SPIE Photonics West: When Lasers Turn Green

At this year’s edition of SPIE Photonics West in San Francisco, the focus was on green laser-assisted manufacturing and micro/nano fabrication. No less than 16 presentations and an online symposium were devoted to this area of green photonics, where lasers are  used to manufacture products with a more sustainable design.

Green photonics can aid in environmental monitoring, reductions in power consumption and newer, cleaner manufacturing and energy generation. Laser R&D advances, in turn, allow fabrication of micro/nano-scaled features while at the same time providing a potential energy source.

Optoelectronics technologist Stephen J. Eglash, executive director of the Stanford University Data Science Initiative and chair of the online Green Photonics symposium:

Green lasers allow you to initiate chemical reactions and produce new kinds of materials and compounds. They can not only cut holes in steel, but assist in the creation of designer drugs and enable semiconductor processes, drive renewable energy in solar cells, save energy in solid-state LED lighting and provide more cost-efficient storage in lithium batteries.”

This opens a multiplicity of applications. DirectIndustry e-magazine is highlighting 3 areas of industrial usage.

1. Super-Fast Laser Light Boosts Fuel Efficiency

Amplitude Systèmes designed a new generation of diode-pumped ultrafast lasers for micromachining that can improve automobile fuel efficiency. While conventional lasers focus energy for great spatial accuracy, ultrashort pulse lasers add temporal focus—in the picosecond to femtosecond range—changing the light-matter interaction. The cutting benefits are huge: lack of heat diffusion eliminates defects and orifices smaller than 100 μm offer extreme precision. Gasoline Direct Injection (GDI) spray nozzles drilled with high-speed lasers enhance fuel flow and fuel distribution accuracy in vehicle engines, improving performance.

2. Laser Scribing Speeds Solar Cell Production

Laser scribing is a key technology for the cost-competitive production of thin-film solar modules based on chalcopyrite Cu(In,Ga)Se2 (CIGS), explained Andreas Burn, from Switzerland’s Berner Fachhochschule Technik und Informatik. This ultrashort pulsed laser process removes layers between deposition processes, creating monolithic cell-to-cell interconnections and resulting in only a small loss of productive area.

His team demonstrated that high-throughput laser scribing could produce CIGS mini-modules with efficiency of around 16%. The team also achieved low dead-zone interconnects of <70 µm width and a high-performance/high-throughput P3 lift-off process, reaching scribing process speeds in excess of 1m/s.

3. Laser Writing: the Future of Solar Cells

Metallic contact fingers are needed on the sun-facing side of solar cells in order to reduce ohmic losses (joule heating). For Martin F. Schumann, from Karlsruher Institut für Technologie (Germany), the loss of heating can be reduced thanks to graded-index metamaterials and free-form surfaces designed by one-dimensional coordinate transformations. Further, he demonstrated how direct laser writing of polymer structures on silicon wafers with opaque metal contacts can significantly reduce fabrication times for “masters”. This could lead to future mass fabrication via imprinting.

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