Yes, you read it right. This is the last complete deluxe SFPI kit I will be selling. (The basic SFPI kit will still be available for the forseeable future.) Inquire for alternatives.
These are the key parts to construct a confocal cavity Scanning Fabry-Perot Interferometer (SFPI, also known as a laser spectrum analyzer) optimized for 633 nm but with good performance to below 594 nm (but NOT to 532 nm) and likely beyond 700 nm. The FSR is 1.75 GHz and the finesse at 633 nm with clean mirrors should be several hundred.
The kit includes the following ONLY:
- A matched pair of high quality dielectric mirrors.
- A silicon photodiode.
- A piezo (PZT) element with a hole drilled through its center.
- Thorlabs cage parts which simplify the mounting of the mirrors and PZT.
- A lens to focus the input beam, which may improve performance.
The first graphic shows most of the parts included. The next 2 graphics show different views of the mirrors, PZT, and PD. Sorry about the poor quality photos - my digital camera isn't very good at rendering mirrors in all their glory. The coatings on these beauties are a fabulous gold color. ;-)
They are AR-coated on the other surface. The AR coating is probably
optimum at 633 nm but should be satisfactory from yellow through far
red. A typical SFPI display of the longitudinal modes of a 4 or 5 mW red HeNe laser is shown in the forth graphic. The last graphic shows the completed SFPI mounted on an adjustable base (NOT included). In that photo, the focusing lens is on the left, the input
mirror is in the center, and the output mirror on PZT is on the right.
The photodiode is hidden behind that mirror. Some mechanical skills and assorted readily available materials will be required to construct the SFPI, which will enable the longitudinal modes of most TEM00 red HeNe lasers to be displayed in real time. The third graphic shows the actual display using a set of parts similar to what's in the kit. A schematic of the confocal SFPI is shown in the fifth graphic.
An electronic function generator with ramp or triangle waveforms may be used as a driver, or one can easily be built. An oscilloscope (almost any type) or data acquisition system (not included) will be required for the display. The photo of the scan is typical of what to expect.
The approximate parameters of the mirrors are radius of curvature: 43 mm; reflectance at 633 nm: >99.5%, diameter: 7.75 mm.
In my tests of one sample of these mirrors, the reflectance was greater than 99.7% at 633 nm and the finesse exceeded 500 which may actually surpass the performance of a $5,000 instrument. The finesse fell to around 250 at 594 nm (yellow HeNe), which is still quite exceptional. At 532 nm the finesse is very low, but still might be adequate to determine if a green laser is single longitudinal mode (single frequency) and suitable for holography. At 655 nm, the reflectance appears to be even higher than at 633 nm, possibly 99.9% or more, though greater finesse may be limited by other factors like coating losses and abberations. Ther reflectance is still around 99% at 680 nm for a finesse of 150. The performance above 680 nm is not known at this time, but the finesse should still be decent to 700 nm or more. However, I cannot guarantee that all mirrors will achieve these high finesses and your mileage may vary.
All parts are new. The PZT has been modified by drilling a hole in its center.
Much more information on SFPIs may be found in Sam's Laser FAQ: Laser Instruments and Applications. Construction guidelines specific to the parts in this kit may be found at Instructions for Scanning Fabry-Perot Interferometer Kit 2 and lifetime (yours or the SFPI) email tech support will be provided.
If you have no idea what this is, I can pretty much guarantee you don't need one. Although the mirrors do make decent fish tank stones, there are much cheaper alternatives. ;-)
Due to the sensitivity of high quality laser cavity mirrors to abuse, there will be a 20 percent restocking fee if returned for any reason other than incorrect parts sent, sorry.
Thanks for looking!