Surface relief waveguides with high refractive index resist
The disclosure describes an improved drop-on-demand, controlled volume technique for dispensing resist onto a substrate, which is then imprinted to create a patterned optical device suitable for use in optical applications such as augmented reality and/or mixed reality systems. The technique enables the dispensation of drops of resist at precise locations on the substrate, with precisely controlled drop volume corresponding to an imprint template having different zones associated with different total resist volumes. Controlled drop size and placement also provides for substantially less variation in residual layer thickness across the surface of the substrate after imprinting, compared to previously available techniques. The technique employs resist having a refractive index closer to that of the substrate index, reducing optical artifacts in the device. To ensure reliable dispensing of the higher index and higher viscosity resist in smaller drop sizes, the dispensing system can continuously circulate the resist.
1. A system for manufacturing an optical device, the system comprising:
a reservoir configured to store resist;
a fluid dispenser that includes an dispensing mechanism configured to dispense drops of the resist onto a substrate;
a meniscus pump configured to cause movement of the resist from the reservoir to the fluid dispenser through a first channel;
a fluid pump configured to cause movement of undispensed resist from the fluid dispenser to the reservoir through a second channel;
a fluid control device that is communicatively coupled to the fluid pump and the meniscus pump, the fluid control device configured to control the operation of the fluid pump and the meniscus pump to maintain a continuous flow of the resist between the reservoir and the fluid dispenser; and
an imprint mechanism that operates to create the optical device by applying an imprint template to the resist that has been dispensed onto the substrate, wherein applying the imprint template creates a pattern of one or more structures in the resist, wherein the pattern corresponds to the imprint template.
2. The system of claim 1 , further comprising:
a control module that is communicatively coupled to the fluid control device, the fluid dispenser, and the imprint mechanism, the control module programmed to send signals that control operations of the fluid control device, the fluid dispenser, and the imprint mechanism.
3. The system of claim 1 , wherein the fluid dispenser is configured to dispense drops of the resist having a volume that is less than 2 picoliters.
4. The system of claim 1 , wherein the fluid dispenser is configured to dispense drops of the resist having a volume that is less than 4 picoliters.
5. The system of claim 1 , wherein the fluid dispenser is configured to dispense drops of the resist having a volume that is less than 6 picoliters.
6. The system of claim 1 , wherein the resist has an index of refraction greater than 1.6 for light with a wavelength of 532 nanometers.
7. The system of claim 1 , wherein the substrate has an index of refraction in a range of 1.5 to 2.7.
8. The system of claim 1 , wherein the imprint template includes at least two zones having structures of different heights.
9. A method for manufacturing an optical device, the method comprising:
operating a fluid dispenser that includes an dispensing mechanism to dispense drops of resist onto a substrate;
operating a meniscus pump to cause movement of the resist from a reservoir to the fluid dispenser through a first channel;
operating a fluid pump to cause movement of undispensed resist from the fluid dispenser to the reservoir through a second channel, wherein the fluid pump and the meniscus pump operate to maintain a continuous flow of the resist between the reservoir and the fluid dispenser; and
operating an imprint mechanism to create the optical device by applying an imprint template to the resist that has been dispensed onto the substrate, wherein applying the imprint template creates a pattern of one or more structures in the resist, and the pattern corresponds to the imprint template.
10. The method of claim 9 , further comprising:
etching at least a portion of the optical device to reduce a residual layer thickness (RLT) of the resist on the substrate, wherein the etching includes one or more of an application of heat or an atmospheric etching.
11. The method of claim 10 , wherein the etching further reduces a dimension of at least one structure of the pattern created by applying the imprint template.