Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Observation of two-photon emission from semiconductors


Two-photon emission is a process in which electron transition between quantum levels occurs through the simultaneous emission of two photons. This phenomenon is important for astrophysics and atomic physics1,2, and semiconductor two-photon emission was recently proposed as a compact source of entangled photons, essential for practical quantum information processing3,4,5, and three orders of magnitude more efficient6 than the existing down-conversion schemes. Two-photon absorption in semiconductors has been extensively investigated7,8,9,10,11; however, spontaneous semiconductor two-photon emission has not been observed, nor has it been fully analysed theoretically so far. We report the first experimental observations of two-photon emission from semiconductors and develop a corresponding theory. Spontaneous two-photon emission is demonstrated in optically pumped bulk GaAs and in electrically driven GaInP/AlGaInP quantum wells. Singly stimulated two-photon emission measurements demonstrate the theoretically predicted two-photon optical gain in semiconductors12,13,14,15—a necessary ingredient for any realizations of future two-photon semiconductor lasers. A photon-coincidence experiment is presented to validate the simultaneity of the electrically driven GaInP/AlGaInP two-photon emission, limited only by the detector's temporal resolution.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Bulk GaAs TPE measurements and calculations with optical pumping by a 514-nm Ar laser.
Figure 2: Experimental false-colour IR emission imaging of the facet of the GaInP/AlGaInP QWs waveguide.
Figure 3: Measured and calculated IR emission spectrum from GaInP/AlGaInP QWs at 200 mA injection current.
Figure 4: Calculated and measured photon coincidences in electrically pumped GaInP/AlGaInP QWs TPE versus relative delay between detectors.


  1. 1

    Goldman, S. P. & Drake, G. W. F. Relativistic two-photon decay rates of 2s1/2 hydrogenic ions. Phys. Rev. A 24, 183–191 (1981).

    ADS  Article  Google Scholar 

  2. 2

    Shapiro, J. & Breit, G. Metastability of 2s states of hydrogenic atoms. Phys. Rev. 113, 179–181 (1959).

    ADS  Article  Google Scholar 

  3. 3

    Kumar, P. et al. Photonic technologies for quantum information processing. Quantum Inf. Process. 3, 215–231 (2004).

    Article  Google Scholar 

  4. 4

    Walton, Z. D., Abouraddy, A. F., Sergienko, A. V., Saleh, B. E. A. & Teich, M. C. One-way entangled-photon autocompensating quantum cryptography. Phys. Rev. A 67, 062309 (2003).

    ADS  Article  Google Scholar 

  5. 5

    Clauser, J. F., Horne, M. A., Shimony, A. & Holt, R. A. Proposed experiment to test local hidden-variable theories. Phys. Rev. Lett. 23, 880–884 (1969).

    ADS  Article  Google Scholar 

  6. 6

    Hayat, A., Ginzburg, P. & Orenstein, M. High-rate entanglement source via two-photon emission from semiconductor quantum wells. Phys. Rev. B 76, 035339 (2007).

    ADS  Article  Google Scholar 

  7. 7

    Nathan, V., Guenther, A. H. & Mitra, S. S. Review of multiphoton absorption in crystalline solids. J. Opt. Soc. Am. B 2, 294–316 (1985).

    ADS  Article  Google Scholar 

  8. 8

    Lee, C. C. & Fan, H. Y. Two-photon absorption with exciton effect for degenerate valence bands. Phys. Rev. B 9, 3502–3516 (1974).

    ADS  Article  Google Scholar 

  9. 9

    Basov, N. G. et al. Semiconductor lasers using optical pumping. J. Phys. Soc. Jpn 21, 277–282 (1966).

    Google Scholar 

  10. 10

    Hutchings, D. C. & Van Stryland, E. W. Nondegenerate two-photon absorption in zinc blende semiconductors. J. Opt. Soc. Am. B 9, 2065–2074 (1992).

    ADS  Article  Google Scholar 

  11. 11

    Sheik-Bahae, M., Hutchings, D. C., Hagan, D. J. & Van Stryland, E. W. Dispersion of bound electron nonlinear refraction in solids. IEEE J. Quant. Electron. 27, 1296–1309 (1991).

    ADS  Article  Google Scholar 

  12. 12

    Ironside, C. N. Two-photon gain semiconductor amplifier. IEEE J. Quant. Electron. 28, 842–847 (1992).

    ADS  Article  Google Scholar 

  13. 13

    Ning, C. Z. Two-photon lasers based on intersubband transitions in semiconductor quantum wells. Phys. Rev. Lett. 93, 187403 (2004).

    ADS  Article  Google Scholar 

  14. 14

    Marti, D. H., Dupertuis, M.-A. & Deveaud, B. Feasibility study for degenerate two-photon gain in a semiconductor microcavity. IEEE J. Quant. Electron. 39, 1066–1073 (2003).

    ADS  Article  Google Scholar 

  15. 15

    Heatley, D. R., Firth, W. J. & Ironside, C. N. Ultrashort-pulse generation using two-photon gain. Opt. Lett. 18, 628–630 (1993).

    ADS  Article  Google Scholar 

  16. 16

    Lipeles, M., Novick, R. & Tolk, N. Direct detection of two-photon emission from the metastable state of singly ionized helium. Phys. Rev. Lett. 15, 690–693 (1965).

    ADS  Article  Google Scholar 

  17. 17

    Lange, W., Agarwal, G. S. & Walther, H. Observation of two-photon decay of Rydberg atoms in a driven cavity. Phys. Rev. Lett. 76, 3293–3296 (1997).

    ADS  Article  Google Scholar 

  18. 18

    Ali, R. et al. Shape of the two-photon-continuum emission from the 1s2s1S0 state in He-like krypton. Phys. Rev. A 55, 994–1006 (1997).

    ADS  Article  Google Scholar 

  19. 19

    Myles, C. W., Dow, J. D. & Sankey, O. F. Theory of alloy broadening of impurity electronic spectra. Phys. Rev. B 24, 1137–1139 (1981).

    ADS  Article  Google Scholar 

  20. 20

    Pfister, O., Brown, W. J., Stenner, M. D. & Gauthier, D. J. Polarization instabilities in a two-photon laser. Phys. Rev. Lett. 86, 4512–4514 (2001).

    ADS  Article  Google Scholar 

  21. 21

    Gauthier, D. J., Wu, Q., Morin, S. E. & Mossberg, T. W. Realization of a continuous-wave, two-photon optical laser. Phys. Rev. Lett. 68, 464–467 (1992).

    ADS  Article  Google Scholar 

  22. 22

    Fainman, Y., Guest, C. C. & Lee, S. H. Optical digital logic operations by two-beam coupling in photorefractive material. Appl. Opt. 25, 1598–1603 (1986).

    ADS  Article  Google Scholar 

  23. 23

    Goppert-Mayer, M. Űber Elementarakte mit zwei Quanenspruengen. Ann. Phys. 9, 273–294 (1931).

    Article  Google Scholar 

  24. 24

    Boyd, R. W. Nonlinear Optics (Academic, New York, 1992).

    Google Scholar 

  25. 25

    Rosencher, E. & Bois, Ph. Model system for optical nonlinearities: Asymmetric quantum wells. Phys. Rev. B 44, 11315–11327 (1991).

    ADS  Article  Google Scholar 

  26. 26

    Sipe, J. E. & Shkrebtii, A. I. Second-order optical response in semiconductors. Phys. Rev. B 61, 5337–5352 (2000).

    ADS  Article  Google Scholar 

  27. 27

    Flatté, M. E., Young, P. M., Peng, L.-H. & Ehrenreich, H. Generalized superlattice K·p theory and intersubband optical transitions. Phys. Rev. B 53, 1963–1978 (1996).

    ADS  Article  Google Scholar 

  28. 28

    Joyce, W. B. & Dixon, R. W. Analytic approximations for the Fermi energy of an ideal Fermi gas. Appl. Phys. Lett. 31, 354–356 (1977).

    ADS  Article  Google Scholar 

  29. 29

    Kleinman, D. A. & Miller, R. C. Band-gap renormalization in semiconductor quantum wells containing carriers. Phys. Rev. B 32, 2266–2272 (1985).

    ADS  Article  Google Scholar 

  30. 30

    Buller, G. S. et al. Semiconductor avalanche diode detectors for quantum cryptography. IEEE–LEOS Newsletter 20, 20–24 (2006).

    Google Scholar 

Download references

Author information



Corresponding author

Correspondence to Alex Hayat.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Hayat, A., Ginzburg, P. & Orenstein, M. Observation of two-photon emission from semiconductors. Nature Photon 2, 238–241 (2008).

Download citation

Further reading


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing