Second harmonic generation in gallium phosphide photonic crystal nanocavities with ultralow continuous wave pump power

Abstract

We demonstrate second harmonic generation in photonic crystal nanocavities fabricated in the semiconductor gallium phosphide. We observe second harmonic radiation at 750 nm with input powers of only nanowatts coupled to the cavity and conversion effciency P(out)/P(2)(in,coupled)=430%/W. The large electronic band gap of GaP minimizes absorption loss, allowing effcient conversion. Our results are promising for integrated, low-power light sources and on-chip reduction of input power in other nonlinear processes.

Multimode nanobeam cavities for nonlinear optics: high quality resonances separated by an octave

“…Recently, Raman lasing in high Q silicon PCCs was demonstrated [6], while the χ (2) processes of second harmonic generation (SHG) and sum frequency generation (SFG) have also been demonstrated in such cavities in III-V semiconductors [17][18][19][20][21][22][23], as well as in other materials such as lithium niobate [24], SiC [25] and Si [26]. However, as described above, the difficulty in engineering cavities with modes that are far apart in frequency has limited the ability to increase the efficiency at low power levels.…”

Fast quantum dot single photon source triggered at telecommunications wavelength

“…Electrical excitation [8,9] can circumvent this; however, resonant optical excitation [7] improves the indistinguishability of output photons, and many desirable microcavity structures such as photonic crystal cavities have geometries that are challenging to pump electrically [10]. Furthermore, while telecommunications wavelengths are desirable for transporting photons over long distances, excitation and emission in many quantum dot materials systems, determined by material parameters, occurs at much shorter wavelengths.Recently [11,12], we demonstrated that photonic crystal cavities fabricated in III-V semiconductors with large χ (2) nonlinearities can greatly enhance nonlinear frequency conversion efficiency, as a result of light recirculation inside an ultrasmall volume. Here, we apply a similar approach to excite a single InAs quantum dot (with transitions ∼900 nm) using a commercially available telecommunications wavelength (∼1550 nm) laser that can serve as a trigger at * Electronic address: krivoire@stanford.edu…”

“…Recently [11,12], we demonstrated that photonic crystal cavities fabricated in III-V semiconductors with large χ (2) nonlinearities can greatly enhance nonlinear frequency conversion efficiency, as a result of light recirculation inside an ultrasmall volume. Here, we apply a similar approach to excite a single InAs quantum dot (with transitions ∼900 nm) using a commercially available telecommunications wavelength (∼1550 nm) laser that can serve as a trigger at * Electronic address: krivoire@stanford.edu…”

“…GaAs has a noncentrosymmetric cubic crystal lattice with 43m symmetry; the only non-zero elements of the bulk χ (2) tensor have i = j = k. Since normally incident light couples to the TE-like photonic crystal cavity mode (Fig. 1c, with dominant E x and E y in-plane field components), the generated nonlinear polarization (and accordingly second harmonic, as described in [11]) isẑ-polarized, i.e., transverse magnetic-like (TM-like) mode. For a photonic crystal, this corresponds to guided resonances in the TM-like air-band [11].…”

“…1c, with dominant E x and E y in-plane field components), the generated nonlinear polarization (and accordingly second harmonic, as described in [11]) isẑ-polarized, i.e., transverse magnetic-like (TM-like) mode. For a photonic crystal, this corresponds to guided resonances in the TM-like air-band [11]. The second harmonic at 750 nm is used to excite the quantum dot above the GaAs band gap.…”