It is a π day. Consider twitter a π. Mine is there.

Here is the 140 character Pi, suitable for twitter:

3.14159265358979323846264338327950288419716939937510582097494459230781
6406286208998628034825342117067982148086513282306647093844609550582231

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.

In the past half year, we have improved our narrow linewidth Raman fiber amplifier to 20.7 W and 3.5 MHz linewidth. By external resonant cavity frequency doubling, we have obtained up to 14.5 W CW at 589nm with an optical to optical efficiency of 83% (after an optical isolator and other optics, 17.2 W 1178 nm laser is left to couple to the cavity).

My colleagues will present the work at Photonics West 2009 (LASE 2009, 7195: Fiber Lasers VI: Technology, Systems, and Applications, Post-Deadline Session, Paper 7195-101). Below is the abstract:

20W CW, 4MHz linewidth Raman fiber amplifier with SHG to 589nm

Yan Feng, Luke Taylor, and Domenico Bonaccini Calia
European Southern Observatory, Karl-Schwarzschildstr.2, D-85748 Garching, Germany

Up to 20.7 W CW, 3.5 MHz linewidth, 1178 nm continuous-wave laser has been obtained at ESO laser labs by Raman amplification of a distributed feedback diode laser. The 1178nm laser has a linear polarization-extinction-ratio of 25dB. Frequency doubling with an LBO-based SHG commercial cavity has given 83% conversion efficiency and 14.5W CW at 589nm. The source is suitable to produce mesospheric laser guide stars as reference stars for adaptive optics. The presented narrow-band, high power Raman amplification technique might be used for a large number of different wavelength ranges.

Download the 2-page summary:
Y. Feng, L. Taylor, D. Bonaccini Calia, “20W CW, 4 MHz linewidth Raman fiber amplifier with SHG to 589 nm,” Photonics West 2009, San Jose (postdeadline paper 7195-101).

My second daughter was born earlier this month. I become a father of two just as my father. :)

Nice Sunday, but I remember I have one paper to review (it is already one week late). So I spend one hour reading the paper and preparing the report. After all these, I login in the reviewing system, there is nothing in the review queue anymore. The editor cancelled it already, without notice.

What a waste of time. I could be out with my family.

We have a new publication online now: multiwatts narrow linewidth fiber Raman amplifiers. Basically, the paper shows fiber Raman amplifier can be used to amplify narrow linewidth laser to a useful power level, while linewidth keeping narrow. This would be a surprise to most laser researchers. In this specific report, we have obtained 4.8 W, ~10MHz 1178nm laser with 27dB gain and more than 10% efficiency.

Photo by skalms

Laser 2007 is less than 20km away. But I am stuck in the lab.

I studied a little bit on Google Ajax search API over weekend. So Science Blogs Search is now Ajax-powered. :) So does Googlaser, another custom search engine I maintain.

A few photos from my Vancouver trip. I enjoy the time in Vancouver. The surrounding landscape is beautiful. Food is good as well.