New single-mode semiconductor laser delivers power with scalability:
Berkeley engineers have created a new type of semiconductor laser that accomplishes an elusive goal in the field of optics: the ability to maintain a single mode of emitted light while maintaining the ability to scale up in size and power. It is an achievement that means size does not have to come at the expense of coherence, enabling lasers to be more powerful and to cover longer distances for many applications.
A research team [...] showed that a semiconductor membrane perforated with evenly spaced and same-sized holes functioned as a perfect scalable laser cavity. They demonstrated that the laser emits a consistent, single wavelength, regardless of the size of the cavity.
The study's results are particularly relevant to vertical-cavity surface-emitting lasers, or VCSELs, in which laser light is emitted vertically out of the chip. Such lasers are used in a wide range of applications, including fiber optic communications, computer mice, laser printers and biometric identification systems.
VCSELs are typically tiny, measuring a few microns wide. The current strategy used to boost their power is to cluster hundreds of individual VCSELs together. Because the lasers are independent, their phase and wavelength differ, so their power does not combine coherently.
"This can be tolerated for applications like facial recognition, but it's not acceptable when precision is critical, like in communications or for surgery," said study co-lead author Rushin Contractor, an EECS Ph.D. student.
The study found that the BerkSEL design enabled the single-mode light emission because of the physics of the light passing through the holes in the membrane, a 200-nanometer-thick layer of indium gallium arsenide phosphide, a semiconductor commonly used in fiber optics and telecommunications technology. The holes, which were etched using lithography, had to be a fixed size, shape and distance apart.
[...] The semiconductor material and the dimensions of the structure used in this study were selected to enable lasing at telecommunications wavelength. Authors noted that BerkSELs can emit different target wavelengths by adapting the design specifications, such as hole size and semiconductor material.
Journal Reference: Scalable single-mode surface emitting laser via open-Dirac singularities, Nature (2022). DOI: 10.1038/s41586-022-05021-4
(Score: 2) by crafoo on Friday July 01 2022, @06:02PM (2 children)
I was reading a little bit about lasers the other day for fun. I didn't know that we worked on a nuclear-powered x-ray laser. Part of the Star Wars program that Reagan initiated. Here is the article I started with (from 2008): https://www.optica-opn.org/home/articles/volume_19/issue_5/features/the_history_of_the_x-ray_laser/ [optica-opn.org]
The article has a good set of references.
Anyway, really cool development in the original topic. Single-mode solid-state laser that scales well is incredibly useful. Multi-mode diode lasers are a PITA with terrible beam shapes.
(Score: 0) by Anonymous Coward on Friday July 01 2022, @06:27PM (1 child)
Yeah, coherence is really useful for a number of things. One mostly thinks about lasing from stimulated emission, since that is how it was originally done, but as long as you can generate coherent monochromatic radiation you've got a laser. For instance, the free electron laser [wikipedia.org].
(Score: 2) by kazzie on Friday July 01 2022, @07:24PM
Even more mind-bending (as I learned about in a talk yesterday) is the use of cheaper lasers to pump more expensive/complex lasers. (e.g. using a laser diode to inject coherent light into an alexandrite laser).
Back on topic, the structure of a VCSEL is so much more conductive to cheap interfacing (no need to neatly cut the edge of the silicon diode, as the light comes out of the top), that improvements in its power output and mode selectivity can only be a good thing.
(Score: 2) by Snotnose on Friday July 01 2022, @08:57PM
Back in 81/82 I took a college class in "How to build a CO2 laser". Ran across the notes from that class some 10 years ago. If memory serves, if you have basic glass blowing skills (which I had, thanks to toy chemistry sets in the 60's and 70's) and a modicum of $$$ you could build a laser that could, um, speaking hypothetically here, melt a hole is a cop car's tire from my apartment living room window.
Not that I would ever do such a thing. Mostly considering at the time I was working 40 hours a week and carrying 12 units of college credit and didn't have time to build such a thing.
The most interesting thing about that notebook was it had my phone numbers in it. 2 pages, I think I remembered 4-5 people, and knew what happened to 1-2 of them.
Why shouldn't we judge a book by it's cover? It's got the author, title, and a summary of what the book's about.