Skip to main content

What quantum physicists and movie/music industry have in common

Recent attempts to purchase 780 nm laser diodes for my experiment, made me realize how much atomic physics and laser cooling labs have become entangled with the optical disk industry. Rapid developments in optical drive industry, which made Rubidium so easily accessible to every Tom, Dick and Harry working on  atomic physics few years back is now making our lives difficult by rendering, once easily available technology, obsolete faster than ever. 150 mW 780 nm laser diodes which formed the heart of 48X CD burners, could be picked up for a few bucks from Digikey or Farnell, a few years back. Diodes with similar specs are now only available from specialized industrial and research laser vendors for a price that is atleast 2 orders of magnitude higher than the price when CD burners were ubiquitous.
Ofcourse the silver lining is, with the shift towards Blu-ray, wavelengths around 400nm, which once could only be achieved with the not-so-cheap non-linear frequency doubling crystals, have now become much more easily accessible.

(Anyway, have been successful in getting a handful of obsolete 150mW 780nm diodes from some random Chinese seller on eBay at dirt cheap prices! Yet to check their mode stability though, but quite hopeful from the specs! All hail the great Chinese manufacturers. Someone said it right-- God made the Chinese, rest was "Made in China"!)
Labels:
Location: 3 Science Drive 2, National University of Singapore, Singapore 117543

Comments

Post a Comment

Popular posts from this blog

Making inactve USB Hard Disk spin down automatically in Linux.

I have a 400GB Seagate IDE HDD connected to Mars, our hostel's file-server using an USB enclosure. The USB enclosure is a cheap "Made in China" product. Consequently it has some special "features". One such notable "feature" is that the disk is kept spinning by the controller even if there has been no disk I/O for a long time. I have three other USB disks connected to the same machine, a 1TB Seagate FreeAgent Desk External Drive, a 500GB Maxtor Basics External Drive and a 2.5" 60GB Fujitsu SATA Disk inside a Transcend USB enclosure. All of these spin down themselves if there has been no I/O for sometime. Keeping the hard disk spinning unnecessarily for ever, not only wastes power but also overheats the drive, thereby reducing its life. I tried noflushd, which is supposed to force idle hard disks to spin down, but found it to be of no help. USB enclosure generally work by performing an SCSI emulation over USB. sdparm is an utility which can be use
6 comments
Read more

Force an application to use VPN, using iptables in Linux

Enforcing an application, for example a torrent client like Transmission , to always use the VPN interface or any particular network interface for that matter, is trivially simple using iptables on Debian, Ubuntu or any other GNU/Linux distro. Personally, I am running Debian Sid on the Raspberry Pi . Occasionally I use it for downloading files ( legal stuff, seriously, believe me :D  ) using Transmission Bittorrent client over a VPN connection. Sometimes it happens that the VPN connection fails and doesn't reconnect for whatever reason and Transmission continues pulling stuff directly over my internet connection, which I would like to avoid. Fortunately it is very straightforward to enforce rules based on application owner UID. Transmission runs under the owner debian-transmission in Debian (use htop to check this) and the following two lines of iptables ensures that any process with owner having UID, debian-transmission , will not use any other network interface apart from the
9 comments
Read more

Rendering LaTeX in Blogger.

Rendering LaTeX in Blogger is pretty easy thanks to the JavaScript LaTeX equation render engine from http://www.yourequations.com . To enable LaTeX rendering go to the Blogger Dashboard --> Layout --> Edit HTML . Then add the line <script> type="text/javascript" src="http://tex.yourequations.com/"></script> <script type="text/javascript" src="http://tex.yourequations.com/"></script> just before <body/> . Half the job is now done. Then, for example to render: \int_{0}^{\pi}\frac{x^{4}\left(1-x\right)^{4}}{1+x^{2}}dx =\frac{22}{7}-\pi Use the code: <pre lang="eq.latex"> \int_{0}^{1}\frac{x^{4}\left(1-x\right)^{4}}{1+x^{2}}dx =\frac{22}{7}-\pi </pre> The LaTeX code will now be displayed as: \int_{0}^{1}\frac{x^{4}\left(1-x\right)^{4}}{1+x^{2}}dx=\frac{22}{7}-\pi Ofcourse Javascript needs to be enabled in the Browser for the renderer to work.
9 comments
Read more