laser guide star – Page 4

CLEO Europe 2009, laser guide star, and Astrophotonics

On the CLEO Europe 2009 (which was already one month ago!), I presented our recent progresses in developing 589 nm laser for laser guide star adaptive optics. We had coherently beam combined two high power narrow linewidth Raman fiber amplifiers with an efficiency of 95%. After frequency doubling in an external resonant cavity, we have achieved 25 W 589 nm laser with a linewidth less than 2.3 MHz, which is limited by measurement resolution. I have put the slides online: 25 W CW Raman-fiber-amplifier-based 589 nm source for laser guide star.

The conference was intensive and very interesting for me. I noticed many talks and posters on yellow laser generation aiming at laser guide star application. Besides our works, most notable are optically pumped semiconductor lasers, long wavelength Yb fiber lasers, and Bismuth doped fiber lasers. Some new technologies may appear in the coming years, since so many researchers are looking at this direction.

I attended the talk by Prof. Joss Bland-Hawthorn on Astrophotonics. It appears that he had come to my blog and noticed my “concern“. He agreed that laser guide star is an important part of Astrophotonics. 🙂

Astrophotonics

In the current issue of Optics Express, there is a focus issue on Astrophotonics. The coordinators, Joss Bland-Hawthorn and Pierre Kern, have an introductory paper, Astrophotonics: a new era for astronomical instruments. The abstract is

Astrophotonics lies at the interface of astronomy and photonics. This burgeoning field has emerged over the past decade in response to the increasing demands of astronomical instrumentation. Early successes include: (i) planar waveguides to combine signals from widely spaced telescopes in stellar interferometry; (ii) frequency combs for ultra-high precision spectroscopy to detect planets around nearby stars; (iii) ultra-broadband fibre Bragg gratings to suppress unwanted background; (iv) photonic lanterns that allow single-mode behaviour within a multimode fibre; (v) planar waveguides to miniaturize astronomical spectrographs; (vi) large mode area fibres to generate artificial stars in the upper atmosphere for adaptive optics correction; (vii) liquid crystal polymers in optical vortex coronographs and adaptive optics systems. Astrophotonics, a field that has already created new photonic capabilities, is now extending its reach down to the Rayleigh scattering limit at ultraviolet wavelengths, and out to mid infrared wavelengths beyond 2500nm.

I think laser guide star should be an important part of Astrophotonics. They mentioned in (vi), but didn’t mention in the main text at all. Also I don’t understand why large mode area fibers are the key to generate artificial stars.

It is a very interesting issue for me, although laser guide star is suprisingly absent.