3719 Warren Avenue Bellwood,
Illinois 60104 USA






Applications of Acousto-Optic Tunable Filter

Acousto-optic tunable filter (AOTF) is an optical bandpass filter which operates using acousto-optic modulation. When an RF signal excite an attached piezoelectric transducer, vibration of its crystal of tellurium oxide (TeO2) vibrates.

As the acoustic waves travel throughout a TeO2 crystal, periodic changes in its refractive index produce periodic variations which act like diffraction gratings. Diffraction occurs only within a narrow wavelength range when phase-matching conditions exist between acoustic and optical waves.

Optical Coherence Microscopy (OCM)

Optical coherence microscopy (OCM) is a non-invasive micrometer resolution imaging technique with sub-millimeter resolution that offers a non-invasive alternative to live fluorescence microscopy, and has become the standard method for 3D structural and functional imaging in vivo. OCM can be used for imaging various biological systems including oogenesis and embryonic development, in situ gastrointestinal tissues and eye. Furthermore, it’s used in diagnosis and treatment of diseases such as glaucoma, age-related macular degeneration and cone rod dystrophies.

OCT uses a low-coherence, broad bandwidth light source to perform imaging using interferometry (Fig. 1). Light is split and combined from reference arm and sample arm; its path length between these arms is then measured to detect whether any photon has returned through tissue in return for measurement; this data enables reconstruction of tissue surface in pixels.

Acousto-optic tunable filters (AOTFs) are electro-optical devices that simultaneously change both intensity and wavelength of multiple laser lines from multiple sources without moving mechanical components. An AOTF uses a birefringent crystal which changes optical properties when an acoustic wave interacts with it, altering diffraction properties of its crystal for rapid wavelength tuning.

OCT microscopy stands out from other types of optical microscopy in that it does not suffer from scattering caused by light reflection or backscattering, making it particularly well suited for high resolution imaging. Furthermore, its unique acousto-optic filter makes synchronizing laser illumination with other microscopy operations such as automated stage movements or time-lapse recording more manageable than with other forms.

OCM can be an invaluable tool for visualizing cellular processes, including pronuclei formation and movement, cell division and nuclear architecture analysis not available with traditional imaging. Furthermore, OCM offers unique insight into tumor molecular mechanisms.

As part of an effort to enhance OCM image quality and the monitoring of embryonic cellular processes, we developed the Diversified Time Interval Scanning Protocol (DTIsp). This protocol allows a beam to scan samples for various milliseconds (Fig. 1c), seconds (Fig. 1e), or tens of seconds (Fig. 1f), before returning back to their same position within an appropriate period. Spatial and temporal averaging is then performed on acquired data in order to reduce speckle noise and produce high quality structural images; OCM images acquired are presented either linearly or logarithmically according to mappings (Figs 1,2).

Biological Microscopy

Biological microscopy has quickly become an indispensable tool in studying biological materials. Over the past several years, this field has significantly advanced, with new methods developed for analyzing living cells and tissues for everything from molecular imaging to the detection of cancerous tissue.

An Acousto-Optic Tunable Filter (AOTF) is one of the most frequently employed tunable filtering technologies for microscopes, using sound waves to attenuate light by changing both its amplitude and frequency – this versatility makes AOTFs highly adaptable for use across many applications.

Acoustic tunable filtering is a straightforward process: two coherent acoustic waves interact and interfere to form a periodic structure known as a refractive index grating, which matches well the periodic variation in refractive index that often occurs among crystals.

Acoustic tunable filters have many applications, from the detection of bacteria pathogens to use in spectral imaging systems that capture spatial and spectral information about samples. A double-path acousto-optic spectrometer uses double transducer filters to gather spectral information from both line polarized beams then organize it into the entire spectrum of samples being scanned.

Hyperspectral imaging is another use for acousto-optic tunable filters. Here, both spatial and spectral information is acquired using an AOTF coupled with an intensified charge-coupled device detector for image analysis.

Spectral imaging provides a high level of detail when it comes to detecting various diseases in living organisms, such as cancer. Scientists can use this technology to visualize cellular and molecular structures of their target organism. Furthermore, this tool is particularly beneficial when assessing animal health statuses through identification of cancerous tissues through fluorescent molecules’ differences in spectrum – one way of doing this being through identification of cancerous tissues by their fluorescent emission wavelength differences.

An innovative method for performing double-path spectroscopic imaging in an HSI system relies on using a multi-layered thin-film acoustic tunable filter which can be rotated according to incident light, providing greater versatility than existing technologies and potentially wide applicability in HSI.

Optical Interference Reduction (OIR)

Confocal laser microscopy utilizes acousto-optic tunable filters to adjust both wavelength and intensity of illumination for regions of interest, making them particularly helpful when performing photobleaching experiments where higher intensity beams must be targeted at specific features in order to measure excitation ratios or fluorescence recovery after photobleaching (FRAP).

An acousto-optic diffraction filter is an optical device that works by altering the refractive index of solid crystal in response to acoustic waves, controlled by digital signal processor. This modification affects its diffraction properties and its ability to tailor laser wavelengths at specific values.

Acoustic-optic tunable filters use birefringent crystals that exhibit periodic variations in their lattice structure and refractive index due to oscillating acoustic waves; when these waves interact with the crystal they cause periods of compression and rarefaction that change its refractive index to produce diffraction.

Acousto-optic tunable filter performance can be altered through the addition of metallic thin-film coatings in various spacer elements or structures that serve as blocking/attenuating components, including spacer elements used as spacer elements or blocking components. These interference coatings typically utilize either one dielectric material or multiple dielectric materials; some broadband devices, however, utilize metallic-dielectric-metal (MDM) cavities with both interference coating and blocking/attenuating coating in one spacer element – an MDM cavity incorporates both.

Due to their primary function as filters of collimated light, interference coatings’ performance and bandwidth will vary when incidence occurs from different angles in relation to their optical path.

Another element that can have an effect on the performance of an acousto-optic filtration device is the presence of absorptive or reflective elements. These may be placed either within the interference coating itself, or alternatively positioned separately on separate substrates but integrated into its primary coating system.

Based on their intended application, acousto-optic filters come in two main varieties: collinear and non-collinear. A collinear acousto-optic spectrometer is designed to operate in Bragg regime, and the acoustic transducer must operate at an acoustic frequency which corresponds with phase matching conditions of crystal crystal interaction; additionally an absorber is typically attached at opposite end of crystal for more efficient operation.

Microscopy Applications

Optic microscopes are devices that use lenses and light sources to magnify and view specimens. They are widely used across laboratories for conducting various experiments; depending on the instrument, there may be single or binocular eyepieces and different light sources – illumination (emitting), reflection, or both – used.

Microscopy applications span from single-molecule imaging to high-resolution whole organism analysis. Over the past decades, this field of microscopy has experienced unprecedented expansion with superresolution techniques and fluorescent labels providing nanoscale resolution images of cell structures and processes allowing scientists to probe complex biological systems more thoroughly than ever.

Fluorescence microscopy involves emitting fluorescent dyes from samples under a microscope to provide detailed information about their chemistry, structure and function of proteins or organic compounds. Fluorescent dyes generally emit specific colors which can be detected using either filters or detectors allowing researchers to see them both in their native state as well as any reaction products formed in situ.

Fluorescence microscopy comes with various methods and each technique offers specific advantages. Phase contrast microscopy can be particularly helpful in detecting lipid membranes; its use involves surrounding the objective with a ring to block direct light and create an artificial phase difference of approximately 1/4 wavelength.

Digital Holographic Microscopy (DHM) is another technique which uses interfering wave fronts from a coherent light source to produce phase shift images, providing another method for imaging different objects and environments and is also suitable for most cell biology research studies.

Scanning probe microscopy (SPM) allows scientists to analyze particles at both the nanoscale and individual atomic levels by deflecting laser light off a cantilever tip. SPM can detect various forces including electrostatic, magnetic, chemical bond, Vander Waals or capillary pressure.

Acousto-optic tunable filters are electronic bandpass filters which utilise the acousto-optic interaction to deviate some of the laser light coming through them, creating an adjustable passband across various incident beam angles. When used with multi-line lasers, such filters provide precise passbands over their full spectrum.
Scroll to Top