Fabricating photonic devices from bulk substrate
A fabrication process for fabricating, from a bulk substrate material, devices configured to interface with light is described. Sequential directionally-dependent etching process steps may be used to form interior features of a given device prior to undercutting remaining portions of the bulk substrate material in order to locally isolate the formed device from the remaining portions of the bulk substrate material. Layers of conformally deposited material may be used to protect the interior features from being unintentionally etched during said undercutting step(s). Such devices fabricated from bulk substrate material may be used in photonics, for example, in which interior features may be patterned into a bulk substrate material rather than into a thin film in order to preserve higher-quality material properties (e.g., for diamond). Collectively, interior features of such a photonics device may be configured to act as a photonic cavity to store and/or capture light with improved performance.
1 . A method of fabricating, from a bulk substrate, a device configured to interact with light, the method comprising:
receiving the bulk substrate, the bulk substrate having a first width and a first depth, wherein the bulk substrate is to be used to form the device, the device comprising:
a top surface;
a bottom surface;
a first side surface extending between the top surface and the bottom surface;
a second side surface extending between the top surface and the bottom surface; and
one or more interior features located within the first and second side surfaces and extending between the top surface and the bottom surface;
removing material from the bulk substrate to form the first and second side surfaces of the device, the first and second side surfaces having a second width and a second depth;
removing material from a portion of the bulk substrate between the first and second side surfaces to form the one or more interior features of the device, wherein:
the one or more interior features have one or more respective widths that are less than the second width;
the one or more interior features have the second depth; and
subsequent to said removing the material from the portion of the bulk substrate between the first and second side surfaces, remaining portions of the bulk substrate remain connected at a depth extending beyond the second depth; and
removing, via an isotropic etching technique, the remaining portions of the bulk substrate extending beyond the second depth to form a continuous channel having a planar surface,
wherein:
the continuous channel has a width extending to a width of the device; and
said removing to form the continuous channel causes the planar surface along the bottom surface of the device to be formed from the removal of the remaining portions.
2 . The method of claim 1 , wherein:
the device is a quantum information storage device; and
the one or more interior features are configured, via the fabrication process, to form a photonic cavity, wherein the photonic cavity is configured to:
receive quantum information via respective super-positioned particles of light; and
store the quantum information.
3 . The method of claim 1 , wherein said removing the material from the bulk substrate to form the first and second side surfaces of the device comprises:
etching, via a vertical plasma etching technique, the material.
4 . The method of claim 1 , wherein said removing the material from the portion of the bulk substrate between the first and second side surfaces to form the one or more interior features of the device comprises:
etching, via a vertical plasma etching technique, the material from the portion of the bulk substrate between the first and second side surfaces.
5 . The method of claim 1 , wherein said removing the remaining portions of the bulk substrate extending beyond the second depth to form the continuous channel comprises:
etching, via a vertical plasma etching technique, portions of the bulk substrate material extending beyond the second depth and outwards beyond the first and second side surfaces of the device, wherein said etching causes additional side surfaces of the bulk substrate material to be exposed.
6 . The method of claim 5 , further comprising:
depositing, prior to said etching, via the vertical plasma etching technique, a layer of an additional material onto the top surface, the first side surface, and the second side surface of the device.
7 . The method of claim 6 , wherein said removing the remaining portions of the bulk substrate extending beyond the second depth to form the continuous channel further comprises:
etching, via the isotropic etching technique, the material from the portion of the bulk substrate located between the first and second side surfaces of the device and extending beyond the second depth to form the bottom surface of the device.
8 . The method of claim 7 , wherein said removing the remaining portions of the bulk substrate extending beyond the second depth to form the continuous channel further comprises:
prior to said etching, via the vertical plasma etching technique, the material from the portion of the bulk substrate located between the first and second side surfaces and vertically beneath the bottom surface of the device,
depositing an additional layer of the additional material onto the top surface of the device, the first side surface of the device, the second side surface of the device, and the additional side surfaces of the bulk substrate material.