRef] [PubMed]

Ploog, K. H.

C. W. Luo, K. Reimann, M. Woerner, T. Elsaesser, R. Hey, and K. H. Ploog, "Phase-resolved nonlinear response of a two-dimensional electron gas under Femtosecond intersubband excitation," Phys. Rev. Lett. 92, 047402 (2004).
[CrossRef] [PubMed]

Reimann, K.

C. W. Luo, K. Reimann, M. Woerner, T. Elsaesser, R. Hey, and K. H. Ploog, "Phase-resolved nonlinear response of a two-dimensional electron gas under Femtosecond intersubband excitation," Phys. Rev. Lett. 92, 047402 (2004).
[CrossRef] [PubMed]

R. A. Kaindl, M. Wurm, K. Reimann, P. Hamm, A. M. Weiner, M. Woerner, "Generation, shaping, and characterization of intense femtosecond pulses tunable from 3 to 20μm," J. Opt. Soc. Am. B 17, 2086-2094 (2000).
[CrossRef]

Ryan, J. F.

R. A. Kaindl, M. Woerner, T. Elsaesser, D. C. Smith, J. F. Ryan, G. A. Farnan, M. P. McCurry, and D. G. Walmsley, "Ultrafast mid-infrared response of YBa2Cu3O7−δ," Science 287, 470-473 (2000).
[CrossRef] [PubMed]

Sansone, G.

Sartania, S.

Schapper, F.

T. Kampfrath, L. Perfetti, F. Schapper, Ch. Frischkorn, and M. Wolf, "Strongly coupled optical phonons in the ultrafast dynamics of the electronic energy and current relaxation in graphite," Phys. Rev. Lett. 95, 187403 (2005).
[CrossRef] [PubMed]

Schlup, P.

Smith, D. C.

R. A. Kaindl, M. Woerner, T. Elsaesser, D. C. Smith, J. F. Ryan, G. A. Farnan, M. P. McCurry, and D. G. Walmsley, "Ultrafast mid-infrared response of YBa2Cu3O7−δ," Science 287, 470-473 (2000).
[CrossRef] [PubMed]

R. A. Kaindl, D. C. Smith, M. Joschko, M. P. Hasselbeck, M. Woerner, and T. Elsaesser, "Femtosecond infrared pulses tunable from 9 to 18 μm at an 88-MHz repetition rate," Opt. Lett. 23, 861-863 (1998).
[CrossRef]

Spielmann, Ch.

Stagira, S.

Sugita, A.

A. Sugita, K. Yokoyama, H. Yamada, N. Inoue, M. Aoyama, and K. Yamakawa, "Generation of broadband mid-infrared pulses by noncollinear difference frequency mixing," Jpn. J. Appl. Phys. 46, 226-228 (2007).
[CrossRef]

Svelto, O.

Tauser, F.

R. Huber, F. Tauser, A. Brodschelm, M. Bichler, G. Abstreiter, and A. Leitenstorfer, "How many-particle interactions develop after ultrafast excitation of an electron-hole plasma," Nature 414, 286-289 (2001).
[CrossRef] [PubMed]

R. Huber, A. Brodschelm, F. Tauser, and A. Leitenstorfer, "Generation and field-resolved detection of femtosecond electromagnetic pulses tunable up to 41 THz," Appl. Phys. Lett. 76, 3191-3193 (2000).
[CrossRef]

Teisset, C. Y.

Tempea, G.

Tübel, S.

R. Huber, C. Kübler, S. Tübel, A. Leitenstorfer, Q. T. Vu, H. Haug, F. Köhler, and M.-C. Amann, "Femtosecond formation of phonon-plasmon coupled modes in InP: ultrabroadband THz experiment and quantum kinetic theory," Phys. Rev. Lett. 94, 027401 (2005).
[CrossRef] [PubMed]

C. Kübler, R. Huber, S. Tübel, and A. Leitenstorfer, "Ultrabroadband detection of multi-terahertz field transients with GaSe electro-optic sensors: approaching the near infrared," Appl. Phys. Lett. 85, 3360-3362 (2004).
[CrossRef]

Udem, T.

Vozzi, C.

Vu, Q. T.

R. Huber, C. Kübler, S. Tübel, A. Leitenstorfer, Q. T. Vu, H. Haug, F. Köhler, and M.-C. Amann, "Femtosecond formation of phonon-plasmon coupled modes in InP: ultrabroadband THz experiment and quantum kinetic theory," Phys. Rev. Lett. 94, 027401 (2005).
[CrossRef] [PubMed]

Walmsley, D. G.

R. A. Kaindl, M. Woerner, T. Elsaesser, D. C. Smith, J. F. Ryan, G. A. Farnan, M. P. McCurry, and D. G. Walmsley, "Ultrafast mid-infrared response of YBa2Cu3O7−δ," Science 287, 470-473 (2000).
[CrossRef] [PubMed]

Weiner, A. M.

Woerner, M.

C. W. Luo, K. Reimann, M. Woerner, T. Elsaesser, R. Hey, and K. H. Ploog, "Phase-resolved nonlinear response of a two-dimensional electron gas under Femtosecond intersubband excitation," Phys. Rev. Lett. 92, 047402 (2004).
[CrossRef] [PubMed]

R. A. Kaindl, M. Wurm, K. Reimann, P. Hamm, A. M. Weiner, M. Woerner, "Generation, shaping, and characterization of intense femtosecond pulses tunable from 3 to 20μm," J. Opt. Soc. Am. B 17, 2086-2094 (2000).
[CrossRef]

R. A. Kaindl, M. Woerner, T. Elsaesser, D. C. Smith, J. F. Ryan, G. A. Farnan, M. P. McCurry, and D. G. Walmsley, "Ultrafast mid-infrared response of YBa2Cu3O7−δ," Science 287, 470-473 (2000).
[CrossRef] [PubMed]

R. A. Kaindl, F. Eickemeyer, M. Woerner, and T. Elsaesser, "Broadband phase-matched difference frequency mixing of femtosecond pulses in GaSe: experiment and theory," Appl. Phys. Lett. 75, 1060-1062 (1999).
[CrossRef]

R. A. Kaindl, D. C. Smith, M. Joschko, M. P. Hasselbeck, M. Woerner, and T. Elsaesser, "Femtosecond infrared pulses tunable from 9 to 18 μm at an 88-MHz repetition rate," Opt. Lett. 23, 861-863 (1998).
[CrossRef]

Wolf, M.

T. Kampfrath, L. Perfetti, F. Schapper, Ch. Frischkorn, and M. Wolf, "Strongly coupled optical phonons in the ultrafast dynamics of the electronic energy and current relaxation in graphite," Phys. Rev. Lett. 95, 187403 (2005).
[CrossRef] [PubMed]

Woutersen, S.

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Figures (4)

Fig. 1.
Fig. 1.

(a) Oscillator-based setup for THz pulse generation in LiIO3 and for interfero-metric field correlations. W: 1-mm thick fused-silica window, CM: chirped mirrors with ≈ -200 fs2 group delay dispersion, Ge: Germanium window. (b) interferogram generated with a 113-μm thick crystal near normal incidence.

Fig. 2.
Fig. 2.

Spectra of THz pulses generated in LiIO3 with a 9-fs Ti:sapphire oscillator: (a) measured spectrum from a 113-μm thick crystal (dots) and model curve (line) at θ = 19°. (b) as above, but for a 1-mm thick crystal and θ = 19.3°.

Fig. 3.
Fig. 3.

(a) Spectra of 9-fs Ti:sapphire oscillator pulses (solid line) and of 7-fs pulses from a hollow fiber compressor, HFC (dashed). (b) normal incidence transmission of 113-mm thick LiIO3. (c)-(e) Calculations of phase-matched difference frequency mixing in this crystal. Results are for θ = 19° pumped by the oscillator (solid lines), and for θ = 21.5° pumped by the HFC (dashed): (c) THz spectra, (d) frequency space (shaded) with LC > 100 μm, (e) time-domain THz electric fields.

Fig. 4.
Fig. 4.

Octave-spanning THz spectrum (circles) generated in LiIO3 with 7-fs pulses from a hollow fiber compressor (inset). The visible pulses from the hollow-core fiber are re-compressed using chirped mirrors (CM) and thin fused silica wedges [23]. The dips in the spectrum arise from absorption in the spectrometer path. Model curves with θ = 21.5° are shown for unchirped pump pulses (dashed line) as in Fig. 3, and for 6 fs2 quadratic chirp (thick solid line). Both theory curves are scaled equally.

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