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With the establishment of validity using authoritative experimental results, an analytical investigation of an SPR-based fiber optic sensor, employing a wave-theory-based technique for determining breast cancer by shining a radially polarized Bessel–Gauss (RPBG) beam, is proposed. First, by using a radially polarized Gaussian (RPG) beam, the observed sensitivity is 9404.61 dB/RIU, where the acquired results are in good concurrence with the experimental data reported by Yan et al. [Chin. Opt. Lett. 7, 909 (2009)COLHBT1671-7694]. Thus, the proposed theory has been validated with the reported experimental data. This theoretical analysis is further extended by utilizing an RPBG beam, where the observed sensitivity is 21,699.26 dB/RIU and 5846 nm/RIU, with a resolution of 4.61 × 10 − 7 , which is 2.5 times superior to the reported results to date. By using an RPBG beam, the proposed method, to our best knowledge, is the first to achieve much higher sensitivity in the area of fiber optic breast cancer detection. The higher sensitivity achieved at lower concentrations of an HER2 biomarker has led to the idea of early diagnosis of breast cancer by optically assessing it at its earlier stage using a high-resolution wavelength-interrogation technique.

With the experimental corroboration employing a transfer matrix method, an analytical observation of optical bistability using long-range surface plasmon resonance (LRSPR) through the external magnetic field is presented for a very low threshold value. The proposed analytical method has been verified with the reported experimental data provided by Liu et al. [Curr. Appl. Phys. 29, 66 (2021)1567-173910.1016/j.cap.2021.06.003]. Now theoretical analysis is further extended in the proposed multilayered structure comprising an InAs layer sandwiched between two graphene layers, whose electromagnetic response at 2 THz can be regulated by employing a magnetic field and may tune the optical bistability without modifying the geometry or the characteristics of the structure. The observed threshold intensity for the switch-up is 6.6615×104W/cm2 at 0.001 T; thus, this analytical approach is able to achieve 2 orders lower threshold for magnetically tunable upswitching of the optical bistable process. This suggested magnetically adjustable optical bistable arrangement gives a possibility for the comprehension of optical logic gates, optic memory, opto-transistors, and switches at a low switching threshold due to extraordinary features of the composite layers due to local field amplification of the graphene layer.

Measurement of vibration without having contact with the target is crucial for many applications. However, real time vibration signals are frequently mixed with various levels of dynamic noises. In this research, a non-contact type vibration measurement system based on laser triangulation method is proposed by using a PSD (Position sensitive detector) and here a single axis Brüel and Kjaer piezoelectric accelerometer is used to validate the experimental results. The primary goal of this measurement system is to develop a Gabor Transform based signal denoising technique, in order to eliminate noise from the real-time vibration data. Furthermore, PSD platform vibration, which might cause unanticipated inaccuracies in the detected vibration data, has also been eliminated by utilizing a self-vibration compensation approach using an ADXL-345 three-axis accelerometer. The self-vibration compensated vibration measurement technique has been designed using an NI (national instruments) cRIO (CompactRIO) 9074 real-time FPGA (field programmable gate array) based embedded controller. Consequently, a Gabor Transform and Expansion-based Signal Processing Technique is designed using NI cRIO-9074 real time platform to reduce external noise from the self-vibration compensated vibration data. It has been observed that the implementation of Gabor Transform has improved the performance of the system in term of enhancing the SNR (Signal-to-noise ratio).

This study presents a winding open‐circuit fault‐tolerant control scheme for an open‐end induction motor drive with common DC bus for dual inverters. The proposed control scheme also permits balanced three‐phase operation of the same motor under healthy operation. It can suppress common mode current easily, yet permits maximum DC bus utilisation in both operating modes. It is mathematically established here that during fault‐tolerant operation, the magnetising current increases by a factor of √3. As a result, the airgap flux during fault‐tolerant operation is same as that during balanced three‐phase operation. An analytical relation is proposed for maximum torque capability of the machine during fault‐tolerant operation, taking into account the limit of winding current to its rated value and increase of magnetising current during such an operation. Extensive mathematical analysis is supported by simulation and experimental results to validate the performance of the proposed scheme during balanced three‐phase operation as well as winding open‐circuit fault‐tolerant operation.

An analytical exploration of a fiber-optic biosensor with a tapered structure for the detection of breast cancer at its early stage by illuminating the Bessel–Gauss beam in a multilayer structure, using wave-theory-based technique, is proposed to acquire closer results between experimental and theoretical models. By using a Gaussian beam, the observed sensitivity is 2688.5 dB/RIU and 0.204 nm/ng/mL, where all the results are in good agreement with the experimental outcomes reported by Sun et al. [Opt. Commun. 463, 125375 (2020)10.1016/j.optcom.2020.125375]. Thus, this proposed theory is experimentally validated. Now, this tapered theoretical analysis is further extended utilizing the Bessel–Gauss beam, where for the first time, to the best of our knowledge, the discerned sensitivity is enhanced to 14,979.8 dB/RIU and 0.33 nm/ng/mL with a resolution of 6. 68 × 1 0 − 7 , which is 6.59 times superior to the reported results to date. Higher spectral shifts are noticed using the wavelength interrogation technique for the concentration of (2–15) ng/mL of HER2 biological marker. Thus improvement in sensitivity and resolution at lower concentrations is achieved, which indicates the proposed idea for the identification of breast cancer at its early stage.

This study presents a novel fast Fourier transform (FFT)-based non-contact vibrational harmonics measurement system using a position sensitive detector (PSD) along with calibration using a piezoelectric accelerometer. Frequency-domain vibrational analysis is required as the changes in machine dynamics are directly related to its failures and could provide more insight into the vibration signal. In this regard, FFT is used for spectral analysis to detect the harmonics in the vibration signal. The novelty of the applied technique for detecting vibrational harmonics lies in its innate contactless nature where the vibration detection sensor i.e. PSD is placed at a particular distance from the vibrating target. Additionally, the parasitic and external vibrations, which might pose unforeseen errors in the detected vibration data, have been nullified by employing a self-vibration technique using an ADXL-345 three-axis accelerometer. The results obtained through PSD have been calibrated via a standard Bruel & Kjaer (B & K) vibration measurement system which uses a piezoelectric accelerometer (B & K accelerometer). The proposed measurement technique is equipped with NI compact RIO-9074 that features a real-time processor and an FPGA. The system was observed to effectively measure the frequency range 5–600 Hz with a maximum relative error of 2% in FFT amplitudes.

An idea towards the low threshold optical bistability and tunability of bistable thresholds at THz frequency under realistic situation is analyzed through a proposed multilayered configuration. The proposed configuration comprises a coupling prism of silicon, and monolayer graphene sheets spatially separated through 35 nm thick polymer which is sandwiched between an air gap of thickness 4.6 μm and a kerr polymer (GaAs) at 300 K temperature and at an incident light frequency of 2 THz. Utilizing the large nonlinear effect of the configuration obtained by the nonlinearity of the kerr polymer and the high local field effect due to long-range graphene surface plasmon resonance, the switching-down and switching-up threshold values for optical bistability have been markedly reduced upto 1.21×105 V/m and 1.24×105 V/m respectively thereby rendering a minimum threshold intensity of 7.2 kW/cm2 than the articles reported till date. Tunability of the switching-down and switching-up threshold values have also been realized from 1.21×105 V/m to 5.18×105 V/m and 1.24×105 V/m to 1.424×106 V/m respectively through electrical or chemical modification of the charge carrier density and hence fermi energy of the graphene from 0.23 eV to 0.41 eV and from 1.21×105 V/m to 1.56×105 V/m and 1.24×105 V/m to 2.12×105 V/m respectively for the variation in incident angle from 70° to 88°. The effect of damping rate of graphene on optical bistability behavior has also been observed. Therefore the proposed optical bistable configuration finds potential applications in the field of all-optical switching, optical transistor, optical logic, nano-illumination and optical memory with low input threshold at THz frequency and can also be used to realize tunable optical bistable device for future THz optical communication technology.

This paper deals with the development of an effective theoretical approach to generate spatial optical soliton in exceptionally beneficial bulk beta-barium-borate crystal by utilizing cascaded second-order nonlinearity through electro-optic tuning. The proposed methodology paves the way for novel nonlinear optical interactions conceptualized in bulk material depending upon an effective nonlinear refractive index for a broad range of crystal lengths. The development of ( 2 + 1 ) D spatial bright soliton has been analytically demonstrated at 800 nm wavelength of the incident continuous-wave optical radiation, and the implication of tunable electro-optic effect to the crystal’s nonlinear response is also presented here. Involvement of the generalized nonlinear Schrödinger equation has been utilized to develop the necessary and sufficient criteria for self-trapping optical beams considering both linear and nonlinear absorption losses. In conformity with the findings of the simulation, the beam diameter of a generated spatial soliton within this anisotropic crystal is near 56 µm while maintaining precise peak intensity ∼ 0.8 G W / c m 2 .

With experimental validation, an analytical exploration of a surface-plasmon-resonance- and evanescent-wave-based fiber optic biosensor, using Bessel–Gauss beams for early detection of breast cancer, is proposed and designed here. The observed sensitivity is 0.58 nm/ng/mL and 11,928.25 dB/RIU with a resolution of 8.38 × 10 − 7 , which is 10 times better than the reported ray-theory-based articles reported to date using a Gaussian beam. To analyze more effectively the higher-order modes and to achieve more similarity between the analytical and experimental solutions, the wave-theory-based approach is adopted here. With this approach, for the first time to our knowledge using a Bessel–Gauss beam, higher sensitivity is achieved for fiber optic breast cancer detection. The enhanced sensitivity at lower concentrations of the Human Epidermal Growth Factor Receptor 2 biomarker has conceptualized the idea of early detection of breast cancer by optically quantifying the earlier stage of cancer.

The present work introduces the concept of a total-internal-reflection (TIR)-based optical rotation, quasi-phase-matching (QPM) technique for generating highly efficient second-harmonic optical output in a rectangular slab of magnesium oxide-doped lithium niobate crystal coated with a thin layer of yttrium oxide. Combinational effects of TIR optical rotation QPM and fractional QPM techniques are experienced at certain bounce points inside the slab, thereby enhancing the conversion efficiency. In this analysis, the thin-film is used for controlling the phase-shifts accompanying the propagation of p- and s-polarized light at the slab-film interface during TIR. A conversion efficiency of 32%, corresponding to a second-harmonic wavelength of 532 nm has been observed using computer-aided simulation. Optical losses such as surface roughness, absorption, and interference effect due to the nonlinear law of reflection have also been incorporated.

This paper explores the notion and efficacy of harnessing the advantages of position sensitive detector (PSD) in the paradigm of noncontact vibration measurements. The study peruses an innovative foray into the domain of calibrated vibration measurement systems, wherein a first-of-its-kind strategy has been explored to nullify the self-vibration effect of the PSD platform by incorporating a micro-elctromechanical system digital accelerometer. The self-vibration compensated system has been designed and experimentally validated through NI-CompactRIO. The proposed system has been calibrated with a single axis Bruel&Kjaer piezoelectric accelerometer. The system was observed to yield a maximum absolute error of 0.34 Hz in the measuring frequency range of 20–600 Hz. Furthermore, the system was observed to effectively measure displacement in the range of 2.32– $1300~\mu \text{m}$ with a maximum relative error of 2.7% across the span of gain settings varied at designated set of frequencies tested. Successive measurements yielded good repeatability characterized by a maximum standard deviation of $1 ~\mu \text{m}$ . A commendable system linearity was also achieved for its intended range of measurement as characterized by a correlation coefficient of 99.8%. The accuracy and robustness of the noncontact PSD system coupled with its inherent simplicity of system integration establishes itself as a potent and cost-effective tool in the realm of vibration measurements of highly sensitive systems susceptible to microvibrations (

A highly enhanced broadband conversion scheme of Second Harmonic Generation is analytically described in a hyperbolic profiled single crystal GaAs slab using Total Internal Reflection Quasi Phase Matching. The inclusion of the effect arising from the basic law of Non Linear Reflection has interestingly boosted up the conversion efficiency, which otherwise trims down the same as revealed in the conversion schemes comprising parallel, tapered and reverse tapered structures of isotropic semiconductors. Here, the simulated result indicates an enhancement both in terms of efficiency and bandwidth due to higher compensation of the spatial walk-off between the generated Second Harmonic waves along the slab length owing to the hyperbolic profiled upper surface configuration. Consequently, an extremely broad 3 dB bandwidth of 800 nm is obtained in a 32 mm GaAs slab and the conversion efficiency rises to a value of 2.151% which is as high as 1.7 times compared to that without considering the effect of the Non-linear Reflection phenomenon.

In this research, a theoretical perception on the notion of an ultra-high sensitive evanescent wave-based fiber-optic refractive index sensor has been proposed by shining an optical Airy beam. The sensing configuration consists of a multimode fiber which is decladded from the middle to aptly sculpt the evanescent wave. In presence of the Airy beam, effectual coupling of high-order modes within the sensing structure has been affirmed by using the classical wave-optic model. To corroborate our theoretical study, an Eigenmode expansion solver (EME) propagation analysis was conducted in commercially offered Mode solution software (Lumerical Inc.) to investigate the transmission characteristics of Airy beam within the waveguide structure. Compared with conventional Gaussian beam-based sensor, the proposed refractive index sensor renders a maximum 19.15 fold superior sensitivity of 992.39 dB/RIU with an admirable sensing resolution of ∼1.00 × 10−5 RIU. Thus, this nascent-class of beam called Airy beam manifests a new degree of freedom which demonstrates the viability of the proposed scheme for the usage of chemical and biological sensing.

We propose an electro-optically controllable cascaded second-order optical process that mimics as a third-order nonlinear process which is utilized for the compression of ultrashort pulses. Effective compression of optical pulses has been achieved by making efficient use of frequency doubling into an extraordinarily advantageous crystal like beta-barium-borate which is capable of generating shorter pulses within a few cycles. In accordance with simulation, it endeavors ≈ threefold compression in femtosecond pulse, i.e., 47 fs has been achieved by applying a voltage of ∓ 6.2 kV which delivers a phase mismatch (Δk) = ± 117.236 m−1 and effective cascaded refractive index (n2cascade) of ± 3.045 × 10–20 m2/W. This competent compression leads to an increase in the value of peak intensity from 50 to 288 GW/cm2. On account of the decent control in peak intensity, this promising methodology can be utilized for advanced scientific research, and also implemented easily in a large variety of applications in solid-state physics and medical field.

Wavelength Exchanged Optical Phase Conjugation (WE-OPC) through Difference Frequency Generation (DFG) employing two identical Titanium doped Periodically Poled Lithium Niobate (Ti:PPLN) waveguides having same grating period and a single pump source is theoretically analyzed and simulated resulting in higher conversion efficiency of OPC. WE-OPC has been found very effective in mitigating nonlinearity and increasing spectral efficiency in optical transmission systems. In our proposed model with 10 channels, much higher conversion efficiencies of about 3.3 dB and 3.49 dB are obtained for higher frequency band to lower frequency band and vice versa respectively.

Bend-induced loss in microbending fiber-optic sensor has proved to be an effective one for the direct and indirect measurement of various physical parameters. In this research, a novel and highly sensitive microbend sensor has been explored by launching a zero order Bessel-Gauss beam inside a waveguide arrangement having a No-core fiber bonded amidst two special higher-order mode supporting fibers. By harnessing the special characteristics of the Bessel-Gauss beam, pairing of manifold high-order modes has been affirmed inside the sensor structure. The captivating feature of such sensor is that it defies the conventional wisdom and significantly improves the sensitivity without any intricate fabrication techniques like in tapering, bending etc. To our knowledge, such realization of Bessel-Gauss beam-shined microbend sensor has not been reported earlier in any of the contemporary literature. In support of our theoretical analysis; a Beam propagation method is employed in OptiBPM software (Optiwave Systems Inc.) to envisage the full transmission spectrum of the waveguide. For different bend radii, the sensor response has been numerically investigated and it is anticipated that the sensitivity is expected to be enhanced by a gentle reduction in the bend radius. With the presence of six microbends, the proposed sensor manifests an average bend sensitivity of 2.8 dB/mm which is 3.2 times superior to the classical microbend sensing configuration. Due to such superior sensing performance, the present paradigm paves the way for many potential applications, like damage detection of various engineering structures, and measurement of different physical parameters like temperature and pressure.

This research explores the possibility of using non-Gaussian class of beam like Bessel-Gauss beam towards the investigation of a highly-sensitive modal interference-based salinity sensor. Such fiber-optic sensor involves a No-core fiber which is being spliced amid two specialty higher order mode supporting fibers. The main motivation behind our proposed work is that Bessel-Gauss beam has higher amount of energy at the beam's edge which will create larger overlap between the guided modes with the sensing medium without any complex fabrication process. By harnessing such advantages of Bessel-Gauss beam, the efficient excitation of various high-order linearly polarized modes within the sensor structure has been analyzed with emphasis on the coupled mode theory (CMT). To corroborate this, a detailed optical modeling and simulation study on the proposed sensing scheme was performed in mode solutions software (Lumerical Inc, Canada) to predict the propagation behavior of Bessel-Gauss beam within the waveguide structure. Owing to a large number of high-order mode coupling, the proposed sensor unveils a 3.12 fold superior sensitivity as compared to the conventional Gaussian beam-based sensor, with a commendable sensing resolution of 0.005%. Moreover, a detailed simulation study has been executed to examine the sensor behavior for various No-core fiber radii, and axicon apex angles. As the proposed all-fiber salinity sensor features the advantages of higher sensitivity and better sensing resolution, so it has a great prospect in any physical, biological or chemical sensing needs.

This paper explores a comprehensive study at the application of second harmonic generation in low power laser generation by introducing electro-optically adjustable nonlinear phase shift inside a LiNbO 3 crystal. Research on electro-optically adjustable nonlinear phase shift in high power laser generation is completed already by way of the usage of special crystals having higher electro-optic coefficients and higher damage threshold. However, crystal having lower damage threshold can withal be habituated to create this mentioned phenomenon if having better electro-optic coefficients. Hence, on this paper the advanced traits of LiNbO 3 like higher electro-optic coefficients and lower damage threshold that makes this crystal very much handy to increase cascaded nonlinearity in low power laser generation are proposed. As consistent with our theoretical analysis, the propagating fundamental wave is oscillating at 1064 nm parallel to y-axis of the crystal having crystal cut at $\theta=67.14737^{\circ}$ and $\phi=90^{\circ}$ in phase matching direction. A analytical voltage of ±2.5 kV is applied across the crystal's thickness of 5 mm along z-axis of the crystal that creates the phase shift in between the incident and reconveretd fundamental waves which is nonlinear in nature. This nonlinear phase shift can be facilely tuned from maximum to minimum value by adjusting the applied external electric field.

A proposal towards analytical implementation of optical bistability in a multilayered configuration comprising a ZnSe prism, 1-µm-thick PMMA-DR1 (Polymethylmethacrylate-Disperse red) as dielectric layer, nano-Ag: polymeric composite material as a Kerr polymer and a 15-nm thin film of silver which is sandwiched between the dielectric layer and the Kerr polymer at incident light wavelength of 1550 nm with a beam waist of 0.5 mm is presented at 25 °C temperature. Here, the nonlinear Kerr medium is having quadratic dependence on the long-range surface plasmon polariton mode resonance-enhanced local electric field amplitude. Through the larger nonlinear effect of the optimized design by employing high local field effect in the nonlinear regime, a low threshold optical bistability of about 1.6 MW/cm2 in the transmitted light intensity is achieved. The reported threshold is less compared to the previous efforts where the works were carried out with a wavelength other than the important telecommunication wavelength within the C-band. The design also provides tunability of bistable threshold by exploitation of Kerr effect-induced refractive index change through varying pump light intensity. The proposed system proffers potential applications in all-optical networks.

By using the concept of multimode-interference, an ultra-high sensitive fiber optic strain sensor is conceptualized theoretically through the use of a Bessel-Gauss beam. In presence of such non-Gaussian beam, effectual coupling of high-order modes within the sensing structure has been affirmed by using the classical wave-optic model. To corroborate our theoretical study, an Eigenmode expansion solver (EME) propagation analysis was conducted in commercially offered Lumerical Mode solution software to analyze the properties of Bessel-Gauss beam propagation within the waveguide system. Our simulation outcome reveals that the projected sensing system has 3.5 times greater sensitivity than the conventional sensor focused on Gaussian beam. In addition, the influence of No-core fiber radius on the sensing performance was also studied in detail. Due to this high-performance feature, the proposed sensing configuration expedites a new avenue in various industrial and process control applications.

The present work is to numerically investigate the properties of the defect mode in a one-dimensional photonic crystal made of magnetized cold plasma, doped by semiconductor. The defect mode of such kind of multilayer structure is analyzed by applying the character matrix method to each individual layer. Numerical results illustrate that the defect mode frequency can be tuned by varying the external magnetic field, the electron density, and the thickness of the defect layer. Moreover, the behavior of the defect mode was found to be quite interesting when study the oblique incidence. It was found that for both right- and left-hand polarized transversal magnetic waves, the defect mode of the proposed defective structure disappears when the angle of incidence is larger than a particular oblique incidence. For the left-hand polarized transversal electric wave, however, an additional defect mode was noticed. The results lead to some new information concerning the designing of new types of tunable narrowband microwave filters.

This paper describes the design of a real-time non-contact vibration measurement system which can be used to measure both amplitude and frequency of vibration accurately in two dimensions (X-Y plane). This measurement scheme is optical in nature and uses 2D position sensitive detector (PSD) as the primary sensor for measuring the displacement amplitude of vibration directly. For the first time, to the best of our knowledge, a micro-electro-mechanical systems (MEMS) digital accelerometer is integrated on the same platform where the PSD is mounted to nullify the effect of self-vibration. The complete measurement system is configured over National Instruments-field programmable gate array (NI-FPGA), which enables it to be entirely digitalized, stand alone and reconfigurable. The entire system is enabled to be remotely monitored on a mobile phone with the help of NI-Data dashboard android application within the effective range of a Wi-Fi network. This system can very accurately measure the vibration frequency from 20 Hz to 800 Hz for minimum peak to peak amplitude of 6.36 μm along X-axis and 8.54 μm along Y axis with a maximum 0.058% error in measured frequency.

Theoretically, the transmission properties of a symmetric double-negative metamaterial one-dimensional photonic crystal containing an extrinsic random layer thickness magnetized cold plasma photonic quantum-well defect structure have been investigated. From the numerical results performed by characteristics matrix method, it is found that, such type of structure possesses a transmission peak within the zero- n ¯ gap. To design a tunable microwave filter, the effects of many parameters such as randomness of layer thickness of the multilayer defect in terms of standard deviation ( σ ), strength of external magnetic field ( B ) and electron density of magnetized cold plasma ( n e ) on transmission peak is discussed. Our findings show that the histogram for the central frequency of the transmission peaks becomes wider with respect to smaller values of σ . In addition, in the case of B , our investigations also reveal that the histogram shifts to the higher frequency range and vice versa while considering the case of n e . These findings help to design a tunable filter for different microwave applications.

In this paper, the characteristics matrix method is employed to theoretically investigate the propagation of electromagnetic waves through one-dimensional extrinsic Octonacci magnetized cold plasma (MCP) quasicrystal. Compared with the periodic structure, the results show that such type of structure has more numbers of photonic band gaps (PBGs) within the selected computational range. These PBGs can be easily manipulated by tuning the external magnetic field ( B ), electron density ( n e ) and the thickness ratio ( ρ ). When considering the case of B and n e , the analysis of the results shows that the pattern of change in the transmittance spectrum is opposite to each other. Moreover, the influence of the structural configuration of parameter ρ on PBGs is noteworthy and quite different from B and n e . The observed results are of technical use in the design of a multichannel microwave reflector.

Curiosity in the properties of non-Gaussian beam-based optical devices has seen a recent resurgence on account of large volume of higher order modes as supported by the platform. By harnessing the advantages of higher-order Bessel-Gauss beam, the present research unveils the concept of an extremely-sensitive optical sensor to detect the limit of kerosene adulteration in petrol. The sensory method works on the concept of modal interference, in which the transmitted power differs with changeable cladding refractive index as induced by the varying kerosene concentration in petrol. To corroborate this, the commercially available Lumerical’s Mode solution software and its Eigenmode expansion solver were exploited to investigate the transmitting property of the sensing device. If the sensing length is set to 7 cm, the procured average sensitivity of 0.41 dB/% is 4.1-fold higher in contrast to the typical Gaussian beam-shined sensor. The presence of ~0.02% kerosene contaminant in petrol can be sensed with the proposed methodology, while the conventional Gaussian beam-shined technology is able to sense the presence of ~0.10% of the same. Therefore such a nascent-class of beam called higher-order Bessel-Gauss beam accelerates new possibilities in the area of fiber optic sensing and can be useful in various petrochemical and automotive industries.

In this work, a simple cavity configuration for simultaneous observation of twelve oscillating wavelengths around 1.3 µm in a quasi-CW side pumped Nd:YAG laser is proposed and demonstrated experimentally. The experiment has been studied in free running condition and by placing a position tunable Brewster plate within a linear cavity where new wavelengths viz. 1318.71 nm, 1338.14 nm, 1338.16 nm, 1338.18 nm, 1338.21 nm, 1338.23 nm, 1338.25 nm and 1338.27 nm have been observed. By introducing a Brewster plate within the cavity it is possible to maintain almost equal spectral contributions around 1318 nm and 1338 nm wavelength’s regions at the highest as well as lowest pump power levels. The maximum average output power of 20 W and 13.87 W at slope efficiencies of 42.22% and 35.37% are obtained in both conditions respectively. In this work it is also possible to measure the average output powers around 1319 nm and 1338 nm regions simultaneously at different average pump powers. The experimental results indicate the higher and better stability of power contributions of observed oscillating wavelengths around 1.3 µm. The beam quality factor varies from 1.11 to 1.44 with the rise in average pump power simultaneously. The proposed work may enhance the application of 1.3 µm laser in spectroscopic field and tunable laser generation. Moreover, by difference frequency mixing within these closely spaced wavelengths this configuration may also be a good source of coherent THz generation.

In this report, a linear electro-optically tunable non-phase matched second-order nonlinear process is transformed into a cascaded second-order nonlinear process in a bulk BBO crystal to generate the effect of electro-optically tunable Kerr-type nonlinearity. A phase mismatch condition is created by applying an electric field to the x–z plane of the crystal which introduces a nonlinear phase shift between the launched and reconverted fundamental waves from the generated second harmonic wave. The sign of this nonlinear phase shift is easily changed by changing the polarity of applied electric field. The nonuniform radial intensity distribution of incident Gaussian beam introduces a curvature to the fundamental wavefront which focuses or defocuses the incident beam while propagating through the medium. Hence, a positive or negative lens is established within the crystal. The focal length of that lens is also tuned by tuning the applied electric field. The maximum calculated effective nonlinear refractive index due to nonlinear phase shift is ±6.6508 × 10 −14 cm 2 /W.

We report analytically an electro-optically tuned non-critical phase-matched second harmonic generation of a diode pumped solid-state laser in LiNbO3 crystal at room temperature (25 °C).The direction of propagation of fundamental wave of 1064 nm is on x-y plane, making an angle of θ = 90° with z-axis and ϕ = 33° with x-axis of the crystal. By applying an electric field of −7.87 kV/mm along z-axis of the crystal, ordinary and extra ordinary refractive indices of fundamental wave and second harmonic wave are matched to each other respectively. The calculated angular acceptance is 55.7 mrad mm1/2.

A new theoretical approach towards the exact identification of the output reflected beam position by the effect of spatial Goos-Hanchen (GH) shift and Imbert-Fedorov (IF) shift using Gaussian beam, Laguerre-Gaussian beam and Bessel beam are observed, designed and simulated with the three layered Kretschmann geometry at a free space wavelength of 1550 nm, where the proposed configuration comprising a BK7 prism (n=1.5007) and a 50 nm thin metal layer of silver (n= 0.4096+10.048i). To the best of our knowledge several articles have been discussed, separately considering the Gaussian beam, Laguerre-Gaussian beam and Bessel beam in which without the composite effect of spatial GH shift and IF shift whereas the exact beam position can only be identified with the effect of these shifts. In our proposed configuration by varying incident angle through Bessel beam, the observed spatial GH shift is tuned from 44.267 µm to 0.261 µm and the spatial IF shift is tuned from 39.301 µm to -13.024 µm. With the same variation of incident angle, the spatial GH shift and IF shift are also observed for Gaussian beam and as well as for Laguerre Gaussian beam. This new idea explores the accurate tuning of output beam position with varying incident angle which expedites the path of fine tuning in optical switching within µm ranges.

A new theoretical approach towards the composite effect of spatial and angular Goos–Hanchen (GH) shift and Imbert–Fedorov (IF) shift for the Gaussian beam, Laguerre–Gaussian beam and Bessel beam with long range surface plasmon (LRSP) resonance is observed, designed and simulated through the variation of incident angle at a wavelength of 1550 nm where the four layered Kreschmann–Rather geometry comprises a ZnSe prism, a liquid crystal layer of E44 and two metal layers of silver. To the best of our knowledge several articles have been devoted, separately considering the Gaussian beam, Laguerre–Gaussian beam and Bessel beam without considering the effect of spatial and angular GH shift and IF shift whereas the exact output beam position can only be identified with the composite effect of these shifts. The investigation of these spatial and angular shifts for Gaussian beam and different orders of Laguerre–Gaussian beam are calculated and represented where these lateral shifts increase with the increment of the modes and further these lateral shifts for Bessel beam have also been analyzed. With this new approach various avenues expedite the way of futuristic applications in the field of fine tuning in optical switching with the accurate beam position using different beams.

A novel scheme of additive Solc filter (ASF) is proposed in a single aperiodically poled BaMgF 4 biaxial crystal comprising of aperiodic domains having four different grating periods. This filter is designed to reject a narrow band of selected wavelength in Deep ultra-violet (DUV) region. The fibonacci sequence is followed in domains of aperiodic optical super lattice for poling design. Proposed filter finds its application in Swept Wavelength Optical Resonance Raman Diagnostic process utilizing tunable lasers, the condition for blocking multiple discrete wavelengths by one filter can be particularly useful.

The generations of a highly intense non resonant localized sub-wavelength size spots (Photonic nanojets) from an array of cuboied profile microstep have been theoretically investigated. The computations of photonic nanojets are based on numerical solution of Maxwell equations which was performed by using a graphical user interface based finite difference time domain method. From investigation it was found that the propagation length of the photonic nanojets generated from the array of cuboied profile Polydimethylsiloxane microstep decreases as increase in the matrix dimesion. In addition, the field distributions of the core PNJs are likely to be uniform as the matrix dimension increases.

The aim of this manuscript focus on the effect of the number of grating period on the performance of the photonic jet produce from a rectangular grooves based finite length finite diffraction grating. The computational analysis is carried out using three dimensional finite difference time domain method. From simulation result it is evident that, propagation length and Full width half maxima of the PNJ produce from the central period of the FRGG decreases with increase in number of grating period of the proposed rectangular grooves based finite length grating. Whereas in case of maximum possible length (MPL) which appears due to the increase in grating period, a reverse situation was observed. Therefore, PNJs generated from proposed FRGG having below defection limit can be used for high resolution microscopy.

The presented proposal of surface plasmon resonance (SPR) configuration with tapered fiber structure and radially polarized light beam is a new and different analysis towards the sensitivity enhancement in the field of SPR based fiber optic sensors. Here the taper waist region of optical fiber having diameter around 330 μm is deposited with 40 nm thin Ag layer, 10 nm thin Au layer and the sensing layer with refractive index 1.333–1.353 respectively for achieving the bimetal coated taper fiber optic sensor with SPR configuration. The cylindrical symmetry and special radial field distribution of radially polarized light make its more interesting SPR study and leads to the enhanced excitation of surface plasmon wave. This results 10 times better sensitivity of fiber optic sensor output response as compared to p-polarized light beam with wavelength interrogation technique and 2.307 times better sensitivity with intensity interrogation technique. Also including the temperature effect in proposed taper bimetallic structure, this sensitivity analysis provides an evidence, for exploring a new idea towards the enhanced excitation of SPR which expedites the new avenues in the field of sensor applications with radially polarized light.

A novel scheme of tunable folded Solc filter is proposed using Total Internal Reflection (TIR) in a 50 mm long, 1000 μm thick, bulk single crystal trapezoidal slab of LiNbO3. Fresnel phase shift for each TIR and propagation phase shift between two successive TIR points have been utilized for finding required polarization rotation by Jones calculus for folded solc action. Analytical expressions for central wavelength and bandwidth for transmission maxima have been formulated. Results indicate a narrow 3 dB bandwidth of 0.8 nm for transmission bands having transmission maxima around 1550 nm for the proposed slab with a temperature tunable rate approximately 0.008 nm/°C.

Open end induction motor drive fed from a common DC source faces the problem of Common Mode Voltages which creates flow of zero sequence currents. These currents lead to additional power loss without contributing to the torque. A new technique to eliminate such zero sequence currents is presented here. The two inverters with common DC bus are switched with Pulse Width Modulation scheme, but with a phase difference of 120°. Analysis shows that the resulting dominant zero sequence voltage, a 3rd harmonic, gets shifted by 360° and hence no resultant zero sequence current can flow. The proposed method is simple and can be implemented in all topologies of multilevel inverter. Detailed analysis presented shows that the DC bus utilization of the proposed topology is same as in other conventional methods. The proposed technique is experimentally validated in a 2hp, 3-phase, 415V open end induction motor drive.

This theoretical study is mainly focused on to show the behavior of photonic nanojet from highly intense to higher propagation produce from a set of purposed droplet type microstructures. Simulation result clearly indicated that the proposed combined structure of a hemisphere and a cone of equal radius can able to produce a photonic nanojet having the intensity larger than the conventional spherical microstructure. By decreasing the height offered by the spherical part of the micro structure gives an increased zigzag type response for the propagation length which was found to be maximum for cone. However the intensity of photonic nanojet decreases with decrease in height offered by spherical part of the proposed microstructure.

In this present study the behavior of photonic jet produced from an axicon immersed in aqueous solution of NaCl was investigated, where the aqueous solution NaCl act as a propagating medium. From simulation study it was found that the behavior of photonic jet varies with the different concentration of aqueous solution. In this study the rate of change in the propagation length of photonic jet was found to be 0.0903 μm per gm/lit up to a concentration level of 100 gm/lit. However from FDTD analysis minimal variation in intensity level and FWHM of photonic jet were revealed.

The present work has been focused on precise measurement technique of osmolality, total dissolved solids and specific gravity of human urine using diamond based one-dimensional photonic crystal structure. The photonic bandgap of the proposed structure has been computed using finite difference time domain method. Result showed that the linear relationship between key parameters with respect to output energy. During measurement of various samples using proposed biosensor, the sensitivity was found to be 0.09 which was comparably larger than the earlier report.