Optics is an important branch of physics.It is also a discipline related to optical engineering technology.In a narrow sense, optics is the science of light and vision. In the early days, the word "optics" was only used for things related to eyes and vision.It is often said that optics is in a broad senseinfrared、visible light、ultraviolet raysuntilX-rayandGamma rayWithin a wide band ofelectromagnetic radiationThe generation, transmission, reception and display of, as well as the science of interaction with matter, focus on the research range from infrared toUltraviolet band。It is an important part of physics.[1]
The origin of optics has long been recorded in the West,ancient GreekOfEuclid（Euclid, about 330-260 BC)（Catoptrica）The reflection of light is studied;Arab scholarAl Hazen(AI Hazen, 965-1038) wrote a Complete Book of Optics and discussed many optical phenomena.Optics is really a discipline, which should be established fromReflection lawandLaw of refractionSince the era ofgeometrical optics The foundation of.
Development history
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optics
Optics is a discipline with a long history. Its development history can be traced back to more than 2000 years ago.At the beginning, human's research on light mainly tried to answer such questions as "how can people see the objects around".About 400 BC, Chinese《Ink classics》The earliest optical knowledge in the world was recorded in.It has eight records about optics, describing the definition and generation of shadow,Linear propagation of lightSex andPinhole imaging, and discussed in strict wordsPlane mirror、Concave spherical mirrorAnd object and image in convex spherical mirror (seeHistory of Chinese Physics）。[1]
Since the "Mohist Book", over 2000 years of history, Arab people in the 11th centuryIbn HaisaimInventedConvex lensFrom 1590 to the early 17th century, HJason and HLipsey invented the microscope independently at the same time. It was not until the first half of the 17th century that WSnell and RDescartes willReflection of lightAnd refraction, which is attributed to theReflection lawandLaw of refraction。[1]
Newton in 1665sunlightIt can decompose sunlight into simple components to form a certain colorSequential arrangementThe light distribution spectrum.It is the first time that people are exposed to the objective and quantitative characteristics of lightMonochromatic lightThe separation in space is determined by the nature of light.Newton also discoveredRadius of curvatureThe large convex lens is placed on the optical planeGlass plateWhen white light is used, a group of coloredConcentric ringShape stripe;When a certain monochromatic light is used to illuminate, a group of concentric ring stripes with light and shade will appear. Later generations called this phenomenonNewtonian ring。With the help of this phenomenon, the firstDark ringOfAir gapTo quantitatively characterize the corresponding monochromatic light.[1]
When Newton discovered these important phenomena, he believed that light is a kind ofParticulate flow, particles fly out of the light sourceHomogeneous mediumThe phenomenon of refraction and reflection is explained from this point of view.Huygens isCorpuscular theory of lightHe foundedFluctuation theoryIn 1690On LightThe book wrote: "Like sound, light is sphericalWavefrontDisseminated. "And points out that every point reached by the optical vibration can be regarded asSecondary waveSecondaryEnvelope surfaceFor propagating waveWavefront(wavefront).Throughout the 18th century, the particle flow theory of light and thewave theory They were raised roughly, but not completely.[1]
1846FaradayFound lightVibrating surfaceRotation in magnetic field;In 1856, W. Weber found that the speed of light in vacuum is equal toelectric currentThe ratio of the electromagnetic unit of intensity to the electrostatic unit.They represent optical phenomena andelectromagneticsThere are certain phenomenaIntrinsic relationship。[1]
Around 1860maxwellIt is pointed out that the changes of electric field and magnetic field cannot be limited to a certain part of space, but spread at a speed equal to the ratio of electromagnetic unit of current to electrostatic unit. Light is such a kind ofElectromagnetic phenomenon。This conclusion in 1888 washertzThe experiment proved that.According to Maxwell's theory, ifcRepresents the speed of light in vacuum,vRepresent light inDielectric constantbyεandPermeabilitybyμOfTransparent mediaThe speed in is:
The above formula gives the optical constants of transparent medianFollowelectric constant εandmagnetismconstantμRelationship.In understanding the lightphysical propertyaspect,Maxwell theoryIt is a big step forward compared with previous theories.[1]
However, this theory cannot explain that electricity with a frequency as high as that of lightVibratorAnd cannot explain the change of refractive index with the frequency of lightDispersion of light。In 1896, HLorentz foundElectronic theory, explained the phenomenon of light emission and material absorption, and also explained various characteristics of light propagation in materials, includingdispersionExplanation of the phenomenon.In Lorenz's theory, the ether is a vast and infinite motionless medium, whose only feature is that the light vibration in this medium has certainpropagation velocity。[1]
Lorentz theory can not give a satisfactory explanation for such important problems as the distribution of energy according to wavelength in the radiation of a hot black body.Moreover, if Lorenz's concept of the ether is correct, the moving ether can be selected asFrame of reference, enabling people to distinguishAbsolute motion。In fact, in 1887 AMichelsonEtcInterferometerMeasurement“Ether wind”The negative result shows that people's understanding of the nature of light still has a lot of one sidedness in the period of Lorenz's electron theory.[1]
In 1900,PlonkBorrowed from the molecular structure theory of matterDiscontinuityThe concept of radiationQuantum theory, think thatelectromagnetic wave(including light) can only be separated fromVibratorEmitting, this energy particle is called quantum, and the quantum of light is called photon.Quantum theory not only explains the hot body naturallyRadiant energyAccording to the law of wavelength distribution, and with a new concept, the problem of the interaction between light and matter is proposed.Quantum theory not only provides new concepts for optics, but also for the whole physics. It is generally regarded as the starting point of modern physics.[1]
In 1905,EinsteinApply quantum theory tophotoelectric effectIn, we give a very clear representation of photons.He especially pointed out that when light interacts with matter, light also takes photons as the smallest unit.In addition, many experiments at the end of the 19th century and the beginning of the 20th century have well proved theQuantum property。[1]In September 1905, the German "Physics Yearbook" published Einstein's "Electrodynamics of Moving Media".For the first timeSpecial relativityFundamentals.This paper clarifies that classical physics, which has dominated since Galileo and Newton's timesScope of applicationOnly when the speed is far less than the speed of light, and hisNew theoryIt can explain the characteristics of the process related to high-speed movement.He basically abandoned the concept of ether and successfully explained theOptical phenomenon。[1]
In the early 20th century, on the one handInterference of light, diffraction, polarization and optical phenomena of moving objects confirm that light iselectromagnetic wave；On the other hand, from thermal radiationphotoelectric effect、Light pressureAs well as the chemical action of light, it can no doubt prove the quantum nature of light - particle nature.[1]
Research from several basic principles obtained from experimentsPropagation of lightThe subject of questions.Based on the concept of ray and the refractionReflection lawTo describe the propagation of light in media.[1-2]
Wave optics
optics
Starting from the fact that light is a wave, the discipline of studying the propagation law of light in the medium.Can be used for researchInterference of light、Diffraction of light、Polarization of lightAnd inAnisotropic mediumThe phenomenon of communication in.Since the speed of light and the propagation speed of electromagnetic wave are the same, it is inferred that light is also an electromagnetic wave, which is confirmed by all subsequent experiments.The results obtained by using geometrical optics are always the approximation or limit of wave optics under certain conditions.[1]
Unlike geometrical optics,Wave opticsNot only the apertureMuch greater thanAt wavelengthPropagation of lightAnd study the optical properties of any apertureCommunication process。Wave optics can always get the correct solution, but sometimes it is more complicated to use wave optics, so it is usually decided to use geometric optics or wave optics, or both, according to the nature of the problem.For example, in generalOptical system designMedium, multi-purposeGeometrical optics methodTo determine the system'sStructural elementsHowever, the wave optics method must be used to obtain the distribution of light energy and evaluate its imaging quality.[1-2]
The theoretical basis of wave optics isClassical electrodynamicsOfMaxwell's equations。Macroscopic parameters of light in mediumDielectric constantεandPermeabilityμ, Maxwell's equations are expressed as coefficients.And the refractive index of transparent mediumnThere is a simple relationship between:n=(εμ)1/2。Wave optics will not be discussed in detailεandμAndMaterial structureAnd focuses on explaining the propagation law of light waves.On establishingεandμWith molecules andcrystal structureThe study of these contents is sometimes calledMolecular optics。Wave optics can explain light in scattering medium andAnisotropic mediumThe process of propagation and its behavior near the medium interface;It can also explain the dispersion phenomenon and the influence of pressure, temperature, sound field, electric field and magnetic field on optical phenomena in various media.[1]
Although wave optics canPropagation of lightSatisfactory explanation is given, but generally the process of light emission and absorption cannot be explained, which shows thatClassical physicsDifficulties.[1]
quantum optics
In 1900,PlonkStudyingBlackbody radiationIn order to deduce theoretically what he had got at that time was in good agreement with the realityEmpirical formula, boldly proposed a hypothesis that is completely different from the classical concept, namelyVibratorThe energy of cannot be changed continuously, and only one copy of the discrete value can be taken: 0,hv，2hv，…，nhv, wherenbypositive integer，νIs the oscillator frequency,hbyPlanck constant, the value is 6.626 × 10－34In 1905, Einstein popularized Planck's above quantum theory when studying the photoelectric effect, and then proposed the concept of photon.He thinks that light energy is not likeElectromagnetic wave theoryThe energy is distributed in theWavefrontInstead, they focus on particles called photons.This particle still keeps the concept of frequency, which isνOf photons have energyhν。stayphotoelectric effectWhen the photon shines on the metal surface, it absorbs all the electrons in the metal at one time, without the time of accumulated energy predicted by the electromagnetic theory. The electron uses part of this energy to overcome the attraction of the metal surfaceEscape workThe rest becomes the kinetic energy of the electron leaving the metal surface.It is thus realized that an atom or molecule can transform itsEnergy conversionbecomeelectromagnetic fieldRadiate or obtain energy from the field, but only in photonshνFor the unit.[1-2]
Wave of light and photonicDualityIt is the nature of light.Photons, electrons, protons, neutrons and other microscopic objectsWave particle dualityIs formedquantum mechanicsThe important foundation of.The discipline of studying the nature of light and the interaction between light and matter from the nature of this photon is calledquantum opticsIt is mainly based on quantum mechanics orQuantum electrodynamics。The generation and disappearance of light in molecules and atoms is not only the essence of light, but also related to the structure of molecules and atoms.It is a branch of optics to experimentally verify and theoretically discuss such problemsspectroscopy。[1-2]
The wave of light and the duality of photons are the nature of light.It representsMacro worldContinuous fluctuation andMicrocosmInDiscontinuityThe quantum ofClassical physicsSimplified mechanical concepts are mutually exclusive, but in fact, they are unified.Later, it was proved indisputably not only theoretically but also experimentally:DualityThe substances in the micro world, including electrons, protons, neutrons and atoms, although they are particles, also have the characteristics of fluctuations associated with their own mass and speed (seeWave particle duality）。[2]
With the discovery and development of laser, a series of new optical disciplines have emerged and developed rapidly.[1]
As early as 1917, Einstein was studyingAtomic radiationI have discussed in detail that there are two forms of material radiation: one isSpontaneous emission；The second is caused by the induced excitation of external photonsStimulated radiation。It is predicted that stimulated radiation can produce very high brightnessMonochromatic light。Because of these characteristics, TMaymanFirst makeRuby laserSince then, the study of stimulated light radiation has made laser science andLaser technologyIt has developed rapidly and opened up a number of new branch disciplines closely related to laser itself.exceptquantum opticsIn addition, there arenonlinear optics 、Laser spectroscopy, super fast opticsLaser materialandLaserPhysics, etc.[1]
In classical wave optics, the medium parameters are considered to be independent of the intensity of lightlinear differential equationTo express.However, many new phenomena have been found in the case of intense laser passing through.If we find that the refractive indexfield strengthWhen the beam intensity changesRefraction angleChange accordingly;Self focusing and self defocusing of light beam;The frequency of the light wave changes after passing through some media, resulting in frequency doublingSum frequencyandDifferential frequencyEtc.All these phenomena fall intononlinear optics Research.[1]
LaserNow can produce heightDirectivity, high monochromaticity, polarization, frequency tunable and possibleultrashort pulse Light source, high-resolution spectrum, picosecond (10－12s) Ultra short pulse and tunable laser technology have made the classicspectroscopyHas undergone profound changes and developed intoLaser spectroscopy。At the same time, high powerfemtosecond Ultrashort pulse laser, studying the interaction between this kind of laser and matter has developed into ultraintense ultrafast optics.Above all of these.Emerging disciplinesBecome a research substanceMicrostructure、MicrodynamicsThe important means of process are atomic physicsMolecular physics、Condensed matter physics 、molecular biologyThe study of chemical structure and dynamic process provides an unprecedented new technology.[1-2]
With laser science andLaser technologyThe development of laser and its application in many fieldsLaser materialAnd correspondingLaser deviceThe basic problems involved in the development of new light sources and lasers have become an important part of modern opticsDevelopment trendIt is wavelength expansion and frequency modulationOptical pulseWidth compression, miniaturization and solidification of devices, etc.[1]
The development of decades shows that laser science and laser technology have greatly promoted the development of physics, chemistrylife sciencesThe development of environmental science and other disciplines has formed a group of very active new disciplines andInterdisciplinary, such asLaser chemistryLaser BiologyLaser medicine、Information opticsEtc.At the same time, laser is also used in precision measurement, remote sensing and telemetry, communicationholography, medical treatment, material processingLaser guidanceAnd laser inducednuclear fusionAnd other aspects have been widely used.[1]
In recent decades, optics has developed more rapidly and entered a new periodModern PhysicsAndmodern scienceAnd technology frontier.The most important achievement is to confirm and improve the atomic and molecularStimulated radiationThe theory of stimulated radiation and the creation of many specific technologies.When Einstein studied radiation, he pointed out thatSpontaneous emissionAnd stimulated radiation.The emission of light source is generally spontaneous emission, in which the stimulated emission probability is negligible.However, stimulated radiation has the following characteristics: same direction, same phase, same frequency and samePolarized radiationThe nature of.Under certain conditions, if the stimulated radiation can continue to excite other particles, causing a chain reaction, the amplification effect can be obtained like an avalanche, and finally the monochromatic radiation, the so-called laser, is given.The first time to realize this quantum amplification of radiation was in 1954 when CTownesCompletedMaser。Then in 1960, TMaymanuseRubyMake the first visible lightLaser；Made in the same yearHe Ne laser；It came into being in 1962semiconductor laser ；Created in 1963Tunable dye laser。Various lasers made in recent decades have been covered byX-ray, UV, visibleinfra-redTo the whole band of microwave.Because the laser has excellent monochromaticityHigh brightnessAnd gooddirectionalSince the invention of laser, laser science and laser technology have been rapidly developed and widely applied, causing significant changes in the entire science and technology.[1-2]
Another important branch of modern optics is imaging opticsholographyandOptical information processingComposed of.This branch can be traced back to the microscopic imaging theory proposed by E. Abbe in 1873 and the experimental verification completed by A. Porter in 1906;1935 FZernikeThe phase contrast observation method is proposed and made by Zeiss factoryPhase contrast microscope, for which he obtainedThe nobel prize in physics；1948 DGaborThe forerunner of modern holographyWavefrontFor this reason, Gabor won the Nobel Prize in Physics in 1971.[1-2]
In the 1950s, mathematics, electronic technology andCommunication TheoryCombined with optics, it introduces spectrumspatial filtering , carrierlinear transformation And related operations, updated the classical imaging optics, and formedFourier optics。In addition, due to the coherent light provided by the laser and the fact that ELiz and JThe improved wave front reproduction holography by Alpinnex has formed a new discipline field in recent decades——Optical information processing。[1]For decades, especially since 1978, due to the successful reduction of optical loss in optical fibers,Fiber opticsIts application has developed by leaps and bounds.It is not only for endoscopeoptical system It provides fiber image transmission and light transmission, and it is particularly important that it is successfully applied tocommunication system , optical cable replaces cable, realizingOptical fiber communication。This is another important achievement of modern opticsinformation transmissionAnd processing provide new technologies.[1]
In modern optics itself, exceptnonlinear optics 、Laser spectroscopy, super fast opticsLaser materialIn addition to laser physics, more and more people pay attention to the following fields.Initiated by lasernuclear fusionExploring implementationControlled thermonuclear reactionIt has reached the level of generating "ignition points".laserspectroscopy, including laserRaman spectroscopy, high-resolution spectrum andpicosecondultrashort pulse And tunableLaser technologyThe traditional spectroscopy has changed a lot, and become an in-depth research materialMicrostructure, movement rules andenergy conversion Important means of mechanism.It isCondensed matter physics 、molecular biologyAnd the study of chemical dynamic processes provides unprecedented technology.Laser coolingandBose Einstein condensationImplementation of andAtomic laserIts birth is one of the major breakthroughs in physics at the end of the 20th century.stayQuantum communicationAndQuantum computingIn terms of quantum theory, since P. Shure proposed quantum theory in 1994Parallel algorithmSince then, quantum communication and quantum computing have developed into physics andinformation scienceCombined emergingInterdisciplinaryThe theory and experiment in this field have made significant progress.AndScanning tunneling microscopeSimilarly, a series ofNear-field opticsscanningmicroscopic techniquesThe resolution has reached one tenth of the wavelength of light wave, and a new cross discipline combining optics, scanning probe microscopy and spectroscopy near-field optics has been formed.photonic crystal It is a periodic dielectric (including metal) structure. Its period corresponds to the wavelength of light wavePropagation of lightThe properties and the interactions between photons and atoms, molecules have undergone essential changes, which can control the movement of photons.This is a brand new typePhotonic deviceThe physical basis of.Modern optics not only promotes the development of physicslife sciences, information sciencematerial science And other fields are increasingly extensive and in-depthDevelopment researchIt has provided a broad prospect and has become one of the important disciplinary bases on which the development of high-tech field depends.[1-2]
In October 2022, Tsinghua University team proposed breakthrough opticsaberrationNew Path to World Problems[5]。
International Light Year
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2015arabThe five volume optical works of the scholar Ibn Haisaim were born exactly one thousand years ago.For a thousand years, light technology has broughthuman civilizationGreat progress.To this end,the United NationsDeclare 2015 the International Year of Light and Optical Based TechnologyInternational Light Year）To commemorate the great discoveries made by human beings in the field of light for thousands of years.
