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Adaptive optics (AO) is a technique of precisely deforming a mirror in order to compensate for light distortion. It is used in astronomical telescopes and laser communication systems to remove the effects of atmospheric distortion, in microscopy, optical fabrication and in retinal imaging systems to reduce optical aberrations. Adaptive optics works by measuring the distortions in a wavefront and compensating for them with a device that corrects those errors such as a deformable mirror or a liquid crystal array.
An optical ring resonator is a set of waveguides in which at least one is a closed loop coupled to some sort of light input and output. The concepts behind optical ring resonators are the same as those behind whispering galleries except that they use light and obey the properties behind constructive interference and total internal reflection. When light of the resonant wavelength is passed through the loop from the input waveguide, the light builds up in intensity over multiple round-trips owing to constructive interference and is output to the output bus waveguide which serves as a detector waveguide. Because only a select few wavelengths will be at resonance within the loop, the optical ring resonator functions as a filter. Additionally, as implied earlier, two or more ring waveguides can be coupled to each other to form an add/drop optical filter.
Chirped pulse amplification (CPA) is a technique for amplifying an ultrashort laser pulse up to the petawatt level, with the laser pulse being stretched out temporally and spectrally, then amplified, and then compressed again. The stretching and compression uses devices that ensure that the different color components of the pulse travel different distances.
A fiber laser is a laser in which the active gain medium is an optical fiber doped with rare-earth elements such as erbium, ytterbium, neodymium, dysprosium, praseodymium, thulium and holmium. They are related to doped fiber amplifiers, which provide light amplification without lasing. Fiber nonlinearities, such as stimulated Raman scattering or four-wave mixing can also provide gain and thus serve as gain media for a fiber laser.
In optics and signal processing, wavefront coding refers to the use of a phase modulating element in conjunction with deconvolution to extend the depth of field of a digital imaging system such as a video camera.
Deformable mirrors (DM) are mirrors whose surface can be deformed, in order to achieve wavefront control and correction of optical aberrations. Deformable mirrors are used in combination with wavefront sensors and real-time control systems in adaptive optics. In 2006 they found a new use in femtosecond pulse shaping.
A Shack–Hartmannwavefront sensor (SHWFS) is an optical instrument used for characterizing an imaging system. It is a wavefront sensor commonly used in adaptive optics systems. It consists of an array of lenses of the same focal length. Each is focused onto a photon sensor. If the sensor is placed at the geometric focal plane of the lenslet, and is uniformly illuminated, then, the integrated gradient of the wavefront across the lenslet is proportional to the displacement of the centroid. Consequently, any phase aberration can be approximated by a set of discrete tilts. By sampling the wavefront with an array of lenslets, all of these local tilts can be measured and the whole wavefront reconstructed. Since only tilts are measured the Shack–Hartmann cannot detect discontinuous steps in the wavefront.
Silicon photonics is the study and application of photonic systems which use silicon as an optical medium. The silicon is usually patterned with sub-micrometre precision, into microphotonic components. These operate in the infrared, most commonly at the 1.55 micrometre wavelength used by most fiber optic telecommunication systems. The silicon typically lies on top of a layer of silica in what is known as silicon on insulator (SOI).
Digital holography refers to the acquisition and processing of holograms with a digital sensor array, typically a CCD camera or a similar device. Image rendering, or reconstruction of object data is performed numerically from digitized interferograms. Digital holography offers a means of measuring optical phase data and typically delivers three-dimensional surface or optical thickness images. Several recording and processing schemes have been developed to assess optical wave characteristics such as amplitude, phase, and polarization state, which make digital holography a very powerful method for metrology applications .
A wavefront curvature sensor is a device for measuring the aberrations of an optical wavefront. Like a Shack–Hartmann wavefront sensor it uses an array of small lenses to focus the wavefront into an array of spots. Unlike the Shack-Hartmann, which measures the position of the spots, the curvature sensor measures the intensity on either side of the focal plane. If a wavefront has a phase curvature, it will alter the position of the focal spot along the axis of the beam, thus by measuring the relative intensities in two places the curvature can be deduced.
Phased-array optics is the technology of controlling the phase and amplitude of light waves transmitting, reflecting, or captured (received) by a two-dimensional surface using adjustable surface elements. An optical phased array (OPA) is the optical analog of a radio-wave phased array. By dynamically controlling the optical properties of a surface on a microscopic scale, it is possible to steer the direction of light beams, or the view direction of sensors, without any moving parts. Phased-array beam steering is used for optical switching and multiplexing in optoelectronic devices and for aiming laser beams on a macroscopic scale.
A microlens is a small lens, generally with a diameter less than a millimetre (mm) and often as small as 10 micrometres (µm). The small sizes of the lenses means that a simple design can give good optical quality but sometimes unwanted effects arise due to optical diffraction at the small features. A typical microlens may be a single element with one plane surface and one spherical convex surface to refract the light. Because micro-lenses are so small, the substrate that supports them is usually thicker than the lens and this has to be taken into account in the design. More sophisticated lenses may use aspherical surfaces and others may use several layers of optical material to achieve their design performance.
Francisco Javier "Frank" Duarte is a laser physicist and author/editor of several books on tunable lasers.
Beam expanders are optical devices that take a collimated beam of light and expand its width.
A subwavelength-diameter optical fibre is an optical fibre whose diameter is less than the wavelength of the light being propagated through it. An SDF usually consists of long thick parts at both ends, transition regions (tapers) where the fibre diameter gradually decreases down to the subwavelength value, and a subwavelength-diameter waist, which is the main acting part. Due to such a strong geometrical confinement, the guided electromagnetic field in an SDF is restricted to a single mode called fundamental.
A common-path interferometer is a class of interferometers in which the reference beam and sample beams travel along the same path. Examples include the Sagnac interferometer, Zernike phase-contrast interferometer, and the point diffraction interferometer. A common-path interferometer is generally more robust to environmental vibrations than a "double-path interferometer" such as the Michelson interferometer or the Mach–Zehnder interferometer. Although travelling along the same path, the reference and sample beams may travel along opposite directions, or they may travel along the same direction but with the same or different polarization.
An electromagnetic metasurface refers to a kind of artificial sheet material with sub-wavelength thickness. Metasurfaces can be either structured or unstructured with subwavelength-scaled patterns in the horizontal dimensions.
Xiaoyi Bao is a Chinese Canadian physicist, recognized for her contributions to the field of fiber optics. She is a professor at the University of Ottawa, where she holds the Canada Research Chair in Fiber Optics and Photonics. Bao was awarded an honorary doctorate from the University of Lethbridge; the citation for the honour called her "a world-renowned scholar in her field."
Debora M. Kane is a Professor of Physics at Macquarie University, where her research interests are in non-linear optics and laser physics. She is a Fellow of The Optical Society and has edited four books on nanotechnology, nanomaterials and semiconductor lasers.
Pascuala García Martínez is a Spanish physicist and Professor of Optics at the University of Valencia, where her research specialises in developing new optical and digital techniques for pattern recognition and imaging applications. She is a Fellow of the International Society for Optics and Photonics (SPIE).
References
- ↑ Ragazzoni, Roberto (1996). "Pupil plane wavefront sensing with an oscillating prism". Journal of Modern Optics. 43 (2): 289–293. Bibcode:1996JMOp...43..289R. doi:10.1080/09500349608232742.
- ↑ Esposito, S.; Riccardi, A. (2001). "Pyramid Wavefront Sensor behavior in partial correction Adaptive Optic systems". Astronomy & Astrophysics. 369 (2): L9–L12. Bibcode:2001A&A...369L...9E. doi: 10.1051/0004-6361:20010219 .
- ↑ Iglesias, Ignacio; Ragazzoni, Roberto; Julien, Yves; Artal, Pablo (2002). "Extended source pyramid wave-front sensor for the human eye". Optics Express. 10 (9): 419–428. Bibcode:2002OExpr..10..419I. doi: 10.1364/OE.10.000419 . PMID 19436376.
- ↑ Ragazzoni, Roberto; Diolaiti, Emiliano; Vernet, Elise (2002). "A pyramid wavefront sensor with no dynamic modulation". Optics Communications. 208 (1–3): 51–60. Bibcode:2002OptCo.208...51R. doi:10.1016/S0030-4018(02)01580-8.
- ↑ Akondi, Vyas; Castillo, Sara; Vohnsen, Brian (2013). "Digital pyramid wavefront sensor with tunable modulation". Optics Express. 21 (15): 18261–18272. Bibcode:2013OExpr..2118261A. doi: 10.1364/OE.21.018261 . PMID 23938697.
- ↑ Akondi, Vyas; Castillo, Sara; Vohnsen, Brian (July 2014). "Multi-faceted digital pyramid wavefront sensor". Optics Communications. 323: 77–86. Bibcode:2014OptCo.323...77A. doi:10.1016/j.optcom.2014.03.004. hdl: 10197/13061 . ISSN 0030-4018.