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Mode locking is a technique in optics by which a laser can be made to produce pulses of light of extremely short duration, on the order of picoseconds (10−12 s) or femtoseconds (10−15 s). A laser operated in this way is sometimes referred to as a femtosecond laser, for example, in modern refractive surgery. The basis of the technique is to induce a fixed phase relationship between the longitudinal modes of the laser's resonant cavity. Constructive interference between these modes can cause the laser light to be produced as a train of pulses. The laser is then said to be "phase-locked" or "mode-locked".
Titanium-sapphire lasers (also known as Ti:sapphire lasers, Ti:Al2O3 lasers or Ti:sapphs) are tunable lasers which emit red and near-infrared light in the range from 650 to 1100 nanometers. These lasers are mainly used in scientific research because of their tunability and their ability to generate ultrashort pulses thanks to its broad light emission spectrum. Lasers based on Ti:sapphire were first constructed and invented in June 1982 by Peter Moulton at the MIT Lincoln Laboratory.
A spatial light modulator (SLM) is a device that can control the intensity, phase, or polarization of light in a spatially varying manner. A simple example is an overhead projector transparency. Usually when the term SLM is used, it means that the transparency can be controlled by a computer.
Kerr-lens mode-locking (KLM) is a method of mode-locking lasers via the nonlinear optical Kerr effect. This method allows the generation of pulses of light with a duration as short as a few femtoseconds.
In optics, an ultrashort pulse, also known as an ultrafast event, is an electromagnetic pulse whose time duration is of the order of a picosecond or less. Such pulses have a broadband optical spectrum, and can be created by mode-locked oscillators. Amplification of ultrashort pulses almost always requires the technique of chirped pulse amplification, in order to avoid damage to the gain medium of the amplifier.
In nonlinear optics, filament propagation is propagation of a beam of light through a medium without diffraction. This is possible because the Kerr effect causes an index of refraction change in the medium, resulting in self-focusing of the beam.
Ultrafast laser spectroscopy is a category of spectroscopic techniques using ultrashort pulse lasers for the study of dynamics on extremely short time scales. Different methods are used to examine the dynamics of charge carriers, atoms, and molecules. Many different procedures have been developed spanning different time scales and photon energy ranges; some common methods are listed below.
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.
A frequency comb or spectral comb is a spectrum made of discrete and regularly spaced spectral lines. In optics, a frequency comb can be generated by certain laser sources.
Multiphoton intrapulse interference phase scan (MIIPS) is a method used in ultrashort laser technology that simultaneously measures, and compensates femtosecond laser pulses using an adaptive pulse shaper. When an ultrashort laser pulse reaches a duration of less than a few hundred femtosecond, it becomes critical to characterize its duration, its temporal intensity curve, or its electric field as a function of time. Classical photodetectors measuring the intensity of light are still too slow to allow for a direct measurement, even with the fastest photodiodes or streak cameras.
Coherent addition of lasers is a method of power scaling. It allows increasing the output power and brightness of single-transversal mode laser.
Self-focusing is a non-linear optical process induced by the change in refractive index of materials exposed to intense electromagnetic radiation. A medium whose refractive index increases with the electric field intensity acts as a focusing lens for an electromagnetic wave characterized by an initial transverse intensity gradient, as in a laser beam. The peak intensity of the self-focused region keeps increasing as the wave travels through the medium, until defocusing effects or medium damage interrupt this process. Self-focusing of light was discovered by Gurgen Askaryan.
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. In usual optical fibres, light both excites and feels shear and longitudinal bulk elastic waves, giving rise to forward-guided acoustic wave Brillouin scattering and backward-stimulated Brillouin scattering. In a subwavelength-diameter optical fibre, the situation changes dramatically.
An Airy beam, is a propagation invariant wave whose main intensity lobe propagates along a curved parabolic trajectory while being resilient to perturbations (self-healing).
Time stretch microscopy, also known as serial time-encoded amplified imaging/microscopy or stretched time-encoded amplified imaging/microscopy' (STEAM), is a fast real-time optical imaging method that provides MHz frame rate, ~100 ps shutter speed, and ~30 dB optical image gain. Based on the photonic time stretch technique, STEAM holds world records for shutter speed and frame rate in continuous real-time imaging. STEAM employs the Photonic Time Stretch with internal Raman amplification to realize optical image amplification to circumvent the fundamental trade-off between sensitivity and speed that affects virtually all optical imaging and sensing systems. This method uses a single-pixel photodetector, eliminating the need for the detector array and readout time limitations. Avoiding this problem and featuring the optical image amplification for improvement in sensitivity at high image acquisition rates, STEAM's shutter speed is at least 1000 times faster than the best CCD and CMOS cameras. Its frame rate is 1000 times faster than the fastest CCD cameras and 10–100 times faster than the fastest CMOS cameras.
High Harmonic Generation (HHG) is a non-perturbative and extremely nonlinear optical process taking place when a highly intense ultrashort laser pulse undergoes an interaction with a nonlinear media. A typical high order harmonic spectra contains frequency combs separated by twice the laser frequency. HHG is an excellent table top source of highly coherent extreme ultraviolet and soft X-ray laser pulses.
Cornelia Denz is a German Professor of Physics at the University of Münster. She works in nonlinear optics and nanophotonics, and is a Fellow of The Optical Society and The European Optical Society. Denz is the current president of the PTB.
You Look Like a Thing and I Love You: How Artificial Intelligence Works and Why It's Making the World a Weirder Place is a 2019 nonfiction book by optics research scientist Janelle Shane. The book documents experiences the author and others have had with machine learning programs, and discusses what "intelligence" means in the context of "artificial intelligence" (AI).
Debabrata Goswami FInstP FRSC, is an Indian chemist and the Prof. S. Sampath Chair Professor of Chemistry, at the Indian Institute of Technology Kanpur. He is also a professor of The Department of Chemistry and The Center for Lasers & Photonics at the same Institute. Goswami is an associate editor of the open-access journal Science Advances. He is also an Academic Editor for PLOS One and PeerJ Chemistry. He has contributed to the theory of Quantum Computing as well as nonlinear optical spectroscopy. His work is documented in more than 200 research publications. He is an elected Fellow of the Royal Society of Chemistry, Fellow of the Institute of Physics, the SPIE, and The Optical Society. He is also a Senior Member of the IEEE, has been awarded a Swarnajayanti Fellowship for Chemical Sciences, and has held a Wellcome Trust Senior Research Fellowship. He is the third Indian to be awarded the International Commission for Optics Galileo Galilei Medal for excellence in optics.
Spectral interferometry (SI) or frequency-domain interferometry is a linear technique used to measure optical pulses, with the condition that a reference pulse that was previously characterized is available. This technique provides information about the intensity and phase of the pulses. SI was first proposed by Claude Froehly and coworkers in the 1970s.
References
- 1 2 3 "Janelle Shane". emerald.ucsd.edu. Archived from the original on 2017-11-12. Retrieved 2019-08-15.
- 1 2 3 Feldman, Brian (30 May 2017). "Janelle Shane's Neural Network Keeps Producing Hilarious, Terrifying Creations". Intelligencer. Retrieved 2019-08-15.
- ↑ "Janelle Shane's schedule for IDEA Week". ideaweek2019.sched.com. Retrieved 2019-08-15.
- 1 2 3 4 "BNS Awarded Multiple NASA Contracts". Boulder Nonlinear Systems (BNS). Retrieved 2019-08-15.
- ↑ "Janelle Shane | Eyeo Festival" . Retrieved 2019-08-15.
- ↑ "Janelle Shane - O'Reilly Media". www.oreilly.com. Retrieved 2019-08-15.
- ↑ "Meet Janelle Shane, one of Fast Company's 100 Most Creative People 2019". Fast Company. Retrieved 2019-08-15.
- 1 2 Shane, Janelle. "Janelle Shane | Speaker | TED". www.ted.com. Retrieved 2019-08-15.
- ↑ "Play: Notes from Session 9 of TED2019". TED Blog. 2019-04-18. Retrieved 2019-08-15.
- ↑ You Look Like a Thing and I Love You. 2019-03-05. ISBN 9781549171529.
