OSA's Digital Library

Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 18, Iss. 6 — Mar. 15, 2010
  • pp: 5974–5983
« Show journal navigation

High-speed asynchronous optical sampling with sub-50fs time resolution

R. Gebs, G. Klatt, C. Janke, T. Dekorsy, and A. Bartels  »View Author Affiliations


Optics Express, Vol. 18, Issue 6, pp. 5974-5983 (2010)
http://dx.doi.org/10.1364/OE.18.005974


View Full Text Article

Acrobat PDF (1045 KB)





Browse Journals / Lookup Meetings

Browse by Journal and Year


   


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools

Share
Citations

Abstract

We report an ultrafast time-domain spectroscopy system based on high-speed asynchronous optical sampling operating without mechanical scanner. The system uses two 1 GHz femtosecond oscillators that are offset-stabilized using high-bandwidth feedback electronics operating at the tenth repetition rate harmonics. Definition of the offset frequency, i.e. the time-delay scan rate, in the range of a few kilohertz is accomplished using direct-digital-synthesis electronics for the first time. The time-resolution of the system over the full available 1 ns time-delay window is determined by the laser pulse duration and is 45 fs. This represents a three-fold improvement compared to previous approaches where timing jitter was the limiting factor. Two showcase experiments are presented to verify the high time-resolution and sensitivity of the system.

© 2010 OSA

1. Introduction

Ultrafast time-domain spectroscopy (TDS) with femtosecond lasers is one of the pivotal techniques to elucidate dynamic processes in the natural sciences occurring on time scales between a few tens of femtoseconds to a few nanoseconds. Examples are studies of charge carrier dynamics [1

1. J. Demsar, B. Podobnik, V. V. Kabanov, Th. Wolf, and D. Mihailovic, “Superconducting gap ∆c, the pseudogap ∆p, and pair fluctuations above Tc in overdoped Y1-xCaxBa2Cu3O7-δ from femtosecond time-domain spectroscopy,” Phys. Rev. Lett. 82(24), 4918–4921 (1999). [CrossRef]

], energy relaxation and spin dynamics in semiconductors, metals and their nanostructures [2

2. M. Krauß, H. C. Schneider, R. Bratschitsch, Z. Chen, and S. T. Cundiff, “Ultrafast spin dynamics in optically excited bulk GaAs at low temperatures,” Phys. Rev. B 81(3), 035213 (2010). [CrossRef]

4

4. A. Crut, P. Maioli, N. D. Fatti, and F. Vallée, “Anisotropy effects on the time-resolved spectroscopy of the acoustic vibrations of nanoobjects,” Phys. Chem. Chem. Phys. 11(28), 5882–5888 (2009). [CrossRef] [PubMed]

], phonon dynamics in solid state materials [5

5. T. Dekorsy, G. C. Cho, and H. Kurz, “Coherent phonons in condensed media”, in Light Scattering in Solids VIII, Book Series: Topics in Applied Physics, 76, 169–209, (Springer, Berlin, 1999).

,6

6. F. Hudert, A. Bruchhausen, D. Issenmann, O. Schecker, R. Waitz, A. Erbe, E. Scheer, T. Dekorsy, A. Mlayah, and J.-R. Huntzinger, “Confined longitudinal acoustic phonon modes in free-standing Si membranes coherently excited by femtosecond laser pulses,” Phys. Rev. B 79(20), 201307 (2009). [CrossRef]

], detection of picosecond ultrasound [7

7. C. Thomsen, H. T. Grahn, H. J. Maris, and J. Tauc, “Surface generation and detection of phonons by picosecond light pulses,” Phys. Rev. B 34(6), 4129–4138 (1986). [CrossRef]

,8

8. O. Matsuda, O. B. Wright, D. H. Hurley, V. E. Gusev, and K. Shimizu, “Coherent shear phonon generation and detection with ultrashort optical pulses,” Phys. Rev. Lett. 93(9), 095501 (2004). [CrossRef] [PubMed]

], or the phase-sensitive detection of THz electric fields in time-domain THz spectroscopy [9

9. X.-C. Zhang and D. H. Auston, “Optoelectronic measurement of semiconductor surfaces and interfaces with femtosecond optics,” J. Appl. Phys. 71(1), 326–338 (1992). [CrossRef]

11

11. G. Klatt, R. Gebs, C. Janke, T. Dekorsy, and A. Bartels, “Rapid-scanning terahertz precision spectrometer with more than 6 THz spectral coverage,” Opt. Express 17(25), 22847–22854 (2009). [CrossRef]

]. The functional principle of ultrafast TDS systems is to drive a sample into a defined non-equilibrium state using an optical pump pulse and use a time-delayed probe pulse to monitor the sample's response as function of the time delay between pump and probe pulses. In a conventional experiment, the time delay between pump and probe pulses originating from the same pulsed femtosecond laser is scanned via a variation of the travel distance of one pulse train versus the other. This is mostly accomplished with a retro-reflector mounted onto a linear mechanical scanner. Typical measurement time windows have durations between a few tens of picoseconds and a few nanoseconds and require a retro-reflector motion between several millimeters up to a few tens of centimeters. Scan rates can be a few tens of Hertz for short time-delays (picoseconds) accomplished with vibrating membranes and are well below 1 Hz for long time-delays (nanoseconds) accomplished with stepper motors. The time resolution with such setups is usually given by the laser pulse duration. Other approaches using rotating mirrors have been demonstrated with scan rates of up to 400 Hz and up to 1 ns time delay [12

12. J. Xu and X.-C. Zhang, “Circular involute stage,” Opt. Lett. 29(17), 2082–2084 (2004). [CrossRef] [PubMed]

,13

13. G. J. Kim, S. G. Jeon, J. I. Kim, and Y. S. Jin, “Terahertz pulse detection using rotary optical delay line,” Jpn. J. Appl. Phys. 46(11), 7332–7335 (2007). [CrossRef]

]. While these present an important advance with respect to linear stages, mechanical masses rotating at >10,000 rpm on an optical table are a significant noise source. A key disadvantage of all mechanical scanning approaches is that the scan rates are lower than the frequencies of technical noise with significant Fourier content typically up to 1 kHz present on ultrafast TDS lasers. Thus, this noise will inherently be present on the time-domain signals and prevents measurements directly at the shot-noise limit. Another disadvantage of mechanical time-delay scanning is that the change of physical path length causes spot size variations on a sample due to the inherent divergence of the laser beams. Furthermore, slight misalignments of the scanner can lead to position changes of the laser beam on the sample as the time delay is scanned and lead to signal artifacts, in particular if long time-delays are used. Other advanced techniques are based on encoding the pump induced temporal dynamics on a chirped optical probe beam. This technique has been employed for the single-shot detection of THz field transients without using a mechanical delay line [14

14. Z. Jiang and X.-C. Zhang, “Electro-optic measurement of THz field pulses with a chirped optical beam,” Appl. Phys. Lett. 72(16), 1945–1947 (1998). [CrossRef]

]. The limit of this technique is the accessible time delay given by the length to which a broadband pulse can be temporally stretched.

2. High-speed ASOPS setup

Approximately 700 mW of average power from each laser is reflected by BS3 and BS4 and is used for ultrafast time-domain spectroscopy as described previously [15

15. A. Bartels, F. Hudert, C. Janke, T. Dekorsy, and K. Köhler, “Femtosecond time-resolved optical pump-probe spectroscopy at kilohertz-scan-rates over nanosecond-time-delays without mechanical delay line,” Appl. Phys. Lett. 88(4), 041117 (2006). [CrossRef]

,16

16. A. Bartels, R. Cerna, C. Kistner, A. Thoma, F. Hudert, C. Janke, and T. Dekorsy, “Ultrafast time-domain spectroscopy based on high-speed asynchronous optical sampling,” Rev. Sci. Instrum. 78(3), 035107 (2007). [CrossRef] [PubMed]

]. The pump laser induced transient reflectivity changes of a sample are probed with the probe laser that is detected with a 125-MHz bandwidth photoreceiver with a Si-pin photodiode as the photoactive element. The photoreceiver output is digitized with a 100-MS/s 14-Bit A/D converter. The A/D converter is triggered by a cross-correlation signal between master- and slave laser generated via two-photon absorption in a GaP diode (PD3) using split off beams from both lasers (BS1 and BS2) with ≈100 mW average power. It should be pointed out that the photoreceiver has an AC-coupled signal output with 40 V/mA and a DC monitor output with 1 V/mA transimpedance gain. This allows to amplify the signal to a level at which the detection shot-noise exceeds the A/D converter noise (~0.3 mV peak-to-peak) enabling measurements directly at shot-noise limit and at the same time avoiding saturation of the transimpedance amplifier and A/D converter with the DC contribution. The low-frequency 3-dB cutoff of the signal output is at 25 kHz. Thus, if slow signal contributions with Fourier content below (f × 25 kHz)/Δf (e.g. 5 GHz in the case of Δf = 5 kHz) are to be faithfully resolved (e.g. slow electronic signal decay), Δf must be set to values greater than 25 kHz. The AC-coupling has no effect on experiments focussing on fast signal dynamics as discussed in the following.

3. High-speed ASOPS characterization

4. High-speed ASOPS experiments

To test the time resolution of the high-speed ASOPS system, optically excited coherent E2low phonons at 3 THz and E2high phonons at 13.2 THz in ZnO are measured in reflection geometry at room temperature [18

18. J. M. Calleja and M. Cardona, “Resonant Raman scattering in ZnO,” Phys. Rev. B 16(8), 3753–3761 (1977). [CrossRef]

,19

19. I. H. Lee, K. J. Yee, K. G. Lee, E. Oh, D. S. Kim, and Y. S. Lim, “Coherent optical phonon mode oscillations in wurzite ZnO excited by femtosecond pulses,” J. Appl. Phys. 93(8), 4939 (2003). [CrossRef]

]. The ZnO sample was hydrothermally grown in a wurtzite structure with a (0001) orientation and a thickness of 0.33 mm. The pump- and probe powers are set to 680 mW and 160 mW, respectively, and both lasers have a center-wavelength of 825 nm. The offset frequency is set to ∆f = 1 kHz to obtain one data point per 10 fs, which is sufficient to clearly resolve the 76 fs oscillation period of the 13.2 THz optical phonons. In ZnO, excitation and detection of the optical phonon modes below the optical band gap occurs via impulsive stimulated Raman scattering [19

19. I. H. Lee, K. J. Yee, K. G. Lee, E. Oh, D. S. Kim, and Y. S. Lim, “Coherent optical phonon mode oscillations in wurzite ZnO excited by femtosecond pulses,” J. Appl. Phys. 93(8), 4939 (2003). [CrossRef]

]. Thus the reflected probe light is spectrally modulated at the coherent phonon frequencies. To obtain a non-zero signal, the detection was performed using the short wavelength edge of the probe light spectrum isolated by means of an 815 nm short-wavelength-pass filter and an amplified photodiode [20

20. A. Bartels, T. Dekorsy, and H. Kurz, “Impulsive excitation of phonon-pair combination states by second-order Raman scattering,” Phys. Rev. Lett. 84(13), 2981 (2000). [CrossRef] [PubMed]

,21

21. Y. X. Yan, E. B. Gamble, and K. A. Nelson, “Impulsive stimulated scattering: General importance in femtosecond laser pulse interactions with matter, and spectroscopic applications,” J. Chem. Phys. 83(11), 5391–5399 (1985). [CrossRef]

]. Figure 3(a)
Fig. 3 High-speed ASOPS measured data of wurzite ZnO. a) Zoom into first 2.5 ps of the recorded time domain transient revealing optical phonon oscillations. b) Fast Fourier transform of the ZnO transient showing peaks at 2.97 THz, 10.02 THz and 13.15 THz. Inset: Amplitude zoom into the 10.02 THz and 13.15 THz peak by a factor of 100.
shows the first 2.5 ps of the transient after subtraction of a slow exponential decay caused by optically excited electrons. Oscillations with a period of 337 fs are observable which are superimposed by faster oscillations with a 76 fs period. Figure 3(b) shows the fast Fourier transform (FFT) of the full transient (500 ps length for ∆f = 1 kHz, due to the limited memory of the A/D converter). A large peak at 2.97 THz, corresponding to low-frequency optical phonons E2low, and a small peak at 13.15 THz, corresponding to high-frequency optical phonons E2high, are observed [19

19. I. H. Lee, K. J. Yee, K. G. Lee, E. Oh, D. S. Kim, and Y. S. Lim, “Coherent optical phonon mode oscillations in wurzite ZnO excited by femtosecond pulses,” J. Appl. Phys. 93(8), 4939 (2003). [CrossRef]

]. The inset in Fig. 3(b) shows a magnified view of the FFT and displays a small peak at 10.02 THz which has to our knowledge not yet been reported in TDS measurements. This peak has previously been observed by Raman spectroscopy [18

18. J. M. Calleja and M. Cardona, “Resonant Raman scattering in ZnO,” Phys. Rev. B 16(8), 3753–3761 (1977). [CrossRef]

,22

22. R. Cuscó, E. Alarcon-Llado, J. Ibanez, L. Artus, J. Jimenez, B. Wang, and M. J. Callahan, “Temperature dependence of Raman scattering in ZnO,” Phys. Rev. B 75(16), 165202 (2007). [CrossRef]

] and is assigned to the second order Raman scattering process E2high-E2low [22

22. R. Cuscó, E. Alarcon-Llado, J. Ibanez, L. Artus, J. Jimenez, B. Wang, and M. J. Callahan, “Temperature dependence of Raman scattering in ZnO,” Phys. Rev. B 75(16), 165202 (2007). [CrossRef]

]. The visibility of this peak, which represents the combined density-of-states of the involved phonons, in a TDS experiment is a good demonstration of the high sensitivity of high-speed ASOPS. To verify the 45-fs time-resolution of the system at late delays after the trigger signal, we modified the optical trigger beam path such that the signal appears around 900 ps time-delay and find no changes to the signal.

In a second example, we focus on non-destructive inspection of a multilayer structure via laser induced picosecond ultrasound. We investigate Si/Mo superlattices sputter-deposited on a mono-crystalline Si wafer, which are promising candidates for future soft-X-ray or extreme ultraviolet mirrors (λ≈13 nm) [23

23. L. Belliard, A. Huynh, B. Perrin, A. Michel, G. Abadias, and C. Jaouen, “Elastic properties and phonon generation in Mo/Si superlattices,” Phys. Rev. B 80(15), 155424 (2009). [CrossRef]

]. Our sample is composed of 60 periods, each nominally consisting of 4.1 nm Si and 2.7 nm Mo [24

24. S. Braun, H. Mai, M. Moss, R. Scholz, and A. Leson, “Mo/Si multilayers with different barrier layers for application as extreme ultraviolet mirrors,” Jpn. J. Appl. Phys. 41(Part 1, No. 6B), 4074–4081 (2002). [CrossRef]

]. The nominal period and total stack thickness are thus 6.8 nm and 408 nm, respectively. The Si- and Mo layers are amorphous [24

24. S. Braun, H. Mai, M. Moss, R. Scholz, and A. Leson, “Mo/Si multilayers with different barrier layers for application as extreme ultraviolet mirrors,” Jpn. J. Appl. Phys. 41(Part 1, No. 6B), 4074–4081 (2002). [CrossRef]

]. The high-speed ASOPS TDS system is employed for rapid measurements of the mirror’s acoustic response to optical excitation. Mapping of the acoustic signal permits extraction of information about the spatial distribution and homogeneity of the structure period and variations of the total stack thickness, which is essential information required to optimize the mirror performance. Measurements are performed in reflection geometry [16

16. A. Bartels, R. Cerna, C. Kistner, A. Thoma, F. Hudert, C. Janke, and T. Dekorsy, “Ultrafast time-domain spectroscopy based on high-speed asynchronous optical sampling,” Rev. Sci. Instrum. 78(3), 035107 (2007). [CrossRef] [PubMed]

]. The pump- and probe powers are set to 200 mW and 20 mW, respectively. Both lasers are operated at a center wavelength of 825 nm and ∆f is set to 5 kHz. Figure 4
Fig. 4 Transient reflectivity changes of a Si/Mo-multilayer superlattice following optical excitation for different averaging times 0.2 s (103 averages), 2 s (104 averages) and 20 s (105 averages). “Zoom 1” shows ≈1 THz phonon oscillations and “Zoom 2” shows an acoustic echo caused by the mirror/substrate interface.
shows transient reflectivity changes of the sample after optical excitation at a fixed position for different averaging times. The optical pump pulse excites hot electrons at the top of the superlattice which lead to ultrafast heating and expansion of the crystal lattice via electron-phonon-scattering. This causes the initial signal peak and launches a picosecond ultrasound pulse into the structure [23

23. L. Belliard, A. Huynh, B. Perrin, A. Michel, G. Abadias, and C. Jaouen, “Elastic properties and phonon generation in Mo/Si superlattices,” Phys. Rev. B 80(15), 155424 (2009). [CrossRef]

,25

25. V. E. Gusev, and A. A. Karabutov, Laser Optoacoustics, (Springer, Berlin, 1993).

]. The exponential signal decay due to carrier relaxation and lattice cooling on a 10 ps time scale is superimposed by a coherent acoustic phonon signature at frequency fph≈1 THz that is detected in the transient reflectivity of the mirror surface via the elasto-optic effect [5

5. T. Dekorsy, G. C. Cho, and H. Kurz, “Coherent phonons in condensed media”, in Light Scattering in Solids VIII, Book Series: Topics in Applied Physics, 76, 169–209, (Springer, Berlin, 1999).

,23

23. L. Belliard, A. Huynh, B. Perrin, A. Michel, G. Abadias, and C. Jaouen, “Elastic properties and phonon generation in Mo/Si superlattices,” Phys. Rev. B 80(15), 155424 (2009). [CrossRef]

,26

26. A. Bartels, T. Dekorsy, H. Kurz, and K. Köhler, “Coherent zone-folded longitudinal acoustic phonons in semiconductor superlattices: excitation and detection,” Phys. Rev. Lett. 82(5), 1044–1047 (1999). [CrossRef]

28

28. N. W. Pu, “Ultrafast excitation and detection of acoustic phonon modes in superlattices,” Phys. Rev. B 72(11), 115428 (2005). [CrossRef]

]. The analysis of the Fourier spectra of these coherent phonons reveal a combination of zone-folded acoustic modes of the superlattice and a localized surface mode [23

23. L. Belliard, A. Huynh, B. Perrin, A. Michel, G. Abadias, and C. Jaouen, “Elastic properties and phonon generation in Mo/Si superlattices,” Phys. Rev. B 80(15), 155424 (2009). [CrossRef]

,27

27. N. W. Pu and J. Bokor, “Study of surface and bulk acoustic phonon excitations in superlattices using picosecond ultrasonics,” Phys. Rev. Lett. 91(7), 076101 (2003). [CrossRef] [PubMed]

,28

28. N. W. Pu, “Ultrafast excitation and detection of acoustic phonon modes in superlattices,” Phys. Rev. B 72(11), 115428 (2005). [CrossRef]

]. These oscillations are visible at short time delays (≈25 ps, see Fig. 4 “Zoom 1”) and are correlated to the period dSL = vl /fph of the superlattice if the phonon dispersion is approximated linearly. vl is the longitudinal sound velocity in the superlattice averaged over the constituting layers. In addition, the optically generated ultrasound pulse propagates through the superlattice, is reflected at the interface to the Si-substrate and propagates back to the surface causing an acoustic echo in the transient reflectivity at a time delay of τrefl ≈132 ps (see “Zoom 2” of Fig. 4). The position of the echo maximum τrefl is correlated to the superlattice total stack thickness via d = (vl × τrefl)/2. Thus, in principle, the Si/Mo-period dSL and the multilayer total stack thickness d can be derived from fph and τrefl, respectively. However, the sound velocities of the amorphous constituting thin films and thus the average sound velocity in the superlattice are largely unknown at present. Thus, we use the echo position τrefl = 132 ps measured at sufficient distance from the wafer edge (8 mm) and the nominal stack thickness to determine vl to 6180 m/s and use this value in the following. The error of this value for vl is below 5% and stems from the uncertainty in the determination of the exact position of τrefl and from the maximum possible error in the actual layer period and total stack thickness that would still yield the experimentally confirmed reflection band at the design wavelength of the soft-X-ray mirror at 13.4 nm [24

24. S. Braun, H. Mai, M. Moss, R. Scholz, and A. Leson, “Mo/Si multilayers with different barrier layers for application as extreme ultraviolet mirrors,” Jpn. J. Appl. Phys. 41(Part 1, No. 6B), 4074–4081 (2002). [CrossRef]

]. Due to the requirement to extract vl from the measurement, our data do not yield absolute values for dSL and d without additional structural information from X-ray analysis. Yet, the technique is able to estimate variations of the superlattice period and total stack thickness when mapping a wafer and is thus well suited to analyze the structure homogeneity. Figure 5
Fig. 5 Si/Mo-multilayer superlattice period (plotted versus left axis) and total stack thickness (plotted versus right axis) versus the radial distance from the wafer edge for different total line-scan acquisition times. The values of the total stack thickness are plotted upside-down to distinguish the curves from the period plots. The color-code (red, green, black) of these curves corresponds to the transients of Fig. 4 used for the evaluation at a fixed position.
shows the extracted superlattice period dSL and total stack thickness d over a 10 mm long radial line-scan from the Si/Mo-multilayer wafer edge towards the wafer center for different acquisition times per data point. Data were acquired at 200 equidistant positions separated by 50 μm with optical spot sizes of ≈30μm (FWHM). Transients with 0.2 s acquisition time were low-pass filtered before evaluation of dSL and d to eliminate high frequency noise. Owing to the 5 kHz scan rate and our measurement capability directly at the shot-noise limit, the line scan with 0.2 s acquisition time per data point (i.e. 5 Hz pixel acquisition frequency, 48 s per line-scan) readily permits clear identification of a reduction of the mirror period and total stack thickness when approaching the wafer edge. This effect is expected and is caused by the inhomogeneity of the sputtering process. Increasing the averaging time by factors of 10 and 100 reduces the statistical error but essentially yields the same qualitative result as a scan at 5 Hz pixel acquisition frequency. More than 6 mm away from the wafer edge the extracted mean multilayer period <dSL> is 6.2 nm, with a standard deviation of 43 pm, 16 pm, and 8 pm for the data with 0.2 s, 2 s, and 20 s per pixel, respectively. The deviation of this value from the nominal 6.8 nm period can be explained by the fact that the linear approximation of the phonon dispersion used to extract dSL ignores phonon bandgaps at the Brillouin-zone center and possible excitation of localized surface modes in the bandgaps [27

27. N. W. Pu and J. Bokor, “Study of surface and bulk acoustic phonon excitations in superlattices using picosecond ultrasonics,” Phys. Rev. Lett. 91(7), 076101 (2003). [CrossRef] [PubMed]

,28

28. N. W. Pu, “Ultrafast excitation and detection of acoustic phonon modes in superlattices,” Phys. Rev. B 72(11), 115428 (2005). [CrossRef]

]. The mean total stack thickness <d> is 408 nm, with a standard deviation of 3.1 nm, 1.8 nm, and 0.8 nm for the data with 0.2 s, 2 s, and 20 s per pixel, respectively. This value for <d> is expected since the nominal total stack thickness has been used to determine vl. The presented data suggest that our technique is capable of detecting superlattice period variations on the order of 0.1 nm and total stack thickness variations on the order of 1 nm with a measurement time on the order of just 1 s per pixel. While we are currently limited to thickness variations, an exact determination of the sound velocities should be straightfoward with an analysis of superlattices of different relative Si/Mo composition and comparing those data to absolute thickness measurements performed, e.g. with high resolution X-ray analysis. In this case, our technique would also be capable of yielding absolute thickness values. This example highlights the advantages of high-speed ASOPS for laser induced picosecond ultrasound applications, e.g. non-destructive wafer inspection at the nanometer thickness level. Fast oscillations at THz frequencies and small acoustic signatures (ΔR/R≈10−5) at long time delays of hundreds of picoseconds can simultaneously be resolved with a single measurement lasting only between a few hundreds of milliseconds to a few seconds, depending on the desired signal-to-noise ratio. This is particularly useful for rapid mapping of functional structure properties because imaging of significant areas can be performed in a few minutes.

5. Summary and conclusion

Acknowledgments

We thank H. Schäfer, A. Thoma, S. Eggert and C. Beschle for their vital contributions to this work. We are also grateful to S. Braun for providing the Si/Mo superlattice samples. We gratefully acknowledge support by the Center for Applied Photonics at the University of Konstanz. This work was supported in part by a grant from the Ministry of Science, Research and the Arts of Baden-Württemberg.

References and links

1.

J. Demsar, B. Podobnik, V. V. Kabanov, Th. Wolf, and D. Mihailovic, “Superconducting gap ∆c, the pseudogap ∆p, and pair fluctuations above Tc in overdoped Y1-xCaxBa2Cu3O7-δ from femtosecond time-domain spectroscopy,” Phys. Rev. Lett. 82(24), 4918–4921 (1999). [CrossRef]

2.

M. Krauß, H. C. Schneider, R. Bratschitsch, Z. Chen, and S. T. Cundiff, “Ultrafast spin dynamics in optically excited bulk GaAs at low temperatures,” Phys. Rev. B 81(3), 035213 (2010). [CrossRef]

3.

M. A. El-Sayed, “Some interesting properties of metals confined in time and nanometer space of different shapes,” Acc. Chem. Res. 34(4), 257–264 (2001). [CrossRef] [PubMed]

4.

A. Crut, P. Maioli, N. D. Fatti, and F. Vallée, “Anisotropy effects on the time-resolved spectroscopy of the acoustic vibrations of nanoobjects,” Phys. Chem. Chem. Phys. 11(28), 5882–5888 (2009). [CrossRef] [PubMed]

5.

T. Dekorsy, G. C. Cho, and H. Kurz, “Coherent phonons in condensed media”, in Light Scattering in Solids VIII, Book Series: Topics in Applied Physics, 76, 169–209, (Springer, Berlin, 1999).

6.

F. Hudert, A. Bruchhausen, D. Issenmann, O. Schecker, R. Waitz, A. Erbe, E. Scheer, T. Dekorsy, A. Mlayah, and J.-R. Huntzinger, “Confined longitudinal acoustic phonon modes in free-standing Si membranes coherently excited by femtosecond laser pulses,” Phys. Rev. B 79(20), 201307 (2009). [CrossRef]

7.

C. Thomsen, H. T. Grahn, H. J. Maris, and J. Tauc, “Surface generation and detection of phonons by picosecond light pulses,” Phys. Rev. B 34(6), 4129–4138 (1986). [CrossRef]

8.

O. Matsuda, O. B. Wright, D. H. Hurley, V. E. Gusev, and K. Shimizu, “Coherent shear phonon generation and detection with ultrashort optical pulses,” Phys. Rev. Lett. 93(9), 095501 (2004). [CrossRef] [PubMed]

9.

X.-C. Zhang and D. H. Auston, “Optoelectronic measurement of semiconductor surfaces and interfaces with femtosecond optics,” J. Appl. Phys. 71(1), 326–338 (1992). [CrossRef]

10.

A. Dreyhaupt, S. Winnerl, T. Dekorsy, and M. Helm, “High-intensity terahertz radiation from a microstructured large-area photoconductor,” Appl. Phys. Lett. 86(12), 121114 (2005). [CrossRef]

11.

G. Klatt, R. Gebs, C. Janke, T. Dekorsy, and A. Bartels, “Rapid-scanning terahertz precision spectrometer with more than 6 THz spectral coverage,” Opt. Express 17(25), 22847–22854 (2009). [CrossRef]

12.

J. Xu and X.-C. Zhang, “Circular involute stage,” Opt. Lett. 29(17), 2082–2084 (2004). [CrossRef] [PubMed]

13.

G. J. Kim, S. G. Jeon, J. I. Kim, and Y. S. Jin, “Terahertz pulse detection using rotary optical delay line,” Jpn. J. Appl. Phys. 46(11), 7332–7335 (2007). [CrossRef]

14.

Z. Jiang and X.-C. Zhang, “Electro-optic measurement of THz field pulses with a chirped optical beam,” Appl. Phys. Lett. 72(16), 1945–1947 (1998). [CrossRef]

15.

A. Bartels, F. Hudert, C. Janke, T. Dekorsy, and K. Köhler, “Femtosecond time-resolved optical pump-probe spectroscopy at kilohertz-scan-rates over nanosecond-time-delays without mechanical delay line,” Appl. Phys. Lett. 88(4), 041117 (2006). [CrossRef]

16.

A. Bartels, R. Cerna, C. Kistner, A. Thoma, F. Hudert, C. Janke, and T. Dekorsy, “Ultrafast time-domain spectroscopy based on high-speed asynchronous optical sampling,” Rev. Sci. Instrum. 78(3), 035107 (2007). [CrossRef] [PubMed]

17.

V. A. Stoica, Y. M. Sheu, D. A. Reis, and R. Clarke, “Wideband detection of transient solid-state dynamics using ultrafast fiber lasers and asynchronous optical sampling,” Opt. Express 16(4), 2322–2335 (2008). [CrossRef] [PubMed]

18.

J. M. Calleja and M. Cardona, “Resonant Raman scattering in ZnO,” Phys. Rev. B 16(8), 3753–3761 (1977). [CrossRef]

19.

I. H. Lee, K. J. Yee, K. G. Lee, E. Oh, D. S. Kim, and Y. S. Lim, “Coherent optical phonon mode oscillations in wurzite ZnO excited by femtosecond pulses,” J. Appl. Phys. 93(8), 4939 (2003). [CrossRef]

20.

A. Bartels, T. Dekorsy, and H. Kurz, “Impulsive excitation of phonon-pair combination states by second-order Raman scattering,” Phys. Rev. Lett. 84(13), 2981 (2000). [CrossRef] [PubMed]

21.

Y. X. Yan, E. B. Gamble, and K. A. Nelson, “Impulsive stimulated scattering: General importance in femtosecond laser pulse interactions with matter, and spectroscopic applications,” J. Chem. Phys. 83(11), 5391–5399 (1985). [CrossRef]

22.

R. Cuscó, E. Alarcon-Llado, J. Ibanez, L. Artus, J. Jimenez, B. Wang, and M. J. Callahan, “Temperature dependence of Raman scattering in ZnO,” Phys. Rev. B 75(16), 165202 (2007). [CrossRef]

23.

L. Belliard, A. Huynh, B. Perrin, A. Michel, G. Abadias, and C. Jaouen, “Elastic properties and phonon generation in Mo/Si superlattices,” Phys. Rev. B 80(15), 155424 (2009). [CrossRef]

24.

S. Braun, H. Mai, M. Moss, R. Scholz, and A. Leson, “Mo/Si multilayers with different barrier layers for application as extreme ultraviolet mirrors,” Jpn. J. Appl. Phys. 41(Part 1, No. 6B), 4074–4081 (2002). [CrossRef]

25.

V. E. Gusev, and A. A. Karabutov, Laser Optoacoustics, (Springer, Berlin, 1993).

26.

A. Bartels, T. Dekorsy, H. Kurz, and K. Köhler, “Coherent zone-folded longitudinal acoustic phonons in semiconductor superlattices: excitation and detection,” Phys. Rev. Lett. 82(5), 1044–1047 (1999). [CrossRef]

27.

N. W. Pu and J. Bokor, “Study of surface and bulk acoustic phonon excitations in superlattices using picosecond ultrasonics,” Phys. Rev. Lett. 91(7), 076101 (2003). [CrossRef] [PubMed]

28.

N. W. Pu, “Ultrafast excitation and detection of acoustic phonon modes in superlattices,” Phys. Rev. B 72(11), 115428 (2005). [CrossRef]

OCIS Codes
(300.6320) Spectroscopy : Spectroscopy, high-resolution
(300.6500) Spectroscopy : Spectroscopy, time-resolved
(320.7150) Ultrafast optics : Ultrafast spectroscopy
(340.7470) X-ray optics : X-ray mirrors
(140.3425) Lasers and laser optics : Laser stabilization

ToC Category:
Spectroscopy

History
Original Manuscript: January 21, 2010
Revised Manuscript: March 4, 2010
Manuscript Accepted: March 4, 2010
Published: March 10, 2010

Citation
R. Gebs, G. Klatt, C. Janke, T. Dekorsy, and A. Bartels, "High-speed asynchronous optical sampling with sub-50fs time resolution," Opt. Express 18, 5974-5983 (2010)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-18-6-5974


Sort:  Author  |  Year  |  Journal  |  Reset  

References

  1. J. Demsar, B. Podobnik, V. V. Kabanov, Th. Wolf, and D. Mihailovic, “Superconducting gap ∆c, the pseudogap ∆p, and pair fluctuations above Tc in overdoped Y1-xCaxBa2Cu3O7-δ from femtosecond time-domain spectroscopy,” Phys. Rev. Lett. 82(24), 4918–4921 (1999). [CrossRef]
  2. M. Krauß, H. C. Schneider, R. Bratschitsch, Z. Chen, and S. T. Cundiff, “Ultrafast spin dynamics in optically excited bulk GaAs at low temperatures,” Phys. Rev. B 81(3), 035213 (2010). [CrossRef]
  3. M. A. El-Sayed, “Some interesting properties of metals confined in time and nanometer space of different shapes,” Acc. Chem. Res. 34(4), 257–264 (2001). [CrossRef] [PubMed]
  4. A. Crut, P. Maioli, N. D. Fatti, and F. Vallée, “Anisotropy effects on the time-resolved spectroscopy of the acoustic vibrations of nanoobjects,” Phys. Chem. Chem. Phys. 11(28), 5882–5888 (2009). [CrossRef] [PubMed]
  5. T. Dekorsy, G. C. Cho, and H. Kurz, “Coherent phonons in condensed media”, in Light Scattering in Solids VIII, Book Series: Topics in Applied Physics, 76, 169–209, (Springer, Berlin, 1999).
  6. F. Hudert, A. Bruchhausen, D. Issenmann, O. Schecker, R. Waitz, A. Erbe, E. Scheer, T. Dekorsy, A. Mlayah, and J.-R. Huntzinger, “Confined longitudinal acoustic phonon modes in free-standing Si membranes coherently excited by femtosecond laser pulses,” Phys. Rev. B 79(20), 201307 (2009). [CrossRef]

Cited By

Alert me when this paper is cited

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.

Figures

Fig. 1 Fig. 2 Fig. 3
 
Fig. 4 Fig. 5
 

« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited