Abstract

We demonstrate that the transient coherent nonlinearity (coherent artifact) affecting the pump-probe response of semiconductor optical amplifiers can be experimentally separated from the incoherent transient. The technique is based on measuring the mirror component of the coherent artifact which is a background-free four—wave mixing signal at a different frequency with respect to the transmitted probe in a heterodyne detection scheme. Measurements on amplifiers of different length reveal strong deviations from the commonly expected symmetric shape of the coherent artifact in case of long waveguides.

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References

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  1. Z. Varden and J. Tauc, "Picosecond Coherence Coupling in the Pump and Probe Technique," Optics Comm. 39, 396-400 (1981).
    [CrossRef]
  2. S. L. Palfre and T. F. Heinz, "Coherent Interactions in Pump-Probe Absorption Measurements: The Effect of Phase Gratings," J. Opt. Soc. Am. B 2, 674-679 (1985).
    [CrossRef]
  3. K. L. Hall, G. Lenz, E. P. Ippen, and G. Ra bon, "Heterod ne Pump-Probe Technique for Time Domain Studies of Optical Nonlinearities in Wa eguides," Optics Letters 17, 874-876 (1992).
    [CrossRef] [PubMed]
  4. A. Mecozzi and J. M�rk, "Theor of Heterod ne Pump-Probe Experiments with Femtosecond Pulses," J. Opt. Soc. Am. B 13, 2437-2452 (1996).
    [CrossRef]
  5. K. L. Hall, G. Lenz, A. M. Darwish, and E. P. Ippen, "Subpicosecond Gain and Index Nonlinear-ities in InGaAsP Diode Lasers," Optics Commun. 111, 589-612 (1994).
    [CrossRef]
  6. C. F. Klingshirn, Semiconductor Optics (Springer-Verlag, Berlin, German , 1995).
  7. M. Hofmann, S. D. Brorson, J. M�rk, and A. Mecozzi, "Time resolved four-wave mixing technique to meaure the ultrafast coherent dynamics in semiconductor optical amplifiers", Appl. Phys. Lett. 68, 3236-3238 (1996).
    [CrossRef]
  8. P. Borri, W. Langbein, J. M�rk, and J. M. Hvam, "Heterodyne Pump-Probe and Four-Wave Mixing in Semiconductor Optical Amplifiers Using Balanced Lock-in Detection," Optics Comm. 169, 317-324 (1999).
    [CrossRef]
  9. P. Borri, S. Scaffetti, J. M�rk, W. Langbein, J. M. Hvam, A. Mecozzi, and F. Martelli, "Measurement and Calculation of the Critical Pulsewidth for Gain Saturation in Semiconductor Optical Amplifiers," Optics Commun. 164, 51 (1999).
    [CrossRef]

Other (9)

Z. Varden and J. Tauc, "Picosecond Coherence Coupling in the Pump and Probe Technique," Optics Comm. 39, 396-400 (1981).
[CrossRef]

S. L. Palfre and T. F. Heinz, "Coherent Interactions in Pump-Probe Absorption Measurements: The Effect of Phase Gratings," J. Opt. Soc. Am. B 2, 674-679 (1985).
[CrossRef]

K. L. Hall, G. Lenz, E. P. Ippen, and G. Ra bon, "Heterod ne Pump-Probe Technique for Time Domain Studies of Optical Nonlinearities in Wa eguides," Optics Letters 17, 874-876 (1992).
[CrossRef] [PubMed]

A. Mecozzi and J. M�rk, "Theor of Heterod ne Pump-Probe Experiments with Femtosecond Pulses," J. Opt. Soc. Am. B 13, 2437-2452 (1996).
[CrossRef]

K. L. Hall, G. Lenz, A. M. Darwish, and E. P. Ippen, "Subpicosecond Gain and Index Nonlinear-ities in InGaAsP Diode Lasers," Optics Commun. 111, 589-612 (1994).
[CrossRef]

C. F. Klingshirn, Semiconductor Optics (Springer-Verlag, Berlin, German , 1995).

M. Hofmann, S. D. Brorson, J. M�rk, and A. Mecozzi, "Time resolved four-wave mixing technique to meaure the ultrafast coherent dynamics in semiconductor optical amplifiers", Appl. Phys. Lett. 68, 3236-3238 (1996).
[CrossRef]

P. Borri, W. Langbein, J. M�rk, and J. M. Hvam, "Heterodyne Pump-Probe and Four-Wave Mixing in Semiconductor Optical Amplifiers Using Balanced Lock-in Detection," Optics Comm. 169, 317-324 (1999).
[CrossRef]

P. Borri, S. Scaffetti, J. M�rk, W. Langbein, J. M. Hvam, A. Mecozzi, and F. Martelli, "Measurement and Calculation of the Critical Pulsewidth for Gain Saturation in Semiconductor Optical Amplifiers," Optics Commun. 164, 51 (1999).
[CrossRef]

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Figures (4)

Fig. 1.
Fig. 1.

Scheme of a diffraction geometry experiment in the spatial selection geometry. Along the probe direction k2 the first diffracted order of the pump is also present (coherent artifact). The diffracted mirror component is along the background-free direction 2k1-k2.

Fig. 2.
Fig. 2.

Measured differential transmission (dotted) and coherent artifact (solid) in a 100µm-long SOA in the gain region.

Fig. 3.
Fig. 3.

Upper: amplified spontaneous emission in a 1mm-long SOA and pulse laser spectrum used. Lower: Gain changes (in dB) and probe phase changes versus the pump-probe delay, at different bias currents around transperency. In the inset, the values of the long-lived leftovers versus the bias current are shown. The values change sign, going from absorption to gain of the device, and cross zero at transparency.

Fig. 4.
Fig. 4.

Differential transmission (dotted) and coherent artifact (solid) in a 1mm-long SOA at different bias currents as indicated. The small signal gain (excluding internal waveguide losses) is also indicated.

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