A Spatial Light Modulator (SLM) is an electrically programmable device that modulates light according to a fixed spatial (pixel) pattern. SLM are typically used to control incident light in amplitude, phase, or the combination of both.
A Spatial Light Modulator (SLM) is an electrically programmable device that modulates light according to a fixed spatial (pixel) pattern. SLMs have an expanding role in several optical areas where light control on a pixel-by-pixel basis is critical for optimum system performance. SLMs are typically used to control incident light in amplitude, phase, or the combination of both.
Several parameters help define SLM characteristics. Pixel pitch is defined as the center-to-center spacing between adjacent pixels. Interpixel gap describes the edge-to-edge spacing between adjacent pixels.
Polarized light enters the device from the top, passes through the cover glass, transparent electrode and liquid crystal layer, is reflected off the aluminum pixel electrodes, and returns on the same path. Drive signals travel through the pins on the bottom of the pin-grid array package, through the bond wires, and into the silicon die circuitry. The voltage induced on each electrode (pixel) produces an electric field between that electrode and the transparent electrode on the cover glass. This field produces a change in
the optical properties of the LC layer. Because each pixel is independently controlled, a phase pattern may be generated by loading different voltages onto each pixel.
High Voltage Backplanes = Fastest Response Times
Our SLMs use custom backplanes, and proprietary drive schemes to achieve response times down to 1 ms (wavelength dependent). Most other liquid crystal spatial light modulators utilize display backplanes built with standard Nematic liquid crystal, limiting response time to >30 ms.
Highest Phase Stability Commercially Available –Our backplanes are custom designed to allow high refresh rates (up to 6 kHz), and direct analog drive schemes. Refreshing the voltage at the pixel at rates far surpassing the response time of the liquid crystal ensures high temporal phase stability. Further, use of direct analog drive schemes, as opposed to digital dithering, reduces optical flicker as low as 0.1% (0.001 π radians). Low Inter-pixel Cross Talk - Our backplanes are custom designed to offer high voltage at the pixel (5 – 12 V), and a large pixel pitch. Further, our SLMs are built with Meadowlark Optics proprietary liquid crystal which minimizes the required thickness of the LC layer in the SLM. By maximizing the ratio of pixel pitch to LC thickness we are able to offer SLMs with minimal inter-pixel effects.
Broad Wavelength Capabilities - Meadowlark Optics is the only SLM supplier capable of offering SLMs designed for use from UV (>365 nm) up to the LWIR (8 - 12 µm). Analog is Better - All Meadowlark SLMs have been designed for phase modulation. Unlike many display LCoS backplanes which require a pulse width modulation (PWM) scheme, Meadowlark backplanes utilize analog voltages at each pixel. This results in a very stable phase response over time.
High Bit Depth Controllers - Meadowlark offers 8, 12, and 16-bit controllers to provide the most linear resolvable phase levels commercially available (up to 500). Fast transfer speeds from the computer to the SLM are offered up to 2 kHz.
Polarized light enters the device from the top, passes through the cover glass, transparent electrode and liquid crystal layer, is reflected off the aluminum pixel electrodes, and returns on the same path. Drive signals travel through. There are 2 types of special light modulators: reflective analog SLMs and transmissive SLMs.
Reflective Analog SLMs: All of our liquid crystal on silicon (LCoS) backplanes incorporate analog data addressing with high refresh rates to provide the lowest phase ripple SLMs available. User’s can select standard or high speed liquid crystal for optimal performance. Liquid cooling systems are available to remove heat via the back of the SLM chip in order to maximize optical power handling capabilities:
Transmissive SLMs: All of our liquid crystal on glass (LCoG) SLMs enable simple optical systems when low pixel counts are sufficient. Users can select single-mask or configurations for phase or amplitude modulation, or a dual-mask configuration for combined phase and amplitude modulation.
1.1 Small 512 x 512 Reflective Spatial Light Modulators,– Entry Level – Educational – Economical
Our legacy SLM is now available as our E-Series model. It is ideally suited for labs with a limited budget or researchers who do not require the high speed features of our premium SLMs, yet still demand high performance. This entry-level SLM is affordably priced without sacrificing quality.
Our Liquid Crystal on Silicon (LCoS) Spatial Light Modulators (SLMs) are uniquely designed for pure phase applications and incorporate analog data addressing with high refresh rates. This combination provides user’s with the fastest response times and highest phase stabilities commercially available. We offer both transmissive and reflective SLMs in either one or two dimensions. Phase-only SLMs can also be used for amplitude-only or a combination of both.
The 512 x 512 SLM is good for applications requiring high speed, with synchronization / triggering capabilities. The optional dielectric mirror coating provides users with 100% fill factor, which increases optical efficiency.
Features:
High speed
Pure analog phase control
High bit-depth controllers (high phase resolution)
High reflectivity option
High power handling
Synchronization / Triggering
Wavelengths from 400 – 1650 nm
Specifications:
Resolution: 512 x 512
Fill Factor: 83.4 - 100%
Array Size: 7.68 x 7.68 mm
Diffraction Efficiency*: 61 - 99%
Pixel Pitch: 15 x 15 µm
Controller: PCIe 8-bit, PCIe 16-bit, DVI 16-bit
| Wavelength (nm) | Wavefront distortion | Liquid crystal response time [standard / high efficiency] (ms) | AR coatings [Ravg<1%] (nm) | ||
| Model E512/PDM512 | Model HSP512/HSPDM512 | Model ODP512/ODPDM512 | |||
| 405 | λ/5 | 25 / 33.3 | N/A | 3 / 4 | 400 - 850 |
| 532 | λ/7 | 33.3 / 45 | 7 / 10 | 3.5 / 4.5 | 400 - 850 |
| 635 | λ/8 | 33.3 / 45 | 12 / 16.7 | 4 / 5 | 400 - 850 |
| 785 | λ/10 | 55.5 / 80 | 17.2 / 22.2 | 4.5 / 5.5 | 600 - 1300 |
| 1064 | λ/10 | 66.7 / 100 | 10 / 16.7 | 5 / 6 | 600 - 1300 |
| 1550 | λ/12 | 100 / 130 | 20 / 28.5 | 6 / 7 | 850 - 1650 |
* Diffraction efficiency of silicon backplane. Performance varies as a function of wavelength and pixel value.
Controller Models
| Model | PCIe 8-bit | PCIe 16-bit | DVI 16-bit |
| Controller phase levels | 256 / 8-bits | 65536 / 16-bits | 65536 / 16-bits |
| CPU to controller transfer time (computer dependent) | 0.6ms | 2.1ms | 16.7ms |
OverDrive Plus (ODP) for Ultra-High Speed Operation
The use of ODP has shown reductions of the liquid crystal response times by a factor of up to 8x through use of the transient nematic effect, phase wrapping, and regional calibrations. The base technology is the transient nematic effect, utilizing intermediate transition voltages beyond the target voltage needed to achieve the desired phase value. The second technology development is the use of phase wrapping, which is based on the cyclical nature of light wherein adding or subtracting 2π from any phase value in a hologram results in an equivalent hologram. Often times it is faster to switch from ϕ1 → ϕ2 ± 2π instead of switching from ϕ1 → ϕ2. ODP automatically implements the faster of the two transitions, based on the calibration data. The third technology development is the utilization of regional calibrations of an SLM. Because most optical applications require precision on the order of a fraction of a wavelength, nearly all SLMs will have some inherent phase errors across the aperture that may impact the performance of the optical system. OverDrive Plus utilizes the phase modulation capabilities of the SLM to calibrate these errors out of the reflected wave, while also utilizing the regional calibrations when determining the length of time required for the transient nematic effect on a pixel by pixel basis.
OverDrive Plus for Ultra-High Speed Modulations
Low Phase Ripple - Our Spatial Light Modulators are known for having the highest phase stability on the market. Our backplanes are custom designed with high refresh rates and direct analog drive schemes resulting in phase ripple less than 1% - 3% (depending on SLM model). Phase ripple is quantified by measuring the 1st order ripple as compared to the mean intensity while writing a repeating linear phase ramp to the SLM.
1 st order intensity when writing a phase ramp to the SLM
High Power Capability - our Spatial Light Modulators have been tested for compatibility with high power pulsed and CW lasers. In the measurements below, the optical response of the 512 x 512 pixel SLM was measured as the incident power was incremented up to a peak power density of 112 MW/cm2 . Thermal effects resulted in a reversible reduction in modulation depth, however no permanent damage was observed.
512x512 SLM tested at 1064nm
* Average power of 1W to 16W with a repetition rate of 1MHz, pulse width of 600fs, and 5.5mm beam diameter results in a peak power density of up to 112MW/cm^2, without dielectric mirror coating or active cooling
This high voltage, large pixel SLM is optimized for high power applications requiring faster response times. The analog, high fill factor, high refresh rate backplane provides better optical efficiency and high temporal stability. Large pixels reduce pixel-to-pixel crosstalk.
Our Liquid Crystal on Silicon (LCoS) Spatial Light Modulators (SLMs) are uniquely designed for pure phase applications and incorporate analog data addressing with high refresh rates. This combination provides user’s with the fastest response times and highest phase stabilities commercially available. We offers both transmissive and reflective SLMs in either one or two dimensions. Phase-only SLMs can also be used for amplitude-only or a combination of both.
The Large 512x512 SLM is good for applications requiring high speed, with synchronization / triggering capabilities. The large active area is also good for high laser power density applications.
Features:
High speed
Pure analog phase control
High bit-depth controllers (high phase resolution)
High power handling
Synchronization / Triggering
Wavelengths from 400–1650 nm, customization for MWIR or LWIR
Specifications
Resolution: 512x512
Fill Factor: 96%
Array Size: 12.8x12.8 mm
Diffraction Efficiency*: 92%
Pixel Pitch: 25x25 µm
Controller: PCIe 8/16-bit, DVI 16-bit
| Wavelength (nm) | Wavefront distortion | Liquid crystal response time [standard / high efficiency] (ms) | AR coatings [Ravg<1%] (nm) | |
| Model P512L/PDM512L | Model HSP512L/HSPDM512L | |||
| 405 | λ/5 | 3.0 / 4.5 | N/A | 400 - 850 |
| 532 | λ/5 | 4.0 / 6.0 | 1.2 / 2.0 | 400 - 850 |
| 635 | λ/6 | 4.5 / 7.0 | 1.7 / 3.0 | 400 - 850 |
| 785 | λ/7 | 7.5 / 12.0 | 2.5 / 4.0 | 600 - 1300 |
| 1064 | λ/10 | 10.0 / 15.0 | 3.3 / 5.0 | 600 - 1300 |
| 1550 | λ/12 | 15.0 / 25.0 | 4.2 / 6.5 | 850 - 1650 |
*Silicon backplane, performance varies as a function of mirror coating, wavelength and pixel value
Large 512x512 Controller Models
| Model | PCIe 8-bit | DVI 16-bit |
| Computer to controller resolution | 256 / 8-bits | 65536 / 16-bits |
| Controller to SLM resolution | 65536 / 16-bits | 65536 / 16-bits |
| CPU to controller transfer time (computer dependent) | 1.4ms | 16.7ms |
Ultra-High Speed Operation – The Large 512 x 512 SLM was designed to minimize the liquid crystal response time without the need for the OverDrive Plus approach developed for the Small 512 x 512 SLM. This native high-speed performance results in liquid crystal response times as fast as 1.2 ms, with computer-to-controller transfers speeds as fast as 1.4 ms, the combination provides a
continuous 2π phase stroke at throughputs exceeding 700 Hz.
Two Controllers – PCIe or DVI. The high-speed performance is best achieved using a PCIe controller offering 8-bits per pixel image transfers from the computer to the controller. A hardware-based lookup table (LUT) converts the 8-bits to 16-bits prior to the analog conversion for the SLM chip. The result is a linear 2π phase stroke with a phase resolution of λ/256 at frame rates up to 714 Hz. The PCIe controller also offers both input and output triggering capabilities to ease synchronization with other equipment.
A DVI controller with 16-bits of analog voltage resolution from the computer to the SLM is also available. With this controller the SLM can easily obtain more than 1000 linear resolvable phase levels. This λ/1000 phase resolution can be maintained over a broad wavelength range by tuning the look-up-tables / calibrations for the incident wavelength. The frame rate is dependent upon the graphics card used (typically 60 – 200 Hz).
Low Phase Ripple – Our Spatial Light Modulators are known for having the highest phase stability on the market. Our backplanes are custom designed with high refresh rates and direct analog drive schemes resulting in phase ripple less than 1% - 3% (depending on SLM model). Phase ripple is quantified by measuring the 1st order ripple as compared to the mean intensity while writing a repeating linear phase ramp to the SLM.
High Power Capability – Our Spatial Light Modulators have been tested for compatibility with high power pulsed and CW lasers. In the chart below, the optical response of the Large 512 x 512 pixel SLM was measured as the incident power was incremented up to a peak power density of 527 MW/cm2 , and an average power density of 518 W/cm2 . A liquid cooling system is also available to offset any thermal effects
Peak power density up to 527 MW/cm2 , average power density up to 518 W/cm2 , with a repetition rate of 123 Hz, pulse width of 8 ns, and 0.227 mm beam diameter, without dielectric mirror coating or active cooling. Damage occurred when the Ratio of Ein to Eout started climbing.
Our Liquid Crystal on Silicon (LCoS) Spatial Light Modulators (SLMs) are uniquely designed for pure phase applications and incorporate analog data addressing with high refresh rates. This combination provides user’s with the fastest response times and highest phase stabilities commercially available. We offer both transmissive and reflective SLMs in either one- or two dimensions. Phase-only SLMs can also be used for amplitude-only or a combination of both. The 1920x1152 SLM is good for applications requiring high speed, high diffraction efficiency, low phase ripple and high power lasers.
High Speed with High Phase Stability - Great care was taken in the design of the 1920 x 1152 silicon backplane to enable high speed operation while simultaneously maximizing phase stability . Engineers successfully incorporated high refresh rates with analog drive schemes to suppress phase instabilities to an unprecedented 0 . 50 – 2 . 0 % which, until recently, rivaled our standard speed systems . With the launch of our new 19 x 12 SLM, phase ripple was reduced even further to 0 . 10 – 0 . 30 % . If your application requires extremely low phase ripple, please contact a Meadowlark Solutions Engineer for more information on the 19 x 12 SLM .
Phase ripple is quantified by measuring the variation in intensity of the 1 st order diffracted spot as compared to the mean intensity while writing a blazed phase grating to the SLM.
SLM Features:
High resolution
High speed
High phase stability
Pure analog phase control
High first order efficiency
High reflectivity
High power handling
Compact design
Wavelengths from 488–1650 nm
Software Features
Input and output triggers
Image generation
Automated sequencing
Wavefront calibration
Global and regional look up tables
Hardware Interface - The 1920 x 1152 SLM system includes a PCIe controller with input and output triggers and low latency image transfers .
Diffraction Efficiency ( 1 st - order) - This is the percentage of light measured in the 1 st - order when writing a linear repeating phase ramp to the SLM as compared to the light in the 0 th order when no pattern is written to the SLM . Diffraction efficiency varies as a function of the number of phase levels in the phase ramp . An example measurement, taken at 1064 nm is shown below left, for phase ramps with 4 to 32 phase levels between 0 and 2 π . The plot below right shows sample 1 st order diffraction efficiency measurements, as a function of the phase ramp period, taken at various wavelengths.
Software - Our SLMs are supplied with a graphical user interface and software development kits that support LabVIEW, Matlab , Python, and C++ . The software allows the user to generate images, to correct aberrations, to calibrate the global and/or regional optical response over ‘n’ waves of modulation, to sequence at a user defined frame rate, and to monitor the SLM temperature.
Global or Regional Calibration s - Regional calibrations provide the highest spatial phase fidelity commercially available by regionally characterizing the phase response to voltage and calibrating on a pixel by pixel basis.
Image Generation Capabilities
Bessel Beams: Spiral Phase, Fork, Concentric Rings, Axicons
Lens Functions: Cylindrical, Spherical
Gratings: Blazed, Sinusoid
Diffraction Patterns: Stripes, Checkerboard, Solid, Random Phase Holograms, Zernike Polynomials, Superimpose Images.
High Power Capability - Our Spatial Light Modulators have been tested for compatibility with high power pulsed and CW lasers . In the graphs below, the optical response of the 1920 x 1152 pixel SLM with and without liquid cooling was measured as the incident power was incremented up to 15 GW/cm2 peak power or 410 W/cm2 average power .
A copper block is attached to the back of the SLM to draw heat out of the SLM. The copper block is attached with 2 meters of quick-disconnect tubing to cooling unit containing an external pump, radiator, and fan to cool the liquid down to ambient temperature. Includes one bottle of liquid coolant.
1920 x 1152 Analog Spatial Light Modulator Specifications
Resolution: 1920 x 1152
Array Size: 17.6 x 10.7 mm
Zero-Order Diffraction Efficiency*: 88%
Fill Factor: 95.7%
Pixel Pitch: 9.2 x 9.2 µm
Controller: PCIe 8/12-bit
*Silicon backplane, performance varies as a function of wavelength.
High Speed System –High Speed Liquid Crystal with High Speed PCIe Controller
PCIe 1920 x 1152 System Dimensions
E - Series: Educational, Economical & Entry - level
We are pleased to introduce our latest E - Series Spatial Light Modulator (SLM) . Don’t let the name fool you ; with improved specifications over our previous model, it is anything but entry - level . It is, however, economical and ideally suited for educational labs with a limited budget . Liquid Crystal on Silicon ( LCoS ) Spatial Light Modulators (SLMs) are uniquely designed for pure phase applications and incorporate analog data addressing with high refresh rates . This combination provides users with the fastest response times and highest phase stabilities commercially available . We offer both transmissive and reflective SLMs in either one - or two - dimensions . Phase - only SLMs can also be used for amplitude - only or a combination of both.
SLM Features:
High resolution
High phase stability
Pure analog phase control
High first order efficiency
High reflectivity
High power handling
Compact design
Wavelengths from 400–1650 nm
Software Features
Output triggers
Image generation
Automated sequencing
Wavefront calibration
Global and regional look up tables
High Phase Stability – We are known for having the fastest SLMs with the least amount of phase ripple on the market . Our backplanes are custom designed with high refresh rates and direct analog drive schemes, resulting in phase ripple for standard products ranging between 0.10 - 0.30% . For customers who require even better performance, customization is possible with phase ripple as low as 0.025% ( 0.0008 π radians) . Phase ripple is quantified by measuring the variation in intensity of the 1 st order diffracted spot as compared to the mean intensity while writing a blazed phase grating to the SLM.
Hardware Interface Options - The 1920 x 1200 SLM is offered with a 60 Hz HDMI Controller enabling customers to take advantage of our fast liquid crystal response times. Standard hardware includes output trigger for synchronization.
Diffraction Efficiency (1st - order) - This is the percentage of light measured in the 1st - order when writing a linear repeating phase ramp to the SLM as compared to the light in the 0th order when no pattern is written to the SLM. Diffraction efficiency varies as a function of the number of phase levels in the phase ramp. The plot to the right shows sample 1 st order diffraction efficiency measurements, as a function of the phase ramp period, taken at various wavelengths.
Global or Regional Calibrations - Regional calibrations provide the highest spatial phase fidelity commercially available by regionally characterizing the phase response to voltage and calibrating on a pixel-by-pixel basis.
Image Generation Capabilities
Bessel Beams: Spiral Phase, Fork, Concentric Rings, Axicons
Lens Functions : Cylindrical, Spherical
Gratings : Blazed, Sinusoid
Diffraction Patterns : Stripes, Checkerboard, Solid, Random Phase, Holograms, Zernike Polynomials, Superimpose Images
1920 x 1152 Analog Spatial Light Modulator Specifications
Resolution: 1920 x 1152
Array Size: 15.36x9.60 mm
Phase Ripple: 0.10-0.30% (custom as low as 0.025%)
Fill Factor: 95.6%
Pixel Pitch: 8.0x8.0 µm
Controller: HDMI 8-bit
*Silicon backplane, performance varies as a function of wavelength.
Standard Speed System -Standard Liquid Crystal with HDMI Controller
A copper block is attached to the back of the SLM to draw heat out of the SLM. The copper block is attached with 2 meters of quick-disconnect tubing to cooling unit containing an external pump, radiator, and fan to cool the liquid down to ambient temperature. Includes one bottle of liquid coolant.
Depending on the application of the XY Phase Series SLM, many different optical setups can be used for either combined phase-amplitude mode or phase-only mode.
Dimensions of E19x12 ; Dimensions of E19x12 with optional tip/tilt stage
Specifications Comparison - P1920-400-700-HDMI vs. P19x12-400-700-HDMI
| Standard 1920 x 1152 Nematic SLM System | E-Series 1920 x 1200 Nematic SLM System | |
| Part Number | P1920-400-800-HDMI | E19X12-400-700-HDMI |
| Design Wavelength (Ad) | 400 - 800 nm | 400 - 700 nm |
| Calibration Wavelength (Ac) | Select from one of 405, 532, 635 nm | Select from one of 405, 473, 532,or 635 nm |
| Array Size | 17.70 x 10.60 mm | 15.36 x 9.60 mm |
| External Window | AR coated, Ravg < 1 %, 400 - 800 nm | AR coated, Ravg < 1 %, 350 - 850 nm |
| Format | 1920 x 1152 (2,211,840 active pixels) | 1920 x 1200 (2,304,000 active pixels) |
| Pixel Pitch | 9.2 x 9.2 pm | 8.0 x 8.0 pm |
| Fill Factor | 95.7% | 95.6% |
| Zero-Order Diffraction Efficiency | 78% @ 635 nm (max varies w/ pixel val.) | 84 - 89% @ 635 nm |
| 76% @ 532 nm (max varies w/ pixel val.) | 80 - 88% @ 532 nm | |
| 74% @ 405 nm (max varies w/ pixel val.) | 84 - 90% @ 473 nm 83 - 90% @ 405 nm | |
| Phase Stroke (Double Pass) | 2n @ Ac, calibrated, ~3n @ 635, uncal. | 2n @ Ac, calibrated, ~2.5n @ 635, uncal. |
| Reflected Wavefront Distortion (RMS Calibrated) | Ac/6 @ 635 nm | Ac/6 @ 635 nm |
| Ac/5 @ 532 nm | Ac/5 @ 532 nm | |
| Ac/3 @ 405 nm | Ac/4 @ 473 nm Ac/3 @ 405 nm | |
| Liquid Crystal Response Time (10-90%) | < 12.0 ms @ 635 nm | < 14.5 ms @ 635 nm |
| < 9.0 ms @ 532 nm | < 14.0 ms @ 532 nm | |
| < 6.0 ms @ 405 nm | 13.7 ms @ 473 nm; 13.4 ms @ 405 nm | |
| Maximum Liquid Crystal Switching Frequency | > 83.3 Hz @ 635 nm | > 69.0 Hz @ 635 nm |
| > 111.1 Hz @ 532 nm | > 71.0 Hz @ 532 nm | |
| > 166.7 Hz @ 405 nm | 73.0 Hz @ 473 nm; 74.6 Hz @ 405 nm | |
| SLM Phase Levels (resolvable) | 256 linear, 2n phase, over Ad, when calibrated | 256 linear, 2n phase, over Ad, when calibrated |
| HDMI Controller Output Trigger Signal | If ordered | Included - SMA connector provides normally high TTL signal which goes low for ~200 ns when image data from CPU changes |
| CPU to HDMI Controller Phase Levels | 256 / 8 bits | 256 / 8 bits |
| HDMI Controller to SLM Phase Levels | 4,096 analog | 4,096 analog |
| CPU to SLM Transfer Time (one image) | 32.3 ms | 16.7 ms |
| Maximum System Frame Rate | 31 Hz, limited by HDMI frame rate | 60 Hz, limited by HDMI frame rate |
| Tip/Tilt Stage: | Included | Optional |
Specifications Comparison - P1920-500-1200-HDMI vs. E19x12-500-1200-HDMI
| Standard 1920 x 1152 Nematic SLM System | E-Series 1920 x 1200 Nematic SLM System | |
| Part Number | P1920-500-1200-HDMI | E19x12-500-1200-HDMI |
| Design Wavelength (Ad): | 500 - 1200 nm | 500 - 1200 nm |
| Calibration Wavelength (Ac): | Select from one of 532, 635, 785 and 1064 nm | Select from one of 532, 635, 785, 1064 nm |
| Array Size: | 17.70 x 10.60 mm | 15.36 x 9.60 mm |
| External Window: | AR coated, Ravg < 1 %, 500 - 1200 nm | AR coated, Ravg < 1 %, 500 - 1200 nm |
| Format: | 1920x1152(2,211,840 active pixels) | 1920 x 1200 (2,304,000 active pixels) |
| Pixel Pitch: | 9.2 x 9.2 pm | 8.0 x 8.0 pm |
| Fill Factor: | 95.7% | 95.6% |
| Zero-Order Diffraction Efficiency: | 79% @ 1064 nm | 85 - 88% @ 1064 nm |
| (Maximum, varies with pixel value) | 68% @ 785 nm | 76 - 79% @ 785 nm |
| 78% @ 635 nm | 84 - 89% @ 635 nm | |
| 76% @ 532 nm | 80 - 88% @ 532 nm | |
| Phase Stroke (Double Pass): | 2n @ Ac, calibrated, ~3n @ 635, uncal. | 2n @ Ac, calibrated, ~3n @ 1064, uncal. |
| Reflected Wavefront Distortion (RMS Calibrated): | Ac/10 @ 1064 nm | Ac/10 @ 1064 nm |
| Ac/7 @ 785 nm | Ac/7 @ 785 nm | |
| Ac/6 @ 635 nm | Ac/6 @ 635 nm | |
| Ac/5 @ 532 nm | Ac/5 @ 532 nm | |
| Liquid Crystal Response Time (10-90%): | < 25.0 ms @ 1064 nm | < 25.0 ms @ 1064 nm |
| < 19.0 ms @ 785 nm | < 20.5 ms @ 785 nm | |
| < 12.0 ms @ 635 nm | < 19.5 ms @ 635 nm | |
| < 9.0 ms @ 532 nm | < 16.5 ms @ 532 nm | |
| Maximum Liquid Crystal Switching Frequency: | > 40.0 Hz @ 1064 nm | > 40.0 Hz @ 1064 nm |
| > 52.6 Hz @ 785 nm | > 48.8 Hz @ 785 nm | |
| > 83.3 Hz @ 635 nm | > 51.3 Hz @ 635 nm | |
| > 111.1 Hz @ 532 nm | > 60.6 Hz @ 532 nm | |
| SLM Phase Levels (resolvable): | 256 linear, 2n phase, over Ad, when calibrated | 256 linear, 2n phase, over Ad, when calibrated |
| HDMI Controller Output Trigger Signal: | If ordered | Included - SMA connector provides normally high TTL signal which goes low for ~200 ns when image data from CPU changes |
| CPU to HDMI Controller Phase Levels: | 256 / 8 bits | 256 / 8 bits |
| HDMI Controller to SLM Phase Levels: | 4,096 analog | 4,096 analog |
| CPU to SLM Transfer Time (one image): | 32.3 ms | 16.7 ms |
| Maximum System Frame Rate: | 31 Hz, limited by HDMI frame rate | 30 Hz at 1064, 785, and 635 nm, 60 Hz at 532 nm, limited by HDMI (CPU to Controller Transfer Time) |
| Tip/Tilt Stage | Included | Optional |
Specifications Comparison - P1920-850-1650-HDMI vs. E19x12-850-1650-HDMI
| Standard 1920 x 1152 Nematic SLM System | E-Series 1920 x 1200 Nematic SLM System | |
| Part Number | P1920-850-1650-HDMI | E19x12-850-1650-HDMI |
| Design Wavelength (Ad): | 850 - 1650 nm | 850 - 1650 nm |
| Calibration Wavelength (Ac): | Select from one of 1064 or 1550 nm | Select from one of 1064 or 1550 nm |
| Array Size: | 17.70 x 10.60 mm | 15.36 x 9.60 mm |
| External Window: | AR coated, Ravg < 1 %, 850 - 1650 nm | AR coated, Ravg < 1 %, 850 - 1650 nm |
| Format: | 1920 x 1152 (2,211,840 active pixels) | 1920 x 1200 (2,304,000 active pixels) |
| Pixel Pitch: | 9.2 x 9.2 pm | 8.0 x 8.0 pm |
| Fill Factor: | 95.7% | 95.6% |
| Zero-Order Diffraction Efficiency: | 84%@1550nm (max varies with pixel value) | 85 - 91% @ 1550 nm |
| 79%@1064nm (max varies with pixel value) | 85 - 88% @ 1064 nm | |
| Phase Stroke (Double Pass): | 2n@Ac, calibrated, ~3n@ 550, uncalibrated | 2n @ Ac, calibrated, ~3n @ 1550, uncalibrated |
| Reflected Wavefront Distortion (RMS Calibrated): | Ac/12 @ 1550 nm | Ac/12 @ 1550 nm |
| Ac/10 @ 1064 nm | Ac/10 @ 1064 nm | |
| Liquid Crystal Response Time (10-90%): | < 33.0 ms @ 1550 nm | < 45.0 ms @ 1550 nm |
| < 25.0 ms @ 1064 nm | < 25.0 ms @ 1064 nm | |
| Maximum Liquid Crystal Switching Frequency: | > 30.0 Hz @ 1550 nm | > 22.2 Hz @ 1550 nm |
| > 40.0 Hz @ 1064 nm | > 40.0 Hz @ 1064 nm | |
| SLM Phase Levels (resolvable): | 256 linear, 2n phase, over Ad, when calibrated | 256 linear, 2n phase, over Ad, when calibrated |
| HDMI Controller Output Trigger Signal: | If ordered | Included - SMA connector provides normally high TTL signal which goes low for ~200 ns when image data from CPU changes |
| CPU to HDMI Controller Phase Levels: | 256 / 8 bits | 256 / 8 bits |
| HDMI Controller to SLM Phase Levels: | 4,096 analog | 4,096 analog |
| CPU to SLM Transfer Time (one image): | 32.3 ms | 16.7 ms |
| Maximum System Frame Rate: | 31 Hz, limited by HDMI frame rate | 15 Hz at 1550, 30 Hz at 1064 nm, limited by HDMI (integer multiples of CPU to Controller Transfer Time) |
| Tip/Tilt Stage: | Included | Optional |
All of our liquid crystal on glass (LCoG) SLMs enable simple optical systems when low pixel counts are sufficient. Users can select single-mask or configurations for phase or amplitude modulation, or a dual-mask configuration for combined phase and amplitude modulation.
Our two dimensional SLMs are designed for adaptive optics applications. A two dimensional array of Liquid Crystal Variable Retarders acts as a real time programmable phase mask for wavefront correction of a linear polarized source. Unwanted aberration effects are removed by introducing the opposite phase shift through the Hex SLM. The most common applications involve high-resolution imaging where viewing through an aberrant medium is unavoidable. Examples include astronomical imaging with ground-based telescopes and medical imaging through bodily fluids. High-energy laser users also benefit from active phase compensation for beam profile correction.
The linear SLM has a linear pixel array geometry. This system can be used to alter the temporal profile of femtosecond light pulses via computer control. Applications requiring these short pulses include analysis and quantum control of chemical events, optical communication and biomedical imaging. This linear SLM offers high fill factor, good transmitted wavefront distortion, and options for single or dual-plane for modulating phase, amplitude, or both simultaneously. These SLMs find use in other applications including Hadamard spectroscopy, optical data storage and wavefront compensation.
| Pixel format | Response time | Pixel pitch | Efficiency | Fill factor | Active area (mm) |
| 1x128 | 35 – 70 ms | 100 um | 85 – 92% | 98.0% | 12.80 x 5.00 |
| Hex | 1 mm | 》90% | 93.1 | 12.00Ø |
2.3 Spatial Light Modulator Controller
Our spatial light modulator controller allows for independent voltage control of up to 128 liquid crystal cells or pixels. The SLM Controller connects via USB cable to a Windows™ based computer. Supplied software allows for convenient setting of inpidual pixel retardance and for the programming of retardance profiles across a pixelated device. Custom software can be written using the included LabVIEW™ Virtual Instrument Library to allow for integration into custom applications.
Key Features
High transmission
Compact optical housing design
Computer controlled
Phase or amplitude modulation
| Optical head specifications | |
| Retarder material | Nematic liquid crystal |
| Substrate material | Optically quality synthetic fused silica |
| Center wavelength | 450-1800nm (specify) |
| Modulation range | |
| Phase (min) amplitude | 1λ optical path difference 0-100% |
| Retardance uniformity | <2%rms variation over clear aperture |
| Transmitted wavefront distortion | ≤ λ/4 (P-V @ 633) [≤ λ/10 (RMS @ 633)] |
| Surface quality | 40-20 scratch-dig |
| Beam deviation | < 2 arc min |
| Transmittance | > 90% (without polarizers) |
| Reflectance (per surface) | ≤ 0.5% at nominal incidence |
| Dimension | 7.00 x 2.96 x 0.74 in |
| Recommended safe operating limit | 500W/cm², CW 300mJ/cm², 10ns, 532nm |
| Temperature range | 10 - 45 °C |
| Controller specifications | |
| Output voltage | 2kHz ac square wave digitally adjustable 0-10 Vrms |
| Voltage resolution | 2.44mV (12 bit) |
| Computer interface | USB |
| Power requirements | 100 – 240VAC @ 47-63Hz, 1A |
| Dimensions | 9.50 x 6.25 x 1.50 in |
| Weight | 2 lbs. |
| Note that the D31258 in included with the purchase of the SLM system | |
| Ordering information | |||
| Name | Pixel geometry | Version | Part number |
| 1 x 128 | 98 μm x 4 mm linear | Phase | SSP – 128P - λ |
| Amplitude | SSP – 128A - λ | ||
| Hexagonal 127 | 1 mm across flat | Phase | SSP – 127P - λ |
| Amplitude | SSP – 127A - λ | ||
| Please specify your operating wavelength λ in nm when ordering. Custom SLM sizes and formats are available | |||
| Optional polarizers | ||
| Type | Wavelength range (nm) | Part number |
| Visible | 450 - 700 | SDP – VIS |
| Near infrared 1 | 775 – 890 | SDP – IR1 |
Includes optics & mounts for simple phase or amplitude experiments. Available pre-aligned and ready to use over 405 - 1550 nm. Available with optional camera and laser.
Spend your time on important research rather than designing an optical system for your SLM. The SLM Optics Kit provides you with a set of optics and cage-mount components enabling the user to start research with the SLM system immediately. The kit includes a Half-Wave Retarder, a pair of Linear Polarizers, lenses, and all necessary mount hardware, including a custom adapter plate to quickly align the SLM system to the optics in an off-axis configuration. Optional items are also available including a laser, beam expander optics, and a camera. This approach provides optimum efficiency with minimal design effort.
Optics Kit includes:
Polarizers and waveplates
Beam expander
Lenses
Tip/tilt stage
Base plate and posts
Laser and camera (optional)
The 1-Photon SLM Microscopy Kit is a scan-less SLM-based epi-fluorescence upright microscope that enables three dimensional calcium imaging and/or photoactivation of neurons in brain slices. The microscope can be used to excite and monitor activity of neuronal ensembles, enabling studies of neuronal circuit activity both in vitro and in vivo. Add-on to existing microscope or use as stand-alone microscope.
KEY FEATURES
Scan-less SLM-based
Fully functional programmable excitation system
Brightfield and/or Epifluorescence microscope
3D calcium imaging capability
Point and click software to define excitation patterns
Our cube provides researchers with a portable, stand-alone, optical tweezers system just one cubic foot in size. This compact instrument allows a user to optically trap and thus physically manipulate hundreds of microscopic objects in three dimensions (3D) using computer control to set and move each optical trap independently.
Optical trapping can be used to manipulate objects ranging in size from 10’s of nanometers to 10’s of microns and objects with a variety of material characteristics. Trapping examples include cellular organisms, dielectric spheres, metallic spheres, metallic nanoshells, carbon nanotubes, air bubbles, and even water droplets in air.
One application of the CUBE includes biological research. This tool enables measurements of cell properties and controlled studies of how cells interact with foreign objects. Another application example is trapping metallic objects and carbon nanotubes for engineering materials with unique thermal and electrical properties.
KEY FEATURES
Complete optical trapping system
3D particle manipulation using holographic beam control
100’s of traps (demonstrated 400)
High temporal trap stability
Spatially uniform trapping across 200x200 micron field of view
Modifications with SLMs to existing two-photon microscopes can provide noninvasive probes deep within the cortex.
Despite extensive research, brain function and neurological diseases are poorly understood. Complexities arise from the quantity of neurons in the brain and from the densely interconnected networks of intermixed cell types. Tools neuroscientists have traditionally relied upon include the patch clamp, which probes electrical activity of a single neuron, and fMRI, which images activity in volumes containing millions of neurons.
These approaches target two vastly different scales. However, it is possible that the brain functions through firing patterns in neural circuits and that neurological disease is the result of alterations to the physical structure of circuits or circuit dynamics. These circuits exist at an intermediate scale that neither patch clamp nor fMRI can readily address. In order to give neuroscientists a range of tools to study brain function, there is a need for methods that noninvasively probe the underlying microcircuitry in the brain with single-cell resolution.
Figure 1. By manipulating the wavefront of a single incident beam, the spatial light modulator (SLM) can be used to superimpose lens and grating functions with weighting functions to redirect light to arbitrary locations to simultaneously create hundreds of focal points within a 3D volume. Courtesy of Meadowlark Optics.
Over the last decade, calcium imaging and photoactivation have emerged as solutions to this problem, providing all-optical means to monitor and manipulate circuit activity1. Calcium imaging uses calcium indicators that bind with calcium to alter the fluorescence characteristics of neurons. When a neuron fires, there is an uptake of calcium into the cell body. If the firing neuron is illuminated with an excitation source during the firing event, then the fluorescence emission increases, generating an optical response that corresponds to electrical activity.
Complementary to calcium imaging is photoactivation, which can use photosensitive proteins (optogenetics) or opto-chemical (caged) compounds to manipulate firing patterns either by causing neurons to fire or by silencing neurons. This combination of calcium imaging and photoactivation offers a means for neuroscientists to record the spatiotemporal dynamics of activity and map physical structure of circuits with single-cell resolution. However, without advanced microscopes for neuroscience, the benefits of calcium imaging and photoactivation cannot be realized.
Confocal microscopes have become a core technology for biology, but have fundamental limitations that hinder their use for neuroscience. The first is slow temporal resolution from raster scanning a laser through the sample to build an image pixel by pixel. Without the ability to parallelize excitation to arbitrary locations within a 3D volume, it is impossible to monitor firing patterns of multiple cells simultaneously. This is critical for mapping connectivity of neural circuits and understanding circuit dynamics.
The second limitation is two-dimensional imaging, which is inappropriate for studies of neural circuits. This restricts studies to a small subset of the neurons and limits the scope of the circuits that neuroscientists are trying to map and understand. The third limitation is confocal microscopy’s coupling of one-photon excitation with a pinhole to block out-of-focus fluorescence emission. This results in low signal from trivially low depths in strongly scattering and absorbing samples, such as neurons within the cortex.
Two-photon microscopy provides submicron lateral and axial excitation confinement without requiring a pinhole, and the longer wavelength simultaneously minimizes scattering. When coupled with spatial light modulators (SLMs), two-photon microscopes are capable of parallelized excitation for photoactivation and volumetric imaging. SLMs can come in a variety of forms, including micromirror arrays and liquid-crystal (LC)-on-silicon modulators.
In a two-photon microscope, the micromirror array is imaged to the sample so that pixels turned on reflect light to neurons for excitation, and pixels turned off reflect light to a block. This allows a simple method to illuminate cell bodies. Micromirror arrays also offer response times on the order of 20 kHz, far surpassing the current response time requirements of neuroscience. However, because the micromirror array is an amplitude modulator as opposed to a phase modulator, it is not possible to generate lens functions for probing activity in a 3D volume or to actively redirect light from pixels that are turned off to desired focal point locations in the sample.
These limitations are overcome through use of LC-SLMs in microscopes. The SLM acts as a programmable lens manipulating the wavefront of the excitation source. In its simplest form, the SLM can be used as a programmable prism, redirecting light to a single focal point with a lateral shift. By adding prism functions together, the SLM can be used to create multiple focal points within a 2D plane. Furthermore, by adding weighting functions and lens functions, the SLM can redirect light to hundreds of focal points with a programmable intensity in a 3D volume (Figure 1).
In two-photon microscopes, LC-SLMs enable multisite 3D scanless excitation for photoactivation2,3,4,5,6, as well as high-speed volumetric imaging to record a volume of circuit activity7. This combination provides neuroscientists with a toolbox for in vivo studies deep within the cortex to better understand the physical structure of neural circuits, the relationship of firing patterns, external stimuli and the resulting behavior, and how these processes are altered in the presence of neurological disease.
Traditional two-photon microscopes contain galvanometer-scanning mirrors used to raster scan the laser focus through the sample. The mirrors are conjugate to the back focal plane of the objective. The SLM is added to the system through an additional relay prior to the galvanometer scanning mirrors (Figure 2). The addition of the SLM and two lenses transforms the function of the microscope so that it can deliver light to any location in the field of view and simultaneously excite multiple 3D sites and use a fast camera to capture their responses.
Figure 2. Optical layout of a two-photon microscope with an SLM to enable 3D photoactivation (a). Traditional scanning is used to map the locations of neurons in the sample (b, top). After the cell bodies have been found, specific cells in the field of view can be targeted using the SLM (b, middle). As the cells are excited, the response of the cell bodies can be recorded to map connectivity and record circuit dynamics (b, bottom). Courtesy of A. Packer, L. Russell, H. Dalgleish and M. Hausser, University College London.
In a typical experiment, the galvanometer mirrors raster scan the sample to find the location of cell bodies in the field of view. Holograms then are generated to modulate the wavefront of the source to illuminate inpidual neurons. This can be used to photoactivate specific cells to replicate firing patterns that have been identified or to manipulate firing patterns that have been observed. Following photoactivation, the response of the surrounding cells can be monitored to understand the impact of photoactivation on the response of the circuit.
When designing the microscope, there are several key criteria that should be considered. The resolution of the SLM determines the number of locations where light can be directed in the sample. The resolution and pixel pitch together determine the dimensions of the volume within the sample that the SLM can excite9. Ideally, the SLM will have a small pixel pitch with high resolution so it can steer to wide angles without under-filling the objective and sacrificing the lateral and axial excitation confinement.
The temporal phase stability of the SLM also is important to ensure reliable excitation. This is particularly important when piding the light among many neurons and operating near the minimum threshold for excitation. Finally, the response time of the SLM will have significant impact on replicating the spatiotemporal dynamics, which can occur at rates up to 1 kHz110,11.
The ability to manipulate firing patterns is critical to understanding circuit activity, but equally important is the ability to record the response of surrounding neurons at the highest possible frame rate. Traditional two-photon imaging systems build an image volume by mechanically scanning the objective and collecting 2D images (Figure 3). The time required to image the volume can be on the scale of minutes, which is sufficient for static samples. In neuroscience, the dwell time requirement coupled with indicators with limited brightness results in the inability of traditional two-photon imaging to monitor action potentials in complete neural circuits. This opens up the possibility of misinterpretation of action potentials because of the interaction of localized excitation with animal movement.
Figure 3. Comparison of Gaussian and Bessel imaging of a mouse dendritic spine (left). Scanning of a Gaussian focus coupled with dwell time requirements for fluorescence excitation leaves a small portion of the sample illuminated and an increased likelihood of activity occurring without fluorescence excitation. Bessel imaging monitors a volume at the same rate of 2D imaging with Gaussian illumination. The “Bessel module” easily integrates with existing 2P microscopes without software changes, enabling easy adaptation of existing microscopes and significantly enhanced capability (middle). A demonstration of the Bessel module used for imaging inhibitory neurons in a mouse. With Gaussian imaging, a series of 2D scans are required to build the 3D projection, but the Bessel module enables imaging the entire volume without axial scanning (right). Courtesy of Na Ji, Janelia Research Campus.
One solution for high-speed volumetric imaging, presented by Na Ji, group leader at the Janelia Research Campus of the Howard Hughes Medical Institute, uses a Bessel focus-scanning technology (BEST) that samples activity in a volume with hundreds of microns in each dimension in the equivalent time that a Gaussian two-photon microscope images a 2D plane6.
The module for 3D imaging is simple and widely compatible with existing microscopes, consisting of an SLM, a static amplitude mask and three lenses (Figure 3). The lenses relay the image of the SLM to the sample. The amplitude mask is a static patterned mirror that selectively transmits the first diffracted order. The optional flip mirrors at the entrance and exit of the module allow optical addition or removal of volumetric imaging so that structures can be imaged with traditional Gaussian illumination if desired. The use of SLMs here allows flexible generation of Bessel foci of varying lateral sizes, axial lengths and axial intensity distribution, permitting users to optimize BEST for specific samples.
Ji has demonstrated the approach for enabling discoveries for neurobiology by imaging the calcium dynamics of volumes of neurons and synapses in fruit flies, zebrafish larvae, mice and ferrets in vivo. Calcium signals in objects as small as dendritic spines could be resolved at video rates. High-speed volumetric imaging is a critical advancement for microscopes adapted specifically to the needs of the neuroscience community.
The combination of SLMs, two-photon microscopy, calcium imaging and photoactivation is leading to advanced tools for neuroscientists to monitor and manipulate the activity of neural circuits in the brain. The methods require minor modifications to existing microscopes, allowing researchers to inexpensively and readily adapt existing tools to support 3D photoactivation with high-speed volumetric imaging. This significantly enhances capabilities of microscopes, providing a complete tool enabling studies of neural circuits, expanding the field of view, the depth and the temporal limits at which neuroscientists can monitor and manipulate circuit activity.
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