Nonlinear Properties of Photonic Crystals:
We are actively investigating the nonlinear properties of photonic crystal nanobeam cavities [1] for a number of applications such as single-photon frequency conversion and efficient THz generation. This work leverages the very high Q-factors and small mode volumes which can be achieved with photonic crystal nanocavities. The conversion efficiency of a nonlinear process is improved in a cavity due to the resonantly enhanced local field intensity, and the high-Q factors which can be realized lead to long photon lifetimes (i.e. many “round-trips” in the cavity), increasing the effective interaction length of the photon with the nonlinear medium (e.g. GaAs or InP).
We are actively investigating the nonlinear properties of photonic crystal nanobeam cavities [1] for a number of applications such as single-photon frequency conversion and efficient THz generation. This work leverages the very high Q-factors and small mode volumes which can be achieved with photonic crystal nanocavities. The conversion efficiency of a nonlinear process is improved in a cavity due to the resonantly enhanced local field intensity, and the high-Q factors which can be realized lead to long photon lifetimes (i.e. many “round-trips” in the cavity), increasing the effective interaction length of the photon with the nonlinear medium (e.g. GaAs or InP).
1. Single-photon frequency conversion
In recent years, there has been a concerted research effort to develop on-demand single-photon sources using single quantum emitters strongly coupled to resonant optical microcavities (cavity QED). The strong coupling of the emitter to a resonant cavity results in preferential emission into the cavity mode of a single photon with frequency near the atomic resonance. Connecting pairs of such systems would form the basis for distributed quantum networks, where the emitters serve as processors and photons carry information between the nodes. In practice, however, the photon emission occurs at wavelengths determined by the atomic resonance frequency. This is impractical, as it does not exploit the low-loss telecom frequency band for long-distance transmission and requires all emitters in a quantum network to be identical.
We have proposed [2] the use of a dual-mode photonic crystal nanobeam cavity to realize the frequency conversion of single photons from the visible (637 nm) or near-IR (930 nm) to the telecom band (1550 nm). The single photons are emitted from a quantum emitter which is strongly coupled to one mode of the cavity (mode a in the figure below). The emitter could be a quantum dot, a diamond NV center, or even a single atom which has a transition frequency strongly coupled with the cavity mode. At the same time, the cavity is irradiated with a pump laser which drives the difference-frequency generation between modes a and c, such that the photon exits the cavity at mode c rather than mode a. It can then be channeled into an on-chip or fiber-coupled waveguide.
This idea makes use of our design of a dual-mode TE-TM photonic crystal nanobeam [3], which has two ultra-high Q-factor (Q > 106) resonant modes with a wide spectral separation. These double-mode nanocavities could also be useful for other applications in optical signal processing, such as all-optical switching.
2. Terahertz generation
We have proposed theoretically [4], and are initiating experimental investigations, into the use of a dual-mode nanocavity with a χ(2) nonlinearity as an efficient source of THz photons. Our scheme takes advantage of the high Q/V of the two cavity modes (designed to be resonant in the telecom wavelength range); if both modes are excited, they give rise to difference-frequency generation in the THz range of the spectrum (~1 -3 THz, or about 100-300 μm). If there is a third resonance at the difference-frequency, this process can be highly efficient. A triply-resonant system could be realized by embedding the dual-mode nanocavity (pictured in the figure) inside a larger cavity which is resonant at the difference-frequency of the two modes.
[1] M. W. McCutcheon and M. Lončar, "Design of an ultrahigh Quality factor silicon nitride photonic crystal nanocavity for coupling to diamond nanocrystals," Optics Express, Vol. 16, 19136 (2008)
[2] M. W. McCutcheon, D. E. Chang, Y. Zhang, M.D. Lukin, and M. Lončar, "Broad-band spectral control of single photon sources using a nonlinear photonic crystal cavity," submitted for peer review and posted on arXiv: 0903.4706
[3] Y. Zhang, M.W. McCutcheon, I.B. Burgess, and M. Lončar, "Ultra-high-Q TE/TM dual-polarized photonic crystal nanocavities," Optics Letters, Vol. 34, 2694 (2009)
[4] I.B. Burgess, A.W. Rodriguez, M. W. McCutcheon, J. Bravo-Abad, Y. Zhang, S. G. Johnson, and M. Lončar, "Difference-frequency generation with quantum-limited efficiency in triply-resonant nonlinear cavities," Optics Express, Vol. 17, 9241 (2009)
We are actively investigating the nonlinear properties of photonic crystal nanobeam cavities [1] for a number of applications such as single-photon frequency conversion and efficient THz generation. This work leverages the very high Q-factors and small mode volumes which can be achieved with photonic crystal nanocavities. The conversion efficiency of a nonlinear process is improved in a cavity due to the resonantly enhanced local field intensity, and the high-Q factors which can be realized lead to long photon lifetimes (i.e. many “round-trips” in the cavity), increasing the effective interaction length of the photon with the nonlinear medium (e.g. GaAs or InP).
1. Single-photon frequency conversion
In recent years, there has been a concerted research effort to develop on-demand single-photon sources using single quantum emitters strongly coupled to resonant optical microcavities (cavity QED). The strong coupling of the emitter to a resonant cavity results in preferential emission into the cavity mode of a single photon with frequency near the atomic resonance. Connecting pairs of such systems would form the basis for distributed quantum networks, where the emitters serve as processors and photons carry information between the nodes. In practice, however, the photon emission occurs at wavelengths determined by the atomic resonance frequency. This is impractical, as it does not exploit the low-loss telecom frequency band for long-distance transmission and requires all emitters in a quantum network to be identical.
We have proposed [2] the use of a dual-mode photonic crystal nanobeam cavity to realize the frequency conversion of single photons from the visible (637 nm) or near-IR (930 nm) to the telecom band (1550 nm). The single photons are emitted from a quantum emitter which is strongly coupled to one mode of the cavity (mode a in the figure below). The emitter could be a quantum dot, a diamond NV center, or even a single atom which has a transition frequency strongly coupled with the cavity mode. At the same time, the cavity is irradiated with a pump laser which drives the difference-frequency generation between modes a and c, such that the photon exits the cavity at mode c rather than mode a. It can then be channeled into an on-chip or fiber-coupled waveguide.
This idea makes use of our design of a dual-mode TE-TM photonic crystal nanobeam [3], which has two ultra-high Q-factor (Q > 106) resonant modes with a wide spectral separation. These double-mode nanocavities could also be useful for other applications in optical signal processing, such as all-optical switching.
2. Terahertz generation
We have proposed theoretically [4], and are initiating experimental investigations, into the use of a dual-mode nanocavity with a χ(2) nonlinearity as an efficient source of THz photons. Our scheme takes advantage of the high Q/V of the two cavity modes (designed to be resonant in the telecom wavelength range); if both modes are excited, they give rise to difference-frequency generation in the THz range of the spectrum (~1 -3 THz, or about 100-300 μm). If there is a third resonance at the difference-frequency, this process can be highly efficient. A triply-resonant system could be realized by embedding the dual-mode nanocavity (pictured in the figure) inside a larger cavity which is resonant at the difference-frequency of the two modes.
[1] M. W. McCutcheon and M. Lončar, "Design of an ultrahigh Quality factor silicon nitride photonic crystal nanocavity for coupling to diamond nanocrystals," Optics Express, Vol. 16, 19136 (2008)
[2] M. W. McCutcheon, D. E. Chang, Y. Zhang, M.D. Lukin, and M. Lončar, "Broad-band spectral control of single photon sources using a nonlinear photonic crystal cavity," submitted for peer review and posted on arXiv: 0903.4706
[3] Y. Zhang, M.W. McCutcheon, I.B. Burgess, and M. Lončar, "Ultra-high-Q TE/TM dual-polarized photonic crystal nanocavities," Optics Letters, Vol. 34, 2694 (2009)
[4] I.B. Burgess, A.W. Rodriguez, M. W. McCutcheon, J. Bravo-Abad, Y. Zhang, S. G. Johnson, and M. Lončar, "Difference-frequency generation with quantum-limited efficiency in triply-resonant nonlinear cavities," Optics Express, Vol. 17, 9241 (2009)