Optics career prospects

Optics’ employment direction

Optics is the study of the generation, propagation, reception and processing of electromagnetic radiation in a wide range of wavelengths from microwaves, infrared, visible light, ultraviolet to X-rays and gamma rays. The science of displays, and interactions with matter, focuses on the range from infrared to ultraviolet.

Optics major research direction

The major research directions of this major include: quantum optics and quantum information, optoelectronics science and technology, optical information processing and computing design, Powerful lasers and laser creatures.

Training objectives of the optics major

This major cultivates students with a solid theoretical foundation of optics and basic experimental skills, and strong innovation ability; understands the development status and research trends in this field, and is familiar with International cutting-edge trends in optical development; senior talents who can engage in scientific research, teaching or undertake specialized technical work, and have strong comprehensive ability, language expression ability and writing ability.

Employment direction of optics majors

In addition to a certain proportion of graduates of this major getting doctoral degrees to continue their studies, they can also go to colleges and universities to engage in related teaching and scientific research, or engage in R&D in optoelectronic companies. , engineering technology and sales.

History of the development of the optics profession

Optics is a discipline with a long history, and its development history can be traced back to more than 2,000 years ago. Human research on light initially focused on trying to answer questions such as "How can people see the objects around them?" About 400 BC, the world's earliest optical knowledge was recorded in China's "Mo Jing". It contains 8 records about optics, describing the definition and generation of shadows, the linear propagation of light and pinhole imaging, and discusses the relationship between objects and images in plane mirrors, concave spherical mirrors and convex spherical mirrors in rigorous writing (see China History of Physics).

Since the beginning of the "Mo Jing", in a historical period of more than 2,000 years, after the 11th century Arab Ibn Haitham invented and made convex lenses, from 1590 to the early 17th century, H. James Sen and H. Lipsch invented the microscope simultaneously and independently of each other. It was not until the first half of the 17th century that W. Snell and R. Descartes summarized the observations of light reflection and refraction into the reflection laws of light commonly used today. and the law of refraction.

In 1665, Newton conducted experiments on sunlight, which could decompose sunlight into simple components and form a light distribution in which colors are arranged in a certain order - a spectrum. It brought people into contact with the objective and quantitative characteristics of light for the first time. The spatial separation of each monochromatic light is determined by the nature of light. Newton also discovered that when a convex lens with a large radius of curvature is placed on an optical flat glass plate, when illuminated with white light, a group of colored concentric annular stripes appear at the contact point between the lens and the glass plate; when a certain monochromatic light is used, When irradiated, a group of concentric ring stripes of alternating light and dark appear. Later generations called this phenomenon Newton's rings. By means of this phenomenon, the thickness of the air gap of the first dark ring can be used to quantitatively characterize the corresponding monochromatic light.

While discovering these important phenomena, Newton believed that light is a flow of particles based on the linear propagation of light. The particles fly out from the light source and follow the laws of mechanics to move in a straight line at a constant speed in a uniform medium. And use this point of view to explain the phenomena of refraction and reflection. Huygens was an opponent of the particle theory of light. He founded the wave theory. In 1690, he wrote in "On Light": "Light, like sound, propagates in a spherical wave surface." He also pointed out that the vibration of light achieves Each point can be regarded as the vibration center of the secondary wave, and the envelope surface of the secondary wave is the wave front (wave front) of the propagating wave. Throughout the 18th century, the particle flow theory of light and the wave theory of light were roughly proposed, but neither was complete.

At the beginning of the 19th century, wave optics was initially formed, represented by the works of T. Yang and A. Fresnel. Yang successfully explained the "color of the film" and the double-slit interference phenomenon.

Fresnel supplemented Huygens' principle with Young's interference principle in 1818, thus forming the Huygens-Fresnel principle that is well known today. It can be used to perfectly explain the interference and diffraction phenomena of light, and also Can explain the linear propagation of light. In further studies, polarization of light and interference of polarized light were observed. To explain these phenomena, Fresnel postulated that light is a transverse wave propagating in a continuous medium (the ether). However, the characteristics of an elastic solid have to be imposed on the ether. An ether with such properties is unimaginable, and even if the ether is admitted, the optical phenomena cannot be connected with other physical phenomena.

In 1846, Faraday discovered that the vibration surface of light rotates in a magnetic field; in 1856, W. Weber discovered that the speed of light in a vacuum is equal to the ratio of the electromagnetic unit and the electrostatic unit of current intensity. They indicate that there is a certain internal relationship between optical phenomena and electromagnetic phenomena.

Maxwell’s theoretical research around 1860 pointed out that changes in electric and magnetic fields cannot be limited to a certain part of space, but propagate at a speed equal to the ratio of the electromagnetic unit of the current to the electrostatic unit. Light is Such an electromagnetic phenomenon. This conclusion was confirmed experimentally by Hertz in 1888. According to Maxwell's theory, if c represents the speed of light in vacuum, and v represents the speed of light in a transparent medium with dielectric constant ε and magnetic permeability μ, then:

c/ v=(εμ)1/2

Where c/v is exactly the refractive index of the medium, so there is:

n=(εμ)1/2

The above formula gives the relationship between the optical constant n of a transparent medium, the electrical constant ε and the magnetic constant μ. In terms of understanding the physical properties of light, Maxwell's theory has taken a big step forward compared with previous theories.

However, this theory cannot explain the properties of electric oscillators that produce frequencies up to the frequency of light, nor can it explain the dispersion of light caused by the change of the refractive index with the frequency of light. It was not until H. Lorenz founded the electron theory in 1896 that he explained the phenomenon of luminescence and light absorption by matter, and also explained the various characteristics of light propagation in matter, including the explanation of dispersion. In Lorenz's theory, the ether is a vast and infinite immovable medium. Its only characteristic is that the light vibration in this medium has a certain propagation speed.

For important issues such as the wavelength distribution of energy in the radiation of a hot black body, Lorentz theory cannot yet give a satisfactory explanation. Moreover, if Lorenz's concept of ether is considered correct, the moving ether can be chosen as the frame of reference, allowing people to distinguish absolute motion. In fact, in 1887 A. Michelson and others used an interferometer to measure the "ether wind" and obtained negative results. This shows that in the period of Lorentz's electron theory, people's understanding of the nature of light was still very one-sided.

In 1900, Planck borrowed the concept of discontinuity from the molecular structure theory of matter and proposed the quantum theory of radiation. He believed that electromagnetic waves (including light) of various frequencies can only be determined by their respective Discrete energy is emitted from the oscillator. This energy particle is called a quanta, and the quanta of light is called a photon. Quantum theory not only naturally explains the distribution of energy radiated by hot bodies according to wavelength, but also raises the issue of the interaction between light and matter with a completely new concept. Quantum theory provides new concepts not only to optics, but also to the entire physics. Its birth is usually regarded as the starting point of modern physics.

In 1905, Einstein used quantum theory in the photoelectric effect and gave a very clear expression to photons. He specifically pointed out that when light interacts with matter, light also interacts with photons as the smallest unit. In addition, many experiments in the late 19th and early 20th centuries well demonstrated the quantum nature of light. In September 1905, the German "Annals of Physics" published Einstein's article "On the Electrodynamics of Moving Mediums". The basic principles of special relativity were proposed for the first time. The article clarifies that classical physics, which has been dominant since the days of Galileo and Newton, has applications limited to speeds much smaller than the speed of light, while his new theory can explain the characteristics of processes related to high-speed motion. He fundamentally gave up the concept of ether and successfully explained the optical phenomena of moving objects.

In this way, at the beginning of the 20th century, on the one hand, it was confirmed that light is an electromagnetic wave from the optical phenomena of light interference, diffraction, polarization and moving objects; on the other hand, it was confirmed from the thermal radiation, photoelectric effect, light pressure and The chemical effects of light, etc., prove beyond any doubt the quantum nature of light - the particulate nature.

The Compton effect discovered in 1922, the Raman effect discovered in 1928, and the ultra-fine structure of atomic spectra that could be obtained experimentally at that time undoubtedly showed that the development of optics cannot be independent of quantum physics. physics.

The concept of light quantum in modern optics is not exclusive of the wave concept of light, but it requires the help of the concepts created by Heisenberg, Schr?dinger, Dirac, Feynman, Schwinger and Tomonaga Shinichiro. And the developed quantum mechanics and quantum electrodynamics can unify the two. Applying their theories can clarify atomic spectra, molecular spectra and ion spectra; can explain the effects of electric fields, magnetic fields and acoustic fields on spectra; can establish the relationship between excitation conditions and spectral characteristics. The history of optics shows that the two most important basic theories in modern physics, quantum mechanics and special relativity, were both born and developed in human research on light. ;