Tags: deformable mirror, adaptive optics, boston micromachines, Boston University, pulse, pulse width, peak power, laser beam, laser science, BMC, laser pulse shaping, ultrafast lasers, laser pulse compression, Mirrors
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.
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:
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.
Tags: deformable mirror, adaptive optics, boston micromachines, retinal imaging, free-space communication, modulating retroreflector, segmented, laser beam, SLM, spatial light modulator, deep tissue microscopy, SPIE, BMC, imaging systems, Photonics West, microscopy, two photon, optical chopper, optical modulator, chopper, Adaptive Optics Scanning Laser Ohphthalmoscope, Joslin Diabetes Center, Mirrors
Just a few weeks ago we arrived back from the Photonics West 2014 exhibition and conference in San Francisco, CA. I wanted to share details and further observations on the show for those present at the show and those not being able to attend this year.
For the first time we made the decision to also attend the BiOS exhibition for the few days prior to PWest. Not being quite sure what to expect for booth traffic, especially since it conflicted with the superbowl, we still generated a good amount of interest for the smaller show. Our main presentations focused on our new adaptive optics-enhanced scanning laser ophthamoscope (AOSLO), the Apaeros Retinal Imaging System, which includes our Multi-DM, and the Superpenetration Multiphoton Microscopy technique, which is enabled by our Kilo-SLM and high speed S-Driver. Although both exhibits generated respectable notice and positive feedback, most people were familiar with the Superpentration Multiphoton work being done. Either wanting to try two-photon microscopy themselves or already in the process of doing so, our Kilo-SLM paired with our high speed S-driver presented data that was intriguing to most.
After wrapping up BiOS, we headed to the opposite side of the South hall at the Moscone Center for a larger booth setup for PWest. Here we had our entire mirror family on display, as well as live demonstrations of the Reflective Optical Chopper and Wavefront Sensorless Adaptive Optics Demonstrator for Beam Shaping (WSAOD-B). For this part of the exhibition, I would say our deformable mirrors produced the most attention, most likely due to our wide assortment of shapes and actuator counts up to 4092. The WSAOD-B live demonstration did generate a great deal of attention, as most people are unaware of how sensorless AO works. Besides our deformable mirror line, I would still say the Multiphoton Microscopy overview was initiating even further interest here as well.
Overall BMC had a great show and it seemed well worth it to expand our exhibit onto BiOS beforehand. Although this was my first time attending the show, I noticed every inch of space at PWest being used for exhibitor tables and booths, even setting up in front of the bathrooms! I hope to see PWest advance even larger, maybe one day expanding to its third space, West Hall. I look forward to next year’s show and hope to reconnect with you all again throughout the year.
If you were not able to attend the show and would like any information on the products mentioned, please visit our website and download our whitepapers.
Happy New Year! Hope everyone had a great holiday and is staying warm.
To continue addressing our FAQ's, another recurring question BMC recieves is on the flatness of our deformable mirrors. The figure below shows an unpowered BMC DM and a flattened BMC DM.
The surface figure of our unpowered deformable mirrors has a low-order surface bow. The amount of stroke needed to flatten the DM is between .5 µm and 1 µm, depending on the model. We can guarantee that the stroke needed to flatten the deformable mirror will not exceed this amount and tends to be lower for the lower stroke devices.
However, researchers in the past have been able to achieve flattening the wavefront without using up any stroke on the DM. If you are able to include additional optics into your setup, the low order bow can be taken out with static optics. Just something to keep in mind as you are designing your system and trying to determine how much stroke is required to achieve your wavefront correction needs.
If you have any additional questions in regards to the flatness of our mirrors or are interested in seeing what the typical unpowered surface figure is, please contact us at firstname.lastname@example.org or visit us online at www.bostonmicromachines.com
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.
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.
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
It has been quite some time since our last blog post due to a great deal going on at BMC! Alongside some new product releases, we recently made a few adjustments and updates to our ophthalmic imaging instrument, the Adaptive Optics Scanning Laser Ophthalmoscope (AOSLO) which we are releasing early next year.
This next-generation instrument allows in vivo retinal imaging on a cellular level and is currently undergoing beta testing at the Beetham Eye Institute at Joslin Diabetes Center, led by Dr. Jennifer Sun and her team. There it is being used to directly quantify features such as cone density, microaneurysm size and measure blood flow through the microvasculature in the retina. By pairing a Scanning Laser Ophthalmoscope (SLO) with advanced Adaptive Optics, it offers the advantage of imaging the retina at a resolution 2-3 times that of a standard SLO.
The AOSLO is also capable of measuring various properties of retinal cone physiology. Due to its enhanced imaging and software, it enables evaluation of the following attributes:
- Cone Density
- Nearest Neighbor Distance
- Voronoi Tessellation Tile Area
- Effective Radius
- Packing Factor
The AOSLO’s ability to measure such features allows early stage detection of visual decline due to diabetes. This can be identified by the decrease in cone regularity, cone mosaic changes, cone reflectance and a decrease regularity of cone spacing. This function of the AOSLO can help determine early treatment plans for patients and generate further investigative studies.
When testing out the AOSLO at Joslin, we found something very interesting out about our CEO, Paul Bierden. The pictures below depict his own retina, discovering that he has a microaneurysm! This was unexpected news, since normally it would be undetectable by any other retinal imaging systems. 30% of the microaneurysms imaged using the AOSLO at Joslin were not visible in fundus photos. The AOSLO is able to accomplish this by evaluating the vascular and neural retinal planes in vivo with cell-scale resolution. The pictures below also point out the microaneurysm attributes that can be measured. They are:
- Presence of lumen clot
- Wall reflectivity
Lastly, the AOSLO is able to measure small-vessel blood flow. This is done with the help of its enhanced imaging qualities, instrument optimization and post-processing software. By stopping a horizontal scan over a blood vessel, it can measure the blood velocity by tracking the moving erythrocytes over a scanning line. With this information, researchers can produce a blood velocity profile for retinal vessels. See the video below to see how it’s done!
If you have any interest in using the AOSLO, let us know! Please give us a call and let us know about your research. We are accepting orders for the new instrument and are open to collaborative grant applications to secure funding. If you are interested in seeing the AOSLO in action, we are setting up appointments now for the next few months. We hope to hear from you soon!
Tags: deformable mirror, adaptive optics, boston micromachines, UAV, free-space communication, modulating retroreflector, pulse, pulse width, laser beam, CLEO, laser science, biological imaging, deep tissue microscopy, BMC, laser pulse shaping, ultrafast lasers, two photon, optical chopper, optical modulator, chopper, AOM, acousto-optic modulator, speed, shutter
It's been a few weeks since we returned from 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.
Tags: adaptive optics, boston micromachines, product information, response time, free-space communication, modulating retroreflector, pulse, CLEO, BMC, ultrafast lasers, optical chopper, optical modulator, chopper, AOM, acousto-optic modulator, SNR, signal-to-noise, speed, shutter
As Boston Micromachines' newest member, I would first and foremost like to introduce myself. My name is Angelica and I have joined the BMC team as their Marketing and Communications Associate. It has been some time now since our last blog and I thought it would be appropriate to discuss our most recent product; The Reflective Optical Chopper, or ROC.
Optical Choppers, being frequently used for signal recovery in improving signal-to-noise ratio, are used to convert a continuous laser beam into a chopped one. Traditional Optical Choppers offer various pains, such as the need to alter the beam size to fit through wheel spokes, challenging stability at low speeds, the need for costly lock-in amplifier equipment and complex calibration procedures. The innovative, low-cost ROC simply eliminates all of these, outperforming traditional optical choppers.
Drive electronics are paired with BMC’s MEMS Optical Modulator technology to create the ROC. The ROC provides beam chopping at impressive speeds without beam size modification. With a frequency range of DC to 150 kHz with better than 40 µs response time, control increments of .01 Hz and a contrast ratio exceeding 90% up to 100 kHz, the value of the ROC ‘speaks’ for itself. For signal-to-noise ratio improvement, the drive signal can be used as the sync signal, allowing it to be painlessly synchronized.
Many industrial, scientific, medical, aerospace and military applications call for the need of reliable and advanced equipment. The ROC has superior capabilities such as high speed, large frequency range, reliability, stability and usefulness in SNR improvement applications. Basically, the Reflective Optical Chopper is an advance in optical chopping technology which is available at a low price.
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
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.
Ultrafast 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.
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.
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