Rajib Ahmed

All Publications

• Engineering the Interaction Dynamics between Nano-Topographical Immunocyte-Templated Micromotors across Scales from Ions to Cells. Small (Weinheim an der Bergstrasse, Germany) Wang, J., Ahmed, R., Zeng, Y., Fu, K., Soto, F., Sinclair, B., Soh, H. T., Demirci, U. 2020: e2005185

  Abstract

  Manufacturing mobile artificial micromotors with structural design factors, such as morphology nanoroughness and surface chemistry, can improve the capture efficiency through enhancing contact interactions with their surrounding targets. Understanding the interplay of such parameters targeting high locomotion performance and high capture efficiency at the same time is of paramount importance, yet, has so far been overlooked. Here, an immunocyte-templated nano-topographical micromotor is engineered and their interactions with various targets across multiple scales, from ions to cells are investigated. The macrophage templated nanorough micromotor demonstrates significantly increased surface interactions and significantly improved and highly efficient removal of targets from complex aqueous solutions, including in plasma and diluted blood, when compared to smooth synthetic material templated micromotors with the same size and surface chemistry. These results suggest that the surface nanoroughness of the micromotors for the locomotion performance and interactions with the multiscale targets should be considered simultaneously, for they are highly interconnected in design considerations impacting applications across scales.

  View details for DOI 10.1002/smll.202005185

  View details for PubMedID 33174334

• Tunable Fano-Resonant Metasurfaces on a Disposable Plastic-Template for Multimodal and Multiplex Biosensing. Advanced materials (Deerfield Beach, Fla.) Ahmed, R., Ozen, M. O., Karaaslan, M. G., Prator, C. A., Thanh, C., Kumar, S., Torres, L., Iyer, N., Munter, S., Southern, S., Henrich, T. J., Inci, F., Demirci, U. 2020: e1907160

  Abstract

  Metasurfaces are engineered nanostructured interfaces that extend the photonic behavior of natural materials, and they spur many breakthroughs in multiple fields, including quantum optics, optoelectronics, and biosensing. Recent advances in metasurface nanofabrication enable precise manipulation of light-matter interactions at subwavelength scales. However, current fabrication methods are costly and time-consuming and have a small active area with low reproducibility due to limitations in lithography, where sensing nanosized rare biotargets requires a wide active surface area for efficient binding and detection. Here, a plastic-templated tunable metasurface with a large active area and periodic metal-dielectric layers to excite plasmonic Fano resonance transitions providing multimodal and multiplex sensing of small biotargets, such as proteins and viruses, is introduced. The tunable Fano resonance feature of the metasurface is enabled via chemical etching steps to manage nanoperiodicity of the plastic template decorated with plasmonic layers and surrounding dielectric medium. This metasurface integrated with microfluidics further enhances the light-matter interactions over a wide sensing area, extending data collection from 3D to 4D by tracking real-time biomolecular binding events. Overall, this work resolves cost- and complexity-related large-scale fabrication challenges and improves multilayer sensitivity of detection in biosensing applications.

  View details for DOI 10.1002/adma.201907160

  View details for PubMedID 32201997

• Medical Micro/Nanorobots in Precision Medicine Medical Micro/Nanorobots in Precision Medicine Soto, F., Wang, J., Ahmed, R., Demirci, U. 2020: 2002203

  View details for DOI 10.1002/advs.202002203

• Lateral and Vertical Flow Assays for Point-of-Care Diagnostics ADVANCED HEALTHCARE MATERIALS Jiang, N., Ahmed, R., Damayantharan, M., Unal, B., Butt, H., Yetisen, A. K. 2019; 8 (14)

  View details for DOI 10.1002/adhm.201900244

  View details for Web of Science ID 000477042600006

• Lateral and Vertical Flow Assays for Point-of-Care Diagnostics. Advanced healthcare materials Jiang, N., Ahmed, R., Damayantharan, M., Ünal, B., Butt, H., Yetisen, A. K. 2019: e1900244

  Abstract

  Lateral flow assays (LFAs) have been the pillar of rapid point-of-care (POC) diagnostics due to their simplicity, rapid process, and low cost. Recent advances in sensitivity, selectivity, and chemical stability enhancement have ensured the foothold of LFAs in commercial POC diagnostics. This paper reviews recent developments in labeling strategies and detection methods of LFAs. Moreover, vertical flow assays (VFAs) have emerged as an alternate paper-based assay due to faster detection time and unique multiplexing capabilities. Smartphones as LFA readers have been transformed into a universal integrated platform for imaging, data processing, and storage, providing quantitative results in low-resource settings. Commercial LFAs and VFAs products are evaluated with regards to their performance, market trends, and regulatory issues. The future outlook of the flow-based assays for POC diagnostics is also discussed.

  View details for PubMedID 31081270

• Diffractive Surface Patterns through Single-Shot Ns-Pulsed Laser Ablation ACS Photonics Ahmed, R., et al 2019; 6 (7): 1572-1580

  View details for DOI 10.1021/acsphotonics.9b00087

• Graphene-Reinforced Advanced Composite Materials Handbook of Graphene, Volume 4: Graphene Composite Materials Ji, X., Qi, S., Ahmed, R. John Wiley & Sons. 2019
• Holographic Writing of Ink-Based Phase Conjugate Nanostructures via Laser Ablation (vol 7, 10603, 2017) SCIENTIFIC REPORTS Khalid, M., Ahmed, R., Yetisen, A. K., AlQattan, B., Butt, H. 2018; 8: 6363

  Abstract

  A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

  View details for DOI 10.1038/s41598-018-24169-6

  View details for Web of Science ID 000430283400005

  View details for PubMedID 29670120

  View details for PubMedCentralID PMC5906469

• Highly sensitive selectively coated photonic crystal fiber-based plasmonic sensor OPTICS LETTERS Rifat, A. A., Haider, F., Ahmed, R., Mahdiraji, G., Adikan, F., Miroshnichenko, A. E. 2018; 43 (4): 891–94

  Abstract

  Highly sensitive and miniaturized sensors are highly desirable for real-time analyte/sample detection. In this Letter, we propose a highly sensitive plasmonic sensing scheme with the miniaturized photonic crystal fiber (PCF) attributes. A large cavity is introduced in the first ring of the PCFs for the efficient field excitation of the surface plasmon polariton mode and proficient infiltration of the sensing elements. Due to the irregular air-hole diameter in the first ring, the cavity exhibits the birefringence behavior which enhances the sensing performance. The novel plasmonic material gold has been used considering the chemical stability in an aqueous environment. The guiding properties and the effects of the sensing performance with different parameters have been investigated by the finite element method, and the proposed PCFs have been fabricated using the stack-and-draw fiber drawing method. The proposed sensor performance was investigated based on the wavelength and amplitude sensing techniques and shows the maximum sensitivities of 11,000 nm/RIU and 1,420  RIU-1, respectively. It also shows the maximum sensor resolutions of 9.1×10-6 and 7×10-6  RIU for the wavelength and amplitude sensing schemes, respectively, and the maximum figure of merits of 407. Furthermore, the proposed sensor is able to detect the analyte refractive indices in the range of 1.33-1.42; as a result, it will find the possible applications in the medical diagnostics, biomolecules, organic chemical, and chemical analyte detection.

  View details for DOI 10.1364/OL.43.000891

  View details for Web of Science ID 000425123700067

  View details for PubMedID 29444020

• Functionalized Flexible Soft Polymer Optical Fibers for Laser Photomedicine ADVANCED OPTICAL MATERIALS Jiang, N., Ahmed, R., Rifat, A. A., Guo, J., Yin, Y., Montelongo, Y., Butt, H., Yetisen, A. K. 2018; 6 (3)

  View details for DOI 10.1002/adom.201701118

  View details for Web of Science ID 000424153300018

• Remote Thermal Sensing by Integration of Corner-Cube Optics and Thermochromic Materials Advanced Optical Materials Khalid, M., Whitehouse, C., Ahmed, R., et al 2018; 1801013

  View details for DOI 10.1002/adom.201801013

• Spiral Photonic Crystal Fiber-Based Dual-Polarized Surface Plasmon Resonance Biosensor IEEE SENSORS JOURNAL Hasan, M., Akter, S., Rifat, A. A., Rana, S., Ahmed, K., Ahmed, R., Subbaraman, H., Abbott, D. 2018; 18 (1): 133–40

  View details for DOI 10.1109/JSEN.2017.2769720

  View details for Web of Science ID 000418076100014

• Flexible corner cube retroreflector array for temperature and strain sensing RSC ADVANCES Khalid, M., Ahmed, R., Yetisen, A. K., Butt, H. 2018; 8 (14): 7588–98

  Abstract

  Optical sensors for detecting temperature and strain play a crucial role in the analysis of environmental conditions and real-time remote sensing. However, the development of a single optical device that can sense temperature and strain simultaneously remains a challenge. Here, a flexible corner cube retroreflector (CCR) array based on passive dual optical sensing (temperature and strain) is demonstrated. A mechanical embossing process was utilised to replicate a three-dimensional (3D) CCR array in a soft flexible polymer film. The fabricated flexible CCR array samples were experimentally characterised through reflection measurements followed by computational modelling. As fabricated samples were illuminated with a monochromatic laser beam (635, 532, and 450 nm), a triangular shape reflection was obtained at the far-field. The fabricated flexible CCR array samples tuned retroreflected light based on external stimuli (temperature and strain as an applied force). For strain and temperature sensing, an applied force and temperature, in the form of weight suspension, and heat flow was applied to alter the replicated CCR surface structure, which in turn changed its optical response. Directional reflection from the heated flexible CCR array surface was also measured with tilt angle variation (max. up to 10°). Soft polymer CCRs may have potential in remote sensing applications, including measuring the temperature in space and in nuclear power stations.

  View details for DOI 10.1039/c7ra13284k

  View details for Web of Science ID 000425647000032

  View details for PubMedID 29568510

  View details for PubMedCentralID PMC5819368

• Photonic crystal fiber based plasmonic sensors SENSORS AND ACTUATORS B-CHEMICAL Rifat, A. A., Ahmed, R., Yetisen, A. K., Butt, H., Sabouri, A., Mandiraji, G., Yun, S., Adikan, F. 2017; 243: 311–25

  View details for DOI 10.1016/j.snb.2016.11.113

  View details for Web of Science ID 000395969100040

• Highly Sensitive D-Shaped Photonic Crystal Fiber-Based Plasmonic Biosensor in Visible to Near-IR IEEE SENSORS JOURNAL Rifat, A. A., Ahmed, R., Mahdiraji, G., Adikan, F. 2017; 17 (9): 2776–83

  View details for DOI 10.1109/JSEN.2017.2677473

  View details for Web of Science ID 000399767900024

• High Numerical Aperture Hexagonal Stacked Ring-Based Bidirectional Flexible Polymer Microlens Array ACS NANO Ahmed, R., Yetisen, A. K., Butt, H. 2017; 11 (3): 3155–65

  Abstract

  Flexible imprinted photonic nanostructures that are able to diffract/focus narrow-band light have potential applications in optical lenses, filters, tunable lasers, displays, and biosensing. Nanophotonic structures through holography and roll-to-roll printing may reduce fabrication complexities and expenses and enable mass production. Here, 3D photonic nanostructures of a stacked ring array were imprinted on acrylate polymer (AP) over poly(ethylene terephthalate) (PET) substrate through holography and lift-off processes to create a microlens array (MLA). The surface structure of the array consisted of circular nonostepped pyramids, and repeated patterns were in hexagonal arrangements. Stacked-ring-based MLA (SMLA) on a flexible AP-PET substrate showed efficient bidirectional light focusing and maximum numerical aperture (NA = 0.60) with a reasonable filling factor. The nanostructures produced a well-ordered hexagonally focused diffraction pattern in the far field, and power intensities were measured through angle-resolved experiments. The variation of nanostep dimensions (width and height) and the number of steps resulted in different photonic bandgaps, and the arrays produced distance-dependent narrow-band light focusing. The validation of the SMLA was demonstrated through the text, image, and hologram projection experiments. It is anticipated that imprinted bidirectional SMLA over flexible substrates may find applications in optical systems, displays, and portable sensors.

  View details for DOI 10.1021/acsnano.7b00211

  View details for Web of Science ID 000398014900081

  View details for PubMedID 28252935

• Color-selective holographic retroreflector array for sensing applications LIGHT-SCIENCE & APPLICATIONS Ahmed, R., Yetisen, A. K., Yun, S., Butt, H. 2017; 6

  View details for DOI 10.1038/lsa.2016.214

  View details for Web of Science ID 000395834200004

• Printable ink lenses, diffusers, and 2D gratings NANOSCALE Ahmed, R., Yetisen, A. K., El Khoury, A., Butt, H. 2017; 9 (1): 266–76

  Abstract

  Advances in holography have led to applications including data storage, displays, security labels, and colorimetric sensors. However, existing top-down approaches for the fabrication of holographic devices are complex, expensive, and expertise dependent, limiting their use in practical applications. Here, ink-based holographic devices have been created for a wide range of applications in diffraction optics. A single pulse of a 3.5 ns Nd:YAG laser allowed selective ablation of ink to nanofabricate planar optical devices. The practicality of this method is demonstrated by fabricating ink-based diffraction gratings, 2D holographic patterns, optical diffusers, and Fresnel zone plate (FZP) lenses by using the ink. The fabrication processes were rationally designed using predictive computational modeling and the devices were fabricated within a few minutes demonstrating amenability for large scale printable optics through industrial manufacturing. It is anticipated that ink will be a promising diffraction optical material for the rapid printing of low-cost planar nanophotonic devices.

  View details for DOI 10.1039/c6nr07841a

  View details for Web of Science ID 000391739300034

  View details for PubMedID 27906403

• Phase-conjugated directional diffraction from a retroreflector array hologram RSC ADVANCES Ahmed, R., Rifat, A. A., Hassan, M., Yetisen, A. K., Butt, H. 2017; 7 (41): 25657–64

  View details for DOI 10.1039/c7ra04131d

  View details for Web of Science ID 000401535100059

• Color-Selective 2.5D Holograms on Large-Area Flexible Substrates for Sensing and Multilevel Security ADVANCED OPTICAL MATERIALS Yetisen, A. K., Butt, H., Mikulchyk, T., Ahmed, R., Montelongo, Y., Humar, M., Jiang, N., Martin, S., Naydenova, I., Yun, S. 2016; 4 (10): 1589–1600

  View details for DOI 10.1002/adom.201600162

  View details for Web of Science ID 000386356900019

• Multiwall carbon nanotube microcavity arrays JOURNAL OF APPLIED PHYSICS Ahmed, R., Rifat, A. A., Yetisen, A. K., Dai, Q., Yun, S., Butt, H. 2016; 119 (11)

  View details for DOI 10.1063/1.4944318

  View details for Web of Science ID 000373383300005

• Highly sensitive multi-core flat fiber surface plasmon resonance refractive index sensor OPTICS EXPRESS Rifat, A. A., Mandiraji, G. A., Sua, Y., Ahmed, R., Shee, Y. G., Adikan, F. 2016; 24 (3): 2485–95

  Abstract

  A simple multi-core flat fiber (MCFF) based surface plasmon resonance (SPR) sensor operating in telecommunication wavelengths is proposed for refractive index sensing. Chemically stable gold (Au) and titanium dioxide (TiO(2)) layers are used outside the fiber structure to realize a simple detection mechanism. The modeled sensor shows average wavelength interrogation sensitivity of 9,600 nm/RIU (Refractive Index Unit) and maximum sensitivity of 23,000 nm/RIU in the sensing range of 1.46-1.485 and 1.47-1.475, respectively. Moreover, the refractive index resolution of 4.35 × 10(-6) is demonstrated. Additionally, proposed sensor had shown the maximum amplitude interrogation sensitivity of 820 RIU(-1), with the sensor resolution of 1.22 × 10(-5) RIU. To the best of our knowledge, the proposed sensor achieved the highest wavelength interrogation sensitivity among the reported fiber based SPR sensors. Finally we anticipate that, this novel and highly sensitive MCFF SPR sensor will find the potential applications in real time remote sensing and monitoring, ultimately enabling inexpensive and accurate chemical and biochemical analytes detection.

  View details for DOI 10.1364/OE.24.002485

  View details for Web of Science ID 000371427100060

  View details for PubMedID 26906823

• Copper-Graphene-Based Photonic Crystal Fiber Plasmonic Biosensor IEEE PHOTONICS JOURNAL Rifat, A. A., Mahdiraji, G., Ahmed, R., Chow, D. M., Sua, Y. M., Shee, Y. G., Adikan, F. 2016; 8 (1)

  View details for DOI 10.1109/JPHOT.2015.2510632

  View details for Web of Science ID 000367824400012

• Optical microring resonator based corrosion sensing RSC ADVANCES Ahmed, R., Rifat, A. A., Yetisen, A. K., Salem, M., Yun, S., Butt, H. 2016; 6 (61): 56127–33

  View details for DOI 10.1039/c6ra11538a

  View details for Web of Science ID 000378275400055

• Holographic direct pulsed laser writing of two-dimensional nanostructures RSC ADVANCES AlQattan, B., Butt, H., Sabouri, A., Yetisen, A. K., Ahmed, R., Mahmoodi, N. 2016; 6 (112): 111269–75

  Abstract

  The development of accurate and rapid techniques to produce nanophotonic structures is essential in data storage, sensors, and spectroscopy. Existing bottom-up and top-down approaches to fabricate nanophotonic devices are high cost and time consuming, limiting their mass manufacturing and practical applications. Here, we demonstrate a strategy to rapidly create 25-40 nm thick 1/2D Au-Ti nanopatterns using holographic direct laser interference patterning (DLIP). Pulses of an Nd:YAG laser (1064 nm) in holographic Denisyuk reflection mode were used to create ablative interference fringes. The constructive interference antinode regions of the standing wave selectively ablated a Au-Ti layer in localized regions to controllably form nanogratings. Varying the laser exposure parameters allowed for rapid patterning of 2D square and rectangular arrays within seconds. Controlling the distances between the laser source, recording medium, and the object, allowed for achieving a 2D spatial grating periodicity of 640 nm × 640 nm. Diffracted and transmitted light spectra of 2D nanostructure arrays were analyzed using angle-resolved measurements and spectroscopy.

  View details for DOI 10.1039/c6ra22241b

  View details for Web of Science ID 000389463600088

  View details for PubMedID 28066547

  View details for PubMedCentralID PMC5171911

• Surface Plasmon Resonance Photonic Crystal Fiber Biosensor: A Practical Sensing Approach IEEE PHOTONICS TECHNOLOGY LETTERS Rifat, A. A., Mahdiraji, G., Sua, Y. M., Shee, Y. G., Ahmed, R., Chow, D. M., Adikan, F. 2015; 27 (15): 1628–31

  View details for DOI 10.1109/LPT.2015.2432812

  View details for Web of Science ID 000357830000014

• Photonic Crystal Fiber-Based Surface Plasmon Resonance Sensor with Selective Analyte Channels and Graphene-Silver Deposited Core SENSORS Rifat, A. A., Mahdiraji, G., Chow, D. M., Shee, Y., Ahmed, R., Adikan, F. 2015; 15 (5): 11499–510

  Abstract

  We propose a surface plasmon resonance (SPR) sensor based on photonic crystal fiber (PCF) with selectively filled analyte channels. Silver is used as the plasmonic material to accurately detect the analytes and is coated with a thin graphene layer to prevent oxidation. The liquid-filled cores are placed near to the metallic channel for easy excitation of free electrons to produce surface plasmon waves (SPWs). Surface plasmons along the metal surface are excited with a leaky Gaussian-like core guided mode. Numerical investigations of the fiber's properties and sensing performance are performed using the finite element method (FEM). The proposed sensor shows maximum amplitude sensitivity of 418 Refractive Index Units (RIU-1) with resolution as high as 2.4 × 10(-5) RIU. Using the wavelength interrogation method, a maximum refractive index (RI) sensitivity of 3000 nm/RIU in the sensing range of 1.46-1.49 is achieved. The proposed sensor is suitable for detecting various high RI chemicals, biochemical and organic chemical analytes. Additionally, the effects of fiber structural parameters on the properties of plasmonic excitation are investigated and optimized for sensing performance as well as reducing the sensor's footprint.

  View details for DOI 10.3390/s150511499

  View details for Web of Science ID 000357183100099

  View details for PubMedID 25996510

  View details for PubMedCentralID PMC4481892

• Carbon nanotube biconvex microcavities APPLIED PHYSICS LETTERS Butt, H., Yetisen, A. K., Ahmed, R., Yun, S., Dai, Q. 2015; 106 (12)

  View details for DOI 10.1063/1.4916236

  View details for Web of Science ID 000351876700008

• Asymmetric core-guided polarization-dependent plasmonic biosensor APPLIED OPTICS Haider, F., Mashrafi, M., Haider, R., Aoni, R., Ahmed, R. 2020; 59 (26): 7829–35

  Abstract

  A modified solid-core photonic crystal fiber (PCF)-based plasmonic sensor is proposed where light propagation through the PCF is controlled by scaling down of air holes. The modified core facilitates the easy excitation of the plasmonic surface, resulting in improved sensor performance. The chemically stable gold is externally coated on the PCF surface, which helps to establish surface plasmon resonance phenomena. The response of the sensor is analyzed based on the numerical method, and the design parameters are optimized to enhance the sensing performance. The asymmetric fiber-core structure provides the polarization controllability and significantly suppresses the y-polarized response to achieve a dominant x-polarized response and additional functionalities. The sensor exhibits a maximum wavelength sensitivity of 11,000 nm/RIU (refractive index unit) and sensing resolution of 9.09×10-6 RIU in the x-polarized mode. Also, the sensor exhibits maximum amplitude sensitivity of 631RIU-1, and a good figure of merit is 157RIU-1. Furthermore, the sensor can detect the unknown analytes' refractive index (RI) in the sensing analyte RI range of 1.33 to 1.40, which will lead to finding the potential applications in biomolecules, organic chemicals, and environment monitoring.

  View details for DOI 10.1364/AO.400301

  View details for Web of Science ID 000571484700011

  View details for PubMedID 32976453

• Mode-multiplex plasmonic sensor for multi-analyte detection OPTICS LETTERS Haider, F., Aoni, R., Ahmed, R., Mahdiraji, G., Azman, M., Adikan, F. 2020; 45 (14): 3941–44

  Abstract

  Highly sensitive mode-multiplex miniaturized sensors enable the detection and quantification of multiple biomolecules simultaneously through their real-time interactions. Here, we demonstrate a grapefruit photonic crystal fiber (PCF)-based mode-multiplex surface plasmon resonance (SPR) sensor that detects multiple analytes simultaneously. Three grapefruit-shaped air-holes are internally coated with plasmonic gold (Au) material, which allows them to act as mode-multiplex channels that detect three unknown analytes. The sensor performance was investigated using the finite element method (FEM), and the optimized fiber structure was fabricated with the standard stack-and-draw method. For the y-polarized mode, channels one and three showed the maximum wavelength sensitivities of 2000 and 18,000 nm/RIU (refractive index unit) at the analyte refractive indices of 1.34 and 1.41, respectively. On the other hand, channel two showed the maximum wavelength sensitivity of 3000 nm/RIU at the analyte refractive index (RI) of 1.36 for the x-polarized mode. To the best of our knowledge, this is the first demonstration of a mode-multiplex grapefruit PCF-based SPR sensor to simultaneously detect and quantify three different analytes. We anticipate that the proposed sensor will find potential applications in the detection of real-time biomolecular interactions and binding affinity.

  View details for DOI 10.1364/OL.396340

  View details for Web of Science ID 000553826600030

  View details for PubMedID 32667324

• Alphabetic-Core Assisted Microstructure Fiber Based Plasmonic Biosensor PLASMONICS Haider, F., Aoni, R., Ahmed, R., Chew, W., Mahdiraji, G. 2020

  View details for DOI 10.1007/s11468-020-01220-9

  View details for Web of Science ID 000544839300001

• Highly Sensitive Grapefruit Fiber-Based Multiplex Plasmonic Sensor Conference on Lasers and Electro-Optics Haider, F., Aoni, R., Ahmed, R., et al 2020
• Real-time Biosensing of Proteins on a DVD Nanoplasmonic Grating Ahmed, R., Ozen, M., Inci, F., Karaaslan, M., Henrich, T. J., Demirci, U., VoDinh, T., Ho, H. P., Ray, K. SPIE-INT SOC OPTICAL ENGINEERING. 2019

  View details for DOI 10.1117/12.2508624

  View details for Web of Science ID 000482226200010

• A Hi-Bi Ultra-Sensitive Surface Plasmon Resonance Fiber Sensor IEEE ACCESS Islam, M., Cordeiro, C. B., Sultana, J., Aoni, R., Feng, S., Ahmed, R., Dorraki, M., Dinovitser, A., Ng, B., Abbott, D. 2019; 7: 79085–94

  View details for DOI 10.1109/ACCESS.2019.2922663

  View details for Web of Science ID 000473819000001

• Colonoscopy Technologies for Diagnostics and Drug Delivery Medical Devices & Sensors Ahmed, R., et al 2019: e10041

  View details for DOI 10.1002/mds3.10041

• Real-time biosensing of proteins on a DVD nanoplasmonic grating Plasmonics in Biology and Medicine XVI Ahmed, R., et al 2019: 108940N
• Subwavelength Direct Laser Nanopatterning via Microparticle Arrays for Functionalizing Metallic Surfaces Subwavelength Direct Laser Nanopatterning via Microparticle Arrays for Functionalizing Metallic Surfaces Romano, J., AHMED, R., et al 2019

  View details for DOI 10.1115/1.4042964

• SOI Waveguide-Based Biochemical Sensors Computational Photonic Sensors Rifat, A. Springer International Publishing AG, part of Springer Nature 2019. 2019; M. F. O. Hameed and S. Obayya: 423–448

  View details for DOI 10.1007/978-3-319-76556-3_16

• Microstructured Optical Fiber-Based Plasmonic Sensors Computational Photonic Sensors Rifat, A. Springer International Publishing AG, part of Springer Nature 2019. 2019; M. F. O. Hameed and S. Obayya: 203–232

  View details for DOI 10.1007/978-3-319-76556-3_9

• Development of Photonic Crystal Fiber-Based Gas/Chemical Sensors Computational Photonic Sensors Rifat, A. Springer International Publishing AG, part of Springer Nature 2019. 2019; M. F. O. Hameed and S. Obayya: 287–317

  View details for DOI 10.1007/978-3-319-76556-3_12

• Photonic crystal fiber-based plasmonic biosensor with external sensing approach (vol 12, 012503, 2017) JOURNAL OF NANOPHOTONICS Rifat, A. A., Hasan, M., Ahmed, R., Butt, H. 2018; 12 (1)

  View details for DOI 10.1117/1.JNP.12.019901

  View details for Web of Science ID 000429259200030

• Propagation Controlled Photonic Crystal Fiber Based Plasmonic Sensor via Scaled-Down Approach IEEE Sensors Journal Haider , F., Aoni, R., Ahmed, R., et al 2018

  View details for DOI 10.1109/JSEN.2018.2880161

• Dual-polarized highly sensitive plasmonic sensor in the visible to near-IR spectrum Optics Express Islam, M., et al 2018; 26 (23): 30347-30361

  Abstract

  We propose and numerically characterize the optical characteristics of a novel photonic crystal fiber (PCF) based surface plasmon resonance (SPR) sensor in the visible to near infrared (500-2000 nm) region for refractive index (RI) sensing. The finite element method (FEM) is used to design and study the influence of different geometric parameters on the sensing performance of the sensor. The chemically stable plasmonic material gold (Au) is used to produce excitation between the core and plasmonic mode. On a pure silica (SiO2) substrate, a rectangular structured core is used to facilitate the coupling strength between the core and the surface plasmon polariton (SPP) mode and thus improves the sensing performance. By tuning the geometric parameters, simulation results show a maximum wavelength sensitivity of 58000 nm/RIU (Refractive Index Unit) for the x polarization and 62000 nm/RIU for the y polarization for analyte refractive indices ranging from 1.33 to 1.43. Moreover, we characterize the amplitude sensitivity of the sensor that shows a maximum sensitivity of 1415 RIU-1 and 1293 RIU-1 for the x and y polarizations, respectively. To our knowledge, this is the highest sensitivity for an SPR in published literature, and facilitates future development of sensors for accurate and precise analyte measurement. The sensor also attains a maximum figure of merit (FOM) of 1140 and fine RI resolution of 1.6 × 10-6. Owing to strong coupling strength, high sensitivity, high FOM and improved sensing resolution, the proposed sensor is suited for real-time, inexpensive and accurate detection of biomedical and biological analytes, biomolecules, and organic chemicals.

  View details for DOI 10.1364/OE.26.030347

• Highly amplitude-sensitive photonic-crystal-fiber-based plasmonic sensor Journal of the Optical Society of America B Haider, F., Aoni, R., AHMED, R., et al 2018; 35 (11): 2816-2821

  View details for DOI 10.1364/JOSAB.35.002816

• Highly amplitude sensitive photonic crystal fiber based plasmonic sensor Journal of the Optical Society of America B Haider, F. 2018; 35 (11): 2816-2821

  View details for DOI 10.1364/JOSAB.35.002816

• Towards large area submicron surface texturing by femtosecond laser irradiation of microparticle arrays World Congress on Micro and Nano Manufacturing Romano, J. 2018
• Bio-Inspired Optical Spectroscopy Advances in Biophotonics AHMED, R. N., et al 2018
• Highly Sensitive Plasmonic Metasensor with Wide Detection Range Frontiers in Optics (FiO) Rifat, A., et al
• Morpho butterfly-inspired optical diffraction, diffusion, and bio-chemical sensing Morpho butterfly-inspired optical diffraction, diffusion, and bio-chemical sensing AHMED, R. N., et al 2018; 8 (48): 27111-27118

  View details for DOI 10.1039/c8ra04382e

• Bio-inspired optical spectroscopy Advance Biophotonics Ahmed, R., et al 2018
• Holographic Writing of Ink-Based Phase Conjugate Nanostructures via Laser Ablation SCIENTIFIC REPORTS Khalid, M., Ahmed, R., Yetisen, A. K., AlQattan, B., Butt, H. 2017; 7: 10603

  Abstract

  The optical phase conjugation (OPC) through photonic nanostructures in coherent optics involves the utilization of a nonlinear optical mechanism through real-time processing of electromagnetic fields. Their applications include spectroscopy, optical tomography, wavefront sensing, and imaging. The development of functional and personalized holographic devices in the visible and near-infrared spectrum can be improved by introducing cost-effective, rapid, and high-throughput fabrication techniques and low-cost recording media. Here, we develop flat and thin phase-conjugate nanostructures on low-cost ink coated glass substrates through a facile and flexible single pulsed nanosecond laser based reflection holography and a cornercube retroreflector (CCR). Fabricated one/two-dimensional (1D/2D) nanostructures exhibited far-field phase-conjugated patterns through wavefront reconstruction by means of diffraction. The optical phase conjugation property had correlation with the laser light (energy) and structural parameters (width, height and exposure angle) variation. The phase conjugated diffraction property from the recorded nanostructures was verified through spectral measurements, far-field diffraction experiments, and thermal imaging. Furthermore, a comparison between the conventional and phase-conjugated nanostructures showed two-fold increase in diffracted light intensity under monochromatic light illumination. It is anticipated that low-cost ink based holographic phase-conjugate nanostructures may have applications in flexible and printable displays, polarization-selective flat waveplates, and adaptive diffraction optics.

  View details for DOI 10.1038/s41598-017-10790-4

  View details for Web of Science ID 000409439900021

  View details for PubMedID 28878232

  View details for PubMedCentralID PMC5587581

• Finite element analysis of nanosecond pulsed laser ablation of various materials WORLD JOURNAL OF ENGINEERING Ren, J., Ahmed, R., Butt, H. 2017; 14 (6): 489–96

  View details for DOI 10.1108/WJE-12-2016-0149

  View details for Web of Science ID 000423966100003

• Multimode waveguide based directional coupler OPTICS COMMUNICATIONS Ahmed, R., Rifat, A. A., Sabouri, A., Al-Qattan, B., Essa, K., Butt, H. 2016; 370: 183–91

  View details for DOI 10.1016/j.optcom.2016.03.015

  View details for Web of Science ID 000373214600032

• A simple photonic crystal fiber based plasmonic biosensor International OSA Network of Students Ahmmed, R., Ahmed, R., et al 2016
• Computational Modelling of Nanophotonic Optical Devices 7th Annual BBEAR PGR Conference Ahmed, R., et al 2016
• Circular Steppted-Pyramid based Microlens Array EPS Research Conference Ahmed, R. 2016
• Holographic Ink-based optical device Photon 16 Ahmed, R., et al 2016
• Mode-multiplexed waveguide sensor JOURNAL OF ELECTROMAGNETIC WAVES AND APPLICATIONS Ahmed, R., Rifat, A. A., Yetisen, A. K., Yun, S., Khan, S., Butt, H. 2016; 30 (4): 444–55

  View details for DOI 10.1080/09205071.2015.1117025

  View details for Web of Science ID 000375469100004

• Design of Dispersion Manage, Low Confinement Loss and High Nonlinearity Photonic Crystal Fiber for Communication Applications The 6th ANU/SEED-Net Regional Conference on Electrical Engineering Ahmmed, R., et al 2014
• Optimum design of a nearly zero ultra-flattened dispersion with lower confinement loss photonic crystal fibers for communication systems International Journal of Scientific and Engineering Research Ahmmed , R., Ahmed, R., et al 2013; 4 (1)
• 2D Photonic Crystal Power Splitter with Finite-Difference-Time-Domain (FDTD) Method Meeting for Young Researcher AHMED, R. N., et al 2013
• Design, simulation & optimization of 2D photonic crystal power splitter Optics and Photonics Journal Ahmed, R., et al 2013; 3 (02)

  View details for DOI 10.4236/opj.2013.32A002

• Electrical and dielectric properties analysis of vanadium penta-oxide (V 2 O 5) doped Ni–Zn ferrite samples The Pacific Journal of Science and Technology Ahad, A., Ahmed, R., et al 2013; 14 (1)
• Design and Simulation of Duel-Concentric-Core Photonic Crystal Fiber for Dispersion Compensation CIOMP-OSA Summer Session on Optical Engineering, Design and Manufacturing Ahmmed, R., Ahmed, R., et al 2013

  View details for DOI 10.1364/SUMSESSION.2013.Tu2

• Design of Ultra-flattened Zero Dispersion Shifted Photonic Crystal Fibers with Lower Confinement Loss for Telecommunication Applications CIOMP-OSA Summer Session on Optical Engineering, Design and Manufacturing Ahmed, R., et al 2013

  View details for DOI 10.1364/SUMSESSION.2013.Tu6

• Design of Large Negative Dispersion and Modal Analysis for Hexagonal, Square, FCC and BCC Photonic Crystal Fibers Ahmmed, R., Ahmed, R., Razzak, S., IEEE IEEE. 2013

  View details for Web of Science ID 000326546900053

• DESIGN, IMPLEMENTATION AND PERFORMANCE STUDY OF LOW COST CYLINDRICAL PARABOLIC CONCENTRATOR WITH FLAT HORIZONTAL ABSORBER Journal of Electrical Engineering Hossen, M., Ahmed, R., et al 2013; 13 (1)
• Design, Analysis and Performance Study of a Hybrid PV-Diesel-Wind System for a Village Gopal Nagar in Comilla Global Journal of Science Frontier Research Hoque, M., Bhuiyan, I., Ahmed, R., et al 2012; 12 (5)
• Synthesis and Investigation of Microstructure, Resistivity and Dielectric Properties of Vanadium penta-oxide (V2O5) Doped Ni-Zn Ferrite International conference on Electrical, Computer and Telecommunication Engineering Ahad, A., AHMED, R. N., et al 2012
• Effect of air fill fraction on modal analysis International conference on Electrical, Computer and Telecommunication Engineering Aoni, R., AHMED, R. N., et al 2012
• Design & Analysis of Optical Lenses by using 2D Photonic Crystals for Sub-wavelength Focusing International Journal of Advance Computer Science and Application Ahmed, R., et al 2012; 3 (12)
• A Text Dependent Speaker Recognition using Vector Quantization Dhaka Univ. J. Eng. & Tech. Ahmed, R., et al 2011; 1 (2): 1-6
• A Proposition for Low Cost Preventive Cardiology for Rural Health Care System in Bangladesh and Design of a Biomedical Data Collection Platform Using a Noninvasive Approach Regional Conference On Medical Physics Rab, M., et al 2011
• Design & Analysis on Silicon Based Optical Micro-Ring Resonator Sensor Device for Biomedica Application at µm Wavelength CIOMP-OSA international Summer Session, Leaser and Their Applications AHMED, R. N., et al 2011
• Low Cost, Noiseless and Patient Safety ECG Amplifier and Filter International conference on Medical Physics in Radiation Oncology & Imaging (ICMPROI-2011) Rab, A., et al 2011: 72
• On chip si-microring resonator for bio-medical applications at µm wavelength International Conference on Medical Physics in Radiation Oncology & Imaging (ICMPROI-2011) AHMED, R. N., et al 2011: 73
• Design & analysis on silicon based optical micro-ring resonator sensor device for biomedical applications at μm wavelength CIOMP-OSA Summer Session: Lasers and Their Applications Ahmed, R., , et al 2011

  View details for DOI 10.1364/SUMSESSION.2011.Tu3

• Effect of Lattice Constant and Air Hole Diameter on the Mode Profile in Triangular and Square Lattice Photonic Crystal Fiber at THz Regime Faruk, M., ul Aftab, M., Ahmed, R., Hussain, B., Islam, M., Alam, S., Ao, S. I., Douglas, C., Grundfest, W. S., Burgstone, J. INT ASSOC ENGINEERS-IAENG. 2010: 1109-+

  View details for Web of Science ID 000292889100212

• High Power Transmission by Elliptical Unit Cell Boundary on 2D Single Line Defect Photonic Crystal Waveguide International Conference on Fiber Optics & Photonics Ahmed, R., et al 2010