Optics and Photonics Journal
ISSN / EISSN : 2160-8881 / 2160-889X
Current Publisher: Scientific Research Publishing, Inc. (10.4236)Former Publisher:
Total articles ≅ 515
Latest articles in this journal
Optics and Photonics Journal, Volume 11, pp 110-120; doi:10.4236/opj.2021.115009
The design of optical instruments is an active subject due to improvement in lens techniques, fabrication technology, and data handling capacity. Much remains to do to expand its application to phytopathology, which would be in particular quite useful to improve crop growth monitoring in countries like Mali. An optical multimodal system for plant samples has been developed to improve the characterization of leaf disease symptoms, provide information on their effects, and avoid their spread. Potentially inexpensive components (laser, lens, turntables camera and sample, filter, lens, camera and computer) have been selected, assembled and aligned on an optical table into a multimodal system operating in transmission, reflection, diffusion and fluorescence. The illumination and observation angles can be adjusted to optimize viewing conditions in the four modes. This scientific contribution has been an initiation into the design and implementation of an optical instrument. Initial results are shown and will now be extended in cooperation with agronomic laboratories in African countries for tests on specific plant diseases in relation with prevailing climate conditions.
Optics and Photonics Journal, Volume 11, pp 105-109; doi:10.4236/opj.2021.115008
Light coming from remote galaxies is redshifted and it is accepted that redshifts are produced by every galaxy running away from each other in a particular manner. According to this theory, galaxies can be grouped by the distance to earth in four spaces: the closer ones with no acceleration, the next ones with acceleration, the next remote ones with deceleration, and the farther ones without characterization. All that complexity is disregarded in this paper by assuming that the photons are ruled by longitudinal and transverse gravitational potentials. These relativistic invariant potentials create coherence quantum states of energy and subsequently the light redshift is created by photons moving down across those energetical levels.
Optics and Photonics Journal, Volume 11, pp 89-103; doi:10.4236/opj.2021.114007
GeSe nanosheets were prepared by ultrasonic-assisted liquid phase exfoliation (LPE), and the nonlinear saturated absorption performance was experimentally studied. The modulation depth and saturation intensity of the prepared GeSe saturable absorber (SA) were 15% and 1.44 MW/cm2, respectively. Using the saturated absorption characteristics of GeSe SA, a passively Q-switched erbium-doped fiber laser was systematically demonstrated. As the pump power increases, the pulse repetition frequency increases from 22.8 kHz to 77.59 kHz. The shortest pulse duration is 1.51 μs, and the corresponding pulse energy is 46.14 nJ. Experimental results show that GeSe nanosheets can be used as high-efficiency SA in fiber lasers. Our results will provide a useful reference for demonstrating pulsed fiber lasers based on GeSe equipment.
Optics and Photonics Journal, Volume 11, pp 79-88; doi:10.4236/opj.2021.114006
This paper proposes a new metamaterial design that can achieve electromagnetic induction transparency-like (EIT-like) effects in the microwave band. The unit structure of metamaterials consists of square rings and metal wires. The square ring acts as the “bright state” and the metal wire acts as the “dark state”. The destructive interference between the bright state and the dark state produces an EIT-like effect. In the simulation results, a transparent window centered at 4.00 GHz can be observed in the transmission spectrum. By studying the phase change of the transparent window, it is found that the group delay of the metamaterial structure can reach 0.39 ns at 4.00 GHz. This paper also studies the influence of the refractive index of the medium on the EIT-like effect. Numerical simulations show that such metamaterial is very sensitive to the refractive index of the medium, and the sensitivity is 15 mm/RIU. Our design can be extended to other frequency bands and may have potential applications in filtering, sensing, slow-light devices, and nonlinear optics.
Optics and Photonics Journal, Volume 11, pp 121-131; doi:10.4236/opj.2021.115010
This paper begins by exploring a useful and neglected detail of a photon—its physical size perpendicular to the direction of propagation in the same way as an atom or neutron has a physical size. Such a photon size would be quite separate from the cross-section of a photonic interaction, which depends on the material interacting. Such a perpendicular dimension of a photon will be invariant under Lorentz transform parallel to the light propagation direction and will thus be the same for all frequencies of light. This study also leads to new details about how a photon interacts, offering an explanation for the familiar physics where light slightly above and below the mean frequency of an excited state can still excite the same state without violation of conservation of energy—a mystery explored thoroughly in a previous paper without finding the solution offered here. As usual, a better elucidation of the details of light interaction also leads to new insights—especially about the vacuum field. The Appendix summarizes some previous research relevant to this discussion
Optics and Photonics Journal, Volume 11, pp 133-139; doi:10.4236/opj.2021.116011
The droplet size, size distribution, refractive index, and temperature can be measured simultaneously by the rainbow technique. In the present work, the rainbow scattering diagram for a spherical droplet in the secondary rainbow region is simulated by the use of the generalized Lorenz-Mie theory. For achieving high spatial resolution in denser droplet sprays, a focused Gaussian beam is used. For droplet characterization, different inversion algorithms are investigated, which includes trough-trough (θmin1 and θmin2) method and inflection-inflection (θinf1 and θinf2) method. For the trough-trough algorithm, the absolute error of the refractive index is between −6.4 × 10−4 and 1.7 × 10−4, and the error of the droplet radius is only between −0.55% and 1.77%. For the inflection-inflection algorithm, the maximum absolute error of the inverted refractive index is less than −1.1 × 10−3. The error of the droplet radius is between −0.75% and 5.67%.
Optics and Photonics Journal, Volume 11, pp 63-78; doi:10.4236/opj.2021.114005
This research presents an improved real-time face recognition system at a low resolution of 15 pixels with pose and emotion and resolution variations. We have designed our datasets named LRD200 and LRD100, which have been used for training and classification. The face detection part uses the Viola-Jones algorithm, and the face recognition part receives the face image from the face detection part to process it using the Local Binary Pattern Histogram (LBPH) algorithm with preprocessing using contrast limited adaptive histogram equalization (CLAHE) and face alignment. The face database in this system can be updated via our custom-built standalone android app and automatic restarting of the training and recognition process with an updated database. Using our proposed algorithm, a real-time face recognition accuracy of 78.40% at 15 px and 98.05% at 45 px have been achieved using the LRD200 database containing 200 images per person. With 100 images per person in the database (LRD100) the achieved accuracies are 60.60% at 15 px and 95% at 45 px respectively. A facial deflection of about 30° on either side from the front face showed an average face recognition precision of 72.25%-81.85%. This face recognition system can be employed for law enforcement purposes, where the surveillance camera captures a low-resolution image because of the distance of a person from the camera. It can also be used as a surveillance system in airports, bus stations, etc., to reduce the risk of possible criminal threats.
Optics and Photonics Journal, Volume 11, pp 12-21; doi:10.4236/opj.2021.111002
A hypothesis explaining the diffraction and interference of light from a pure corpuscular point of view was published in 2018. The author developed the idea by a fortunate combination of intuition and statistics but failed to justify it theoretically. This vagueness can be amended by using relativistic invariants. Adapting Dirac’s equation to gravitational potentials acting over photons yields most of the properties of light. A complete characterization of the properties of light arriving from distant galaxies was performed by modeling the coherence of light. It was assumed that the coherence of light is generated by two orthogonal potentials. Here an idea explains the cosmological redshift data as is done by the combination of Big-Bang, acceleration, and deceleration trilogy.
Optics and Photonics Journal, Volume 11, pp 1-11; doi:10.4236/opj.2021.111001
When the light beam propagates in the atmosphere, the signal will be absorbed and scattered by the gas molecules and water mist in the atmosphere, which will cause the loss of power rate. The complex atmospheric environment will produce a variety of adverse effects on the signal. The interference produced by these effects overlaps with each other, which will seriously affect the strength of the received signal. Therefore, how to effectively suppress the atmospheric turbulence effect in the random atmospheric turbulence channel, ensure the normal transmission of the signal in the atmospheric channel, and reduce the bit error rate of the communication system, is very necessary to improve the communication system. When processing the received signal, it is an important step to detect the transmitted signal by comparing the received signal with the threshold. In this paper, based on the atmospheric turbulence distribution model, the adaptive signal decision threshold is obtained through the estimation of high-order cumulant. Monte Carlo method is used to verify the performance of adaptive threshold detection. The simulation results show that the high-order cumulant estimation of atmospheric turbulence parameters can realize the adaptive change of the decision threshold with the channel condition. It is shown that the adaptive threshold detection can effectively restrain atmospheric turbulence, improve the performance of free space optical and improve the communication quality.
Optics and Photonics Journal, Volume 11, pp 23-49; doi:10.4236/opj.2021.112003
Certain hybrid prototypes of dispersive optical solitons that we are looking for can correspond to new or future behaviors, observable or not, developed or will be developed by optical media that present the cubic-quintic-septic law coupled, with strong dispersions. The equation considered for this purpose is that of non-linear Schrödinger. The solutions are obtained using the Bogning-Djeumen Tchaho-Kofané method extended to the new implicit Bogning’ functions. Some of the obtained solutions show that their existence is due only to the Kerr law nonlinearity presence. Graphical representations plotted have confirmed the hybrid and multi-form character of the obtained dispersive optical solitons. We believe that a good understanding of the hybrid dispersive optical solitons highlighted in the context of this work allows to grasp the physical description of systems whose dynamics are governed by nonlinear Schrödinger equation as studied in this work, allowing thereby a relevant improvement of complex problems encountered in particular in nonliear optaics and in optical fibers.