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Noise-immune Cavity-enhanced Optical Heterodyne Molecular Spectroscopy
Noise-immune cavity-enhanced optical-heterodyne molecular spectroscopy (NICE-OHMS) is an ultra-sensitive laser-based absorption technique that utilizes laser light to assess the concentration or the amount of a species in gas phase by absorption spectrometry (AS). Principles The NICE-OHMS technique combines cavity enhanced absorption spectrometry (CEAS) for prolonged interaction length with the sample with frequency modulation (fm) spectrometry FMS for reduction of 1/f noise. By choosing the fm-modulation frequency equal to the free spectral range (FSR) of the cavity, all components of the spectral fm-triplet are transmitted through the cavity in an identical manner. Therefore, the cavity does not compromise the balance of the fm-triplet, which otherwise would give rise to fm-background signals. It also does not convert any fluctuations of the laser frequency with respect to the transmission mode of the cavity to intensity modulation, which would deteriorate the detectability by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laser Absorption Spectrometry
Laser absorption spectrometry (LAS) refers to techniques that use lasers to assess the concentration or amount of a species in gas phase by absorption spectrometry (AS). Optical spectroscopic techniques in general, and laser-based techniques in particular, have a great potential for detection and monitoring of constituents in gas phase. They combine a number of important properties, e.g. a high sensitivity and a high selectivity with non-intrusive and remote sensing capabilities. Laser absorption spectrometry has become the foremost used technique for quantitative assessments of atoms and molecules in gas phase. It is also a widely used technique for a variety of other applications, e.g. within the field of optical frequency metrology or in studies of light matter interactions. The most common technique is tunable diode laser absorption spectroscopy (TDLAS) which has become commercialized and is used for a variety of applications. Direct laser absorption spectrometry The most a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Absorption Spectrometry
Absorption spectroscopy refers to spectroscopy, spectroscopic techniques that measure the absorption (electromagnetic radiation), absorption of electromagnetic radiation, radiation, as a function of frequency or wavelength, due to its interaction with a sample. The sample absorbs energy, i.e., photons, from the radiating field. The intensity of the absorption varies as a function of frequency, and this variation is the Absorption spectroscopy#Absorption spectrum, absorption spectrum. Absorption spectroscopy is performed across the electromagnetic spectrum. Absorption spectroscopy is employed as an chemical analysis, analytical chemistry tool to determine the presence of a particular substance in a sample and, in many cases, to quantify the amount of the substance present. infrared spectroscopy, Infrared and ultraviolet–visible spectroscopy are particularly common in analytical applications. Absorption spectroscopy is also employed in studies of molecular and atomic physics, ast ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frequency Modulation
Frequency modulation (FM) is the encoding of information in a carrier wave by varying the instantaneous frequency of the wave. The technology is used in telecommunications, radio broadcasting, signal processing, and Run-length limited#FM: .280.2C1.29 RLL, computing. In Analog signal, analog frequency modulation, such as radio broadcasting, of an audio signal representing voice or music, the instantaneous frequency deviation, i.e. the difference between the frequency of the carrier and its center frequency, has a functional relation to the modulating signal amplitude. Digital data can be encoded and transmitted with a type of frequency modulation known as frequency-shift keying (FSK), in which the instantaneous frequency of the carrier is shifted among a set of frequencies. The frequencies may represent digits, such as '0' and '1'. FSK is widely used in computer modems, such as fax modems, telephone caller ID systems, garage door openers, and other low-frequency transmissions. R ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1/f Noise
Pink noise or noise is a signal or process with a frequency spectrum such that the power spectral density (power per frequency interval) is inversely proportional to the frequency of the signal. In pink noise, each octave interval (halving or doubling in frequency) carries an equal amount of noise energy. Pink noise sounds like a waterfall. It is often used to tune loudspeaker systems in professional audio. Pink noise is one of the most commonly observed signals in biological systems. The name arises from the pink appearance of visible light with this power spectrum. This is in contrast with white noise which has equal intensity per frequency interval. Definition Within the scientific literature, the term 1/f noise is sometimes used loosely to refer to any noise with a power spectral density of the form S(f) \propto \frac, where ''f'' is frequency, and 0 < α < 2, with exponent α usually close to 1. One-dimensional signals with α = 1 are usually called pink noise. The f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Free Spectral Range
Free spectral range (FSR) is the spacing in optical frequency or wavelength between two successive reflected or transmitted optical intensity maxima or minima of an interferometer or diffractive optical element. The FSR is not always represented by \Delta\nu or \Delta\lambda, but instead is sometimes represented by just the letters FSR. The reason is that these different terms often refer to the bandwidth or linewidth of an emitted source respectively. In general The free spectral range (FSR) of a cavity in general is given by :\left, \Delta\lambda_\text\ = \frac\left, \left(\frac\right)^ \ or, equivalently, :\left, \Delta\nu_\text\ = \frac\left, \left(\frac\right)^\ These expressions can be derived from the resonance condition \Delta \beta L = 2\pi by expanding \Delta \beta in Taylor series. Here, \beta = k_0 n(\lambda) = \fracn(\lambda) is the wavevector of the light inside the cavity, k_0 and \lambda are the wavevector and wavelength in vacuum, n is the refractive index o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NICE OHMS Typical Signals
Nice ( , ; Niçard: , classical norm, or , nonstandard, ; it, Nizza ; lij, Nissa; grc, Νίκαια; la, Nicaea) is the prefecture of the Alpes-Maritimes department in France. The Nice agglomeration extends far beyond the administrative city limits, with a population of nearly 1 millionDemographia: World Urban Areas , Demographia.com, April 2016 on an area of . Located on the , the southeastern coast of France on the Mediterranean Sea, at the foot of the [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fiber Laser
A fiber laser (or fibre laser in British English) 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. Advantages and applications An advantage of fiber lasers over other types of lasers is that the laser light is both generated and delivered by an inherently flexible medium, which allows easier delivery to the focusing location and target. This can be important for laser cutting, welding, and folding of metals and polymers. Another advantage is high output power compared to other types of laser. Fiber lasers can have active regions several kilometers long, and so can provide very high optical gain. They can support ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Heterodyne Detection
Optical heterodyne detection is a method of extracting information encoded as modulation of the phase, frequency or both of electromagnetic radiation in the wavelength band of visible or infrared light. The light signal is compared with standard or reference light from a "local oscillator" (LO) that would have a fixed offset in frequency and phase from the signal if the latter carried null information. "Heterodyne" signifies more than one frequency, in contrast to the single frequency employed in homodyne detection. The comparison of the two light signals is typically accomplished by combining them in a photodiode detector, which has a response that is linear in energy, and hence quadratic in amplitude of electromagnetic field. Typically, the two light frequencies are similar enough that their difference or beat frequency produced by the detector is in the radio or microwave band that can be conveniently processed by electronic means. This technique became widely applicable to top ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cavity Ring Down Spectroscopy
Cavity ring-down spectroscopy (CRDS) is a highly sensitive optical spectroscopic technique that enables measurement of absolute optical extinction by samples that scatter and absorb light. It has been widely used to study gaseous samples which absorb light at specific wavelengths, and in turn to determine mole fractions down to the parts per trillion level. The technique is also known as cavity ring-down laser absorption spectroscopy (CRLAS). A typical CRDS setup consists of a laser that is used to illuminate a high-finesse optical cavity, which in its simplest form consists of two highly reflective mirrors. When the laser is in resonance with a cavity mode, intensity builds up in the cavity due to constructive interference. The laser is then turned off in order to allow the measurement of the exponentially decaying light intensity leaking from the cavity. During this decay, light is reflected back and forth thousands of times between the mirrors giving an effective path length f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laser Diode
file:Laser diode chip.jpg, The laser diode chip removed and placed on the eye of a needle for scale A laser diode (LD, also injection laser diode or ILD, or diode laser) is a semiconductor device similar to a light-emitting diode in which a diode pumped directly with electrical current can create active laser medium, lasing conditions at the diode's p–n junction, junction. Driven by voltage, the doped p–n-transition allows for Carrier generation and recombination, recombination of an electron with a Electron hole, hole. Due to the drop of the electron from a higher energy level to a lower one, radiation, in the form of an emitted photon is generated. This is spontaneous emission. Stimulated emission can be produced when the process is continued and further generates light with the same phase, coherence and wavelength. The choice of the semiconductor material determines the wavelength of the emitted beam, which in today's laser diodes range from infra-red to the UV spectrum ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tunable Diode Laser Absorption Spectroscopy
Tunable diode laser absorption spectroscopy (TDLAS, sometimes referred to as TDLS, TLS or TLAS) is a technique for measuring the concentration of certain species such as methane, water vapor and many more, in a gaseous mixture using tunable diode lasers and laser absorption spectrometry. The advantage of TDLAS over other techniques for concentration measurement is its ability to achieve very low detection limits (of the order of ppb). Apart from concentration, it is also possible to determine the temperature, pressure, velocity and mass flux of the gas under observation. TDLAS is by far the most common laser based absorption technique for quantitative assessments of species in gas phase. Working A basic TDLAS setup consists of a tunable diode laser light source, transmitting (i.e. beam shaping) optics, optically accessible absorbing medium, receiving optics and detector/s. The emission wavelength of the tunable diode laser, viz. VCSEL, DFB, etc., is tuned over the characteristic ab ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Laser Articles
This is a list of laser topics. A * 3D printing, additive manufacturing * Abnormal reflection * Above-threshold ionization * Absorption spectroscopy * Accelerator physics * Acoustic microscopy * Acousto-optic deflector * Acousto-optic modulator * Acousto-optical spectrometer * Acousto-optics * Active laser medium * Active optics * Advanced Precision Kill Weapon System * Advanced Tactical Laser * Afocal system * Airborne laser * Airborne wind turbine * Airy beam * ALKA * All gas-phase iodine laser * Ambient ionization * Amplified spontaneous emission * Analytical chemistry * Aneutronic fusion * Antiproton Decelerator * Apache Arrowhead * Apache Point Observatory Lunar Laser-ranging Operation * Arago spot * Argon fluoride laser * Argus laser * Asterix IV laser * Astrophysical maser * Atmospheric-pressure laser ionization * Atom interferometer * Atom laser * Atom probe * Atomic clock * Atomic coherence * Atomic fountain * Atomic line filter * Atomic ratio * Atomic spectros ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
