Abstract

We use electric field singularities in biased metal semiconductor microstructures to enhance the generation of terahertz (THz) radiation from semiconductors. We find that, regardless of the mechanism that is responsible for enhanced THz emission near the anode, singular electric fields near sharp anode features will enhance this emission by as much as an order of magnitude. We show scanning THz measurements of several of these structures and discuss the physical mechanism responsible for this enhanced emission. A new family of more efficient terahertz emitters based on these effects can be designed that will improve the dynamic range of THz imaging and spectroscopy systems.

© 1996 Optical Society of America

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  1. D. Krokel, D. Grischkowsky, M. B. Ketchen, Appl. Phys. Lett. 54, 1046 (1989).
    [CrossRef]
  2. N. Katzenellenbogen, D. Grischkowsky, Appl. Phys. Lett. 58, 222 (1991).
    [CrossRef]
  3. U. D. Keil, D. R. Dykaar, IEEE J. Quantum Electron. 32, 1664 (1996).
    [CrossRef]
  4. E. Sano, T. Shibata, Appl. Phys. Lett. 55, 2748 (1989).
    [CrossRef]
  5. S. E. Ralph, D. Grischkowsky, Appl. Phys. Lett. 59, 1972 (1991).
  6. D. R. Dykaur, A. F. J. Levi, M. Anzlowar, Appl. Phys. Lett. 57, 1123 (1990).
    [CrossRef]
  7. B. I. Greene, P. N. Saeta, D. R. Dykaar, S. Schmitt-Rink, S. L. Chuang, IEEE J. Quantum Electron. 28, 2302 (1992).
    [CrossRef]
  8. U. D. Keil, D. R. Dykaar, R. F. Kopf, S. B. Darack, Appl. Phys. Lett. 64, 1812 (1994).
  9. M. R. Pinto, Proc. Electrochem. Soc. 91–11, 43 (1991).
  10. M. van Exter, D. Grischkowsky, IEEE Trans. Microwave Theory Tech. 38, 1684 (1990).
    [CrossRef]

1996

U. D. Keil, D. R. Dykaar, IEEE J. Quantum Electron. 32, 1664 (1996).
[CrossRef]

1994

U. D. Keil, D. R. Dykaar, R. F. Kopf, S. B. Darack, Appl. Phys. Lett. 64, 1812 (1994).

1992

B. I. Greene, P. N. Saeta, D. R. Dykaar, S. Schmitt-Rink, S. L. Chuang, IEEE J. Quantum Electron. 28, 2302 (1992).
[CrossRef]

1991

M. R. Pinto, Proc. Electrochem. Soc. 91–11, 43 (1991).

S. E. Ralph, D. Grischkowsky, Appl. Phys. Lett. 59, 1972 (1991).

N. Katzenellenbogen, D. Grischkowsky, Appl. Phys. Lett. 58, 222 (1991).
[CrossRef]

1990

D. R. Dykaur, A. F. J. Levi, M. Anzlowar, Appl. Phys. Lett. 57, 1123 (1990).
[CrossRef]

M. van Exter, D. Grischkowsky, IEEE Trans. Microwave Theory Tech. 38, 1684 (1990).
[CrossRef]

1989

D. Krokel, D. Grischkowsky, M. B. Ketchen, Appl. Phys. Lett. 54, 1046 (1989).
[CrossRef]

E. Sano, T. Shibata, Appl. Phys. Lett. 55, 2748 (1989).
[CrossRef]

Anzlowar, M.

D. R. Dykaur, A. F. J. Levi, M. Anzlowar, Appl. Phys. Lett. 57, 1123 (1990).
[CrossRef]

Chuang, S. L.

B. I. Greene, P. N. Saeta, D. R. Dykaar, S. Schmitt-Rink, S. L. Chuang, IEEE J. Quantum Electron. 28, 2302 (1992).
[CrossRef]

Darack, S. B.

U. D. Keil, D. R. Dykaar, R. F. Kopf, S. B. Darack, Appl. Phys. Lett. 64, 1812 (1994).

Dykaar, D. R.

U. D. Keil, D. R. Dykaar, IEEE J. Quantum Electron. 32, 1664 (1996).
[CrossRef]

U. D. Keil, D. R. Dykaar, R. F. Kopf, S. B. Darack, Appl. Phys. Lett. 64, 1812 (1994).

B. I. Greene, P. N. Saeta, D. R. Dykaar, S. Schmitt-Rink, S. L. Chuang, IEEE J. Quantum Electron. 28, 2302 (1992).
[CrossRef]

Dykaur, D. R.

D. R. Dykaur, A. F. J. Levi, M. Anzlowar, Appl. Phys. Lett. 57, 1123 (1990).
[CrossRef]

Greene, B. I.

B. I. Greene, P. N. Saeta, D. R. Dykaar, S. Schmitt-Rink, S. L. Chuang, IEEE J. Quantum Electron. 28, 2302 (1992).
[CrossRef]

Grischkowsky, D.

S. E. Ralph, D. Grischkowsky, Appl. Phys. Lett. 59, 1972 (1991).

N. Katzenellenbogen, D. Grischkowsky, Appl. Phys. Lett. 58, 222 (1991).
[CrossRef]

M. van Exter, D. Grischkowsky, IEEE Trans. Microwave Theory Tech. 38, 1684 (1990).
[CrossRef]

D. Krokel, D. Grischkowsky, M. B. Ketchen, Appl. Phys. Lett. 54, 1046 (1989).
[CrossRef]

Katzenellenbogen, N.

N. Katzenellenbogen, D. Grischkowsky, Appl. Phys. Lett. 58, 222 (1991).
[CrossRef]

Keil, U. D.

U. D. Keil, D. R. Dykaar, IEEE J. Quantum Electron. 32, 1664 (1996).
[CrossRef]

U. D. Keil, D. R. Dykaar, R. F. Kopf, S. B. Darack, Appl. Phys. Lett. 64, 1812 (1994).

Ketchen, M. B.

D. Krokel, D. Grischkowsky, M. B. Ketchen, Appl. Phys. Lett. 54, 1046 (1989).
[CrossRef]

Kopf, R. F.

U. D. Keil, D. R. Dykaar, R. F. Kopf, S. B. Darack, Appl. Phys. Lett. 64, 1812 (1994).

Krokel, D.

D. Krokel, D. Grischkowsky, M. B. Ketchen, Appl. Phys. Lett. 54, 1046 (1989).
[CrossRef]

Levi, A. F. J.

D. R. Dykaur, A. F. J. Levi, M. Anzlowar, Appl. Phys. Lett. 57, 1123 (1990).
[CrossRef]

Pinto, M. R.

M. R. Pinto, Proc. Electrochem. Soc. 91–11, 43 (1991).

Ralph, S. E.

S. E. Ralph, D. Grischkowsky, Appl. Phys. Lett. 59, 1972 (1991).

Saeta, P. N.

B. I. Greene, P. N. Saeta, D. R. Dykaar, S. Schmitt-Rink, S. L. Chuang, IEEE J. Quantum Electron. 28, 2302 (1992).
[CrossRef]

Sano, E.

E. Sano, T. Shibata, Appl. Phys. Lett. 55, 2748 (1989).
[CrossRef]

Schmitt-Rink, S.

B. I. Greene, P. N. Saeta, D. R. Dykaar, S. Schmitt-Rink, S. L. Chuang, IEEE J. Quantum Electron. 28, 2302 (1992).
[CrossRef]

Shibata, T.

E. Sano, T. Shibata, Appl. Phys. Lett. 55, 2748 (1989).
[CrossRef]

van Exter, M.

M. van Exter, D. Grischkowsky, IEEE Trans. Microwave Theory Tech. 38, 1684 (1990).
[CrossRef]

Appl. Phys. Lett.

E. Sano, T. Shibata, Appl. Phys. Lett. 55, 2748 (1989).
[CrossRef]

S. E. Ralph, D. Grischkowsky, Appl. Phys. Lett. 59, 1972 (1991).

D. R. Dykaur, A. F. J. Levi, M. Anzlowar, Appl. Phys. Lett. 57, 1123 (1990).
[CrossRef]

D. Krokel, D. Grischkowsky, M. B. Ketchen, Appl. Phys. Lett. 54, 1046 (1989).
[CrossRef]

N. Katzenellenbogen, D. Grischkowsky, Appl. Phys. Lett. 58, 222 (1991).
[CrossRef]

U. D. Keil, D. R. Dykaar, R. F. Kopf, S. B. Darack, Appl. Phys. Lett. 64, 1812 (1994).

IEEE J. Quantum Electron

U. D. Keil, D. R. Dykaar, IEEE J. Quantum Electron. 32, 1664 (1996).
[CrossRef]

B. I. Greene, P. N. Saeta, D. R. Dykaar, S. Schmitt-Rink, S. L. Chuang, IEEE J. Quantum Electron. 28, 2302 (1992).
[CrossRef]

IEEE Trans. Microwave Theory Tech.

M. van Exter, D. Grischkowsky, IEEE Trans. Microwave Theory Tech. 38, 1684 (1990).
[CrossRef]

Proc. Electrochem. Soc.

M. R. Pinto, Proc. Electrochem. Soc. 91–11, 43 (1991).

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Figures (5)

Fig. 1
Fig. 1

Two-dimensional scan of the emitted THz radiation of the structure shown in solid black for a bias of 60 V. We obtain the data by scanning the sample and leaving all the optics fixed. Note the enhancement close to the corners of the anode.

Fig. 2
Fig. 2

(a), (b) Two new emitters with anodes designed to increase the overlap between the laser spot and the electric field singularities. (c), (d) The corresponding THz emission scans in the vicinity of the anodes.

Fig. 3
Fig. 3

Polarization dependence of the THz emission relative to the [011] axis of the GaAs wafer.

Fig. 4
Fig. 4

Self-consistent calculation of the electric field close to the surface for a structure similar to the one used in Fig. 1 but with a 90-μm gap. The electric field is calculated along the lines shown in the inset and for a bias of 60 V.

Fig. 5
Fig. 5

High-intensity and low-intensity (inset) THz traces measured with lock-in detection with 30- and 300-ms time constants, respectively, showing nearly 6 orders of magnitude in dynamic range (or signal-to-noise ratio). The low-intensity trace is obtained by attenuation of the optical beam until the noise floor becomes visible.

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