Design of a monolithic source of photon pairs comprising a semiconductor laser and a Bragg reflection waveguide

Abstract

We propose a monolithic, electrically driven source of photon pairs based on a non-linear AlGaAs Bragg reflection waveguide and a laser structure stacked on top. By introducing lateral tapers, the fundamental mode of the lasing waveguide is vertically coupled into a higher order mode of the Bragg reflection waveguide (Bragg mode) such that photon pairs can be generated through a type-II spontaneous parametric down conversion process. According to numerical simulations, a coupling efficiency of 28% is achieved between both modes. Phase matching the Bragg mode with two fundamental modes at 1550 nm results in a photon pair rate of 1.7*10^8 pairs/s for a 2 mm long device assuming 1 mW of power in the Bragg mode. Since the Bragg reflection waveguide does not require doping for this vertically coupled structure, free-carrier absorption losses and parasitic luminescence are avoided.

Figures (8)

• Figure 1: a) 3D-schematic of the tapered stacked waveguide laser based on AlGaAs. b) Top-view of the 3D-schematic shown in Fig. \ref{['Schematic_Taper']}a. The relevant widths within the waveguides and tapers are shown by $W$.
• Figure 2: Vertical profiles of the refractive index (blue) and intensities of the LAS (black solid) and TEB (red solid) modes. The corresponding effective indices of the two modes are shown by the dashed lines.
• Figure 3: a) Intensity distribution of the LAS mode at the at the rear end of the taper at longitudinal position $z=0$. b) Intensity distribution of the TEB mode at the front end of the taper at longitudinal position $z\geq 220$ µm. The etch depths are denoted by $d$ and the lateral waveguide widths are denoted by $W$.
• Figure 4: Effective index of the LAS mode (blue) for a) varying $W_{\mathrm{L}}$ analogous to the tapered region shown in Fig. \ref{['Taper_plots']}a between 0 µm and 30 µm and b) for varying $W_{\mathrm{LS}}$ analogous to the tapered region shown in Fig. \ref{['Taper_plots']}a between 30 µm and 180 µm. The dashed line represents the effective index of the TEB mode. The line connecting the data points has been added to provide a visual guide to the eye.
• Figure 5: a) Top-view of the structure. The color plot represents the vertically integrated longitudinal component of the Poynting vector. b) Side-view of the structure. The color plot represents the laterally integrated longitudinal component of the Poynting vector. c) Laterally and vertically integrated longitudinal component of the Poynting vector as a function of the longitudinal position. The solid horizontal and vertical line in a)-c) separate regions with different refractive indices and etch depths $d$, respectively. The dashed lines mark the edges of each taper segment according to Table \ref{['Taper_params']}. The lateral waveguide widths are denoted by $W$.