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FAQ: BMC Deformable Mirrors for Laser Applications:Power

Posted by Angelica Perrone on Wed, Apr 02, 2014 @ 12:00 PM

Tags: deformable mirror, adaptive optics, boston micromachines, Boston University, laser beam, laser science, BMC, Mirrors, pulse, pulse width, peak power, laser pulse shaping, ultrafast lasers, laser pulse compression

About half of our customers use our deformable mirrors for laser applications, such as beam shaping or steering. We get a lot of questions pertaining to laser power and handling for both our deformable mirrors and modulators.  Below is a summary of the guidelines we use when discussing our technolgy.

The most important specification to note immediately if you are working with lasers is the damage threshold of our DM's. There are two mechanisms of failure to consider: mirror damage due to heating and coating delamination.  The first failure mode is largely governed by the average power experienced by the DM. The rule of thumb that we follow is maximum average power of 20W/cm². For the second failure mode, the peak energy is of greatest concern.  In this case, the threshold that we use is that of a standard thin-film gold metallic coating, in this case, 0.4J/cm². Depending on the DM system, the calculations may be slightly different. In order to ensure a DM is suitable for your application, we typically need to know as many of the following properties as possible: the pulse width of the laser, peak power, frequency, wavelength and beam size. This last pameter will help to determine which aperture size is required and if you need to change your beam size at all. Additional information on laser power can be found on our previous blog here.

From a power threshold standpoint, our modulator technology works similarly to our deformable mirror technology. However, it may have a slightly lower damage threshold due to the fact that the exposed surface is a thin layer of silicon nitride as opposed to the thicker polysilicon surface used for our deformable mirrors. Honestly, we do not have much experience testing the devices.  If you are interested in carrying out testing, we would be glad to lend you some modulators to test.

If you are interested in learning more about customers' experience with high-power lasers used on our DM's, please click here to read Andrew Norton's paper on laser test performed using our DMs. Also, please visit our website or contact us for questions or additional information on how to obtain a device for testing.

Improved Two Photon-Imaging Through Laser Pulse Compression with the Linear Array DM

Posted by Michael Feinberg on Fri, Dec 07, 2012 @ 09:05 AM

Tags: boston micromachines, Howard Hughes Medical Institute, Janelia Farm Research Campus, BMC, two photon, fluorescence, microscopy, laser pulse compression

In our last blog post (Fast and Precise Laser Pulse Compression with the Linear Array DM) we discussed research being done in the Cui Lab at HHMI’s Janelia Farm Research Campus that used our Linear Array DM for laser pulse compression.  In part two we examine a two photon fluorescence microscopy project led by associate Reto Fiolka at Janelia Farm that illustrates the use of the Linear Array’s potential as a pulse compressor for imaging applications using the phase resolved interferometric spectral modulation (PRISM) optimization technique.

The Linear Array pulse compressor setup was used to restore the laser pulse to its transform limited state, thus improving the ability to excite fluorescence by two photon absorption. A sample consisting of 10 micron diameter fluorescence beads (emission: 465 nm) was prepared and spread on a cover-slip. The laser beam first propagated through the pulse compressor and was subsequently focused on the sample using a 20X NA 0.5 Nikon objective. A 2D image was obtained by translating a motorized sample stage. Without spectral pulse shaping, only a weak fluorescence signal could be obtained (See figures a and c). Since the objective adds significant additional dispersion to the laser pulse, the spectral phase correction that had been determined previously using the photodiode could not be used. Therefore PRISM optimization was repeated using the fluorescence signal coming from the beads itself as a feedback signal.

Janelia Farm’s results show a dramatic increase in fluorescence signal for the optimized spectral phase (see figures b and d). The signal strength was increased by a factor of ~6.5

twophoton microscopy resized 600

 

According to Fiolka, “The tested device represents a promising alternative to liquid crystal displays, since the MEMS technology enables high filling factor, high efficiency and operation speed, exceptional phase stability and accuracy and can be used over a very broad wavelength spectrum.”

We're very excited about these results and we are currently working with other groups interested in reproducing these results on tissue samples.  Thanks again to Dr. Fiolka and the Janelia Farm group for their efforts in improving two photon imaging techniques!!

More details can be found in our Linear Array white paper which includes an application overview of this exciting project.  You can also link to the research directly using the links to the Cui Lab and the scientific publication above.