Spatial Light Modulator (SLM) for beam steering, optical communications, advanced microscopy and biomedical imaging

Rajesh Uppal March 7, 2023 Industry, Photonics Comments Off on Spatial Light Modulator (SLM) for beam steering, optical communications, advanced microscopy and biomedical imaging 515 Views

A spatial light modulator (SLM) is a special device that can manipulate light by modulating the amplitude, phase or polarization of the light waves in the two dimensions of space and time. This means that light is manipulated in order to obtain a desired output, and SLM is commonly used in overhead projectors such as those used in schools and office conference rooms.

A spatial light modulator is an electronically programmable device that can modulate light output based on a specific fixed spatial pattern (pixel), essentially projecting light that is controlled in either amplitude only, phase only or both (phase-amplitude). Spatial light modulator or SLM is a transmissive or reflective device that is mainly utilized for spatially modulating the phase, polarization or amplitude of a light wave in two dimensions.

The digital holography technology such as holographic imaging and holographic display are the representative field that get benefit from the SLM technology. Moreover, the SLMs have been extensively used to wave optic technologies such as beam steering, optical communications, advanced microscopy and biomedical imaging.

In particular, the complex SLM, which modulates the amplitude and phase of the incident light, is highly applicable to numerous engineering fields with display applications. The complex SLM is crucial for digital three-dimensional (3D) holographic displays. Recently, augmented reality based advanced holographic vision for metaverse or mixed reality, and emerging optical computing technology such as all optical neural networks have become the promising application fields of complex SLM technology

Spatial light modulator (SLM) technology

Synthesis of wave field is a fundamental technology. The spatial light modulator (SLM), an essential device that directly modulates wavefront of light wave, provides a way of wave field synthesis and modification at the design level. The main principle of a spatial light modulator is primarily based on the usages of either a microelectromechanical system (MEMS) or an LCD (Liquid Crystal Display) technology.

The use of LC materials in SLMs is based on their optical and electrical anisotropy. A certain gray level represents a defined average voltage across the LC cell. This voltage leads to a variable tilt of the LC molecules due to their electrical anisotropy. As LC molecules also show optical anisotropy this tilt changes the refractive index of the LC molecules (for suitable incident polarization, dependent on device version) which causes a modified optical path length within the LC cell. The addressed gray level is now converted into a phase level.

There are many types of SLMs, and one common type is the electrically addressed SLM (EASLM), wherein the image is created and changed electronically just like in most electronic displays, and which usually receives input via conventional digital interfaces such as VGA or DVI. Another type is the optically addressed SLM (OASLM), which requires a separate light input encoded with an image that it can then project on its surface, again using liquid crystals. This means that an OASLM is a secondary display that takes input from an EASLM. In a process called image tiling, the images produced with an EASLM are then sequentially transferred to different parts of an OASLM before the whole image is displayed for the viewers. This can result in high-resolution images above 100 megapixels.

The modulation performance of SLMs sets a fundamental limitation to the overall performance of wave-optic based technologies. Achieving the controllability of wave optic field distribution with high efficiency and low noise is highly desirable in common for the transmission-type SLM and reflection-type SLM

Spatial Light Modulator Enables High-Power Applications

Together with Hamamatsu, the Fraunhofer Institute for Laser Technology (Fraunhofer ILT) launched an application lab for advanced laser material processing with ultrashort pulsed (USP) laser radiation, located in Aachen, Germany. The partners jointly developed an industrial processing spatial light modulator (SLM) head that can use customized, dynamic beam shaping combined with large laser average output powers for a wide range of applications.

The new SLM from Hamamatsu can be operated up to 150 W of average output power, according to Fraunhofer ILT.

To increase the economic benefit of USP processing, research uses different hardware approaches to address the handing of increased high average laser powers with more than 100 W, which upscales processing speeds and lowers unit costs. One popular method to implement these large laser powers is to split the high-energy radiation into many individual beams. This approach is used industrially, particularly for 2D laser material processing or for the generation of periodic patterns such as filters, according to Fraunhofer ILT.

Phase masks are used to generate a parallelized beam patterns with a large number of partial beams from one incident beam. This works dynamically with SLMs or statically with diffractive optical elements (DOEs) made of glass. SLMs can dynamically change the phase pattern — and, as a result, also the beam matrix — whereas static DOEs can withstand higher average powers, according to the institute.

SLMs are particularly suitable for developing manufacturing processes that use USP laser radiation since the beam properties can be easily adapted and tailored. This applies to both the beam profile as well as the arrangement of the individual beams within a pattern. In series production, SLMs are advantageous if beam patterns must be changed dynamically during the process. If the beam parameters are known and static, DOEs are the better choice due to their insensitivity.

Now, in the joint application lab, an industry-ready prototype is set for the development of manufacturing processes, according to Fraunhofer ILT. This includes a scanner-based process head in which Hamamatsu’s high-power SLM is integrated. The head is integrated into a 3-axis machine with a 150-W USP laser. The SLM has been optimized for high average power, and though it is currently being introduced to the market, in Aachen the system with the new SLM has been used for various processes and applications since May.

The team of Hamamatsu and Fraunhofer ILT investigated the surface and volume ablation with different beam profiles and focus diameters. The flexible liquid modulator eliminates the need for tool changes. The heat distribution in the workpiece has become increasingly important when large average laser powers are applied and USP processes are scaled in speed and efficiency. With additional collaborators, Fraunhofer ILT simulated the processes completely. In this way, the energy distribution and, thus, the heat input within a parallelized beam distribution can be optimized.

Spatial Light Modulator Market

The global Spatial Light Modulators market is projected to reach USD 208.2 million by 2028 from an estimated USD 89 million in 2022, at a CAGR of 15.3% during 2023 and 2028. The rise in the applications across various industries is escalating the growth of spatial light modulator market.

Major factors that are expected to boost the growth of the spatial light modulator market in the forecast period are the quick utilization of hologram and projectors in education sectors around the world. Furthermore, the increasing need for higher bandwidth and long distance data transmission is further anticipated to propel the growth of the spatial light modulator market. Moreover, the rise in the demand of these high resolution displays in gaming, consumer electronics and advertising industries is further estimated to cushion the growth of the spatial light modulator market. On the other hand, the dearth of technical knowledge regarding spatial light modulator technology and lack of awareness amongst the users is further projected to impede the growth of the spatial light modulator market in the timeline period.

The spatial light modulator market is segmented on the basis of type, application and resolution. The growth among segments helps you analyze niche pockets of growth and strategies to approach the market and determine your core application areas and the difference in your target markets.

On the basis of type, the spatial light modulator market has been segmented into optically addressed and electrically addressed.
On the basis of application, the spatial light modulator market has been segmented into beam shaping (pulse shaping), display application, optical application, laser beam steering, holographic data storage and others.
On the basis of resolution, the spatial light modulator market has been segmented into less than 1024 * 768 pixels resolution and equal or more than 1024*768 pixels resolution.

The top 5 players account for approximately 54% of the total global market. Asia-Pacific is the largest consumer market accounting for about 54% followed by Europe and North America. In terms of type, transmissive SLM is the largest segment, with a share about 93%. And in terms of application, the largest application is beam shaping (pulse shaping), followed by optics application.

Geogrphically Spatial light modulator market comprises U.S., Canada, and Mexico in North America, Brazil, Argentina, and the rest of South America as part of South America, Germany, Italy, U.K., France, Spain, Netherlands, Belgium, Switzerland, Turkey, Russia, Rest of Europe in Europe, Japan, China, India, South Korea, Australia, Singapore, Malaysia, Thailand, Indonesia, Philippines, rest of Asia-Pacific (APAC) in the Asia-Pacific (APAC), Saudi Arabia, U.A.E, South Africa, Egypt, Israel, rest of the Middle East and Africa (MEA) as a part of the Middle East and Africa (MEA).

Asia-Pacific dominates the spatial light modulator market due to the expansion in application such as optical application, beam shaping, and display. Furthermore, the broad concentration of spatial light modulator manufacturers and rise in the need for several beam shaping and projection applications will further boost the growth of the spatial light modulator market in the region during the forecast period.

Some of the major players operating in the spatial light modulator market are Hamamatsu Photonics K.K., SANTEC CORPORATION, Forth Dimension Displays Limited., Jenoptik AG, HOLOEYE Photonics AG, Texas Instruments Incorporated., Laser 2000, PerkinElmer Inc., Meadowlark Optics, Inc, American Electric Power, Fraunhofer Institute for Photonic Microsystems, Thorlabs, Inc., and Kopin Corporation among others.