Browsing by Author "Suraj Prakash"

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Acoustically induced forbidden electromagnetic band gaps
(Springer, 2023) Suraj Prakash; Souryadipta Maiti; Gaurav Sharma; Vivek Singh
Lamb wave’s perturbation effect on electromagnetic modes propagating in Y − X lithium niobate slab is theoretically investigated. Rayleigh Lamb dispersion curves are estimated to investigate the behaviour of Lamb waves in micrometer order thick slab. Utilizing the information obtained from dispersion curves, acoustic displacement patterns and strain generated along the plate are evaluated. The modification caused to the refractive index of lithium niobate due to Lamb wave induced strain with photoelastic effect is determined. Further, the features of acoustically modified refractive index are examined using the transfer matrix method. It is found that an acoustically modified refractive index offers forbidden electromagnetic band gaps that can be adjusted by tuning the frequency of Lamb waves and by changing the incidence angle of electromagnetic waves. Hence proposed structure is used as a dynamically tunable photonic crystal for various applications like optical filters and optical switches. © 2023, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
Acoustically tunable photonic band gap generation in MgO doped Lithium Niobate micro-dimension plate
(Academic Press, 2018) Suraj Prakash; Gaurav Sharma; Gulab Chand Yadav; Vivek Singh
Refractive index contrast generation in MgO doped LiNbO3 plate via Lamb wave perturbation for induction of acoustically tunable photonic band gap is theoretically studied. Fundamental symmetric Lamb mode is excited in micro dimension thin plate structure to produce symmetric disturbance for periodic contraction and rarefaction along the length of plate. Effect of contraction and rarefaction on production of refractive index contrast is studied using photo–elastic effect. The generated quasi static low–high optical index region in plate modifies electromagnetic wave propagation and provides photonic band gaps, which are investigated using Bloch's theorem and transfer matrix method. The induced photonic band gap shows great dependency on optical contrast and unit cell dimension created by acoustic frequencies. These acoustically tunable photonic band gaps have rewarding applications in acousto optical devices, laser and sophisticated sensing. © 2018 Elsevier Ltd
Acute kidney injury in pregnancy with special reference to pregnancy-specific disorders: a hospital based study (2014–2016)
(Springer International Publishing, 2018) Jai Prakash; Vivek C. Ganiger; Suraj Prakash; Mohammad Iqbal; Deba Prasad Kar; Usha Singh; Ashish Verma
Introduction: There are numerous reports in the literature describing acute kidney injury in pregnancy (P-AKI) due to various obstetric complications. However, there is a dearth of studies on AKI related to pregnancy-specific disorders from India. We aimed to analyze clinical features and outcome of P-AKI related to pregnancy-specific disorders compared to total pregnancy, in India. Method: All pregnant women attending the department of Obstetrics and Gynecology from November 2014 to July 2016 were screened for AKI based on: (1) sudden elevation of serum creatinine ≥ 1 mg/dl; (2) oligoanuria for > 12 h; and (3) need for dialysis. The detailed clinical profile of AKI in patients with preeclampsia/eclampsia (PE/E), hemolysis/elevated liver enzymes/low platelet count (HELLP) syndrome, acute fatty liver of pregnancy (AFLP), and pregnancy-associated thrombotic microangiopathy (P-TMA) was analyzed. Laboratory investigations included: complete blood count, renal function tests, urinalysis, coagulation profile (platelet count, INR, prothrombin time and activated partial thromboplastin time), and immunological assay (C3, C4, ANA, anti-dsDNA antibody, antiphospholipid antibody). Contrast-enhanced CT scan of kidney ureter and bladder (KUB) and renal biopsy were performed in selected cases. Maternal and fetal outcome were analyzed individually. The patients were followed for 3 months or longer to determine the recovery of renal function or progression to chronic kidney disease (CKD). Results: Overall, 4741 pregnant women (mean age 26.8 ± 4.8 years) were evaluated for AKI. P-AKI was found in 132/4741 (2.78%) patients. In the majority (91.6%), AKI developed in the late 3rd trimester and post-partum period. P-AKI was related to obstetric complications (in 61.4%), pregnancy-specific disorders (in 57.5%) and miscellaneous factors (7.5%). Puerperal sepsis, ante-partum and post-partum hemorrhage were contributing factors for P-AKI in 34 (25.8%), 11 (8.3%) and 28 (21.2%) patients, respectively. P-AKI due to pregnancy-specific disorders developed in 76/4741 patients, i.e. in 1:62 pregnancies. PE/E was the cause of P-AKI in 62 patients (46.9%) followed by HELLP syndrome in 9 (6.8%) and AFLP in 05 (3.8%). P-TMA causing AKI was not observed. Complete recovery of renal function occurred in 89.4% of patients while 6 (4.6%) progressed to CKD (ESRD: 3 and CKD stage IV: 3). Maternal mortality was 6%. Puerperal sepsis was the sole cause of patchy cortical necrosis in 5 (3.7%) cases. Premature delivery occurred in 40.9% patients and full-term delivery in 35.6%. Perinatal mortality was 23.5%, mainly due to intrauterine death (17.5%) and prematurity (6%). Conclusion: PE/E was the commonest cause of P-AKI in our study, similar to the situation in developed countries. Post-partum hemorrhage was the second-most common (21.5%) cause. Puerperal sepsis contributed to AKI in one-fourth of pregnant women. P-TMA was not recorded in this study and AFLP was an uncommon cause of P-AKI in our country. Renal function returned to normal in all patients with P-AKI due to pregnancy-specific disorders. However, perinatal mortality was high despite the good prognosis of P-AKI. © 2018, Italian Society of Nephrology.
Changing epidemiology of acute kidney injury in pregnancy: A journey of four decades from a developing country
(NLM (Medline), 2019) Jai Prakash; Suraj Prakash; Vivek C. Ganiger
The incidence of acute kidney injury in pregnancy (P-AKI) has markedly decreased over the last three decades in India, particularly due to decreased incidence of postabortion AKI. However, P-AKI still accounts for 3%-5% of cases of total AKI. Postabortion sepsis has decreased to between 0.9% and 1.5% in 2014 from 9.4% in 1980-1990 in the new millennium. Currently, in India, majority of P-AKI (70%-90%) occurs in the postpartum period and in late 3rd trimester similar to the developed countries, but causes are different. We observed that preeclampsia/eclampsia is the most common cause of P-AKI in the late 3rd trimester and postpartum period followed by puerperal sepsis and postpartum hemorrhage (PPH). Both puerperal sepsis and PPH are treatable and preventable etiologies of P-AKI. Timely and aggressive management of antepartum hemorrhage (APH/PPH) and puerperal sepsis are required to reduce the burden of P-AKI in developing countries. Specific-pregnancy disorders such as P-aHUS/thrombotic thrombocytopenic purpura, pregnancy-associated thrombotic microangiopathy, and acute fatty liver of pregnancy are the uncommon/rare causes of P-AKI in India and possibly also because of the lack of awareness toward diagnosis. Despite decreasing incidence of P-AKI, fetal mortality remained high and unchanged. However, maternal mortality has decreased to 5% from initial high mortality of 20%-25%. The incidence and severity of renal cortical necrosis have significantly decreased at our center.
Controlling the band structures and electromagnetic density of modes in one-dimensional photonic crystals with Lamb wave
(Taylor and Francis Ltd., 2022) Ayush Aman; Surendra Prasad; Suraj Prakash; Gaurav Sharma; Vivek Singh
We have modeled and investigated band structures and the electromagnetic density of modes in one-dimensional photonic crystal whose refractive index is modulated by the excitation of the fundamental symmetric mode of Lamb wave using the Wigner phase time approach and transfer matrix method. The Rayleigh–Lamb dispersion curves are plotted to select the proper thickness of each sub-layer of considered photonic crystal structure which is comprised of silica (SiO2) and rutile (TiO2) layers as sub-layers of unit cell. The propagation of Lamb wave into the considered structures produced phononic band gaps in gigahertz frequency for acoustic waves. Also, the propagation of Lamb wave into the considered structures causes compression in SiO2 and dilation in TiO2 or vice versa, which can further increase or decrease the refractive index of both layers. Thus, there can be three combinations of change in refractive indices: case 1 (both layers have an unperturbed refractive index), case 2 (maximum change of the refractive index in SiO2 and minimum change in the refractive layer of TiO2), and case 3 (minimum change of the refractive index in SiO2 and maximum change in the refractive layer of TiO2). The band gap structures of considered structures are plotted for both polarized electromagnetic waves. © 2020 Informa UK Limited, trading as Taylor & Francis Group.
Detection of kerosene adulteration in automobile fuel with a novel metal clad planar waveguide
(Elsevier Ltd, 2019) Gulab Chand Yadav; Suraj Prakash; Gaurav Sharma; Sushil Kumar; Vivek Singh
A metal clad planar waveguide having hollow prism filled with adulterated petrol and diesel is fabricated and studied. The confinement of electromagnetic radiation in the film region of proposed structure under resonance condition is large. Observed variation in refractive index of considered automobile fuel is linear with change of percentage concentration of kerosene. Estimated sensitivity of proposed sensor is compared with fabricated sensor for both adulterated automobile fuel. The experimentally obtained maximum sensitivity 105.24 degree/RIU for adulterated petrol and 182.68 degree/RIU for diesel are in good agreement with their respective theoretically obtained maximum sensitivity 105.88 degree/RIU and 190.00 degree/RIU. Also, this study shows that the stability of present approach is high. © 2019 Elsevier Ltd
Dynamic modulation of refractive index in Y-X LiNbO3 slab through lamb wave
(Institute of Electrical and Electronics Engineers Inc., 2018) Suraj Prakash; Gaurav Sharma; Gulab Chand Yadav; Vivek Singh
Refractive index contrast generation, due to induced modulation of refractive index in Y-X LiNbO3 slab by Lamb wave has been studied theoretically. Acoustic frequency and corresponding wavelength is chosen to excite S0 Lamb mode in 400nm thick slab using Rayleigh-Lamb frequency relations. Propagation of Lamb wave produces strain in the slab and modulates refractive index. This modulation is responsible to produce refractive index contrast. Sinusoidal variation of refractive index has been found in slab with a period equals to wavelength of excited Lamb mode. The obtained maximum variation in refractive index along X is of order 0.0166 with respect to unperturbed value 2.28 in 400nm thick Y-X LiNbO3 slab at 5GHz Lamb wave frequency. These contrast variations along both X and Y directions decrease with increase in slab thickness. © 2017 IEEE.
Enhanced sensing performance of tapered profile in the apodized fiber Bragg grating for detection of cancerous cells utilizing their refractive index
(John Wiley and Sons Inc, 2023) Souryadipta Maiti; Suraj Prakash; Vivek Singh
Tapered profiles are introduced in Bessel and Blackman apodized fiber Bragg grating, and their sensing performance is theoretically estimated. Reflectivity equation of proposed apodized tapered profiles is obtained using transfer matrix method and coupled mode theory. Since the effective refractive index (RI) of proposed waveguides varies with core radius therefore amplitude distribution and penetration depth of light in surroundings are modified. It is found that the exponential tapered profile with Bessel apodization shows a higher sensitivity of 682.5 nm/RIU, detection accuracy of 3858.45, and quality parameter 1718.02/RIU with minimum full width at half maxima (FWHM) 0.3972 nm of the reflection spectra. The spectral response of the tapered fiber Bragg grating is also analyzed through a group delay study. Again, exponential profile was found to be particularly effective, producing less group delay ripples 2.98 ps and is maximum slope of 42.43°. Hence, exponential tapered profile is demonstrated for detection of cancer cells lies between the refractive index of 1.3333–1.4412. © 2023 Wiley-VCH GmbH.
Etiopathological study of crescentic glomerulonephritis and its outcome: A retrospective analysis
(Journal of Association of Physicians of India, 2019) Jai Prakash; Prem Shankar Patel; Suraj Prakash; Mohd Iqbal; Shiv Shankar Sharma; Shivendra Singh; Usha Singh
Introduction: Crescentic Glomerulonephritis (CGN) is most aggressive structural phenotype and accounts for 2%-7% of renal biopsy in most series. The aim of study was to assess the clinical feature and outcome of CGN at our centre. Material and Methods: The renal biopsy performed during the period of January 2015 to January 2018 was studied and patients showing crescentic glomerulonephritis on histology were selected for this study. The clinical presentation, immunological assay, biochemical and haematological investigations, treatment protocol and final outcome at three month of these patients were analysed in the present study. Results: Of 380 biopsy, 26 (male=17, female=9) patients had histological evidence of CGN (6.8%). The age of patients ranged between 13-75 (mean=43) years. Fibro cellular and cellular crescent was noted in 84.61% and 15.38% of patients respectively. Small vessels vasculitis and granuloma was observed in 5 (19.23%) cases. Based on immunohistopathology, we observed type I (n=3), type II (n=8), type III (n=5), type IV (n=3), and type V (n=7) crescentic GN in 11.53%, 30.76%, 19.23%, 11.53% and 26.92% of patients respectively. Haemodialysis was given to 22(84.61%) and 4(15.38%) patients were treated with immunosuppressive therapy. Plasmapheresis was used in two double positive (ANCA + Anti GBM Ab) patients. Remaining 21(80.76%) has progressed to ESRD over a period of 2-3 months. Conclusion: Type II (immune complex) CGN was most common type followed by type V (immune negative) and type III (pauci-immune) CGN. The crescentic GN had worse prognosis with >80% of patients progressed to ESRD within 3 month of time from onset of illness. Early diagnosis and treatment is associated with favourable outcome. © 2019 Journal of Association of Physicians of India. All rights reserved.
Garlic (Allium sativum L.) bioactives and its role in alleviating oral pathologies
(MDPI, 2021) Minnu Sasi; Sandeep Kumar; Manoj Kumar; Sandhya Thapa; Uma Prajapati; Yamini Tak; Sushil Changan; Vivek Saurabh; Shweta Kumari; Ashok Kumar; Muzaffar Hasan; Deepak Chandran; Radha; Sneh Punia Bangar; Sangram Dhumal; Marisennayya Senapathy; Anitha Thiyagarajan; Ahmad Alhariri; Abhijit Dey; Surinder Singh; Suraj Prakash; Ravi Pandiselvam; Mohamed Mekhemar
Garlic (Allium sativa L.) is a bulbous flowering plant belongs to the family of Amaryllida-ceae and is a predominant horticultural crop originating from central Asia. Garlic and its products are chiefly used for culinary and therapeutic purposes in many countries. Bulbs of raw garlic have been investigated for their role in oral health, which are ascribed to a myriad of biologically active compounds such as alliin, allicin, methiin, S-allylcysteine (SAC), diallyl sulfide (DAS), S-ally-mercapto cysteine (SAMC), diallyl disulphide (DADS), diallyl trisulfide (DATS) and methyl allyl disulphide. A systematic review was conducted following the PRISMA statement. Scopus, PubMed, Clinicaltrials.gov, and Science direct databases were searched between 12 April 2021 to 4 September 2021. A total of 148 studies were included and the qualitative synthesis phytochemical profile of GE, biological activities, therapeutic applications of garlic extract (GE) in oral health care system, and its mechanism of action in curing various oral pathologies have been discussed. Furthermore, the safety of incorporation of GE as food supplements is also critically discussed. To conclude, GE could conceivably make a treatment recourse for patients suffering from diverse oral diseases. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
Machine learning-enhanced detection of chlorpyrifos using molecularly imprinted polymer-coated optical fibers
(Elsevier B.V., 2025) Ankit Mishra; Rajiv Maurya; Suraj Prakash; Chandan Singh Yadav; Abhishek Upadhyay; Ritu Singh; Meenakshi K. Singh; Vivek B. Singh
This paper explores the use of large core declad optical fibers coated with molecularly imprinted polymers for chlorpyrifos detection, a key marker of organophosphate pesticides. The performance of sensor is evaluated using artificial neural networks and principal component analysis. By varying the declad length, the performance of molecularly imprinted polymer-coated fibers is compared to uncoated fibers, and both are used to identify commercial and pure samples of chlorpyrifos pesticides. Molecularly imprinted polymer-coated declad fiber sensors particularly those with longer declad lengths, exhibit significantly lower detection limits and higher sensitivity. The obtained maximum sensitivity, and minimum detection limit at 4 cm declad fiber length are 0.0027 mV/nM and 60.70 nM respectively. The results obtained also demonstrate that the artificial neural network can make an accurate prediction and the principal component analysis validates the efficacy of our molecularly imprinted polymer-coated fibers in chlorpyrifos detection. © 2025 Elsevier B.V.
Outcome of HIV related kidney diseases treated with combined antiretroviral therapy (CART)
(Journal of Association of Physicians of India, 2019) Jai Prakash; Mohd Iqbal; Prem Shankar Patel; Suraj Prakash; Shyam Sundar; Usha Singh
Introduction: The safe and effective treatment of HIV-associated renal diseases with cART can decrease the progression to ESRD and also improve the morbidity and mortality secondary to renal failure. Material and Methods: HIV positive patients with clinical kidney disease were the subjects of this study. The diagnosis of HIV was established using immunochromatographic assays. The patients were subjected to meticulous history, physical examination, laboratory investigations and kidney biopsy. Patients were treated with combined antiretroviral therapy and enalapril. They were followed at 3 months interval for one year. Short term outcome was assessed using changes in serum creatinine and proteinuria. Long term outcome assessments were done using progression to end stage renal disease and patients survival. Result: Ten (Male=7; Female=3) HIV patients with clinical renal disease were included in this study. Their age ranged between 26-55 (Mean=40.5±8.8) years. The mean serum creatinine at the baseline, three, six, nine and twelve months was 2.46, 2.09, 2.43, 2.46 and 2.58 mg/dl respectively. The mean e-GFR by MDRD equation at 0, 3, 6, 9 and 12 months was 40.9, 45.5, 48.2, 51.1 and 52.5 ml/ min/1.73m2 respectively. The mean twenty four hour urinary protein excretion at 0, 3, 6, 9 and 12 months was 3.01, 2.82, 2.22, 2.02 and 1.79 grams respectively. Six patients showed improvement in creatinine and e-GFR, whereas worsening of renal function was seen in four patients. Proteinuria decreased in seven patients, whereas it remained unchanged in three patients. There was no mortality at the end of one year of follow up. Conclusion: Treatment with combined ART and ACEIs slows the progression of HIV-associated kidney disease, decreases proteinuria and improves the GFR. © 2019 Journal of Association of Physicians of India. All rights reserved.
Performance analysis of a liquid-filled glass prism-coupled metal-clad planar waveguide sensor
(Springer Verlag, 2018) Gulab Chand Yadav; Suraj Prakash; Gaurav Sharma; Sushil Kumar; Vivek Singh
The performance of a metal-clad planar waveguide-based sensor coupled with a liquid-filled prism is studied and is compared with a similar waveguide sensor coupled with a solid prism. The characteristic equations of these waveguides are obtained by matching field components at various boundaries, and the reflectivity of these waveguides is obtained using transfer matrix method. The obtained dispersion characteristic shows that the transverse electric field components are loosely bound in liquid-filled prism-coupled waveguide-based sensor. Unlike to solid prism-coupled waveguide sensor, the performance of liquid-filled prism-coupled waveguide sensor increases with increase of effective refractive index. Hence, the proposed liquid-filled prism-coupled waveguide-based sensor shows better performance at high effective refractive index. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature.
Photonic Band Gap Alteration in LiNbO3-SiO2 Based 1D Periodic Multilayered Structure via Plate Wave
(Springer Netherlands, 2019) Suraj Prakash; Gaurav Sharma; Gulab Chand Yadav; Vivek Singh
Acoustic control on refractive index of periodic nanostructures facilitate a colocalize far-reaching control of light propagation. Static tuning of photonic band gap in lithium niobate and silicon dioxide based one dimensional superlattice through the GHz plate wave perturbation is reported. Acoustic field confinement in proposed structure produces field pattern of mechanical strain, analysed for fundamental symmetric plate mode within the elastic limit constraints of material. Contraction and rarefaction raises and lowers down the refractive index of material along the periodicity of structure. Using appropriate photo-elastic relations, the modified refractive index for both the materials of unit cell of periodic structure is estimated at different instants of perturbation. It is found that the refractive index contrast of unit cell gets altered with acoustic propagation and leads to photonic band gap modification. The available photonic band gap for transverse electric waves in both unperturbed and acoustically perturbed structure is calculated using Bloch’s theorem and transfer matrix method. © 2018, Springer Nature B.V.
Recurrent acute kidney injury in a young female: A rare presentation of ureteral endometriosis
(2016) Pragya Pant; Suraj Prakash; A.N. Dwivedi; Jai Prakash
[No abstract available]
Refractive index modulation in LiNbO3: MgO slab through Lamb wave
(American Institute of Physics Inc., 2018) Suraj Prakash; Gaurav Sharma; Gulab Chand Yadav; Vivek Singh
Present theoretical analysis deals with inducing refractive index contrast in Y-Z LiNbO3:MgO plate via GHz Lamb wave perturbation for photonic applications. Dispersion curves for Lamb wave in plate are plotted by employing displacement potential technique. Selecting wave parameters from dispersion curve, fundamental symmetric Lamb mode (S0) is excited in slab for 6GHz frequency. Produced displacement field by propagating S0 mode and thus developed strain is estimated to calculate refractive index modulation by applying photo-elastic relations. Modulated refractive index is of sinusoidal nature with period of modulation dependence on Lamb's wavelength. This plate having periodically modulated refractive index can be used as photonic crystal for different applications with acoustically tunable photonic band gap. © 2018 Author(s).
Refractive index modulation in lithium niobate slab using lamb wave
(Institute of Electrical and Electronics Engineers Inc., 2017) Suraj Prakash; Gaurav Sharma; Vivek Singh
Refractive index modulation in Y-X Lithium Niobate slab through GHz Lamb wave is theoretically analyzed. Dispersion curves and generated displacement field pattern for acoustic waves in slab have been calculated using Rayleigh-Lamb frequency relations and the displacement potentials techniques respectively. Variation in refractive index of slab due to mechanical strain generated by Lamb wave is estimated using photo-elastic effect. It is found that the maximum change in refractive index for S0 mode at 5 GHz of acoustic frequency is 0.027 along X-direction of wave propagation and 0.012 along Y-Transverse polarization of wave. © 2017 IEEE.
Sensing performance of apodized fiber Bragg gratings having linearly tapered profile
(Springer, 2023) Souryadipta Maiti; Suraj Prakash; Vivek Singh
The sensing performance of a linearly tapered and apodized fiber Bragg grating is estimated and optimized. Coupled mode theory in association with the transfer matrix method is utilized to develop the reflectance formula of the proposed sensor. The reflectance spectra of linearly tapered fiber Bragg gratings are plotted for various apodization profiles. The sensitivity, detection accuracy, and quality parameter of proposed sensor are compared with standard fiber Bragg grating and linearly tapered fiber Bragg gratings-based sensors. It is found that the tapering in the waveguide along with apodization further improves the sensing performance of the sensor. Although the maximum sensitivity 489 nm/RIU is obtained in Hamming apodization and maximum left side lobe − 152 dB is obtained in Barthann apodization function, these apodizations show poor detection accuracy and quality parameters due to their larger value of full width at half maxima of sensing signal. The Bessel apodization function shows maximum detection accuracy (1366) and quality parameter (420/RIU) in our all-considered linearly tapered apodized structures. Followed by Bessel apodized sensor, the Blackman apodized sensor also shows higher detection accuracy (1340) and quality parameter (412/RIU). Therefore, these two apodization functions are recommended for biosensing applications in such a tapered structure. © 2023, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
Tunable photonic band gaps in Lithium Niobate slab waveguide through Lamb waves
(Springer New York LLC, 2018) Suraj Prakash; Gaurav Sharma; Gulab Chand Yadav; Vivek Singh
Tunable photonic band gap generation in Y–Z Lithium Niobate slab through Lamb wave is theoretically studied and presented. The applied 5.5 GHz frequency of Lamb wave able to provide a periodic sinusoidal variation of refractive index through photo-elastic effect in considered 600 nm thick Lithium Niobate slab with period 615 nm. The achieved maximum and minimum change in refractive index along z axis is 0.026 with respect to unperturbed refractive index 2.2 of considered Lithium Niobate slab. The induced photonic band gap in optically modified structure is calculated using Bloch’s theorem and the transmittance of the structure is obtained by transfer matrix method. The obtained photonic band gap at 5.5 GHz Lamb wave frequency is 7.8 THz with central angular frequency is 695.9 THz. Since, the unit cell dimension and central frequency of photonic band gap are highly depend on the applied Lamb wave frequency therefore the possible application of the proposed structure is a tunable photonic crystal. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.
Ultra-fast tuning of refractive index in Lithium Niobate slab by GHz acoustic wave
(Elsevier GmbH, 2019) Suraj Prakash; Gaurav Sharma; Vivek Singh
Refractive index modulation in optical materials facilitates dynamic control on electromagnetic waves. Ultra fast tuning of both refractive index and its spatial distribution in Y−Z Lithium Niobate slab via strain employed through GHz acoustic perturbation has been simulated and studied. To create acoustic disturbance in taken 500 nm thick slab, the fundamental symmetric Lamb mode at 5 GHz acoustic frequency is excited. Displacement field patterns generated by longitudinal and transverse disturbances of perturbing fundamental symmetric Lamb mode are analyzed under reinstate limits of optical material to create elastic strain. Modification in optical index of Lithium Niobate due to strain generated by longitudinal and transverse acoustic disturbance is then examined. The sinusoidal modulation in refractive index with maximum change of 0.070 along nz and 0.036 along ny is observed. The modulated refractive index has a periodic distribution over space with period equals to wavelength of acoustic disturbance created by fundamental Lamb mode. This acoustically induced ultra-fast change in refractive index and in its spatial distribution depends on perturbing acoustic frequency and thickness of slab. Thus, the slab can optimize dynamically, to control electromagnetic wave for various optical applications. © 2018 Elsevier GmbH