The “twisted light” is an interesting concept which has enormous applications in advanced research fields like Super-Resolution Microscopy and optical computing. The idea behind the twisting of light is very simple. Light is an electromagnetic wave, it can be linearly polarized (possess linear momentum) and circularly polarized (possess spin angular momentum). Let us consider the cross-section of a wave perpendicular to its direction of travel, then the cross-sectional area contains oscillating mini waves having varying phases, rotating around the centre and possess orbital angular momentum (OAM). The OAM property of the light plays in the “twisting of light”. The normal prototype, in this case, is the freely propagating twisted beam referred to as optical vortex beams (OV). There are several methods to generate OVs; Computer Generated Holograms (CGH) is one among them which are created by Spatial Light Modulators (SLMs). SLM is a digital optical liquid crystal device that is controlled by a computer. Digital optics changed light manipulation and imaging in an unprecedented manner. LCoS-SLMs are just miniature liquid crystal displays having micro pixels which can modulate the phase/amplitude of a wavefront. Let us see how a SLM differs from traditional lens optics in the case of generating OVs.
- Traditional lens optics can only be able to generate one wavelength and one OAM. But, SLMs can generate dynamic vortices, arrays and several types of beams by holograms having varying refractive indices.
- Conventional optics have alignment issues, OAM mode generation issues and stability issues. On the other hand, SLM is software controlled and operated.
In microscopy, SLMs can play various roles. At the very basic level, without specialized hardware components, all traditional methods of classical microscopy can be realized by displaying the corresponding illumination and/or Fourier filter masks on a suitable SLM system. Let us see how can we exploit the great potential of digital optics through SLM in Optical Microscopy. SLM may display a diffractive optical element or DOE to reshape the illumination beam.
- SLM can be introduced in the imaging path of the microscope which will influence the image contrast by manipulating Fourier components of light coming from the sample. Zernike phase contrast can be emulated by the SLM by introducing a quarter-period phase shift between the zeroth and the first Fourier orders of the image wave.
- A variety of contrast techniques may be implemented and exchanged by simply replacing the phase mask on the SLM.
- SLM can be programmed to perform adaptive optics to correct the aberrations introduced by the optical components including those introduced by the SLM itself.
- Finally, there is also the possibility to combine a first SLM in the illumination path with a second SLM in a Fourier plane of the imaging path. This allows one to match the illumination pattern to a particular Fourier filter, which may give rise to altogether new contrast mechanisms.
Our wide range of LCoS-SLM product lines meets your needs in twisting of light most effectively and effortlessly. Our product categories are designed for Amplitude/monochrome (ARK) and Phase (SRK) applications in a selectable range of wavelength in 2K resolution (1920 x 1080 pixels) and 4K resolution (4094 x 2400 pixels). We are interested to collaborate with various labs for the development of new prototypes in optical microscopy and we can support you for better image acquisition in various optical microscopy techniques.
In addition to microscopy, other application areas of our SLMs are Optical Tweezers, WSS, DOE, HOE, Data Storage, beam shaping, holography, maskless lithography, Structured Illumination Microscopy (SIM), 3D printing, scanning, metrology and AOI.
Our latest member of the SLM family JDN714W has 4K resolution microdisplays offers 2π phase retardation at 1550 nm wavelengths of 4094 x 2400 pixels. This SLM targets diverse telecom and data centre applications, ranging from ROADM, WSS, OCM, VOA, Optical Switch and Optical Flow Switch.
Meera Kanakamma Mohan
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- Ruiz-Corona, Ulises, and Víctor Arrizon-Peña. “Characterization of twisted liquid crystal spatial light modulators.” Sixth Symposium Optics in Industry. Vol. 6422. International Society for Optics and Photonics, 2007.
- Piccardo, Marco, and Antonio Ambrosio. “Recent twists in twisted light: A Perspective on optical vortices from dielectric metasurfaces.” Applied Physics Letters 117.14 (2020): 140501.
- Zhou, Zhi-Yuan, et al. “Generation and reverse transformation of twisted light by spatial light modulator.” arXiv preprint arXiv:1612.04482 (2016).