Evaluation of a Photon Sieve for Lidar Application, Year 2

The project is broken into four primary groups: modeling, manufacturing, characterization, and science application. These groups balance the process and keep the project direction towards a product that is useful in space based atmospheric lidar systems. The project structure allows for a fast turnaround of photon sieves samples from design/theory (modeling) through manufacturing using Langley facilities and into the characterization lab. Over the last year, the photon sieve samples have evolved to 15 million holes with 1500 rings. In addition the team has designed and manufactured both flexible and transparent sample versions for characterization. The photon sieve optics have been coupled with an Orbital Angular Momentum (OAM) laser signal in a characterization laboratory demonstration system. The OAM signal return carries the science data content of the observed target and focuses at the focal plane in the shape of a ring. Solar background noise does not have this OAM property to the extent of the OAM laser. This means the solar background noise focuses to a single point on the focal plane. The difference in the focusing properties between the OAM light and the solar noise light allow of a physical separation between the two signals at the focal plane. This is leveraged to increase the science signal to noise ratio of the lidar system. During the first year the project, the iterations between modeling, manufacturing, and characterization have identified that increasing the optical throughput efficiency is an area to improve the photon sieve design. A transparent photon sieve concept has been designed that shows a significant improvement in focal plane detector models. The manufacturing team has created a prototype sample for characterization. The goals for this year are:- Demonstrate the solar noise separation techniques using the OAM laser in a far field lidar measurement simulation- Manufacture/characterize 1500 ring transparent photon sieve samples- Manufacture/characterize 1500 ring reflective photon sieve samples- Manufacture/characterize 1500 ring flexible photon sieve samples- Conceptually design photon sieve lidar detector techniques. The Langley facilities are now ideal for the manufacturing of theoretical designs. Samples are limited to about 6 inches in diameter. This is enough for characterization of research samples and fast enough to iterate through numerous designs. Larger mission-scale telescope will be manufactured via contract to industry. The laser lithography and direct laser ablation techniques used at Langley are available cost effectively by industry, when an optimized sieve design is provided. The following year will focus on the demonstration of noise reduction detector techniques in a pulsed lidar environment.