Junwei Su, F. Gao, Zhiyong Gu, Wen Dai, G. Cernigliaro, Hongwei Sun
In this work, 3-D nanoscale line patterns were fabricated on SU-8 layers by Ga+ focused ion beam (FIB) lithography and used as Nanoimprint lithography (NIL) mold. Both V-shape side wall and opposing dose deficiency effect were observed and analyzed during the FIB milling process. Different beam currents were utilized to fabricate SU-8 pattern and it is found that the lower beam currents provide higher quality pattern with smooth edges and straight side walls. In addition, the impact of crosslink density of SU-8 material on the FIB milling efficiency was discussed. Both thermal and ultraviolet (UV) NIL were conducted using these line patterns to study the deformation of SU-8 mold and filling ratio of imprinting material. The experiments revealed that the imprint pressure and physic properties of imprinting material are the most critical factors in these NIL processes.
{"title":"Fabrication of SU-8 based nanopatterns and their use as a nanoimprint mold","authors":"Junwei Su, F. Gao, Zhiyong Gu, Wen Dai, G. Cernigliaro, Hongwei Sun","doi":"10.1117/12.2039832","DOIUrl":"https://doi.org/10.1117/12.2039832","url":null,"abstract":"In this work, 3-D nanoscale line patterns were fabricated on SU-8 layers by Ga+ focused ion beam (FIB) lithography and used as Nanoimprint lithography (NIL) mold. Both V-shape side wall and opposing dose deficiency effect were observed and analyzed during the FIB milling process. Different beam currents were utilized to fabricate SU-8 pattern and it is found that the lower beam currents provide higher quality pattern with smooth edges and straight side walls. In addition, the impact of crosslink density of SU-8 material on the FIB milling efficiency was discussed. Both thermal and ultraviolet (UV) NIL were conducted using these line patterns to study the deformation of SU-8 mold and filling ratio of imprinting material. The experiments revealed that the imprint pressure and physic properties of imprinting material are the most critical factors in these NIL processes.","PeriodicalId":395835,"journal":{"name":"Photonics West - Micro and Nano Fabricated Electromechanical and Optical Components","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133618702","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}
Bassem M. Al-Demerdash, M. Medhat, Y. Sabry, B. Saadany, D. Khalil
MEMS spectrometers have very strong potential in future healthcare and environmental monitoring applications, where Michelson interferometers are the core optical engine. Recently, MEMS Michelson interferometers based on using silicon interface as a beam splitter (BS) has been proposed [7, 8]. This allows having a monolithically-integrated on-chip FTIR spectrometer. However silicon BS exhibits high absorption loss in the visible range and high material dispersion in the near infrared (NIR) range. For this reason, we propose in this work a novel MOEMS interferometer allowing operation over wider spectral range covering both the infrared (IR) and the visible ranges. The proposed architecture is based on spatial splitting and combining of optical beams using the imaging properties of Multi-Mode Interference MMI waveguide. The proposed structure includes an optical splitter for spatial splitting an input beam into two beams and a combiner for spatial combining the two interferometer beams. A MEMS moveable mirror is provided to produce an optical path difference between the two beams. The new interferometer is fabricated using DRIE technology on an SOI wafer. The movable mirror is metalized and attached to a comb-drive actuator fabricated in the same lithography step in a self-aligned manner on chip. The novel interferometer is tested as a Fourier transform spectrometer. Red laser, IR laser and absorption spectra of different materials are measured with a resolution of 2.5 nm at 635-nm wavelength. The structure is a very compact one that allows its integration and fabrication on a large scale with very low cost.
{"title":"MMI-based MOEMS FT spectrometer for visible and IR spectral ranges","authors":"Bassem M. Al-Demerdash, M. Medhat, Y. Sabry, B. Saadany, D. Khalil","doi":"10.1117/12.2038641","DOIUrl":"https://doi.org/10.1117/12.2038641","url":null,"abstract":"MEMS spectrometers have very strong potential in future healthcare and environmental monitoring applications, where Michelson interferometers are the core optical engine. Recently, MEMS Michelson interferometers based on using silicon interface as a beam splitter (BS) has been proposed [7, 8]. This allows having a monolithically-integrated on-chip FTIR spectrometer. However silicon BS exhibits high absorption loss in the visible range and high material dispersion in the near infrared (NIR) range. For this reason, we propose in this work a novel MOEMS interferometer allowing operation over wider spectral range covering both the infrared (IR) and the visible ranges. The proposed architecture is based on spatial splitting and combining of optical beams using the imaging properties of Multi-Mode Interference MMI waveguide. The proposed structure includes an optical splitter for spatial splitting an input beam into two beams and a combiner for spatial combining the two interferometer beams. A MEMS moveable mirror is provided to produce an optical path difference between the two beams. The new interferometer is fabricated using DRIE technology on an SOI wafer. The movable mirror is metalized and attached to a comb-drive actuator fabricated in the same lithography step in a self-aligned manner on chip. The novel interferometer is tested as a Fourier transform spectrometer. Red laser, IR laser and absorption spectra of different materials are measured with a resolution of 2.5 nm at 635-nm wavelength. The structure is a very compact one that allows its integration and fabrication on a large scale with very low cost.","PeriodicalId":395835,"journal":{"name":"Photonics West - Micro and Nano Fabricated Electromechanical and Optical Components","volume":"96 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133933773","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}
J. Schmidt, Ulrike A. Dauderstaedt, P. Duerr, M. Friedrichs, T. Hughes, T. Ludewig, D. Rudloff, Tino Schwaten, Daniela Trenkler, M. Wagner, I. Wullinger, A. Bergstrom, Peter Bjoernangen, F. Jonsson, T. Karlin, Peter Ronnholm, Torbjorn Sandstrom
Fraunhofer IPMS has developed a one-dimensional high-speed spatial light modulator in cooperation with Micronic Mydata AB. This SLM is the core element of the Swedish company’s new LDI 5sp series of Laser-Direct-Imaging systems optimized for processing of advanced substrates for semiconductor packaging. This paper reports on design, technology, characterization and application results of the new SLM. With a resolution of 8192 pixels that can be modulated in the MHz range and the capability to generate intensity gray-levels instantly without time multiplexing, the SLM is applicable also in many other fields, wherever modulation of ultraviolet light needs to be combined with high throughput and high precision.
{"title":"High-speed one-dimensional spatial light modulator for Laser Direct Imaging and other patterning applications","authors":"J. Schmidt, Ulrike A. Dauderstaedt, P. Duerr, M. Friedrichs, T. Hughes, T. Ludewig, D. Rudloff, Tino Schwaten, Daniela Trenkler, M. Wagner, I. Wullinger, A. Bergstrom, Peter Bjoernangen, F. Jonsson, T. Karlin, Peter Ronnholm, Torbjorn Sandstrom","doi":"10.1117/12.2036533","DOIUrl":"https://doi.org/10.1117/12.2036533","url":null,"abstract":"Fraunhofer IPMS has developed a one-dimensional high-speed spatial light modulator in cooperation with Micronic Mydata AB. This SLM is the core element of the Swedish company’s new LDI 5sp series of Laser-Direct-Imaging systems optimized for processing of advanced substrates for semiconductor packaging. This paper reports on design, technology, characterization and application results of the new SLM. With a resolution of 8192 pixels that can be modulated in the MHz range and the capability to generate intensity gray-levels instantly without time multiplexing, the SLM is applicable also in many other fields, wherever modulation of ultraviolet light needs to be combined with high throughput and high precision.","PeriodicalId":395835,"journal":{"name":"Photonics West - Micro and Nano Fabricated Electromechanical and Optical Components","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132033908","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}
Bongseok Choi, M. Iwanaga, H. Miyazaki, K. Sakoda, Y. Sugimoto
We fabricated large-area stacked complementary plasmonic crystals (SC PlCs) by employing ultra-violet (UV) nanoimprint lithography (NIL). The SC PlCs was made on silicon on insulator (SOI) substrates, consisting of three layers: the top layer contacting air was perforated Au film, the bottom layer contacting buried oxide (BOX) layer included Au disk array corresponding to the holes in the top layer, and the middle layer was Si photonic crystal slab. The SC PlCs have prominent resonances in the optical wavelengths. It is shown that the fabricated PlCs were precisely made in structure and well uniform in the optical properties. We have examined photoluminescence (PL) enhancement of dye molecules on the SC PlC substrates in the visible range and found large enhancement up to 100-fold in comparison with the dye molecules on non-processed Si wafers.
{"title":"Emission-enhanced plasmonic substrates fabricated by nano-imprint lithography","authors":"Bongseok Choi, M. Iwanaga, H. Miyazaki, K. Sakoda, Y. Sugimoto","doi":"10.1117/12.2037190","DOIUrl":"https://doi.org/10.1117/12.2037190","url":null,"abstract":"We fabricated large-area stacked complementary plasmonic crystals (SC PlCs) by employing ultra-violet (UV) nanoimprint lithography (NIL). The SC PlCs was made on silicon on insulator (SOI) substrates, consisting of three layers: the top layer contacting air was perforated Au film, the bottom layer contacting buried oxide (BOX) layer included Au disk array corresponding to the holes in the top layer, and the middle layer was Si photonic crystal slab. The SC PlCs have prominent resonances in the optical wavelengths. It is shown that the fabricated PlCs were precisely made in structure and well uniform in the optical properties. We have examined photoluminescence (PL) enhancement of dye molecules on the SC PlC substrates in the visible range and found large enhancement up to 100-fold in comparison with the dye molecules on non-processed Si wafers.","PeriodicalId":395835,"journal":{"name":"Photonics West - Micro and Nano Fabricated Electromechanical and Optical Components","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130986685","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}
Matthew Kissel, M. Reinig, O. Azucena, Juan J. Diaz Leon, J. Kubby
The design of an Adaptive Optics (AO) Structured Illumination (SI) microscope is presented. Two key technologies are combined to provide effective super-resolution at significant depths in tissue. AO is used to measure and compensate for optical aberrations in both the system and the tissue by measuring the optical path differences in the wavefront. Uncorrected, these aberrations significantly reduce imaging resolution, particularly as we view deeper into tissue. SI allows us to reconstruct an image with resolution beyond the Rayleigh limit of the optics by aliasing high spatial frequencies, outside the limit of the optics, to lower frequencies within the system pass band. The aliasing is accomplished by spatially modulating the illumination at a frequency near the cutoff frequency of the system. These aliased frequencies are superimposed on the lower spatial frequencies of the object in our image. Using multiple images and an inverse algorithm, we separate the aliased and normal frequencies, restore them to their original frequency positions, and recreate the original spectrum of the object. This allows us to recreate a super-resolution image of the object. A problem arises with thick aberrating tissue. Tissue aberrations, including sphere, increase with depth into the tissue and reduce the high spatial frequency response of a system. This degrades the ability of SI to reconstruct at superresolution and limits its use to relatively shallow depths. However, adding AO to the system compensates for these aberrations allowing SI to work at maximum efficiency even deep within aberrating tissue.
{"title":"Development and testing of an AO-structured illumination microscope","authors":"Matthew Kissel, M. Reinig, O. Azucena, Juan J. Diaz Leon, J. Kubby","doi":"10.1117/12.2044092","DOIUrl":"https://doi.org/10.1117/12.2044092","url":null,"abstract":"The design of an Adaptive Optics (AO) Structured Illumination (SI) microscope is presented. Two key technologies are combined to provide effective super-resolution at significant depths in tissue. AO is used to measure and compensate for optical aberrations in both the system and the tissue by measuring the optical path differences in the wavefront. Uncorrected, these aberrations significantly reduce imaging resolution, particularly as we view deeper into tissue. SI allows us to reconstruct an image with resolution beyond the Rayleigh limit of the optics by aliasing high spatial frequencies, outside the limit of the optics, to lower frequencies within the system pass band. The aliasing is accomplished by spatially modulating the illumination at a frequency near the cutoff frequency of the system. These aliased frequencies are superimposed on the lower spatial frequencies of the object in our image. Using multiple images and an inverse algorithm, we separate the aliased and normal frequencies, restore them to their original frequency positions, and recreate the original spectrum of the object. This allows us to recreate a super-resolution image of the object. A problem arises with thick aberrating tissue. Tissue aberrations, including sphere, increase with depth into the tissue and reduce the high spatial frequency response of a system. This degrades the ability of SI to reconstruct at superresolution and limits its use to relatively shallow depths. However, adding AO to the system compensates for these aberrations allowing SI to work at maximum efficiency even deep within aberrating tissue.","PeriodicalId":395835,"journal":{"name":"Photonics West - Micro and Nano Fabricated Electromechanical and Optical Components","volume":"538 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124526623","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. Reinlein, M. Appelfelder, M. Goy, S. Gebhardt, N. Gutzeit
Laser-induced mirror deformation and thermal lensing in optical high power systems shall be compensated by a thermally-piezoelectric deformable mirror (DM). In our device, the laser-induced thermal lensing is compensated by heating of the DM as previously described with compound loading. We experimentally show the capability of this mirror for wavefront shaping of up to 6.2 kW laser power and power densities of 2 kW/cm2. The laser-induced defocussing of the membrane is compensated by mirror heating. We introduce a new mirror setup with buried heater and temperature sensor elements. Therewith, the compensation of laser-induced mirror deformation is possible within the same time scale. The piezoelectric stroke of the single actuators depends on their position on the membrane, and is not affected by the reflected laser power.
{"title":"Testing of thermally piezoelectric deformable mirror with buried functionality","authors":"C. Reinlein, M. Appelfelder, M. Goy, S. Gebhardt, N. Gutzeit","doi":"10.1117/12.2039353","DOIUrl":"https://doi.org/10.1117/12.2039353","url":null,"abstract":"Laser-induced mirror deformation and thermal lensing in optical high power systems shall be compensated by a thermally-piezoelectric deformable mirror (DM). In our device, the laser-induced thermal lensing is compensated by heating of the DM as previously described with compound loading. We experimentally show the capability of this mirror for wavefront shaping of up to 6.2 kW laser power and power densities of 2 kW/cm2. The laser-induced defocussing of the membrane is compensated by mirror heating. We introduce a new mirror setup with buried heater and temperature sensor elements. Therewith, the compensation of laser-induced mirror deformation is possible within the same time scale. The piezoelectric stroke of the single actuators depends on their position on the membrane, and is not affected by the reflected laser power.","PeriodicalId":395835,"journal":{"name":"Photonics West - Micro and Nano Fabricated Electromechanical and Optical Components","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124789288","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}
L. Dunbar, D. Nguyen, B. Timotijevic, U. Vogler, S. Veseli, G. Bergonzi, S. Angeloni, A. Bramati, R. Voelkel, R. Stanley
In this paper we show that using optical photolithography it’s possible to obtain submicron features for periodic structures using the Talbot effect. To use the Talbot effect without the need of an absolute distance measurement between the mask and the wafer we integrate over several exposures for varying wafer mask distances. Here we discuss the salient features of ‘integrated Talbot lithography’. Particularly, we show that to obtain good contrasts an excellent control of the illumination light is essential; for this we use the MO Exposure Optics (MOEO) developed by SUSS MicroOptics (SMO). Finally we show that 1μm and 0.55μm diameter holes can be made using this technique.
{"title":"Talbot lithography as an alternative for contact lithography for submicron features","authors":"L. Dunbar, D. Nguyen, B. Timotijevic, U. Vogler, S. Veseli, G. Bergonzi, S. Angeloni, A. Bramati, R. Voelkel, R. Stanley","doi":"10.1117/12.2036896","DOIUrl":"https://doi.org/10.1117/12.2036896","url":null,"abstract":"In this paper we show that using optical photolithography it’s possible to obtain submicron features for periodic structures using the Talbot effect. To use the Talbot effect without the need of an absolute distance measurement between the mask and the wafer we integrate over several exposures for varying wafer mask distances. Here we discuss the salient features of ‘integrated Talbot lithography’. Particularly, we show that to obtain good contrasts an excellent control of the illumination light is essential; for this we use the MO Exposure Optics (MOEO) developed by SUSS MicroOptics (SMO). Finally we show that 1μm and 0.55μm diameter holes can be made using this technique.","PeriodicalId":395835,"journal":{"name":"Photonics West - Micro and Nano Fabricated Electromechanical and Optical Components","volume":"84 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124848692","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}
S. Gu-Stoppel, J. Janes, H. Quenzer, U. Hofmann, W. Benecke
This paper presents designs and fabrication process of two single-axis PZT micromirrors with 1 mm diameter and 1.4 mm × 4 mm apertures, whose frequencies are 60 kHz and 17 kHz, respectively. These micromirrors achieve large optical scan angles of about 40° driven by 10 V rectangular pulses and show high Q-factors of more than 1000. The investigation on the long-term stability of a PZT driven micromirror has detected more than 100 Billion cycles. The combined results of experimental diagnostics and FEM analyses give rise to new designs iteratively leading to a larger deflection and appropriate frequencies, which are currently fabricated.
本文介绍了直径为1mm、孔径为1.4 mm × 4mm、频率分别为60khz和17khz的两种单轴PZT微镜的设计和制作工艺。这些微镜在10 V矩形脉冲驱动下实现了约40°的大光学扫描角，并显示出超过1000的高q因子。对PZT驱动微镜的长期稳定性的研究已经检测到超过1000亿次的循环。实验诊断和有限元分析相结合的结果，迭代产生新的设计，导致更大的挠度和适当的频率，目前制造。
{"title":"Two-dimensional scanning using two single-axis low-voltage PZT resonant micromirrors","authors":"S. Gu-Stoppel, J. Janes, H. Quenzer, U. Hofmann, W. Benecke","doi":"10.1117/12.2036565","DOIUrl":"https://doi.org/10.1117/12.2036565","url":null,"abstract":"This paper presents designs and fabrication process of two single-axis PZT micromirrors with 1 mm diameter and 1.4 mm × 4 mm apertures, whose frequencies are 60 kHz and 17 kHz, respectively. These micromirrors achieve large optical scan angles of about 40° driven by 10 V rectangular pulses and show high Q-factors of more than 1000. The investigation on the long-term stability of a PZT driven micromirror has detected more than 100 Billion cycles. The combined results of experimental diagnostics and FEM analyses give rise to new designs iteratively leading to a larger deflection and appropriate frequencies, which are currently fabricated.","PeriodicalId":395835,"journal":{"name":"Photonics West - Micro and Nano Fabricated Electromechanical and Optical Components","volume":"1 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123766978","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}
Yen-Chun Tung, Ming-Han Chung, I-Hui Sung, Chih-Kung Lee
Adopting optical technique to pursue micromachining must make a compromise between the focal spot sizes the depth of focus. The focal spot size determines the minimum features can be fabricated. On the other hand, the depth of focus influences the ease of alignment in positioning the fabrication light beam. A typical approach to bypass the diffraction limit is to adopt the near-field approach, which has spot size in the range of the optical fiber tip. However, the depth of focus of the emitted light beam will be limited to tens of nanometers in most cases, which posts a difficult challenge to control the distance between the optical fiber tip and the sample to be machined optically. More specifically, problems remained in this machining approach, which include issues such as residue induced by laser ablation tends to deposit near the optical fiber tip and leads to loss of coupling efficiency. We proposed a method based on illuminating femtosecond laser through a sub-wavelength annular aperture on metallic film so as to produce Bessel light beam of sub-wavelength while maintaining large depth of focus first. To further advance the ease of use in one such system, producing sub-wavelength annular aperture on a single mode optical fiber head with sub-wavelength focusing ability is detailed. It is shown that this method can be applied in material machining with an emphasis to produce high aspect ratio structure. Simulations and experimental results are presented in this paper.
{"title":"Design and fabrication of sub-wavelength annular apertures on fiber tip for femtosecond laser machining","authors":"Yen-Chun Tung, Ming-Han Chung, I-Hui Sung, Chih-Kung Lee","doi":"10.1117/12.2039148","DOIUrl":"https://doi.org/10.1117/12.2039148","url":null,"abstract":"Adopting optical technique to pursue micromachining must make a compromise between the focal spot sizes the depth of focus. The focal spot size determines the minimum features can be fabricated. On the other hand, the depth of focus influences the ease of alignment in positioning the fabrication light beam. A typical approach to bypass the diffraction limit is to adopt the near-field approach, which has spot size in the range of the optical fiber tip. However, the depth of focus of the emitted light beam will be limited to tens of nanometers in most cases, which posts a difficult challenge to control the distance between the optical fiber tip and the sample to be machined optically. More specifically, problems remained in this machining approach, which include issues such as residue induced by laser ablation tends to deposit near the optical fiber tip and leads to loss of coupling efficiency. We proposed a method based on illuminating femtosecond laser through a sub-wavelength annular aperture on metallic film so as to produce Bessel light beam of sub-wavelength while maintaining large depth of focus first. To further advance the ease of use in one such system, producing sub-wavelength annular aperture on a single mode optical fiber head with sub-wavelength focusing ability is detailed. It is shown that this method can be applied in material machining with an emphasis to produce high aspect ratio structure. Simulations and experimental results are presented in this paper.","PeriodicalId":395835,"journal":{"name":"Photonics West - Micro and Nano Fabricated Electromechanical and Optical Components","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115950048","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}
Fluorescence fluctuation methods, such as fluorescence correlation spectroscopy, are very sensitive to optical aberrations. That is why it is possible to use a fluctuations-based metric, the molecular brightness, to correct aberrations using a sensorless modal adaptive optics approach. We have investigated the performance of this method by correcting known aberrations under various experimental conditions. The signal-to-noise ratio of the brightness measurement was examined theoretically and experimentally and found to be directly related to the accuracy of aberration correction, so that the latter can be predicted for a given sample brightness and measurement duration. We have also shown that the initial measurement conditions play a key role in the correction dynamics and we provide guidelines to optimize the corrections accuracy and speed. The molecular brightness, used as a metric, has the advantage that it depends on aberrations as the square of the Strehl ratio, regardless of the nature of the sample. Therefore, it is straightforward to predict the achievable correction accuracy and the same performance can be obtained in samples with different structure and contrast, which would not be possible with image-based optimization metrics.
{"title":"Accuracy of adaptive optics correction using fluorescence fluctuations","authors":"J. Gallagher, C. Leroux, I. Wang, A. Delon","doi":"10.1117/12.2040428","DOIUrl":"https://doi.org/10.1117/12.2040428","url":null,"abstract":"Fluorescence fluctuation methods, such as fluorescence correlation spectroscopy, are very sensitive to optical aberrations. That is why it is possible to use a fluctuations-based metric, the molecular brightness, to correct aberrations using a sensorless modal adaptive optics approach. We have investigated the performance of this method by correcting known aberrations under various experimental conditions. The signal-to-noise ratio of the brightness measurement was examined theoretically and experimentally and found to be directly related to the accuracy of aberration correction, so that the latter can be predicted for a given sample brightness and measurement duration. We have also shown that the initial measurement conditions play a key role in the correction dynamics and we provide guidelines to optimize the corrections accuracy and speed. The molecular brightness, used as a metric, has the advantage that it depends on aberrations as the square of the Strehl ratio, regardless of the nature of the sample. Therefore, it is straightforward to predict the achievable correction accuracy and the same performance can be obtained in samples with different structure and contrast, which would not be possible with image-based optimization metrics.","PeriodicalId":395835,"journal":{"name":"Photonics West - Micro and Nano Fabricated Electromechanical and Optical Components","volume":"49 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120889739","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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