Evidence of Light Guiding in Ion-Implanted Diamond

We demonstrate the feasibility of fabricating light-waveguiding microstructures in bulk single-crystal diamond by means of direct ion implantation with a scanning microbeam, resulting in the modulation of the refractive index of the ion-beam damaged crystal. Direct evidence of waveguiding through such buried microchannels is obtained with a phase-shift micro-interferometric method allowing the study of the multimodal structure of the propagating electromagnetic field. The possibility of defining optical and photonic structures by direct ion writing opens a range of new possibilities in the design of quantum-optical devices in bulk single-crystal diamond.

Figure 1

Scheme of the implantation geometry. (a) Vacancy density distribution as a function of depth $z$. (b) The same distribution in a gray-scale representation, as a function of $y$ and $z$. (c) Simulation of the defect positions along the buried microchannels. (d) Interference pattern produced by the implantation.

Figure 2

Scheme of the principle of measurement of the micro-interferometer. $S$ is the laser source. $L_1$ and $L_2$ are the focalizing lenses. $D$ is the rotating diffusion disk. BS is the polarizing beam splitter. $O$ is the microscope objective. $Q$ is the quarter wave plate. $M$ is the high quality mirror. CID is the charge-injected-device camera. $\Pi$ is the plane conjugate to the CID camera plane by the objective $O$ (see the dot-dashed lines). $B$ is the block which is displaced by the micrometric actuator with respect to the rest of the apparatus.

Figure 3

(Top left) Map of the damage produced by the ion beam in terms of vacancy density. (Rest of the figure) In the same spatial scale, amplitude maps of nine simulated modes propagating in the waveguide irradiated at a fluence of $2\times {10}^{16}{\mathrm{cm}}^{-2}$.

Figure 4

Comparison between the measured phase-shift maps (left panels) and the fit (right panels) obtained by a linear superposition of mode amplitudes and a background, taking into account multiple reflections effects. (Top and middle panels) Images related to three adjacent guides obtained with irradiation at $2\times {10}^{16}{\mathrm{cm}}^{-2}$ (left) and at $1\times {10}^{16}{\mathrm{cm}}^{-2}$ (middle and right). (Bottom) Images related to three guides irradiated at the fluence of $5\times {10}^{15}{\mathrm{cm}}^{-2}$.