We report on a computational technique that recovers Raman peaks embedded in highly fluorescent contaminated spectra. The method uses a second derivative technique to identify the most intense Raman peak, and a modified Savisty Golay algorithm to filter and recover the embedded Raman peaks iteratively. This technique is an improvement on existing background removal algorithms in both performance and user objectivity.
{"title":"Raman spectra recovery using a second derivative technique and range independent baseline correction algorithm","authors":"A. Huzortey, B. Anderson, Alfred Owusu","doi":"10.1364/osac.432785","DOIUrl":"https://doi.org/10.1364/osac.432785","url":null,"abstract":"We report on a computational technique that recovers Raman peaks embedded in highly fluorescent contaminated spectra. The method uses a second derivative technique to identify the most intense Raman peak, and a modified Savisty Golay algorithm to filter and recover the embedded Raman peaks iteratively. This technique is an improvement on existing background removal algorithms in both performance and user objectivity.","PeriodicalId":19750,"journal":{"name":"OSA Continuum","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2021-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44623408","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In digital holographic microscopy, direct measurement of phase gradient is commonly required for investigations pertaining to cell morphology and feature detection. In this paper, we present the application of the Wigner-Ville distribution method for single shot quantitative phase gradient measurement in digital holographic microscopy. The method allows simultaneous extraction of phase derivatives along the horizontal and vertical dimensions to compute the phase gradient without the need of multiple images, filtering operations, or specialized experimental setups. Experimental results for imaging onion and cheek cells and standard calibration target, validates the potential of the proposed approach in digital holographic microscopy.
{"title":"Single shot quantitative phase gradient estimation using Wigner-Ville distribution in digital holographic microscopy","authors":"Ankur Vishnoi, R. Gannavarpu","doi":"10.1364/osac.431940","DOIUrl":"https://doi.org/10.1364/osac.431940","url":null,"abstract":"In digital holographic microscopy, direct measurement of phase gradient is commonly required for investigations pertaining to cell morphology and feature detection. In this paper, we present the application of the Wigner-Ville distribution method for single shot quantitative phase gradient measurement in digital holographic microscopy. The method allows simultaneous extraction of phase derivatives along the horizontal and vertical dimensions to compute the phase gradient without the need of multiple images, filtering operations, or specialized experimental setups. Experimental results for imaging onion and cheek cells and standard calibration target, validates the potential of the proposed approach in digital holographic microscopy.","PeriodicalId":19750,"journal":{"name":"OSA Continuum","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2021-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47744859","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Natsuki Suzuki, T. Yamauchi, Hidenao Yamada, K. Ishii
We describe an approach for arbitrarily adjusting the focal positions in quantitative phase imaging (QPI) based on a Linnik interferometer. Our setup employs a unique sample configuration in which transparent objects are imaged by a Linnik interferometer. By introducing a focus-tunable lens on top of the Linnik interferometer, we successfully decoupled the spatio-temporal coherence gating from the focal positioning and achieved dynamic focusing without disturbing the optical path length. Depth-sectioned quantitative phase images of polystyrene beads and live cultured cells were obtained without mechanical scanning.
{"title":"Dynamic focusing in low-coherence quantitative phase imaging with decoupling of spatio-temporal coherence gating and geometric focusing","authors":"Natsuki Suzuki, T. Yamauchi, Hidenao Yamada, K. Ishii","doi":"10.1364/osac.433900","DOIUrl":"https://doi.org/10.1364/osac.433900","url":null,"abstract":"We describe an approach for arbitrarily adjusting the focal positions in quantitative phase imaging (QPI) based on a Linnik interferometer. Our setup employs a unique sample configuration in which transparent objects are imaged by a Linnik interferometer. By introducing a focus-tunable lens on top of the Linnik interferometer, we successfully decoupled the spatio-temporal coherence gating from the focal positioning and achieved dynamic focusing without disturbing the optical path length. Depth-sectioned quantitative phase images of polystyrene beads and live cultured cells were obtained without mechanical scanning.","PeriodicalId":19750,"journal":{"name":"OSA Continuum","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2021-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48009345","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Min Jiang, Jianya Zhang, Z. Xing, Dongmin Wu, Hua Qin, L. Bian, Yukun Zhao, Wenxian Yang, Shulong Lu
Energy-saving photodetector (PD) with fast response speed is a key component of the next-generation photonic systems. In this work, self-powered photoelectrochemical (PEC) PD based on vertical (In,Ga)N nanowires (NWs) has been proposed and demonstrated successfully. With deionized water solution, the (In,Ga)N NWs are stable and the PEC PD is eco-friendly. The PEC PD has a good stability in terms of good on/off switching behaviors after continuously working for a few hours. The PD exhibits a high sensitivity under very low light illumination intensity of 6.4 μW/cm2. A fast rise/fall time of ∼54/55 ms with good symmetry can also be achieved. Moreover, the NW core-shell structure is proposed to provide an additional way for electron-hole carrier transport, which could play a key role in accelerating the response speed. This work paves a way to develop high-performance PEC PDs for the wide applications in wireless visible photodetection and communication.
{"title":"Self-powered visible photodetector with fast-response speed and high stability based on vertical (In,Ga)N nanowires","authors":"Min Jiang, Jianya Zhang, Z. Xing, Dongmin Wu, Hua Qin, L. Bian, Yukun Zhao, Wenxian Yang, Shulong Lu","doi":"10.1364/osac.431682","DOIUrl":"https://doi.org/10.1364/osac.431682","url":null,"abstract":"Energy-saving photodetector (PD) with fast response speed is a key component of the next-generation photonic systems. In this work, self-powered photoelectrochemical (PEC) PD based on vertical (In,Ga)N nanowires (NWs) has been proposed and demonstrated successfully. With deionized water solution, the (In,Ga)N NWs are stable and the PEC PD is eco-friendly. The PEC PD has a good stability in terms of good on/off switching behaviors after continuously working for a few hours. The PD exhibits a high sensitivity under very low light illumination intensity of 6.4 μW/cm2. A fast rise/fall time of ∼54/55 ms with good symmetry can also be achieved. Moreover, the NW core-shell structure is proposed to provide an additional way for electron-hole carrier transport, which could play a key role in accelerating the response speed. This work paves a way to develop high-performance PEC PDs for the wide applications in wireless visible photodetection and communication.","PeriodicalId":19750,"journal":{"name":"OSA Continuum","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2021-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41602841","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Collimated ultraviolet (UV) light is generated via four-wave mixing (FWM) in cesium vapor by continuously tuning the wavelength of the pump laser. Terahertz (THz) Stokes light is generated by the stimulated Raman scattering (SRS) effect in the FWM process, and its frequency is adjustable. When exciting the cesium atom to a virtual level using different combinations of pump lasers (P1 and P2), the strength distribution of UV light is asymmetric, which can be explained through a phase-matching mechanism. Furthermore, the SRS effect and phase matching influence the FWM.
{"title":"Collimated ultraviolet light generated by four-wave mixing process in Cs vapor","authors":"Baodong Gai, Shu Hu, Junzhi Chu, Pengyuan Wang, X. Cai, Jingwei Guo","doi":"10.1364/osac.435249","DOIUrl":"https://doi.org/10.1364/osac.435249","url":null,"abstract":"Collimated ultraviolet (UV) light is generated via four-wave mixing (FWM) in cesium vapor by continuously tuning the wavelength of the pump laser. Terahertz (THz) Stokes light is generated by the stimulated Raman scattering (SRS) effect in the FWM process, and its frequency is adjustable. When exciting the cesium atom to a virtual level using different combinations of pump lasers (P1 and P2), the strength distribution of UV light is asymmetric, which can be explained through a phase-matching mechanism. Furthermore, the SRS effect and phase matching influence the FWM.","PeriodicalId":19750,"journal":{"name":"OSA Continuum","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2021-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45308024","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
With substantial improvements on the optical arrangement, we show that significant enhancement of the magneto-optical rotation effect in rubidium vapor can be achieved without using complex and expensive heterodyne polarimetric methods. The huge signal-to-noise ratio performance using low cost photo-detectors opens the door to chip-sized device manufacturing and in-situ applications in biomagnetism.
{"title":"Giant magneto-optical rotation effect in rubidium vapor measured with a low-cost detection system","authors":"C. Zhu, J. Guan, F. Zhou, E. Zhu, Yan Li","doi":"10.1364/osac.435754","DOIUrl":"https://doi.org/10.1364/osac.435754","url":null,"abstract":"With substantial improvements on the optical arrangement, we show that significant enhancement of the magneto-optical rotation effect in rubidium vapor can be achieved without using complex and expensive heterodyne polarimetric methods. The huge signal-to-noise ratio performance using low cost photo-detectors opens the door to chip-sized device manufacturing and in-situ applications in biomagnetism.","PeriodicalId":19750,"journal":{"name":"OSA Continuum","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2021-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46268988","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-09-08eCollection Date: 2021-09-15DOI: 10.1364/OSAC.431444
Richard J Colchester, Callum D Little, Erwin J Alles, Adrien E Desjardins
All-optical ultrasound transducers are well-suited for use in imaging during minimally invasive surgical procedures. This requires highly miniaturised and flexible devices. Here we present optical ultrasound transmitters for imaging applications based on modified optical fibre distal tips which allow for larger transmitter element sizes, whilst maintaining small diameter proximal optical fibre. Three optical ultrasound transmitter configurations were compared; a 400 µm core optical fibre, a 200 µm core optical fibre with a 400 µm core optical fibre distal tip, and a 200 µm core optical fibre with a 400 µm core capillary distal tip. All the transmitters used a polydimethylsiloxane-dye composite material for ultrasound generation. The material comprised a photostable infra-red absorbing dye to provide optical absorption for the ultrasound transduction. The generated ultrasound beam profile for the three transmitters was compared, demonstrating similar results, with lateral beam widths <1.7 mm at a depth of 10 mm. The composite material demonstrates a promising alternative to previously reported materials, generating ultrasound pressures exceeding 2 MPa, with corresponding bandwidths ca. 30 MHz. These highly flexible ultrasound transmitters can be readily incorporated into medical devices with small lateral dimensions.
{"title":"Flexible and directional fibre optic ultrasound transmitters using photostable dyes.","authors":"Richard J Colchester, Callum D Little, Erwin J Alles, Adrien E Desjardins","doi":"10.1364/OSAC.431444","DOIUrl":"10.1364/OSAC.431444","url":null,"abstract":"<p><p>All-optical ultrasound transducers are well-suited for use in imaging during minimally invasive surgical procedures. This requires highly miniaturised and flexible devices. Here we present optical ultrasound transmitters for imaging applications based on modified optical fibre distal tips which allow for larger transmitter element sizes, whilst maintaining small diameter proximal optical fibre. Three optical ultrasound transmitter configurations were compared; a 400 µm core optical fibre, a 200 µm core optical fibre with a 400 µm core optical fibre distal tip, and a 200 µm core optical fibre with a 400 µm core capillary distal tip. All the transmitters used a polydimethylsiloxane-dye composite material for ultrasound generation. The material comprised a photostable infra-red absorbing dye to provide optical absorption for the ultrasound transduction. The generated ultrasound beam profile for the three transmitters was compared, demonstrating similar results, with lateral beam widths <1.7 mm at a depth of 10 mm. The composite material demonstrates a promising alternative to previously reported materials, generating ultrasound pressures exceeding 2 MPa, with corresponding bandwidths <i>ca.</i> 30 MHz. These highly flexible ultrasound transmitters can be readily incorporated into medical devices with small lateral dimensions.</p>","PeriodicalId":19750,"journal":{"name":"OSA Continuum","volume":"4 9","pages":"2488-2495"},"PeriodicalIF":1.6,"publicationDate":"2021-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10575603/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41237448","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A universal method to design gradient-index (GRIN) optical elements is proposed here for a given desired light ray bundle. Fermat’s principle can be transformed into a spatial parametric ray equation where a spatial Cartesian coordinate is used as a parameter of the equation. The ray equation can thus be written in a time-independent form, which ensures that a refractive index distribution is in principle obtainable from a spatial light ray distribution. Based on the ray equation, an iterative GRIN mapping method using the neural network (NN) is then constructed to map a refractive index distribution that enables light rays to trace corresponding desired paths. Maxwell’s fisheye lens is used to demonstrate how well the GRIN mapping method works. The refractive index distribution is shown to be well reconstructed from only knowledge of the light ray paths.
{"title":"Neural network gradient-index mapping","authors":"H. Ohno, Takashi Usui","doi":"10.1364/osac.437395","DOIUrl":"https://doi.org/10.1364/osac.437395","url":null,"abstract":"A universal method to design gradient-index (GRIN) optical elements is proposed here for a given desired light ray bundle. Fermat’s principle can be transformed into a spatial parametric ray equation where a spatial Cartesian coordinate is used as a parameter of the equation. The ray equation can thus be written in a time-independent form, which ensures that a refractive index distribution is in principle obtainable from a spatial light ray distribution. Based on the ray equation, an iterative GRIN mapping method using the neural network (NN) is then constructed to map a refractive index distribution that enables light rays to trace corresponding desired paths. Maxwell’s fisheye lens is used to demonstrate how well the GRIN mapping method works. The refractive index distribution is shown to be well reconstructed from only knowledge of the light ray paths.","PeriodicalId":19750,"journal":{"name":"OSA Continuum","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2021-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48760397","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Light scattering techniques are often used to characterize the particles suspended in a turbid medium, and Monte Carlo simulations are an important part of many such methodologies. In this work, we use the Monte Carlo method to simulate the propagation of light in a turbid mixture, that comprises of different types of particles, and obtain the relevant probability distributions, which are found to be consistent with the works reported in the literature. The simulation model is used to propose a recipe which requires a single measurement of the scattered power and the transmitted power, to determine the concentrations of constituent particles in a bidisperse mixture. The method is experimentally validated for turbid mixtures of polystyrene spheres, and found to be accurate within the limits of experimental error.
{"title":"Method to determine the concentrations of constituents in a bidisperse turbid medium using Monte Carlo simulation for mixtures","authors":"Kalpak Gupta, M. R. Shenoy","doi":"10.1364/osac.422281","DOIUrl":"https://doi.org/10.1364/osac.422281","url":null,"abstract":"Light scattering techniques are often used to characterize the particles suspended in a turbid medium, and Monte Carlo simulations are an important part of many such methodologies. In this work, we use the Monte Carlo method to simulate the propagation of light in a turbid mixture, that comprises of different types of particles, and obtain the relevant probability distributions, which are found to be consistent with the works reported in the literature. The simulation model is used to propose a recipe which requires a single measurement of the scattered power and the transmitted power, to determine the concentrations of constituent particles in a bidisperse mixture. The method is experimentally validated for turbid mixtures of polystyrene spheres, and found to be accurate within the limits of experimental error.","PeriodicalId":19750,"journal":{"name":"OSA Continuum","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2021-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45629178","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}