The present invention, in some embodiments thereof, relates to a system and method for measuring three-photon absorption events, and, more particularly, but not exclusively, to a system and method for measuring a three-photon absorption rate or counting three-photon absorption events, using a photon counting detector.
There is a need for characterizing light sources, including in ways that cannot be achieved by measuring one-photon or two-photon processes. For example, Ian A. Walmsley and Christophe Dorrer, “Characterization of ultrashort pulses,” Advances in Optics and Photonics 1, 308-437 (2009), describe the need to measure the shapes of pulses on femtosecond timescales, far too short to measure directly with any light detector, and reviews some of the techniques that have been developed to do this. Patrick Langlois and Erich P. Ippen, “Measurement of pulse asymmetry by three-photon absorption autocorrelation in a GaAsP photodiode,” Optics Letters 24, 1868-1870 (1999), the contents of which are hereby incorporated by reference, describe using an autocorrelator interferometer, and three-photon absorption in GaAsP, which is a direct band gap material, to measure the asymmetry of such ultrashort pulses, and point out that this cannot be done with one-photon or two-photon absorption. Shaul Pearl, Nir Rotenberg, and Henry M. van Driel, “Three photon absorption in silicon for 2300-3300 nm,” Applied Physics Letters 93, 131102 (2008), describe using silicon, an indirect band gap semiconductor, for three-photon absorption.
Tomoyuki Horokiri et al, “Higher order coherence of exciton-polariton condensates,” Physical Review B 81, 033307 (2010), describes the use of coincidence measurements from three single-photon detectors to measure the third order coherence function g(3)(0) in light emitted by a polariton laser. The authors use the results to show that a polariton condensate differs from a fully coherent state such as the light from an ordinary laser, as well as from light in a definite photon number state, or light in a thermal state, and explains the results with a model involving polariton-polariton and polariton-phonon interactions.
J. M. Roth, T. E. Murphy, and C. Xu, “Ultrasensitive and high-dynamic-range two-photon absorption in a GaAs photomultiplier tube,” Opt. Lett. 27, 2076 (2002), describes two-photon counting of 1.5 μm light with a GaAs photomultiplier tube. Lower power light was detected, and over a greater dynamic range, than in previous work where residual one-photon counting dominated at low power. The light was pulsed, and the width of the pulses was measured using two-photon counting with a Michelson interferometer.
A series of papers by Boitier and colleagues describes using two-photon counting, with a semiconductor detector, to measure the second order coherence function g(2)(τ) of various light sources on a femtosecond timescale, including a blackbody source, a source generating two-photon pairs by parametric fluorescence, a laser, and an Amplified Spontaneous Emission source. These papers are: F. Boitier, A. Godard, E. Rosencher, and C. Fabre, “Measuring photon bunching at ultrashort timescale by two-photon absorption in semiconductors,” Nature Physics 5, 267-270 (2009); Fabien Boitier et al, “Second order coherence of broadband down-converted light on ultrashort time scale determined by two photon absorption in semiconductor,” Optics Express 18, 20401-20408 (2010); and F. Boitier, A. Godard, E. Rosencher, and C. Fabre, “Two photon counting: theory and experiment,” presented at Quantum Electronics and Laser Science Conference (QELS), San Jose, Calif., May 16, 2010, paper QTuE1.
Hannes Hübel et al, “Direct generation of photon triplets using cascaded photon-pair sources,” Nature 466, 601-603 (2010), describes recent advances in producing three-photon entangled states, which can be used for quantum communication and quantum computing.
T. Feurer, S. Niedermeier, and R. Sauerbrey, “Measuring the temporal intensity of ultrashort laser pulse by triple correlation,” Appl. Phys. B 66, 163-168 (1998), the contents of which are hereby incorporated by reference, describes using third harmonic generation of light in a nonlinear crystal to measure the triple autocorrelation function, a function of two time delays, for ultrashort laser pulses, and using the triple autocorrelation function to calculate the shape of the pulses. Tzu-ming Liu et al, “Characterization of Ultrashort Optical Pulses with Third-Harmonic-Based Triple Autocorrelation,” IEEE J Quantum Electronics 38, 1529-1535 (2002), extends the work of Feuer et al, using the optical spectrum, in addition to the triple autocorrelation function, to find not only the pulse shape, but also the color and phase of the light as a function of time within a pulse.