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BMC Optical Modulator used in scanning photocurrent microscopy (SPCM)

Posted by Angelica Perrone on Thu, Dec 11, 2014 @ 11:22 AM

Tags: laser beam, laser science, optical modulator, acousto-optic modulator, pump probe

Ajou University in Korea has recently reported on femtosecond scanning photocurrent microscopy using our Optical Modulator devices. In this application Ti:Sapphire lasers were divided into pump and probe beams, then focused on the samples using an objective lens, while a pair of two-axis steering mirrors were used to manipulate the positions of both focused laser spots. Our optical modulator was then used to modulate the probe pulse at 20 kHz to capture the photocurrent generated by the probe pulse signals and filter out the photocurrents generated directly by the pump pulse. It is noted in their paper that “this modulator is advantageous over the acousto-optic types because it is free from the dispersion effects and delivers better spatial resolution for the focused laser”. Figure 1 shows the setup of the experiment.

 Park  Paper SchematicFigure 1. Schematic of experiments. (a) Schematic diagram of ultrafast carrier dynamics in a semiconductor nanowire device. (b) Schematic diagram of the experimental setup (CM, chirped mirrors; DM, optical modulator).


  For the results on combining scanning photocurrent microscopy and ultrafast pump probe techniques, head to ACS Nano to read the full paper.

If you would like further information on BMC's Optical Modulator technology and the Reflective Optical Chopper, which includes a high-speed driver for the Optical Modulator, please contact us here.

 

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.

FAQ: BMC Deformable Mirrors: Windows

Posted by Angelica Perrone on Wed, Mar 26, 2014 @ 09:51 AM

Tags: deformable mirror, laser beam, laser science, ultrafast lasers, CW, Coatings


For those interested in using our deformable mirrors with laser applications, there are a few common questions which are asked in regards to the AR-coated window and if it is/can be removable.  Below is a summary of what's standard and what's possible:

Both the optical modulator and our DMs are protected by a 3mm thick window, which are standard BK-7 windows from Thorlabs. The options for windows are: 

  • 350-700nm
  • 400-1100nm
  • 650-1050nm
  • 1050-1620nm
  • 550nm-2400nm

This can also be customized upon request. The windows are mounted on a 6° angle in order to prevent ghosting. 

A lot of requests are in regards to removing the protective window. For our standard DMs, the window is not removable as it is attached with an epoxy. For our modulators, the window IS removable. We highly recommend you DO NOT REMOVE the protective window. The only exception to not having an AR-coated window would be if the DM was operated in a clean room environment.  In this case, we can deliver the modulator or DM without the window and include a protective removable lid instead. In addition, we recommend flowing Nitrogen at a very slow pace around the mirror to ensure the humidity remains low around the DM. The required humidity is <30% as the mirror is made of polysilicon which needs to be protected from corrosion. 

 Please visit our website or contact us for additional questions.

deformable mirrors, BMC,adaptive optics

Further focus at CLEO 2013

Posted by Michael Feinberg on Tue, Jul 09, 2013 @ 12:54 PM

Tags: deformable mirror, adaptive optics, boston micromachines, laser beam, laser science, biological imaging, deep tissue microscopy, BMC, two photon, free-space communication, modulating retroreflector, optical chopper, optical modulator, chopper, UAV, pulse, pulse width, laser pulse shaping, ultrafast lasers, CLEO, AOM, acousto-optic modulator, speed, shutter

It's been a few weeks since we returned frocleo resized 600m the Conference on Lasers and Electro-Optics 2013 and now that we're settled back in to the daily routine, I thought I would give some highlights on the show. I was happy to be joined this time by our new Marketing and Communications Specialist, Angelica Perrone, who did a great job navigating the complex photonics market for the first time.

While the conference seems to be chugging along at a nice pace, the tradeshow has most definitely become a smaller venue.  We were once again hosted by our strategic partner, Thorlabs (thanks, again guys!) and being in such a central location on the floor, we were able to get a good flavor for the pace of the show.  Here are my thoughts:

Little, different, yellow, better

Anybody get that Nuprin reference?  Anybody? See what I 'm talking about here.

Okay, so it's not yellow (although yellow lasers are cool), but the show is definitely getting smaller.  I mentioned to a colleague that since the show is in San Jose for the second year in the row, it seemed like the barriers on either end of the tradeshow floor had moved in just a bit. 

As far as different, the show is not like other photonics shows in that it is pretty focused in its applications.  While there were some interesting talks on microscopy, this was a small portion of the material, with most others focussing on more laser-centric applications, as the title of the conference implies. 

As far as better, I would say that for BMC, it was most definitely better for our new products:  The Reflective Optical Chopper(ROC) and the Linear Array DM.  We recieved more interest in these products over our legacy deformable mirror technologies. This is exciting for me as a product marketer and salesperson and even moreso as a member of a company that is always looking for new avenues for our technology. We see the ROC being useful for users who span from pure laser scientists to imaging engineers interested in chopping a beam at high speed with either a constant or variable duty cycle.  The linear array has already proven useful in pulse shaping applications as described in our whitepaper, which is available for download here.  Both products are available for purchase now.

Our Wavefront Sensorless Adaptive Optics Demonstrator for Beam Shaping (WSAOD-B)also generated some buzz. More and more applications which require wavefront correction are surfacing and need a solution without a wavefront sensor.

In all, it was a good show that has given me and my team work to do as we explore more exotic applications for our technology.  I look forward to joining the show again next year and I hope to connect with all of you again in the near future!

For more information on the products mentioned above, please visit our website and download our whitepapers.

Fast and Precise Laser Pulse Compression with the Linear Array DM

Posted by Michael Feinberg on Wed, Nov 07, 2012 @ 10:33 AM

Tags: deformable mirror, adaptive optics, boston micromachines, laser science, Janelia Farm Research Campus, microscopy, laser pulse shaping, ultrafast lasers

Linear ArrayUltrafast lasers have been extensively used in ground breaking  research including two Nobel Prizes.  Applications within spectroscopy, photochemistry, laser processing and microscopy are widespread.  However, to capitalize on such short laser pulses, a pulse compressor is required to compensate for the dispersion induced by optical elements. Liquid crystal based spatial light modulators are most commonly used in laser pulse compressors.  Although a proven technology in display applications, liquid crystals have drawbacks including phase jitter and a limited fill factor.  Researchers at the Cui Lab at HHMI’s Janelia Farm Research Campus looked to Boston Micromachines Corporation’s prototype Linear Array Deformable Mirror (DM) to address these challenges.

To evaluate the performance of the pulse compressor, the laser pulses were analyzed with frequency resolved optical gating (FROG) using a commercial instrument (Grenouille, Swamp Optics, Atlanta, GA). In Figure a and b, the temporal and spectral profile of the pulse is shown when a flat wavefront is displayed on the DM. Evidently, the pulse is distorted and the spectral phase is not flat at all (a flat spectral phase is required for a transform limited pulse). Next, the beam returning from the pulse compressor was focused with a concave mirror onto a GaAsP photodiode and the resulting nonlinear signal was used as a feedback for the correction algorithm. After optimization using a technique called Phase resolved interferometric spectral modulation (PRISM), the temporal profile (Figure c) shows a dramatically shorter, Gaussian shaped pulse. The spectral phase is perfectly flat (Figure d) with less than 0.01 radians phase error and is stable in time. These results suggest that the precision and stability of the Linear Array DM allows close to perfect restoration of transform limited laser pulses.  For more information on the optimization technique, you can access a scientific publication here.

 

 pulse compression, FROG, pulse shaper

 

In our next blog post, we will discuss the results of the use of the Linear Array DM in an interesting two-photon microscopy experiment.

More details can be found in our Linear Array white paper which includes a more detailed description of this application.

What Do You REALLY Want in a Deformable Mirror?

Posted by Michael Feinberg on Wed, Oct 17, 2012 @ 04:00 PM

Tags: deformable mirror, adaptive optics, response time, laser science, mirror technology, microscopy, astronomy

This past summer, Boston Micromachines Corporation conducted a survey of nearly 300 members of the business and scientific community to find out what features were valued in a deformable mirror for adaptive optics and other wavefront correction applications.  Respondents came from our three major vertical markets: microscopy, deformable mirror survey resized 600astronomy and laser science.  In this survey, we asked some fundamental questions and had respondents choose between three DMs with properties varying in categories of actuator count, stroke, response time and price in various combinations. We were able to drill down to what each respondent valued.  Here are some of our key findings:

1)      Actuator count was the most valued property

Across all verticals, this was true.  Overall, respondents preferred an  average of 1000 actuators. While microscopists preferred 140 actuators by almost 2 to 1 over other models, those who identified as laser scientists were looking for an average of 1001 actuators and astronomers preferred, on average, 1800 actuators.

This was very interesting to us considering we are the only player in the market to provide deformable mirrors with these actuator counts as standard products or are developing DM systems which meet these specific needs (we have a 2000 element mirror in the works).

2)      High speed is important

The most frequently chosen option for response time amongst laser scientists was 50μs and all other disciplines preferred average response better than 300μs. This is great news for the industry considering that most mirror architectures can respond adequately to meet the needs of the users. Our DM architectures are available with response times up to 22μs and we are able to drive these mirrors with our X-Driver (response time down to 4μs), satisfying high speed requirements as well.

3)      Low price is desired

As we hear so often, most users were looking for low-priced devices. This was the second    preferred property after actuator count. While those of us in the industry talk about lower prices with higher volumes, the volumes just haven’t been there yet to make this prophecy come true.  The hope in the future is that the DMs based on scalable technologies, such as MEMS, will take off and lower-priced devices will be available.

We definitely learned a lot from this survey, above and beyond what is mentioned above.  If you have any questions about our methods or are interested in discussing more specifics about the responses, I would be glad to chat further.  Just contact me at support@bostonmicromachines.com.

 

Wavefront Sensorless Adaptive Optics Now a Reality

Posted by Michael Feinberg on Mon, Oct 01, 2012 @ 11:57 AM

Tags: deformable mirror, adaptive optics, boston micromachines, laser beam, laser science, mirror technology

WASO for blog

 

Up until recently nearly all adaptive optics (AO) systems used wavefront sensors for correction. But with recent advances, off-the-shelf wavefront sensorless AO is becoming a reality.  Benefits of this type of AO include enhanced aberration correction due to the elimination of non-common path errors and wavefront sensor noise.

BMC has developed a Wavefront Sensorless AO Demonstrator (WS-AOD) which provides a platform for utilizing metric-based wavefront control with BMC MEMS deformable mirror (DM) technology. While conventional AO systems perform closed-loop DM control using direct measurements of the wavefront as feedback, the metric-based approach uses details in the aberrated light to improve clarity. Two versions are available; one is optimized for beam shaping applications and the other is designed for imaging applications.

We see laser beam shaping as a key area in this exciting technology and our demonstrator is built to address the unique challenges of this field. Our WS-AOD serves as an introduction to wavefront sensorless adaptive optics principles. It allows users to understand the details involved in properly implementing a metric-based adaptive optics solution on an optical system. The demonstrator can also be used as a stand-alone aberration compensator. By introducing aberrations in the sample stage, the system can be optimized for a multitude of use cases from laser research applications to scanning laser microscopy. Additionally, the user can easily integrate the hardware into an existing optical system and utilize the open source software code for metric-based correction.

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Schematic of WS-AOD for beam shaping applications. Also available for imaging applications.

To compensate for phase aberrations the WS-AOD uses BMC’s deformable mirror (DM) technology. BMC’s DM is a continuous facesheet deformable mirror that is controlled by hysteresis-free electrostatic actuators located on a square grid. The full DM activemulti DM aperture can be as little as 1.5 mm to as much as 25 mm across. Each actuator can provide up to 5.5 µm of mechanical stroke, which corresponds to about 11 µm of phase control. The electrostatic actuator array is driven using independent high voltage channels with 14-bit resolution. This corresponds to sub-nanometer displacement precision. The drive electronics can provide frame rates of from about 4.6 kHz up to 100 kHz.

The control software for WS-AOD allows the user to correct for aberrations introduced as well as generate a random aberration using the DM. The software is open source code based in Mathwork’s Matlab and runs on platforms using Windows operating systems. By utilizing the included algorithm to manipulate the mirror surface, the mirror compensates for aberrations and converges to an optimal profile. The user has access to the open source code to balance correction capability between maximum signal and minimal time.

To learn more please click here for a copy of our Wavefront Sensorless Adaptive Optics white paper.

CLEO 2012: Concentrated Interest in Adaptive Optics

Posted by Michael Feinberg on Wed, Jun 06, 2012 @ 03:49 PM

Tags: deformable mirror, adaptive optics, boston micromachines, laser science, biological imaging, astronomy, CLEO

BMC at CLEO

This year, the CLEO Conference had its normal interesting character:  A variety of users from hardcore laser scientists to focused business interests to laser scanning imaging folks.  BostonMEMS Optical Modulator Micromachines took our position within the Thorlabs booth for the 5th year(thanks again, guys!) and demonstrated some great technologies that we think will make an impact in the industry.  Our MEMS Optical Modulator  generated a fair amount of interest and prompted some great questions about its capabilities and possibilities.  We showed its flexibility by demonstrating how with a simple input signal and an amplifier, a reflective diffractive element can be used to couple light into a fiber at varying frequency and amplitude.  We went into the show thinking this would be the big topic of conversation.  While we did have some great conversations and we’re more than happy with the response, the real star of the show was our Wavefront Sensorless Adaptive Optics Demonstrator for Beam Shaping. Users from all walks of the laser industry approached me with potential uses from wavefront characterizationWavefront Sensorless Adaptive Optics Demonstrator techniques to photon counting.  I learned that the simplistic nature of the kit (maximize a signal through a pinhole) allows researchers with very different backgrounds to think of interesting ways to take advantage of its versatility.  We found that the simple, clear spot on the screen was enough to entice microscopists and laser scientists alike to brainstorm interesting ways in which to integrate the deformable mirror, detector and algorithm of the system into their latest work.  I am looking forward to some great follow-up conversations!

I did get the chance to venture out of the booth for a few talks as well as touch base with some new and old friends.  Major impressions:

1)      AO is still not a major player in laser science

While there were some interesting topics and uses of deformable mirrors and spatial light modulators, the technique is by no means pervasive as in other industries such as astronomy or biological imaging.  Other techniques such as MIIPS (congratulations again, Dr. Dantus) serve the industry and are well proven to be able to satisfactorily shape pulses. Another theory:  Laser scientists prefer to go after the laser for improvements instead of supplementary hardware.  This could be for a variety of reasons such as: a) extra hardware means lost light, b) this is where they are comfortable and love to tweak things or c) the cost is just too high right now.

2)      Beam characterization is becoming more affordable

With a few companies introducing higher speed and lower cost wavefront sensors, the market is becoming more accessible to more researchers.  This can only be good for everyone.

3)      Booth traffic is down, but more focused

In past years, my conversations were usually an even split between educating the visitor about the basics and having in-depth discussions about the capabilities and possibility of integrating devices into optical systems.  This year, the split was more like 75/25 in favor of detailed discussions.  Many are well aware of the background and of the 75%, at least half approach me with well thought-out ideas.  It is very refreshing and encouraging to have these discussions and I suspect the ratio will continue to grow as years go by.

Overall, it was a productive show.  I look forward to returning to San Jose next year and introduce exciting products that we have in our product roadmap and get more people to shape their light!