Are there any acousto optic effects that are reversible? Like instead of using the acoustic waves to diffract light, light could generate an acoustic wave? Or at least light in the crystal could effect an existing acoustic wave, which could be detected in the RF acoustic driver electronics? This is related to an AOTF, acousto-optic tunable filter:
I'm looking for a device where light of varying frequency can generate a proportional electrical signal, either through plasmonics or mechanical phonon vibrations etc.
Back in the 80's there was a company in either Santa Clara, or Sunnyvale, CA [Exact name and location memory fails me, do remember the people were super sharp there and the principle engineer leading the effort was French] that made a voltage measuring instrument using laser light and acoustic information to infer the voltage on chips. A very interesting non-contact form of probing/measuring voltage IN atmosphere. Again from memory, the principle was based upon piezo effect being generated by the incidence of the laser light, but was not specifically a thermally related transfer.
Another form of light to acoustic energy transfer was used to create a 'very large' NonDestructive Testing Instrument [developed by Honeywell here in AZ] to inspect Beoing aricraft. The principle was to place the laser source near the ariplane, 'bang' the skin of the aircraft with a laser pulse [creating acoustic effect] and then use the same laser to see what happens to the skin of the aircraft. They also used the laser to simply 'size' the aircraft. The idea [as my understanding goes] was to data log the 'new' airplane then compare each data set taken during maintenance to that original data set. The idea was that the fuselage would change measurable amounts and the skin's acoustic transmission characteristics would change measurable amounts if the fuselage developed corrosion in the skin materials or developed cracks around rivets. [Footnote: I haven't seen the product on the market and assume the false positives were never resolvable, so they gave up] I know this isn't quite what you asked for [your question was more about converting light wavelength directly to acoustic energy]. In this case the transfer from light to acoustic was thermal. The prinicple is used in quite a few instruments. Probably find examples using google.
Thermawave. They used a pulsed laser to make the acoustic wave and a CW one to read it out, IIRC. Not very sensitive compared with using a proper acoustic transducer for RX, but noncontact is worth a lot.
On 30/12/2012 5:02 AM, Phil Hobbs wrote:> On 12/30/2012 1:46 AM, Jamie M wrote: >> Hi, >> >> Are there any acousto optic effects that are reversible? Like instead >> of using the acoustic waves to diffract light, light could generate an >> acoustic wave? Or at least light in the crystal could >> effect an existing acoustic wave, which could be detected in the RF >> acoustic driver electronics? This is related to an AOTF, acousto-optic >> tunable filter: >> >>
>> >> I'm looking for a device where light of varying frequency can generate >> a proportional electrical signal, either through plasmonics or >> mechanical phonon vibrations etc. >> >> cheers, >> Jamie > > Sure, stimulated Brillouin scattering, for example. If you crank up > your pulsed laser too high, so that you hit the SBS threshold, the > crystal just breaks into small pieces. > > The effect is pretty weak below the SBS threshold, though. Most optical > materials are amazingly linear.
Thanks, what could be a way to convert the phonons / mechanical vibrations into an electrical signal to determine the spectrum of the light source? Also in this case the light source is very low power, like a sensitive CCD is required to detect the light source.
I would like to somehow measure the phonon vibrations in the crystal, as well as put a reference vibration in the crystal, and read it out electrically or optically by measuring the crystal's vibration maybe.
The potential application could be for a low cost miniature optical spectrometer, to replace the grating and CCD with a single crystal instead, and hopefully keep good sensitivity at the same time.
I was thinking maybe the phonon energy could be magnified locally in a crystal if it the crystal's geometry was shaped to focus the phonon waves to a given location, to create the highest pressure waves at one focal point, for more effective gain in the opto-acoustic conversion. Also if there is a different layer type the phonon waves might impact against and be absorbed, or turned into surface plasmons, then maybe that could be used to generate an electrical signal.