High density fiber optic packaging for cryogenic applications
A quantum network may use long-lived quantum memories with optical interfaces incorporated into a scalable architecture. Color-center quantum emitters in diamond have emerged as a promising quantum-memory modality due to their optical properties and compatibility with scalable integration. Here, we disclose a cryogenically stable and network-compatible quantum-emitter module for use as a quantum memory. This quantum-emitter module includes a diamond microchiplet with quantum emitters in the form of silicon vacancies or other color centers. The diamond microchiplet is integrated with a silicon photonic integrated circuit (PIC), which is secured to a silicon bench with cryo-compatible epoxy. Waveguides in the PIC are butt-coupled to optical fibers in a silicon V-groove array, which is secured to the same silicon bench with more cryo-compatible epoxy. A fast-curing epoxy holds the V-groove array to the PIC while the cryo-compatible epoxy cures for mechanical stability from room temperature to cryogenic temperatures.
1 . A method comprising:
bonding a photonic integrated circuit (PIC) made of substrate material to a support structure made of the substrate material with a first portion of cryo-compatible epoxy;
aligning optical fibers in a V-groove array made of the substrate material to waveguides in the PIC;
bonding the V-groove array to the support structure with a second portion of cryo-compatible epoxy;
bonding the V-groove array to the PIC with epoxy having a shorter cure time than a cure time of the cryo-compatible epoxy;
curing the epoxy to secure the V-groove array to the PIC; and
curing the first portion and the second portion of cryo-compatible epoxy.
2 . The method of claim 1 , wherein the substrate material is silicon.
3 . The method of claim 1 , wherein bonding the PIC to the support structure comprises:
bonding the PIC to a shim made of the substrate material with the first portion of cryo-compatible epoxy; and
bonding the shim to the support structure with a third portion of cryo-compatible epoxy.
4 . The method of claim 3 , wherein the second portion of cryo-compatible epoxy forms a layer of approximately equal in thickness to a sum of a thickness of a layer formed by the first portion of cryo-compatible epoxy and a thickness of a layer formed by the third portion of cryo-compatible epoxy.
5 . The method of claim 1 , wherein aligning the optical fibers in the V-groove array to the waveguides in the PIC comprises sensing light coupled through a waveguide in the PIC.
6 . The method of claim 1 , wherein bonding the V-groove array to the support structure comprises:
after aligning the optical fibers in the V-groove array to the waveguides in the PIC, moving the V-groove array away from the PIC;
applying the second portion of cryo-compatible epoxy to at least one of a surface of the V-groove array or a surface of the support structure; and
re-aligning the optical fibers in the V-groove array to the waveguides in the PIC.
7 . The method of claim 1 , wherein the epoxy is ultraviolet-curable epoxy and curing the ultraviolet-curable epoxy comprises illuminating the ultraviolet-curable epoxy with ultraviolet light.
8 . The method of claim 1 , wherein curing the first portion and the second portion of cryo-compatible epoxy occurs at room temperature.
9 . The method of claim 1 , further comprising:
integrating a diamond microchiplet with the PIC.
10 . The method of claim 9 , wherein integrating the diamond microchiplet with the PIC comprises aligning a waveguide in the diamond microchiplet to a waveguide in the PIC.
11 . A fiber block-chip assembly comprising:
a support structure made of substrate material;
a photonic integrated circuit (PIC) made of the substrate material, comprising a plurality of waveguides, and bonded to the support structure with cryo-compatible epoxy;
a V-groove array made of the substrate material, holding a plurality of optical fibers, and bonded to the support structure with additional cryo-compatible epoxy; and
epoxy with a cure time shorter than a cure time of the cryo-compatible epoxy bonding the PIC to the V-groove array.
12 . The fiber block-chip assembly of claim 11 , wherein the substrate material is silicon.
13 . The fiber block-chip assembly of claim 11 , wherein the PIC comprises a plurality of loopback waveguides for alignment of the plurality of waveguides in the PIC to the plurality of optical fibers held by the V-groove array.
14 . The fiber block-chip assembly of claim 11 , wherein the epoxy is index-matching epoxy.
15 . The fiber block-chip assembly of claim 11 , further comprising:
a shim made of the substrate material, bonded to the PIC with a first portion of the cryo-compatible epoxy, and bonded to the support structure with a second portion of the cryo-compatible epoxy.
16 . The fiber block-chip assembly of claim 15 , wherein the PIC overhangs the shim and the epoxy is not bonded to the support structure.
17 . The fiber block-chip assembly of claim 15 , wherein the additional cryo-compatible epoxy forms a layer of approximately equal in thickness to a sum of a thickness of a layer formed by the first portion of cryo-compatible epoxy and a thickness of a layer formed by the second portion of cryo-compatible epoxy.
18 . The fiber block-chip assembly of claim 15 , wherein the epoxy comprises an ultraviolet (UV) curable epoxy.
19 . The fiber block-chip assembly of claim 11 , further comprising:
a diamond microchiplet heterogeneously integrated with the PIC.
20 . The fiber block-chip assembly of claim 19 , wherein the diamond microchiplet comprises a plurality of qubits in optical communication with the plurality of optical fibers via the plurality of waveguides in the PIC.