B. Ouyang, W. Hou, C. Gong, F. Caimi, F. Dalgleish, A. Vuorenkoski, X. Xiao, D. Voelz
The Compressive Line Sensing (CLS) active imaging system has been demonstrated to be effective in scattering mediums, such as coastal turbid water, fog and mist, through simulations and test tank experiments. The CLS prototype hardware consists of a CW laser, a DMD, a photomultiplier tube, and a data acquisition instrument. CLS employs whiskbroom imaging formation that is compatible with traditional survey platforms. The sensing model adopts the distributed compressive sensing theoretical framework that exploits both intra-signal sparsity and highly correlated nature of adjacent areas in a natural scene. During sensing operation, the laser illuminates the spatial light modulator DMD to generate a series of 1D binary sensing pattern from a codebook to “encode” current target line segment. A single element detector PMT acquires target reflections as encoder output. The target can then be recovered using the encoder output and a predicted on-target codebook that reflects the environmental interference of original codebook entries. In this work, we investigated the effectiveness of the CLS imaging system in a turbulence environment. Turbulence poses challenges in many atmospheric and underwater surveillance applications. A series of experiments were conducted in the Naval Research Lab’s optical turbulence test facility with the imaging path subjected to various turbulence intensities. The total-variation minimization sparsifying basis was used in imaging reconstruction. The preliminary experimental results showed that the current imaging system was able to recover target information under various turbulence strengths. The challenges of acquiring data through strong turbulence environment and future enhancements of the system will be discussed.
{"title":"Experimental study of a DMD based compressive line sensing imaging system in the turbulence environment","authors":"B. Ouyang, W. Hou, C. Gong, F. Caimi, F. Dalgleish, A. Vuorenkoski, X. Xiao, D. Voelz","doi":"10.1117/12.2212426","DOIUrl":"https://doi.org/10.1117/12.2212426","url":null,"abstract":"The Compressive Line Sensing (CLS) active imaging system has been demonstrated to be effective in scattering mediums, such as coastal turbid water, fog and mist, through simulations and test tank experiments. The CLS prototype hardware consists of a CW laser, a DMD, a photomultiplier tube, and a data acquisition instrument. CLS employs whiskbroom imaging formation that is compatible with traditional survey platforms. The sensing model adopts the distributed compressive sensing theoretical framework that exploits both intra-signal sparsity and highly correlated nature of adjacent areas in a natural scene. During sensing operation, the laser illuminates the spatial light modulator DMD to generate a series of 1D binary sensing pattern from a codebook to “encode” current target line segment. A single element detector PMT acquires target reflections as encoder output. The target can then be recovered using the encoder output and a predicted on-target codebook that reflects the environmental interference of original codebook entries. In this work, we investigated the effectiveness of the CLS imaging system in a turbulence environment. Turbulence poses challenges in many atmospheric and underwater surveillance applications. A series of experiments were conducted in the Naval Research Lab’s optical turbulence test facility with the imaging path subjected to various turbulence intensities. The total-variation minimization sparsifying basis was used in imaging reconstruction. The preliminary experimental results showed that the current imaging system was able to recover target information under various turbulence strengths. The challenges of acquiring data through strong turbulence environment and future enhancements of the system will be discussed.","PeriodicalId":122702,"journal":{"name":"SPIE OPTO","volume":"516 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116222549","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}
The essential goal for fast prototyping of microstructures is to reduce the cycle time. Conventional methods up to now consist of creating designs with a CAD software, then fabricating or purchasing a Photomask and finally using a mask aligner to transfer the pattern to the photoresist. The new Maskless Aligner (MLA) enables to expose the pattern directly without fabricating a mask, which results in a significantly shorter prototyping cycle. To achieve this short prototyping cycle, the MLA has been improved in many aspects compared to other direct write lithography solutions: exposure speed, user interface, ease of operation and flexibility.
{"title":"The next generation of maskless lithography","authors":"S. Diez","doi":"10.1117/12.2211052","DOIUrl":"https://doi.org/10.1117/12.2211052","url":null,"abstract":"The essential goal for fast prototyping of microstructures is to reduce the cycle time. Conventional methods up to now consist of creating designs with a CAD software, then fabricating or purchasing a Photomask and finally using a mask aligner to transfer the pattern to the photoresist. The new Maskless Aligner (MLA) enables to expose the pattern directly without fabricating a mask, which results in a significantly shorter prototyping cycle. To achieve this short prototyping cycle, the MLA has been improved in many aspects compared to other direct write lithography solutions: exposure speed, user interface, ease of operation and flexibility.","PeriodicalId":122702,"journal":{"name":"SPIE OPTO","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121549755","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}
F. Wippermann, A. Brückner, A. Oberdörster, A. Reimann
The vast majority of cameras and imaging sensors relies on the identical single aperture optics principle with the human eye as natural antetype. Multi-aperture approaches – in natural systems so called compound eyes and in technology often referred to as array-cameras have advantages in terms of miniaturization, simplicity of the optics and additional features such as depth information and refocusing enabled by the computational manipulation of the system´s raw image data. The proposed imaging principle is based on a multitude of imaging channels transmitting different parts of the entire field of view. Adapted image processing algorithms are employed for the generation of the overall image by the stitching of the images of the different channels. The restriction of the individual channel´s field of view leads to a less complex optical system targeting reduced fabrication cost. Due to a novel, linear morphology of the array camera setup, depth mapping with improved resolution can be achieved. We introduce a novel concept for miniaturized array-cameras with several mega pixel resolution targeting high volume applications in mobile and automotive imaging with improved depth mapping and explain design and fabrication aspects.
{"title":"Novel multi-aperture approach for miniaturized imaging systems","authors":"F. Wippermann, A. Brückner, A. Oberdörster, A. Reimann","doi":"10.1117/12.2211698","DOIUrl":"https://doi.org/10.1117/12.2211698","url":null,"abstract":"The vast majority of cameras and imaging sensors relies on the identical single aperture optics principle with the human eye as natural antetype. Multi-aperture approaches – in natural systems so called compound eyes and in technology often referred to as array-cameras have advantages in terms of miniaturization, simplicity of the optics and additional features such as depth information and refocusing enabled by the computational manipulation of the system´s raw image data. The proposed imaging principle is based on a multitude of imaging channels transmitting different parts of the entire field of view. Adapted image processing algorithms are employed for the generation of the overall image by the stitching of the images of the different channels. The restriction of the individual channel´s field of view leads to a less complex optical system targeting reduced fabrication cost. Due to a novel, linear morphology of the array camera setup, depth mapping with improved resolution can be achieved. We introduce a novel concept for miniaturized array-cameras with several mega pixel resolution targeting high volume applications in mobile and automotive imaging with improved depth mapping and explain design and fabrication aspects.","PeriodicalId":122702,"journal":{"name":"SPIE OPTO","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114820657","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}
Many medical, environmental, and industrial sensing applications could take advantage of uncooled temperature-stable optical sources that are incoherent and un-polarized as such sources do not produce interference fringes, speckle patterns, or intensity variations due to polarization. For this purpose we propose an optical system for stabilization of light-emitting diodes over temperature exhibiting output power variation below 50 ppm/°C which does not employ any kind of TEC elements or even thermometers. This makes it especially suitable for handheld and battery operated instruments.
{"title":"Temperature-stable LED-based light source without temperature control","authors":"M. Bosiljevac, D. Babic, Z. Šipuš","doi":"10.1117/12.2211576","DOIUrl":"https://doi.org/10.1117/12.2211576","url":null,"abstract":"Many medical, environmental, and industrial sensing applications could take advantage of uncooled temperature-stable optical sources that are incoherent and un-polarized as such sources do not produce interference fringes, speckle patterns, or intensity variations due to polarization. For this purpose we propose an optical system for stabilization of light-emitting diodes over temperature exhibiting output power variation below 50 ppm/°C which does not employ any kind of TEC elements or even thermometers. This makes it especially suitable for handheld and battery operated instruments.","PeriodicalId":122702,"journal":{"name":"SPIE OPTO","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125733864","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}
C. Helke, M. Meinig, M. Seifert, J. Seiler, K. Hiller, S. Kurth, Jörg Martin, T. Gessner
Profound developments of miniaturized spectrometry systems enable new breakthrough applications such as online monitoring systems for specific molecules by Surface Enhanced Raman Spectroscopy (SERS). The spectrometry system is based on SERS active surfaces in-situ generating nanoparticles and miniaturized detectors with tunable Fabry-Pérot- Interferometers (FPI) with very sharp transmission peaks and a FWHM bandwidth below 2 nm. The key part of this online monitoring system is a tunable FPI, which is fabricated with MEMS technology. This contribution presents a 7.5 x 7.5 mm² chip size FPI, consisting of a moveable reflector on a 210 nm thin and up to 5.5 mm in diameter Si3N4 membrane on a silicon carrier, and a fixed reflector on glass. The optical resonator with an aperture of 2 mm diameter is designed for the central wavelength of 570 nm and realized by adhesive SU-8 bonding of the silicon on glass substrate. The moveable Si3N4 membrane is fabricated by combined wet and dry etching of silicon. The dielectric (HL)4 Si3N4/ SiO2 reflector stack with a reflectance of 93 % is deposited by PE-CVD on the LP-CVD-Si3N4 and structured by dry etching on the membrane and the glass. The measured peak transmittance is between 52 % and 74 % with a FWHM bandwidth between 1.3 nm and 2.0 nm. It was shown, that the FPIs are tunable over the spectral range from 555 nm to 585 nm which is relevant for this SERS application with a tuning voltage of 25 V.
{"title":"VIS Fabry-Pérot-Interferometer with (HL)4 PE-Si3N4/PE-SiO2 reflectors on freestanding LP-Si3N4 membranes for surface enhanced Raman spectroscopy","authors":"C. Helke, M. Meinig, M. Seifert, J. Seiler, K. Hiller, S. Kurth, Jörg Martin, T. Gessner","doi":"10.1117/12.2208567","DOIUrl":"https://doi.org/10.1117/12.2208567","url":null,"abstract":"Profound developments of miniaturized spectrometry systems enable new breakthrough applications such as online monitoring systems for specific molecules by Surface Enhanced Raman Spectroscopy (SERS). The spectrometry system is based on SERS active surfaces in-situ generating nanoparticles and miniaturized detectors with tunable Fabry-Pérot- Interferometers (FPI) with very sharp transmission peaks and a FWHM bandwidth below 2 nm. The key part of this online monitoring system is a tunable FPI, which is fabricated with MEMS technology. This contribution presents a 7.5 x 7.5 mm² chip size FPI, consisting of a moveable reflector on a 210 nm thin and up to 5.5 mm in diameter Si3N4 membrane on a silicon carrier, and a fixed reflector on glass. The optical resonator with an aperture of 2 mm diameter is designed for the central wavelength of 570 nm and realized by adhesive SU-8 bonding of the silicon on glass substrate. The moveable Si3N4 membrane is fabricated by combined wet and dry etching of silicon. The dielectric (HL)4 Si3N4/ SiO2 reflector stack with a reflectance of 93 % is deposited by PE-CVD on the LP-CVD-Si3N4 and structured by dry etching on the membrane and the glass. The measured peak transmittance is between 52 % and 74 % with a FWHM bandwidth between 1.3 nm and 2.0 nm. It was shown, that the FPIs are tunable over the spectral range from 555 nm to 585 nm which is relevant for this SERS application with a tuning voltage of 25 V.","PeriodicalId":122702,"journal":{"name":"SPIE OPTO","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121609827","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}
A. Brückner, A. Oberdörster, J. Dunkel, A. Reimann, Frank Wippermann
In this contribution, a microoptical imaging system is demonstrated that is inspired by the insect compound eye. The array camera module achieves HD resolution with a z-height of 2.0 mm, which is about 50% compared to traditional cameras with comparable parameters. The FOV is segmented by multiple optical channels imaging in parallel. The partial images are stitched together to form a final image of the whole FOV by image processing software. The system is able to acquire depth maps along with the 2D video and it includes light field imaging features such as software refocusing. The microlens arrays are realized by microoptical technologies on wafer-level which are suitable for a potential fabrication in high volume.
{"title":"Ultra-slim 2D- and depth-imaging camera modules for mobile imaging","authors":"A. Brückner, A. Oberdörster, J. Dunkel, A. Reimann, Frank Wippermann","doi":"10.1117/12.2214062","DOIUrl":"https://doi.org/10.1117/12.2214062","url":null,"abstract":"In this contribution, a microoptical imaging system is demonstrated that is inspired by the insect compound eye. The array camera module achieves HD resolution with a z-height of 2.0 mm, which is about 50% compared to traditional cameras with comparable parameters. The FOV is segmented by multiple optical channels imaging in parallel. The partial images are stitched together to form a final image of the whole FOV by image processing software. The system is able to acquire depth maps along with the 2D video and it includes light field imaging features such as software refocusing. The microlens arrays are realized by microoptical technologies on wafer-level which are suitable for a potential fabrication in high volume.","PeriodicalId":122702,"journal":{"name":"SPIE OPTO","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132167820","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}
Muhammad A. Othman, Y. Sabry, Mohamed Sadek, I. Nassar, D. Khalil
In this work we report a novel optical MEMS deeply-etched mirror with metallic coating and vertical slot, where the later allows reflection and transmission by the micromirror. The micromirror as well as fiber grooves are fabricated using deep reactive ion etching technology, where the optical axis is in-plane and the components are self-aligned. The etching depth is 150 μm chosen to improve the micromirror optical throughput. The vertical optical structure is Al metal coated using the shadow mask technique. A fiber-coupled Fabry-Pérot filter is successfully realized using the fabricated structure. Experimental measurements were obtained based on a dielectric-coated optical fiber inserted into a fiber groove facing the slotted micromirror. A versatile performance in terms of the free spectral range and 3-dB bandwidth is achieved.
{"title":"Deeply-etched micromirror with vertical slit and metallic coating enabling transmission-type optical MEMS filters","authors":"Muhammad A. Othman, Y. Sabry, Mohamed Sadek, I. Nassar, D. Khalil","doi":"10.1117/12.2211323","DOIUrl":"https://doi.org/10.1117/12.2211323","url":null,"abstract":"In this work we report a novel optical MEMS deeply-etched mirror with metallic coating and vertical slot, where the later allows reflection and transmission by the micromirror. The micromirror as well as fiber grooves are fabricated using deep reactive ion etching technology, where the optical axis is in-plane and the components are self-aligned. The etching depth is 150 μm chosen to improve the micromirror optical throughput. The vertical optical structure is Al metal coated using the shadow mask technique. A fiber-coupled Fabry-Pérot filter is successfully realized using the fabricated structure. Experimental measurements were obtained based on a dielectric-coated optical fiber inserted into a fiber groove facing the slotted micromirror. A versatile performance in terms of the free spectral range and 3-dB bandwidth is achieved.","PeriodicalId":122702,"journal":{"name":"SPIE OPTO","volume":"113 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127829742","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}
We studied time-dependent fluctuations of photoluminescence (PL) spectra of single CdSe/ZnS nanocrystals (NCs), which show PL blinking and spectral diffusion. We observed correlations between PL peak energy, intensity, and linewidth, which are due to the quantum confined Stark effect. We found that a characteristic asymmetric shape appears in the PL peak energy histogram, which can be explained by a simple field-fluctuation model. By comparing the experimental results with theoretical calculations, we evaluate the mean value and standard deviation of the fluctuating electric field. We discuss the experimental data using a model considering a few elementary charges around the NCs, which are the origin of the field fluctuation.
{"title":"Photoluminescence blinking and spectral diffusion of single CdSe/ZnS nanocrystals: charge fluctuation effects","authors":"Hiroto Ibuki, T. Ihara, Y. Kanemitsu","doi":"10.1117/12.2210817","DOIUrl":"https://doi.org/10.1117/12.2210817","url":null,"abstract":"We studied time-dependent fluctuations of photoluminescence (PL) spectra of single CdSe/ZnS nanocrystals (NCs), which show PL blinking and spectral diffusion. We observed correlations between PL peak energy, intensity, and linewidth, which are due to the quantum confined Stark effect. We found that a characteristic asymmetric shape appears in the PL peak energy histogram, which can be explained by a simple field-fluctuation model. By comparing the experimental results with theoretical calculations, we evaluate the mean value and standard deviation of the fluctuating electric field. We discuss the experimental data using a model considering a few elementary charges around the NCs, which are the origin of the field fluctuation.","PeriodicalId":122702,"journal":{"name":"SPIE OPTO","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127898427","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}
F. Bulota, P. Bélanger, M. Leduc, C. Boudoux, N. Godbout
We present a linear all-fiber device exhibiting the functionality of a circulator, albeit for multimode fibers. We define a pseudo-circulator as a linear three-port component that transfers most of a multimode light signal from Port 1 to Port 2, and from Port 2 to Port 3. Unlike a traditional circulator which depends on a nonlinear phenomenon to achieve a non-reciprocal behavior, our device is a linear component that seemingly breaks the principle of reciprocity by exploiting the variations of etendue of the multimode fibers in the coupler. The pseudo-circulator is implemented as a 2x2 asymmetric multimode fiber coupler, fabricated using the fusion-tapering technique. The coupler is asymmetric in its transverse fused section. The two multimode fibers differ in area, thus favoring the transfer of light from the smaller to the bigger fiber. The desired difference of area is obtained by tapering one of the fiber before the fusion process. Using this technique, we have successfully fabricated a pseudo-circulator surpassing in efficiency a 50/50 beam-splitter. In all the visible and near-IR spectrum, the transmission ratio exceeds 77% from Port 1 to Port 2, and 80% from Port 2 to Port 3. The excess loss is less than 0.5 dB, regardless of the entry port.
{"title":"Pseudo-circulator implemented as a multimode fiber coupler","authors":"F. Bulota, P. Bélanger, M. Leduc, C. Boudoux, N. Godbout","doi":"10.1117/12.2213378","DOIUrl":"https://doi.org/10.1117/12.2213378","url":null,"abstract":"We present a linear all-fiber device exhibiting the functionality of a circulator, albeit for multimode fibers. We define a pseudo-circulator as a linear three-port component that transfers most of a multimode light signal from Port 1 to Port 2, and from Port 2 to Port 3. Unlike a traditional circulator which depends on a nonlinear phenomenon to achieve a non-reciprocal behavior, our device is a linear component that seemingly breaks the principle of reciprocity by exploiting the variations of etendue of the multimode fibers in the coupler. The pseudo-circulator is implemented as a 2x2 asymmetric multimode fiber coupler, fabricated using the fusion-tapering technique. The coupler is asymmetric in its transverse fused section. The two multimode fibers differ in area, thus favoring the transfer of light from the smaller to the bigger fiber. The desired difference of area is obtained by tapering one of the fiber before the fusion process. Using this technique, we have successfully fabricated a pseudo-circulator surpassing in efficiency a 50/50 beam-splitter. In all the visible and near-IR spectrum, the transmission ratio exceeds 77% from Port 1 to Port 2, and 80% from Port 2 to Port 3. The excess loss is less than 0.5 dB, regardless of the entry port.","PeriodicalId":122702,"journal":{"name":"SPIE OPTO","volume":"111 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114448065","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}
Raghu Dharmavarapu, A. Vijayakumar, R. Brunner, S. Bhattacharya
A binary Fresnel Zone Axilens (FZA) is designed for the infinite conjugate mode and the phase profile of a refractive axicon is combined with it to generate a composite Diffractive Optical Element (DOE). The FZA designed for two focal lengths generates a line focus along the propagation direction extending between the two focal planes. The ring pattern generated by the axicon is focused through this distance and the radius of the ring depends on the propagation distance. Hence, the radius of the focused ring pattern can be tuned, during the design process, within the two focal planes. The integration of the two functions was carried out by shifting the location of zones of FZA with respect to the phase profile of the refractive axicon resulting in a binary composite DOE. The FZAs and axicons were designed for different focal depth values and base angles respectively, in order to achieve different ring radii within the focal depth of each element. The elements were simulated using scalar diffraction formula and their focusing characteristics were analyzed. The DOEs were fabricated using electron beam direct writing and evaluated using a fiber coupled diode laser. The tunable ring patterns generated by the DOEs have prospective applications in microdrilling as well as microfabrication of circular diffractive and refractive optical elements.
{"title":"Composite axilens-axicon diffractive optical elements for generation of ring patterns with high focal depth","authors":"Raghu Dharmavarapu, A. Vijayakumar, R. Brunner, S. Bhattacharya","doi":"10.1117/12.2213037","DOIUrl":"https://doi.org/10.1117/12.2213037","url":null,"abstract":"A binary Fresnel Zone Axilens (FZA) is designed for the infinite conjugate mode and the phase profile of a refractive axicon is combined with it to generate a composite Diffractive Optical Element (DOE). The FZA designed for two focal lengths generates a line focus along the propagation direction extending between the two focal planes. The ring pattern generated by the axicon is focused through this distance and the radius of the ring depends on the propagation distance. Hence, the radius of the focused ring pattern can be tuned, during the design process, within the two focal planes. The integration of the two functions was carried out by shifting the location of zones of FZA with respect to the phase profile of the refractive axicon resulting in a binary composite DOE. The FZAs and axicons were designed for different focal depth values and base angles respectively, in order to achieve different ring radii within the focal depth of each element. The elements were simulated using scalar diffraction formula and their focusing characteristics were analyzed. The DOEs were fabricated using electron beam direct writing and evaluated using a fiber coupled diode laser. The tunable ring patterns generated by the DOEs have prospective applications in microdrilling as well as microfabrication of circular diffractive and refractive optical elements.","PeriodicalId":122702,"journal":{"name":"SPIE OPTO","volume":"40 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114578523","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}
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