Education and Training in Optics and Photonics

Similarities and differences in microwave and optical radiation detection

Negussie Tirfessa, Chandrasekhar Roychoudhuri

Published Jul 2, 2019• 0 citations

Abstract

The differences and similarities between the detection processes involved in the microwave and visible electromagnetic (EM) waves are presented for the case of two beam superposition. A microwave receiver measures the motion of conduction electrons which responds linearly to the superposed time dependent EM field amplitudes. A visible light detector also responds to the superposition of the EM field amplitudes due to interactions with the detecting dipoles. However, the visible light detector measures the quantum of energy absorbed and responds to the square modulus of the superposition of the time dependent amplitudes of the EM fields. The measured current in the microwave detector is directly proportional to the superposed microwave amplitudes. The measured energy in visible light detector is directly proportional to the square modulus of the superposed visible light amplitudes. We will highlight the similarities and differences in the detection processes. These important similarities and difference are not underscored in most optics textbooks.

DOI: 10.1117/12.2525442

Related papers

Can we get any better information about the nature of light by comparing radio and light wave detection processes?

Chandrasekhar Roychoudhuri, Peter Poulos

Comparing the radio and the light wave detection processes, this paper clarifies that what we normally call "interference" of EM waves, is actually the summation of the field induced signals carried out by the detectors. We have also presented a generalized definition of the superposition effects as measured (SEM) due to multiple physical steps behind any detection process. Thus the manipulation of the various physical properties of the detectors to various parameters of the EM waves can yield different "interference" effects for the same set of superposed waves. If EM waves interfered by themselves, such manipulation would not have been possible. We also give simple examples of visibility degradations due to rotation of the states of polarization and underscore that such degradation should not be assigned to degradation of coherence properties of the EM waves. It is due to the change in the stimulating amplitude, reduced by Malus'cosθ law, which is accessible to the uniaxial dipole like response of the detecting molecules.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIEAug 26, 20074 citations

Emergence of Superposition Effects

Chandrasekhar Roychoudhuri

This chapter explains the basic mathematical framework behind the emergence of the superposition effect as experienced by detectors when simultaneously stimulated by more than one EM wave by modeling the light–matter interaction process in view of the Non-Interaction of Waves property. The growing field of quantum optics does treat the atoms and molecules as quantum dipoles and EM waves mostly as classical waves. The summation of amplitudes implied by the superposition principle is actually carried out by the oscillating dipoles as their single conjoint dipolar stimulation, while constrained by their intrinsic quantum properties. The measurable superposition effects, which are always reported by detectors, are colored by their own unique response characteristics. Thus, one can generate different types of measurable superposition effects simply by changing the quantum characteristics of the detectors.

CRC Press eBooksMay 7, 20140 citations

A QED-compatible wave theory of light, electrons, and their interactions

Henry H. Lindner

The photoelectric effect, the Compton effects, and now anticorrelation experiments have been claimed to prove that light consists of particles flying through a void. However the particle model is decisively falsified by the known wave qualities of electromagnetic radiation. Quantum Electrodynamics also uses spreading wave amplitudes; not flying particles. The evidence indicates that light is a wave and electrons are electromagnetic wave-structures that absorb and emit light in discrete wave-packets. These wave-quanta are emitted directionally and then spread in space in proportion to their wavelength. Their waves superposition with all other waves in space. In low intensity experiments, the waves that an electron in a photodetector absorbs come from the superpositioning of the source wave-quanta and background radiation. The importance of background radiation is evidenced by "dark counts". Treating electrons and the quanta they absorb and emit as particles when they are composed of waves is the source of all the paradoxes, unreality and confusion in Quantum Mechanics. The word "photon" should be replaced by "quantum" in the description of this particular electronic process. The conceptual model presented here explains the known phenomena without producing paradoxes and unifies quantum and classical electromagnetics.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIESep 8, 20111 citation

Light detectors

Harry Paul

Light absorption Whereas receiving radio waves is a macroscopic process and hence belongs to the area of classical electrodynamics – in a macroscopic antenna an electric voltage is induced whereby a large number of electrons follow the electric field strength of the incident wave, in a kind of collective motion – the detection of light, so far as the elementary process is concerned, takes place in microscopic type objects such as atoms and molecules. As a consequence, the response of an optical detector is determined by the microstructure of matter. In particular, it is impossible – due to the enormously high frequency of light (in the region of 10 15 Hz) – to measure the electric field strength. What is in fact detectable is the energy transfer from the radiation field to the atomic receiver, and this allows us to draw conclusions about the (instantaneous) intensity of light. We might ask what we can say about the above-mentioned absorption process from an experimentalist's point of view. Among the basic experiences that provide an insight into the structure of the micro-cosmos is the resonance character of the interaction between light and an atomic system. The atomic system, when hit by light, behaves like a resonator with certain resonance frequencies; i.e. it becomes excited (takes up energy) only when the light frequency coincides with a value that is characteristic for the particular atom. Hence, an incident light wave with an initial broadband frequency spectrum that has passed through a gas exhibits in its spectrum dark zones, the so-called absorption lines.

Cambridge University Press eBooksMay 20, 20040 citations

Measurement of Quantized Field and Photon

Yanhua H. Shih

In the Maxwell continuum wave theory of light, a photodetector measures the intensity of the Electro Magnetic wave. The output current of the photodetector is proportional to the intensity of input light. Since the introduction of the concept of photon, or the concept of field quantization, physicists started to premeditate single-photon detection, theoretically and experimentally. Due to slight differences in their optical paths, at certain locations, the radiations superposed constructively, at other locations the field superposed destructively. A sinusoidal modulation is thus observable. However, people found this interpretation may not be appropriate when the experimental physicists improved the sensitivity of their photodetector to the single-photon level. Almost everyone was surprised that the interference was still observable in the observation plane, and the sinusoidal modulation observed from single-photon was exactly the same as before. A single-photon counting detector is able to count photons one by one.

CRC Press eBooksDec 16, 20200 citations

Differentiating the Superposition Principle from the Measurable Superposition Effects in Interferometry

Chandrasekhar Roychoudhuri

The physical interaction processes behind the emergence of dark and bright fringes registered by the detectors at the output of optical interferometers is explained. This knowledge should be helpful to interferometrists to make better physical interpretations of their data. The belief in mysterious “interference of single indivisible photon” will disappear once we recognize that the spatial or temporal energy re-distributions are generated by the physical transformation experienced by the detecting molecules drawing energy from all the light beams. The molecules could be photodetectors at the interferometer output, or the beam combining dielectric boundary. The superposition principle (SP), represented by the linear mathematical sum of two or more wave amplitudes, does not represent an observable phenomenon. The superposition effect (SE), represented by the non-linear square modulus of the joint dipolar stimulation of the detectors by all the superposed waves, is observable. We present two laboratory experiments to clarify these points. Both classical beam combiners and quantum detectors are capable of generating superposition fringes of intensity variations. The logic of “quantumness” of light is narrowly relevant only when a quantum detector deciphers the fringes; it is not valid for classical beam combiners. We will also discuss “entanglement” based on these experiments.

IntechOpen eBooksFeb 7, 20192 citations