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Michael Feinberg is the Director of Product Marketing at Boston Micromachines Corporation.  He has over 10 years of marketing and engineering experience in various technology fields.  He can be reached at mrf@bostonmicromachines.com  and welcomes any comments about the content presented herein.

 

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MEMS Deformable Mirrors vs. Liquid Crystal-Based Devices

Posted by Angelica Perrone on Tue, Sep 30, 2014 @ 02:00 PM
  
  
  
  
  

New Mini mount resized 600Before Deformable Mirrors became popular in the Adaptive Optics industry, consumers would generally turn to liquid crystal-based device (LCOS) spatial light modulators to confront their challenges. Here at BMC, we regularly receive questions on how all deformable mirrors, in addition to our MicroElectroMechanical (MEMS) deformable mirrors, compare to LCOS devices. Below I have touched upon some of the top differences between the two devices that I believe should play an important factor in one’s decision to purchase a wavefront shaping device.

1)      LCOS devices are only available in a segmented architecture, where MEMS DMs offer both continuous and segmented styles in various styles and options. Although both layouts have their own advantages, most researchers favor the continuous model. Due to discontinuities between the actuators, it prevents any sharp edges within the image, making it well suited for imaging applications. Claire Max at UC Santa Cruz has explained and presented calculations on how you can achieve higher level of correction capability with a continuous mirror. Check out slide 47, which goes over her calculations here.  

2)       With MEMS DMs, we are able to offer strokes up to 5.5um (1.5um, 3.5um and 5.5um available), while LCOS SLMs are generally limited to only a stroke of 2PI in the visible region. This can be a major inconvenience for certain applications with higher amplitude aberrations. 

3)      The response time of our devices have always been much faster than any liquid crystal device on the market, while recent updates to our product line achieve even FASTER rates than before. Our devices can operate up to 60 kHz with our new high speed Kilo-S Driver or our Low-Latency Driver, whereas LCOS devices are limited to only a few hundred Hertz at best.  

4)      For the most part, LCOS devices are transmission based, causing light to be absorbed by the medium and resulting in lost light. There have been reflective devices introduced recently, however, they tend to scatter large amounts of light due to the small segment sizes. With a MEMS device, our segmented mirrors are over 98% reflective and our continuous mirrors are greater than 99%. Of course, this is the case only with the appropriate coating for the wavelength at which you are operating.  

If you're interested in learning more about the differences between MEMS DMs and LCOS devices or the differences between any other mirrors currently on the market, please feel free to contact us here.  

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FAQ: BMC Deformable Mirror Reflectivity

Posted by Angelica Perrone on Fri, Dec 20, 2013 @ 08:00 AM
  
  
  
  
  
Over the past couple of months we have been receiving an assortment of questions in regards to our products. We thought it would be a good idea to share the more popular questions and answers as they stream in to keep everyone updated.

One question that tends to be asked quite often is the reflectivity our deformable mirrors can achieve. This depends on a couple of factors such as mirror coating, protective window AR coating and the wavelength of the light. 

Figure 1

We offer gold, aluminum and protected silver coating on almost all of our deformable mirrors. When selecting a coating, you should pay particular attention to the wavelength(s) of light you use. The BMC DM Coating Reflectivity chart to the right illustrates the reflectivity of each of our standard coatings.

Our standard windows with AR coating are BK-7.  We offer a few options, depending on which size mirror you select.  For our smaller DMs, we offer the standard coatings from Thorlabs as well as a few more versatile options.  You may choose either uncoated, 350-700nm, 650-1050nm or 1050-1620nm.  We also offer a 400-1100nm window and 550-2400nm, the latter for an additional cost.  For our larger DMs, various coating options are available. We do offer customizable options for an extra fee, so please contact us with your specifications if you require this.

The N-BK7 Broadband Antireflection Coatings chart from Thorlabs below depicts the percentage of  light lost for each AR coated window. Similar curves are available for our other coatings.Antireflection coatings Thorlabs
               

If you are looking for additional information on our standard windows, please visit our friends at Thorlabs online. If you have any further questions on the reflectivity of our mirrors, click here to send us an e-mail or visit us online at www.bostonmicromachines.com

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