Origins and Development of Photon Science PDF

Origins and Development of Photon Science To understand photonics, photonics is related to understanding light, interference, and diffraction! Light in the Ancient and Modern Era In the beginning, God said, “Let there be light,” and there was light. However, ever since the sixth day of the heavens...

Origins and Development of Photon Science To understand photonics, photonics is related to understanding light, interference, and diffraction! Light in the Ancient and Modern Era In the beginning, God said, “Let there be light,” and there was light. However, ever since the sixth day of the heavens and the earth, the human understanding of the nature of light has been keenly contested. The very earliest ideas are lost to history, no doubt influenced by natural phenomena such as sunlight, starlight, lightning, and fire. The first recorded thoughts on light were offered by the ancient Greeks. 1-The first recorded thoughts on light were offered by the ancient Greeks. In the sixth century BCE, Pythagoras (570–495 BCE) reasoned that sight required visual rays to leave our eyes and shine upon an object. Until 1865 that “the agreement of the results seems to show that light and magnetism are affections of the same substance, and that light is an electromagnetic disturbance propagated through the field according to electromagnetic laws. The first use of the word “photon” is credited to Gilbert Lewis (1875–1946) in 1926 however, with a different meaning to quantized light, four other authors used the term as much as ten years beforehand. Photons are electromagnetic radiation with zero mass, zero charge, and a velocity that is always c, the speed of light. Because they are electrically neutral, they do not steadily lose energy via coulombic interactions with atomic electrons, as do charged particles. Photons travel some considerable distance before undergoing a more interaction leading to a partial or total transfer of the photon energy to electron energy.  Photons are far more penetrating than charged particles of similar energy. Photonics is the technology of generating and harnessing light and other forms of radiant energy whose quantum unit is the photon. It involves cutting -edge uses of lasers, optics, fiber-optics, and electro-optical devices in numerous and diverse fields of technology – alternate energy, manufacturing, health care, telecommunication, environmental monitoring, homeland security, aerospace, solid state lighting, and many others. Why Photonics Is Important? Lasers and other light beams are the “preferred carriers” of energy and information for many applications. For example: ▪ Lasers are used for welding, drilling, and cutting of metals, fabrics, human tissue, and other materials. ▪ Coherent light beams (lasers) have a high bandwidth and can carry far more information than radio frequency and microwave signals. ▪ Fiber optics allow light to be “piped” through cables. ▪ Spectral analyses of gases and solid substances provide positive identification and quantifiable concentrations. ▪ In short, light is a photon. “A photon is a particle of light defined as a discrete bundle of electromagnetic energy”. These discoveries led to the quantum mechanical notion that light is both a wave and a particle. “quanta-plural of quantum” (a discrete quantity of energy proportional in magnitude to the frequency of the radiation it represents) for example photon-a quantum of light energy or A photon is a quantum of electromagnetic energy, which means, that the electromagnetic energy is composed of a number of the smallest particles possible called photons, whose energy depends upon the frequency of them. 2-Photons in the Quantum Era (The blackbody spectrum and the birth of quantum) “The term “blackbody” (which is a perfect absorber) had argued in 1860 by Gustav Kirchhoff (1824– 1887)”. The 1911 Nobel Prize in Physics went to Wilhelm Wein for his blackbody studies. Only in 1918 did Planck receive the Nobel for "his discovery of energy quanta." Einstein followed in 1921 for his work on the photoelectric effect. In 1922, the Nobel went to Bohr for his quantum work. Albert Einstein (1879–1955) was able to provide a complete explanation of the effect (absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence). Two experimental "laws" connected to black-body radiation: 1. Stefan-Boltzmann Law: There is no more important law in environmentally relevant physics than the relationship between the power radiated by a dense hot body and the temperature. The origins of quantum mechanics arose from the failure of classical methods to explain the spectral distribution of light from hot objects. 2. Wien’s Displacement Law: As the temperature of a blackbody varies, so does the frequency at which the emitted radiation is most intense. In fact, that frequency is directly proportional to the absolute temperature: νmax∝T (1.3) where T is the absolute temperature in Kelvins, b is a constant of proportionality, known as Wien’s displacement constant, equal to 2.8978 × 10−3 K.m. Wien’s Law tells us where (meaning at what wavelength) the star's brightness is at a maximum. See the picture below – the red dot under the word “visible” is the peak for the 6000 K object. In other words, Wien's law tells us what color the object is brightest at. As the surface temperature rises, this peak intensity (brightness) shifts toward the bluer end of the spectrum. As the surface temperature decreases, the peak intensity/brightness will shift more towards the redder end of the spectrum as shown by the red dot in the picture below https://chriscolose.wordpress.com/2010/02/18/greenhouse-effect-revisited/ Wien's Law tells us that objects of different temperature emit spectra that peak at different wavelengths. Hotter objects emit most of their radiation at shorter wavelengths; hence they will appear to be bluer. Cooler objects emit most of their radiation at longer wavelengths; hence they will appear to be redder. Remember, at any wavelength, a hotter object radiates more energy (is more luminous or brighter) at all wavelengths than a cooler one. Example: A star like the Sun, with a surface temperature of about 5800 K, emits most of its radiation in the visible spectrum, with the peak wavelength around the yellow- green region (~500 nm). A hotter star, say around 10,000 K, emits its peak radiation at even shorter wavelengths, making it appear bluish. Conversely, cooler stars with temperatures around 3000 K emit peak radiation in the red/infrared region, making them appear red. H.M 1-What wavelength (in nanometers) is the peak intensity of the light coming from a star whose surface temperature is 11,000 Kelvin? (Note: This is about twice the temperature of our Sun’s surface.) 2-Determine the surface temperature of a star whose maximum intensity is at 400nm. Blackbody radiation is about the distribution of frequencies of photons that are emitted, so it's the photons that are emitted in this case - whereas in the photoelectric effect it's the electrons that are emitted. The two are connected as they are both topics that needed the quantum theory to explain. Classical theory didn't explain the photoelectric effect. Also using classical theory there was a problem with black body radiation  Types of Interference: Constructive Interference: Occurs when the crest of one wave meets the crest of another wave, increasing the amplitude (height or strength) of the resulting wave. In this case, the resulting wave is enhanced and becomes stronger or brighter. For example: When two light waves meet so that the crests and troughs are in sync with each other. Destructive Interference: Occurs when the crest of one wave meets the trough of another wave, reducing or canceling out the amplitude of the resulting wave. In this case, the two waves are partially or completely cancelled out, and the result is a wave with a lower amplitude or even no light at some points. For example: If two beams of light interfere in exactly the opposite way, this can result in dark areas. Interference Conditions: For interference to occur significantly, the waves that interfere must be coherent and of a fixed frequency. This means that the waves must have a specific and fixed phase relationship with each other. For example, light emitted by two laser sources can be coherent and cause interference. Examples of interference: Young’s Double-Slit Experiment: In this classic experiment, light from a coherent source passes through two narrow slits, and the light emerging from the slits interferes on a background screen. This results in a pattern of bright and dark lines, with constructive interference occurring in the bright areas and destructive interference in the dark areas. Interference in thin films: This phenomenon can be seen when looking at the changing colors that appear on the surface of soap bubbles or oil slicks. Here, light reflected from different layers of the material interferes, resulting in color patterns that depend on the thickness of the layer and the wavelength of the light. Er = E (n1 - n2)/(n1 + n2) and the transmitted light has the amplitude Et = E (4 n1 n2)/(n1 + n2)2 Practical applications of interference: Optical spectroscopy: The interference phenomenon is used in spectroscopic instruments to analyze different wavelengths of light. Holography: It relies on interference to create three-dimensional images.  Optical fibers: Interference is used in detectors and signal processing in optical communication systems. Interference is the result of the interaction of two or more waves, and can be constructive or destructive. The result of interference depends on how the waves are synchronized in time and space, and this phenomenon is one of the basic principles in the science of light and waves. Diffraction 1-Diffraction is the phenomenon that occurs when light (or any wave) passes through a narrow slit or around the edge of an object, and the light spreads out and interferes behind the obstacle instead of traveling in a straight line. This phenomenon depends on the nature of waves and occurs most clearly when the size of the obstacle or opening is close to the wavelength of the light. Amplitude – for any diffraction to occur, the incident waves must have a higher amplitude than the slit width. If the wave is smaller than the slit width, no diffraction will occur. Slit Width – Assuming an incident plane wave, decreasing the slit width will make diffraction more dramatic, and increase the angle at which the waves spread from the slit. Wavelength – Decreasing wavelength, or increasing frequency has a similar effect as increasing the slit width. A lower wavelength decreases the diffracted angle. 2. Types of Diffraction, There are two main types of diffraction: If a parallel beam of light from a distant source encounters an obstacle, the shadow of the obstacle is not a simple geometric shadow but is, rather, a diffraction pattern. For example, it is well known that the diffraction pattern formed by a slit looks like the function shown in Figure Such diffraction is called Fraunhofer diffraction If, however, the source of light is not distant, but is close to the diffracting obstacle so that the incident waves are not plane waves, the diffraction pattern will look somewhat different. Such diffraction is called Fresnel diffraction, and its theory is, unsurprisingly, a little more difficult than the theory for Fraunhofer diffraction. If the source of light is a point source, so that the incident wavefronts are spherical, the detailed quantitative theory is not at all easy. If the incident wavefronts, however, are cylindrical (say from a linear source) the analysis, which is two dimensional, is a little more tractable. Cornu’s spiral is a graphical device that enables us to compute and predict the Fresnel diffraction pattern from various simple obstacles. Fraunhofer Diffraction: Occurs when the incident wave and the screen are far enough apart for the branching rays to be approximately parallel. This type is used in many practical applications such as spectroscopy. Fresnel Diffraction: This occurs when the incident wave and the screen are close to the obstacle, which results in diverging rays. 5. Diffraction Grating In the case of a diffraction grating, which consists of a large number of parallel slits on a surface, diffraction is more pronounced and detailed. Each slit in the grating acts as a small point source of the light wave. When these waves interfere, they produce fine diffraction patterns. Diffraction Grating Equation: For a slit containing a large number of openings (diffraction grating), the diffraction is the same question before 6. Diffraction in Nature and Practical Applications Sound Diffraction: Diffraction is used in medical ultrasound imaging techniques and in acoustic radars. Optical Fibers: Diffraction is used to analyze how light travels through optical fibers. Spectrometers: Many spectrometers rely on the phenomenon of diffraction to analyze different wavelengths of light. 7. Practical applications in optical devices Cameras: Camera lenses are designed to reduce the effects of diffraction and obtain clearer images. Lasers: Laser beams are directed through diffraction slits or gratings to analyze spectra and make accurate measurements. 8. Conclusion: Diffraction is a fundamental phenomenon in wave and optical physics, and plays an important role in many scientific and industrial applications. Understanding diffraction helps explain many natural phenomena and develop devices that rely on light and waves. What is the difference between interference and diffraction? Interference and diffraction are two physical phenomena related to the behavior of waves, especially light, but they differ in the conditions under which they occur and the physical mechanisms that drive them. Here is a comparison that illustrates the difference between them: 1. Physical Mechanism: Interference: Occurs when two or more waves in the same area interact and intertwine to form a new pattern. The interference pattern depends on how the crests and troughs of the waves coincide. Constructive Interference: When the crests of two waves meet together, increasing the amplitude. Destructive Interference: When the crest of one wave meets the trough of another wave, decreasing or canceling the amplitude. Diffraction: Occurs when a wave (such as light) propagates after passing through an opening or around an obstacle. Diffraction is the bending of waves around the edges, causing the wave to propagate in multiple directions and form light patterns. 2. Conditions: Interference: Requires the presence of coherent sources, such as two waves of the same frequency and wavelength. It usually occurs when there are multiple overlapping waves, such as Young's double-slit experiment. Diffraction: Occurs when waves pass through a narrow opening or around an object that is small relative to the wavelength. Interfering waves are not necessarily coherent, and diffraction occurs even if only one wave passes through an opening. 3. Wave Pattern: Interference: Interference produces a pattern of bright and dark lines due to constructive and destructive interference. This pattern depends on the phase differences between the interfering waves. Diffraction: Diffraction produces a different pattern based on the bending of waves around the edges. It appears as bright and dark fringes, but depends more on the size of the aperture or object. 4. Results: Interference: Interference depends on the superposition of waves, and can produce areas that are completely dark (destructive interference) or completely bright (constructive interference). Interference is used in applications such as precision length measurement and holography. Diffraction: Diffraction produces a pattern of fringes that become weaker as they move away from the center. Diffraction depends on the wavelength of light and the size of the obstacle or aperture, and is used in spectroscopy and many optical applications. 5. Examples: Interference: Young's double slit experiment: Two waves pass through two narrow slits and interfere to form a pattern of bright and dark bands. Thin films: Such as oil on water, where waves reflected from the top and bottom surfaces of the film interfere. Diffraction: Single-slit diffraction: When light passes through a narrow slit, it spreads out in a fringe pattern due to the bending of light around the edges of the slit. Diffraction of light around obstructions: Such as seeing dull shadows due to the bending of light around the edges of an object. 6. Equations: Interference: Interference equations depend on the phase difference between the interfering waves. For example, for Young's double-slit experiment. Diffraction: Diffraction equations depend on the width of the slit or obstacle. For example, in single-slit diffraction, the positions of the dark fringes. 7. Practical Applications: Interference: Used in holographic imaging systems, precision length measurements, and optical communications technology. Diffraction: Used in spectroscopic instruments to analyze light and determine wavelengths, and in the design of optical fibers. Conclusion: Interference occurs when multiple waves interact with each other, and their superposition produces a pattern of bright and dark lines. Diffraction occurs when waves bend around the edges of obstacles or pass through openings, causing them to spread out and form patterns of light and dark. The main difference is that interference is based on the superposition of two or more waves, while diffraction is based on the interaction of a single wave with an obstacle or opening. What is the difference between Conventional photonics and advanced photonics? Conventional photonics and advanced photonics differ fundamentally in the range of technological applications used. This comparison can be summarized as follows: 1. Basic concepts: Conventional photonics: deals with the study of light and its interactions with matter, and its applications are diverse such as lenses, contrast, refraction, and interference. It also includes innovative uses in areas such as lasers, optical fibers, and the design of optical components. Advanced photonics: deals with advanced technologies that rely on the basic principles of photonics, but have been further developed using diverse materials, quantum electronics, and non-traditional technologies. It includes advanced uses in quantum computing, optical radars, and micro-sensing technology. 2. Technology used: Conventional photonics: relies heavily on single optical components such as mirrors, lenses, and conventional lasers. These devices are used in devices such as conventional lasers, wavelength meters, and optical fibers. Advanced photonics: relies on modern technologies such as nanodevices, integrated photonic circuits, and the brilliance of new photonics such as metamaterials. It also includes devices such as advanced photonics, single photon detectors, and advanced lasers “a petawatt-class laser with peak power exceeding a quadrillion (1015) watts. 3. Applications: Conventional photonics: Focuses on applications that rely on the basic principles of optics, such as optical fiber communications, industrial and medical lasers, and optical instruments used in scientific and educational applications. Advanced photonics: Opens new horizons in areas such as optical computing, quantum communications, various optical devices, advanced solar energy, and high-resolution medical imaging. 4. Materials and optical properties: Conventional photonics: We often use conventional materials such as glass, plastic, and silicon in the design of optical components. It takes on linear phenomena such as reflection, refraction, and iodine. Advanced photonics: Cosmetics such as metamaterials are used that can control light in different ways than in conventional materials. In addition to nonlinear phenomena (nonlinear optics) such as the ability to harmonics, Kerr cost (Kerr effect). 5. Scales: Conventional photonics: works on very different scales, using classical components in large electronics such as city-level optical communications. Advanced photonics: works on very small scales up to nanoscales, where light can be controlled at the level of molecules and atoms, allowing for precise details such as diverse optical circuits and molecular detection. 6. Conclusions: Conventional photonics: a technology considered old, as it has reached research aimed at confirmation and goal. Advanced photonics: what we seek in advanced research stages in many applications, with a focus on developing quantum computing, coordinating it using single photons, and developing small, infinite devices. In short, conventional photonics relies on basic alternatives and its interactions in daily industrial applications, while advanced photonics relies on the use of light in future technology that depends on nano and motherhood to improve and enhance new options in advanced fields such as communications and computing.